Science research

RESEARCH & SCIENCE
TABLE OF CONTENTS

1. The effects of mouthpiece use on gas exchange parameters during
steady-state exercise in college-aged men and women
The Journal of the American Dental Association

2. The effects of mouthpiece use on salivary cortisol levels during exercise
The official Journal of the American College of Sports Medicine

3. The effects of mouthpiece use during endurance exercise
on lactate and cortisol levels
The official Journal of the American College of Sports Medicine

4. The effect of mouthpiece use on muscular endurance
Southeast Chapter of the American College of Sports Medicine

5. MP use increases VO2, VCO2 and VO2/kg during steady state running
Southeast Chapter of the American College of Sports Medicine

6. Effects of mouthpiece use on airways Openings Lactate Levels
in Healthy College Males
Compendium: A Supplement of Continuing Education in Dentistry

7. Effects of Mouth Piece Use on Auditory and Visual Reaction Time
in College Males and Females

8. The Role of Intraoral Protective Appliances in the Reduction
of Mild Traumatic Brain Injury

9. A Study on the Effectiveness of a Self-fit Mandibular Repositioning Appliance
on Increasing Human Strength and Endurance Capabilities
Knoxville, University of Tennessee

10. The Effects of ArmourBite® Mouthpiece Use on Baseball Pitching Velocity.
Rod Dedeaux Research & Baseball Institute

Other Research Accepted for Publication
Accepted for publication in renowned medical journals (pending print)

1) The effects of mouthpiece use on cortisol levels during an intensive resistive bout of exercise

The effects of mouthpiece use on gas exchange
parameters during steady-state exercise in
college-aged men and women
Dena P. Garner, Wesley D. Dudgeon, Timothy P.
Scheett and Erica J. McDivitt
J Am Dent Assoc 2011;142;1041-1047

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RESEARCH

The effects of mouthpiece use on gas
exchange parameters during steady-state
exercise in college-aged men and women
Dena P. Garner, PhD; Wesley D. Dudgeon, PhD; Timothy P. Scheett, PhD; Erica J. McDivitt, MS

R
esearch in the late 1970s
and early 1980s indicated
that mouthguards may
AB STRACT
enhance performance during Background. The authors conducted a study to assess the
strength and endurance exercise.1-3 effects of custom-fitted mouthpieces on gas exchange parameters,
However, the research findings were including voluntary oxygen consumption (VO2), voluntary oxygen
difficult to interpret because of the consumption per kilogram of body weight (VO2 /kg) and voluntary
subjective methodology used. carbon dioxide production (VCO2).
Garabee1 reported that endurance Methods. Sixteen physically fit college students aged 18 through
athletes felt they recovered more 21 years performed two 10-minute treadmill runs (6.5 miles per
quickly after endurance training hour, 0 percent grade) for each of three treatment conditions
and could run at a higher intensity (mouthpiece, no mouthpiece and nose breathing). The authors
when wearing a mouthpiece than assigned the conditions randomly for each participant and for each
when not wearing a mouthpiece; session. They assessed gas exchange parameters by using a meta-
however, he provided no physiolog- bolic measurement system.
ical measures from the study. Results. The authors used analysis of variance to compare all
Smith2,3 reported the results of variables. They set the significance level at α = .05 and used a
two studies in which football players Tukey post hoc analysis of treatment means to identify differences
increased their muscular strength between groups. The results showed significant improvements
when wearing a mouthguard (P < .05) in VO2, VO2 /kg and VCO2 in the mouthpiece condition.
adjusted kinesiologically versus Conclusions. The study findings show that use of a custom-
when they wore an unadjusted fitted mouthpiece resulted in improved specific gas exchange
mouthguard. The investigator meas- parameters. The authors are pursuing further studies to explain
ured the participants’ strength by the mechanisms involved in the improved endurance performance
using a stress gauge kinesiometer, exhibited with mouthpiece use.
which measures the amount of pres- Clinical Implications. Dental care professionals have an obli-
sure resistance in kilograms of force gation to understand the increasing research evidence in support of
per unit of time. mouthpiece use during exercise and athletic activity and to educate
The question remains whether their patients.
Smith informed the athletes before Key Words. Mouthpiece; mouthguard; gas exchange; exercise;
the study that their performance voluntary oxygen consumption; carbon dioxide.
might be affected positively by JADA 2011;142(9):1041-1047.
mouthpiece use during testing. If
Dr. Garner is an associate professor, Department of Health, Exercise and Sports Science, The Citadel, 171 Moultrie St., Charleston, S.C. 29409,
e-mail “Dena.garner@citadel.edu”. Address reprint requests to Dr. Garner.
Dr. Dudgeon is an assistant professor, Department of Health, Exercise and Sports Science, The Citadel, Charleston, S.C.
Dr. Scheett is an assistant professor, Department of Health and Human Performance, College of Charleston, Charleston, S.C.
Ms. McDivitt is a research assistant, Department of Health, Exercise and Sports Science, The Citadel, Charleston, S.C.

JADA 142(9) http://jada.ada.org September 2011 1041
Copyright © 2011 American Dental Association. All rights reserved.

RESEARCH

players assumed that their performance would state exercise. The novel aspect of our research
improve, the psychosomatic effect may have was the use of a custom-fitted, unobtrusive
caused the reported improvements in muscular mouthpiece rather than the bulky mouthguard
strength. used in the study by Francis and Brasher.4
In an effort to measure breathing outcomes Therefore, the purpose of this study was to
with a mouthguard, Francis and Brasher4 con- assess the effects of a custom-fitted mandibular
ducted a study composed of 10 participants to mouthpiece on gas exchange parameters in
assess the physiological effects of mouthguard healthy, college-aged participants.
use during five minutes of low-intensity and
high-intensity exercise on a cycle ergometer. PARTICIPANTS AND METHODS
They found that during the higher-intensity We recruited 16 participants (13 men and three
exercise, those wearing a mouthguard exhibited women) aged 18 through 21 years (mean ±
improvement in expiratory volume, with signifi- standard deviation [SD] age, 21.2 ± 0.75 years)
cant decreases in ventilation (Ve). for this study. Participants’ mean (± SD) height
Expanding on the work of Francis and and body mass were 176.37 ± 7.3 centimeters
Brasher,4 Garner and McDivitt5 conducted a and 75.20 ± 12.96 kilograms, respectively. The
study to determine the effects of mouthpiece use men were physically active and had participated

during endurance exercise. In their study, 24 in university-mandated physical exercise, which
participants ran at 75 to 85 percent of maximal consisted of a minimum of two cardiovascular
heart rate (HR) for 30 minutes on two occasions. and two resistance exercise sessions per week.
The investigators assigned mouthpiece use ran- The three women were college athletes, of whom
domly to enable them to determine the effects of two were on the track and field team and one
mouthpiece use on lactate levels before, during was on the soccer team. All participants
and immediately after the protocol. Outcomes reported that they had refrained from physical
from this study demonstrated that mouthpiece exercise the day of testing and were free of
use had a positive effect on blood lactate levels, injury or illness.
which were significantly lower (22.7 percent) at The institutional review board of The Citadel,
30 minutes (4.01 millimoles per liter with Charleston, S.C., approved the study. All partici-
mouthpiece use versus 4.92 mmol/L with no pants provided oral and written consent before
mouthpiece use).5 participating in the study; we asked them
This finding was confirmed in another study whether they understood all of the study’s
by Garner and McDivitt,6 the results of which methods and procedures; and we informed them
showed that lactate levels were 18.1 percent of their right to drop out of the study at any time.
lower after a 30-minute run in the mouthpiece Dental impressions. Before testing, a den-
condition versus that in the no-mouthpiece con- tist made impression molds of each participant’s
dition (4.41 mmol/L versus 5.21 mmol/L, respec- lower teeth. We then sent the molds to the Bite
tively). The study results also showed that Tech laboratory (Danica Beach, Fla.) for fabrica-
mouthpiece use had a significant effect on tion of custom-fitted mandibular mouthpieces
airway area in 10 participants, as measured by (Under Armour Performance Mouthpiece,
computed axial tomography. Specifically, both Under Armour, Baltimore, in cooperation with
width and diameter measurements were 9 per- Bite Tech, Minneapolis) (Figure 1).
cent greater in participants who wore a mouth- Treadmill runs. Participants performed two
piece, with the difference in width measurement 10-minute treadmill runs for each of the three
being statistically significant.6 treatment conditions assessed in this study:
Because we discovered both anatomical and mouthpiece, no mouthpiece and nose breathing.
physiological changes associated with mouth- We assigned the conditions randomly for each
piece use during exercise, our goal was to eluci- participant and for each session. We tested each
date specific mechanisms involved with this phe- condition on a separate day; thus, participants
nomenon. Consequently, we conducted an were required to come to the human perform-
investigation to examine possible gas exchange ance laboratory on three occasions. For both of
differences associated with wearing a mouth- the 10-minute runs on each day of testing, we
piece during steady-state exercise. If partici-
pants experienced an improvement in endurance ABBREVIATION KEY. HR: Heart rate. RR: Respira-
outcomes (that is, lowered lactate levels), as pre- tory rate. VCO2: Voluntary carbon dioxide produc-
vious research findings indicate, then there may tion. Ve: Ventilation. VO2: Voluntary oxygen con-
have been some association with improved sumption. VO2 /kg: Voluntary oxygen consumption
oxygen/carbon dioxide exchange during steady- per kilogram of body weight. Vt: Tidal volume.

1042 JADA 142(9) http://jada.ada.org September 2011

RESEARCH

asked participants to run at 6.5 miles per hour
with 0 percent grade so that we could analyze
respiratory gas levels during steady-state exer-
cise. Before the first run on each test day, par-
ticipants warmed up by running on the tread-
mill for five minutes at 5.0 mph and 0 percent
grade. They then immediately began a 10-
minute run at 6.5 mph and 0 percent grade.
Afterward, the participants cooled down with
three minutes of walking at 3.0 mph and seven
minutes of seated rest.
The second trial of each day was the same as
the first trial, minus the five-minute warm-up.
We scheduled conditions two to three days apart
during which participants were allowed to par-
ticipate in their normal physical fitness routine, Figure 1. Custom-fitted mandibular mouthpiece (Under Armour
but we did not allow them to exercise on the day Performance Mouthpiece, Under Armour, Baltimore, in coopera-

of testing. tion with Bite Tech, Minneapolis) worn by college-aged partici-
One of us (E.J.M.) attached a face mask to each pants in the study. Image reproduced with permission of Under
Armour.
participant for each condition and adjusted it
until she detected no air leaks. We used a meta- ment and exported the data (SigmaStat 3.5,
bolic cart (ParvoMedics, Sandy, Utah) to measure Systat, Point Richmond, Calif.) for statistical
voluntary oxygen consumption (VO2), voluntary analysis. For each of the three conditions, we
oxygen consumption per kilogram of body mass grouped and averaged measurements for both
(VO2 /kg) and voluntary carbon dioxide production trials for each participant to yield mean values,
(VCO2). VO2 is defined as the amount of oxygen in which we used for the statistical analysis. We
liters that the body uses per minute during aer- used analysis of variance (ANOVA) to compare
obic exercise.7 VO2 /kg is the amount of oxygen in variables (HR, RR, Vt, Ve, VCO2, VO2 and
milliliters that a person consumes per minute rel- VO2 /kg). We set the significance level at α = .05
ative to body mass. VCO2 is the expired byproduct and used a Tukey post hoc analysis of treatment
of metabolism that occurs during aerobic exercise means to identify differences between groups.
and is measured in liters per minute. In addition For nonparametric data, we performed a
to VO2, VO2 /kg and VCO2, we measured partici- Kruskal-Wallis ANOVA on ranks and used the
pants’ respiratory rate (RR) (number of breaths Dunn method for post hoc analysis. All values
per minute), tidal volume (Vt) (amount of air are expressed as mean ± SD. We did not perform
inspired and expired per breath), Ve (total volume any ancillary analyses.
of inspired and expired air per minute) and HR
by using the metabolic cart. RESULTS
We measured these parameters every five sec- Data from two of the 16 participants were
onds and averaged the measurements for each incomplete; thus, results for this study are
minute of the 10-minute run for all three condi- based on data from 14 participants. As shown in
tions. On all test days, we calibrated the meta- Figures 2 through 4, VO2, VO2 /kg and VCO2
bolic cart according to the manufacturer’s speci- were statistically significantly (P < .05) higher
fications. For the mouthpiece condition (group in participants in group 1 than in participants
1), we asked participants to bite down on the in groups 2 and 3 during the 10-minute trial,
custom-fitted mouthpiece and breathe through and they were higher in participants in group 2
their mouths while their noses were clamped than in participants in group 3. The results
with a metal clamp attached to the face mask. were similar for minutes 1 through 5 (Table 1,
For the no-mouthpiece condition (group 2), we page 1045). During minutes 6 through 10,
asked participants to breathe through their open VCO2, VO2 and VO2 /kg were significantly
mouths while their noses were clamped. For the (P < .05) higher in participants in group 1 than
nose-breathing condition (group 3), we taped in participants in groups 2 and 3 (Table 2, page
participants’ mouths shut, which forced them to 1045). The results showed no differences
breathe through their noses. (P > .05) in Ve, RR or Vt between groups 1 and
Statistical analysis. One of us (T.P.S.) 2; however, as expected, the results for groups 1
entered all data into a spreadsheet (Excel, and 2 were statistically significantly different
Microsoft, Redmond, Wash.) for data manage- (P < .05) from those for group 3 during the entire


RESEARCH

2.6
10-minute test (Table 3, page 1046), during min-
VOLUNTARY OXYGEN CONSUMPTION

* utes 1 through 5 (Table 1) and during minutes 6
2.4
through 10 (Table 2). Finally, we found no differ-
2.2 ences in HR at any time points between all
*
(LITERS/MINUTE)

†
three conditions (Tables 1 through 3).
2.0

1.8 DISCUSSION
1.6
Athletes and others have worn mouthpieces
† during sports as protective devices against dental
1.4 injuries and concussions. The American Dental
1.2 Association’s Council on Access, Prevention and
Interprofessional Relations and Council on Scien-
1.0
1 (Mouthpiece) 2 (No Mouthpiece) 3 (Nose Breathing) tific Affairs8 concluded that mouthguards provide
GROUP a protective effect against hard-tissue or soft-
tissue damage in the mouth (such as tooth frac-
Figure 2. Voluntary oxygen consumption during steady-state tures, lip lacerations and mandibular damage).
exercise. Asterisk indicates statistically significant difference (P <
.05) from group 3. Dagger indicates statistically significant differ- However, increased use of mouthpieces for per-

ence (P < .05) from group 1. formance enhancement is a recent trend in sport
and exercise. In a study of mouthpiece use
35 during endurance exercise, Garner and McDi-
VOLUNTARY OXYGEN CONSUMPTION

* vitt5,6 reported lower lactate levels in participants
(MILLILITERS/KILOGRAM/MINUTE)

30 who wore a mouthpiece compared with levels in
† those who did not wear a mouthpiece. Thus, the
25
purpose of this study was to explain the lower
20
† lactate levels observed with mouthpiece use
during exercise by elucidating the oxygen/carbon
15
dioxide differences with mouthpiece use.
10
Increases in VCO2 would suggest an improved
ability to buffer the hydrogen ion associated with
5 lactate, thereby lowering hydrogen in the blood
and subsequent lactate levels.
0
1 (Mouthpiece) 2 (No Mouthpiece) 3 (Nose Breathing) Respiratory gas exchange. To elucidate
GROUP the potential mechanisms involved with mouth-
piece use during exercise, we assessed the pat-
Figure 3. Voluntary oxygen consumption per kilogram of body
weight during steady-state exercise. Asterisk indicates statistically
terns of respiratory gas exchange in a mouth-
significant difference (P < .05) from group 3. Dagger indicates sta- piece condition, a no-mouthpiece condition and a
tistically significant difference (P < .05) from group 1. nose-breathing condition. Previous researchers
in the area of airway dynamics have reported
differences between nasal and mouth breathing
VOLUNTARY CARBON DIOXIDE PRODUCTION

2.4
during various intensities of exercise.9-12 Specifi-
* cally, these authors found better gas exchange
2.2 with mouth breathing than with nasal
* breathing. Consequently, we expected to find
2.0
† lower Vt, VO2, VO2 /kg, VCO2 and RR with nasal
(LITERS/MINUTE)

1.8 breathing because these results have been
reported in previous research.9-12
1.6 However, we observed a novel finding when
1.4
comparing mouth breathing with no mouthpiece
† use to mouth breathing with mouthpiece use.
1.2 We had hypothesized that mouth breathing in
the no-mouthpiece condition would elicit out-
1.0
1 (Mouthpiece) 2 (No Mouthpiece) 3 (Nose Breathing) comes similar to those in the mouth-breathing-
GROUP
with-mouthpiece condition; however, this was
not the case. Specifically, the results showed sig-
Figure 4. Voluntary carbon dioxide production during steady- nificant improvements in VCO2 and oxygen
state exercise. Asterisk indicates statistically significant difference
(P < .05) from group 3. Dagger indicates statistically significant parameters and no significant differences in Ve
difference (P < .05) from group 1. when participants wore the mouthpiece versus


RESEARCH

when they did not TABLE 1
wear the mouthpiece Data from minutes 1 though 5 of steady-state
during the entire 10-
minute test; during exercise.
minutes 1 through 5; VARIABLE MEAN (± STANDARD DEVIATION) MEASURE
and during minutes 6 Group 1 Group 2 Group 3
through 10. Thus, the (Mouthpiece) (No Mouthpiece) (Nose Breathing Only)
improvements in VCO * (L†/Minute)
2 2.00 ± 0.55‡ 1.66 ± 0.49‡§ 1.02 ± 0.53
VCO2 and oxygen VO ¶ (L/Minute) 2.21 ± 0.64‡ 1.73 ± 0.54‡§ 1.12 ± 0.57
parameters cannot be
2

# (mL ** /kg/Minute)
VO /kg 29.1 ± 6.7 ‡ 22.5 ± 4.8 ‡§ 15.2 ± 7.3
explained by 2

improved Ve with Ventilation (L/Minute) 49.7 ± 10.8‡ 50.4 ± 12.1‡ 29.8 ± 8.5

mouthpiece use. Respiratory Rate 31 ± 7‡ 32 ± 8‡ 25 ± 6
(Breaths/Minute)
Francis and
Brasher4 assessed the Tidal Volume (L) 2.10 ± 0.61‡ 2.09 ± 0.59‡ 1.60 ± 0.59
physiological effects Heart Rate (Beats/Minute) 157 ± 15 156 ± 15 154 ± 11
of mouthguard use * VCO : Voluntary carbon dioxide production.

2

during five minutes † L: Liters.
‡ Statistically significant difference (P < .05) from group 3 (nose breathing only).
of low- and high- § Statistically significant difference (P < .05) from group 1 (mouthpiece).
intensity exercise on ¶ VO : Voluntary oxygen consumption.
2

a cycle ergometer. For # VO /kg: Voluntary oxygen consumption per kilogram of body weight.
2
** mL: Milliliters.
the low-intensity
cycling, 10 men TABLE 2
cycled at 100 watts
and seven women Data from minutes 6 through 10 of steady-state
cycled at 75 W; for exercise.
the high-intensity VARIABLE MEAN (± STANDARD DEVIATION) MEASURE
cycling, men cycled at
Group 1 Group 2 Group 3
150 W and women (Mouthpiece) (No Mouthpiece) (Nose Breathing Only)
cycled at 125 W.
VCO * (L†/Minute) 2.29 ± 0.59‡ 1.88 ± 0.54‡§ 1.19 ± 0.64
In comparing our 2

¶ (L/Minute)
study results with VO 2 2.43 ± 0.73 ‡ 1.90 ± 0.60 ‡§ 1.31 ± 0.74

those of Francis and VO /kg# (mL**/kg/Minute)
2 31.9 ± 7.5‡ 24.8 ± 5.8§ 18.0 ± 10.5
Brasher,4 we should Ventilation (L/Minute) 56.9 ± 11.5‡ 58.3 ± 13.7‡ 34.3 ± 11.0
note a difference in Respiratory Rate 33 ± 7‡ 35 ± 8‡ 28 ± 8
VO2 /kg between the (Breaths/Minute)
two studies. Francis Tidal Volume (L) 2.28 ± 0.63‡ 2.25 ± 0.63‡ 1.68 ± 0.66
and Brasher4 re- Heart Rate (Beats/Minute) 169 ± 16 167 ± 16 169 ± 10
ported a decreased
* VCO : Voluntary carbon dioxide production.
volume of VO2 /kg † L: Liters.
2

with mouthguard use ‡ Statistically significant difference (P < .05) from group 3 (nose breathing only).
during high-intensity § Statistically significant difference (P < .05) from group 1 (mouthpiece).
¶ VO : Voluntary oxygen consumption.
exercise, whereas we
2
# VO /kg: Voluntary oxygen consumption per kilogram of body weight.
2

measured a signifi- ** mL: Milliliters.
cant increase in
VO2 /kg when participants wore the mouthpiece. ticipants in our study wore a custom-fitted man-
However, Francis and Brasher4 also noted that dibular mouthpiece that did not create any
participants reported a feeling of restricted air- obstruction in breathing.
flow with mouthguard use, whereas the partici- The results of these studies were similar with
pants in our study did not report feeling such a regard to Ve, VCO2 and VO2 parameters with
restriction. We believe the differences between and without mouthguard or mouthpiece use.
our study results and those reported by Francis During the high-intensity protocol, Francis and
and Brasher4 most likely are attributable to the Brasher4 found an improvement in expiratory
type of mouthpiece worn in each study. In the volume, with decreases in Ve with mouthguard
study by Francis and Brasher,4 participants use; these results are similar to those of our
wore one of three different over-the-counter, study. Francis and Brasher4 suggested that
unfitted maxillary mouthguards, whereas par- when participants wore a mouthguard, they


RESEARCH

TABLE 3 breathes through the
Data from minutes 1 through 10 of steady-state mouth versus when
one does not wear a
exercise. mouthpiece and
VARIABLE MEAN (± STANDARD DEVIATION) MEASURE breathes through the
Group 1 Group 2 Group 3
mouth. Thus, the
(Mouthpiece) (No Mouthpiece) (Nose Breathing Only) improved airway
Ventilation (L*/ Minute) 53.4 ± 11.0† 54.6 ± 12.8† 32.3 ± 9.9 dynamics we found in
Respiratory Rate 32 ± 7† 34 ± 8†‡ 26 ± 7
our study may be
(Breaths/ Minute) explained in part by
Tidal Volume (L) 2.16 ± 0.62† 2.14 ± 0.61† Not applicable
anatomical and neu-
romuscular changes
Heart Rate (Beats/Minute) 163 ± 15 162 ± 16 161 ± 11
that occur during
* L: Liters. exercise with custom-
† Statistically significant difference (P < .05) from group 3 (nose breathing only).
‡ Statistically significant difference (P < .05) from group 1 (mouthpiece). fitted mouthpiece use
as the mouthpiece
might have been using a type of breathing called affects the genioglossus.

“pursed lip breathing,” which they defined as Cortisol and epinephrine. We also reported
pursing one’s lips and breathing out deeply. This that the use of a custom-fitted mandibular
type of breathing has been linked to improved mouthpiece is associated with a decrease in the
respiratory measures such as reduced breathing stress hormone cortisol after high-intensity exer-
rates and increased Vt in people with respiratory cise.24 This finding is consistent with the findings
disorders, but it has not been studied exten- of Hori and colleagues,25 who reported a decrease
sively in a healthy population.13-15 in corticotrophin-releasing factor levels (stress-
We propose that a similar, but more plau- induced response of the hypothalamic-pituitary-
sible, mechanism may have occurred when par- adrenal axis and a precursor to corticosterone
ticipants wore the custom-fitted mandibular release, the rat equivalent to cortisol in humans)
mouthpiece. We asked participants to bite down in rats that were allowed to bite down on a
on the mouthpiece, which has two wedges (one wooden stick while experiencing a stressor. If
on either side of the mouthpiece) that create an biting down on the mouthpiece results in a
opening between the maxillary and mandibular decrease in cortisol levels, it stands to reason
teeth (Figure 1). In addition, according to the that it also would affect other stress-related hor-
product description,16 this mouthpiece shifts the mones, namely epinephrine. Epinephrine is
mandible down and into a more forward posi- released quickly in response to a stressor, and
tion, which Garner and McDivitt6 reported one of its many functions is to stimulate the gly-
resulted in increased airway openings. colytic process (that is, breaking down of glucose
Genioglossus muscle. We also propose a to provide energy) to increase the rate of energy
contribution from a neuromuscular response production. Two of the key byproducts of glycol-
that occurs when participants bite down on the ysis are lactate and CO2. We have shown that use
mouthpiece and breathe through the mouth. of the custom-fitted mouthpiece decreases lactate
What might have occurred, and which some par- production and increases VCO2 production. We
ticipants reported anecdotally, is that when a now believe that a decrease in epinephrine
participant bit down on the mouthpiece and release may be the reason for these observed
breathed during steady-state exercise, the changes; however, more research is needed.
tongue moved forward, resulting in a contrac- Thus, if an anatomical and neuromuscular
tion of the genioglossus muscle. The results of improvement in airway dynamics occurs along
extensive research regarding the genioglossus with a diminished stress response (that is, lower
muscle show that contraction of this muscle cortisol and epinephrine levels) with mouthpiece
leads to relaxation of the pharyngeal airway, use during steady-state exercise, this could
thereby improving airway dynamics.17-22 explain the improved oxygen and carbon dioxide
Remmers23 reported that the genioglossus kinetics, as well as the improvements in lactate
may be associated with a reflex that leads to the production, that the results of our study show.
dilation of the pharyngeal area, thereby aiding
in respiration in both humans and animals. Pre- CONCLUSION
liminary research in our laboratory has shown The results of this study show improved airway
differences in electromyographic activity of the dynamics in participants who wore a custom-
genioglossus when one wears a mouthpiece and fitted mandibular mouthpiece during steady-


RESEARCH

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17. Bailey EF, Huang YH, Fregosi RF. Anatomic consequences of
tion26). At the beginning of exercise, there is a lag intrinsic tongue muscle activation. J Appl Physiol 2006;101(5):
of approximately one to two minutes during 1377-1385.
which oxygen is transported to the skeletal mus- 18. Cheng S, Butler JE, Gandevia SC, Bilston LE. Movement of the
tongue during normal breathing in awake healthy humans. J Physiol
cles. Therefore, one theory of how the mouth- 2008;586(part 17):4283-4294.
piece may affect lactate levels is by decreasing 19. Fogel RB, Trinder J, Malhotra A, et al. Within-breath control of
genioglossal muscle activation in humans: effect of sleep-wake state.
the time for oxygen to reach the muscle being J Physiol 2003;550(part 3):899-910.
exercised, thereby decreasing fatigue during 20. Mann EA, Burnett T, Cornell S, Ludlow CL. The effect of neu-
endurance exercise.27 Further research is needed romuscular stimulation of the genioglossus on the hypopharyngeal
airway. Laryngoscope 2002;112(2):351-356.
to fully elucidate the physiological mechanisms 21. Sokoloff AJ. Activity of tongue muscles during respiration: it
involved in improved performance when one takes a village? J Appl Physiol 2004;96(2):438-439.
wears a custom-fitted mouthpiece. I 22. Blumen MB, Perez de La Sota A, Quera-Salva MA, Frachet B,
Chabolle F, Lofaso F. Genioglossal electromyogram during main-
Disclosure. Dr. Garner and Ms. McDivitt received honoraria from tained contraction in normal humans. Eur J Appl Physiol 2002;
Bite Tech, Minneapolis. 88(1-2):170-177.
23. Remmers JE. Wagging the tongue and guarding the airway:
The authors thank Michael Engel, DDS (Charleston, S.C.), for reflex control of the genioglossus. Am J Respir Crit Care Med 2001;
making the models of the mouthpiece and Bite Tech Laboratories 164(11):2013-2014.
(Dania Beach, Fla.) for supplying the custom-fitted mouthpieces to 24. Garner DP, Dudgeon WD, McDivitt E. The effects of mouth-
each participant. piece use on cortisol levels during an intense bout of resistance exer-
cise. J Strength Cond Res. In press.
1. Garabee WF Jr. Craniomandibular orthopedics and athletic per- 25. Hori N, Yuyama N, Tamura K. Biting suppresses stress-
formance in the long distance runner: a three year study. Basal Facts induced expression of corticotropin-releasing factor (CRF) in the rat
1981;4(3):77-81. hypothalamus. J Dent Res 2004;83(2):124-128.
2. Smith SD. Muscular strength correlated to jaw posture and the 26. Wilmore JK, Costill DL, Kenney WL. Physiology of Sport and
temporomandibular joint. N Y State Dent J 1978;44(7):278-285. Exercise. 4th ed. Champaign, Ill.: Human Kinetics; 2007.
3. Smith SD. Adjusting mouthguards kinesiologically in profes- 27. Kilding AE, Winter EM, Fysh M. Moderate-domain pulmonary
sional football players. N Y State Dent J 1982;48(5):298-301. oxygen uptake kinetics and endurance running performance.
4. Francis KT, Brasher J. Physiological effects of wearing mouth- J Sports Sci 2006;24(9):1013-1022.


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The Effects Of Mouthpiece Use During Endurance
Exercise On Lactate And Cortisol Levels: 2416: Board
#61 May 29 9:00 AM - 10:30 AM
Garne, Dena P.; McDivitt, Erica

Medicine & Science in Sports & Exercise . 41(5) Supplement 1:339, May 2009.

doi: 10.1249/01.MSS.0000355581.74244.c0

Author Information

The Citadel, Charleston, SC.

(No relationships reported)

Protective mouthpieces have been used in a variety of sports to decrease the risk of
orofacial injury. However, there is limited research on the physiological effects of
mouthpiece use during exercise.

PURPOSE: To investigate the possible effect on lactate and cortisol levels when wearing
and not wearing a mouthpiece, the wEdge (Bite-Tech Corp).

METHODS: Subjects (n=24), age 18-24, ran at 75 -85% of their maximal heart rate for
30 minutes on 2 separate trials, being randomly assigned the use of the mouthpiece on 1
of the 2 trials. Lactate levels were assessed before, 15 and 30 minutes during, and post 10
minutes exercise. Subjects provided a passive drool sample before and after each exercise
bout to assess salivary cortisol levels.

RESULTS: Lactate data indicated a significant difference between wearing and not
wearing the mouthpiece at 30 minutes exercise (p-value = 0.024). Mean lactate levels at
30 minutes with the mouthpiece was 4.01 mmol/L versus 4.92 mmol/L without the
mouthpiece. Mean cortisol levels showed no significant difference between wearing and
not wearing the mouthpiece (p-value= 0.111). However, there was a trend towards lower
mean cortisol levels with use of the mouthpiece (0.1484 ug/dL) versus no mouthpiece
(0.2201 ug/dL).

CONCLUSION: This study suggests that use of a mouthpiece may reduce lactate and
cortisol increases and thereby improve exercise performance.

©2009The American College of Sports Medicine!

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July/August 2009 — Vol. 30 (Special Issue 2)

A Supplement to

of Continuing Education in Dentistry ®

Published by AEGIS Publications, LLC © 2009

RESEARCH UPDATE

Effects of Mouthpiece Use
on Airway Openings and Lactate Levels
in Healthy College Males
Dena P. Garner, PhD;1 and Erica McDivitt, MS2

Abstract: Research has described the use of mouthpieces not only in preventing oral-facial injuries, but linking use to
improvements in muscular strength and endurance. However, the mechanisms by which these improvements occur have
not been elucidated. The purpose of this study was to understand possible physiological explanations for improvements
in exercise performance with the use of a mouthpiece. Specifically, this study focused on differences in lactate levels after
30 minutes of endurance exercise with and without a mouthpiece. In addition, computed tomography (CT) scans were
taken of the cross-sectional area of the oropharynx in each participant (N = 10) with and without a mouthpiece. CT scans
showed a significant difference in mean width (28.27 mm with the mouthpiece vs 25.93 mm without the mouthpiece,
P = .029) and an increase in mean diameter with a mouthpiece (12.17 mm vs 11.21 mm, P = .096). Lactate levels were
lowered with the mouthpiece at 1.86 mmol/L vs 2.72 mmol/L without mouthpiece. This research suggests that there is
an improvement in endurance performance that may be linked to improved airway openings resulting from the use of a
mouthpiece. Future studies should continue to clarify the possible mechanisms for these exercise outcomes as well as to
understand the optimal mandibular advancement to elicit these exercise improvements.

M
outhpieces have been used for a variety of con- While there is compelling research to support the use of
tact sports to prevent oral-facial injury.1 In a mouthguards to protect against oral-facial injuries during
review of dental trauma literature, Glendor2 contact sports, there is also research to suggest that mouth-
noted that participation in sports is the greatest cause of pieces may enhance performance. Smith6,7 noted that pro-
dental injuries. To minimize injury associated with contact fessional football players exhibited greater arm strength with
sport participation, the American Dental Association (ADA) properly fitted mouthguards that resulted in changes in bite
recommends the use of mouthguards to protect against patterns. Smith also noted that those players with the most
dental trauma during contact sports.3 In addition to the extreme overbite corrected with a mouthguard experienced
recommendation of the ADA, such sport-governing bodies the greatest increase in strength. Specifically, he observed
as the National Alliance of Football Rules Committee have that with a properly adjusted mouthguard, 66% of the play-
mandated mouthguards for use in high school football in ers exhibited significant strength improvements on the iso-
the United States.4 The 2008-2009 National Athletic As- metric deltoid press.7 He stated that the increase in strength
sociation (NCAA) Sports Medicine Handbook mandates with a properly fitted mouthguard was because of decreased
mouthguards for athletes involved with football, field hock- pressure in the temporomandibular joint (TMJ).
ey, lacrosse, and ice hockey in order to minimize dental Not only has improvement in strength been noted, but
trauma during these sports.5 Garabee8 described improvement in 7 runners’ endurance

1Assistant Professor, Department of Health, Exercise and Sport Science, The Citadel, Charleston, South Carolina

2Research Assistant, Department of Health, Exercise and Sport Science, The Citadel, Charleston, South Carolina

Compendium—Volume 30 (Special Issue 2) 9

Research Update—Lactate Levels

and recovery with use of a mouthpiece to promote proper oc- With this data suggesting a physiological improvement
clusion. He observed that when runners wore a wax bite when a mouthpiece is used, the next step was to clarify fur-
mouthpiece, there was an increase in mileage: 64 to 100 miles ther the possible reasons for this improvement. Trenouth
per week in one runner, and 50 to 80-100 miles per week in and Timms 13 found a positive association between the
another. He also noted quicker recovery times and decreased orpharyngeal airway opening and mandibular length, with
perceived exertion with use of the mouthpiece vs without the a narrower opening associated with a shorter mandibular
mouthpiece. Garabee hypothesized that this improvement length. They cited previous research that suggested repo-
was because of decreased stress with mouthpiece use that sitioning the mandible in an anterior position, thereby
reduced clenching and grinding of teeth during exercise. opening airways and promoting respiratory gas exchange
As the research evolved, the to and from the lungs. In the litera-
possible reasons for improvements ture associated with sleep apnea
in performance were elucidated THIS PRESENT STUDY SUGGESTS (where airway openings are dimin-
by Francis and Brasher. 9 In a ished during sleep) and mouth-
study of 10 men and 7 women, MECHANISMS BY WHICH pieces, it can be noted that there
they found that wearing a mouth- is significant improvement in air-
LACTATE PRODUCTION MAY
piece during 20 minutes of high way openings for patients wear-
intensity cycling resulted in im- BE IMPROVED WITH INCREASED ing a mouthpiece (a device that
provements in ventilation (average fits like a retainer and forces the
of 43.13 l/min with mouthpiece
AIRWAY OPENINGS, THEREBY lower teeth to relax in a forward
vs 50.98 l/min without mouth- IMPROVING OXYGEN KINETICS position). Kyung and colleagues14
piece). They noted that this im- advanced the mandible forward
provement may be from pursed SUCH AS LOWERED OXYGEN with an oral appliance in 12
lips breathing which results in DEFICIT AND/OR IMPROVED sleep apnea patients and found a
greater oxygen saturation. Ugalde reduction of the apnea-hypop-
and colleagues10 confirmed that BREATHING WORK RATES. nea index from 44.9 (without
pursed lips breathing resulted in appliance) to 10.9 (with appli-
increased oxygen saturation in ance). Gale and colleagues15 also
myotonic muscular dystrophy patients, while Tiep 11 stated found a significant improvement in mean airway opening
that such breathing results in increased tidal volume, car- with an anterior mandibular device while patients were
bon dioxide removal, and oxygen saturation. supine in a conscious state. Specifically, Gale et al15 found
Drawing from the research by Frances and Brasher, 9 the that in 32 participants, the mean minimal pharyngeal cross-
possible reasons for improvements in endurance perform- sectional area was increased 28 mm2 with the mouthpiece
ance while wearing a mouthpiece provide insight into the vs without the mouthpiece. Gao and collegues16 stated
physiological mechanisms that may be occurring. In order that for their participants, the mandibular advancement was
to first understand if there were improvements in perform- 7.5% with a mouthpiece. They specifically found a signifi-
ance, the authors’ laboratory conducted a series of pilot cant opening of the oropharynx (P = .0258) and velo-
studies primarily to determine if lactate levels were affect- pharynx areas (P = .006). Zhao et al17 also found that the
ed by the use of a mouthpiece. If, as Frances and Brasher9 velopharynx opening increased significantly with an ad-
suggested, there was improvement in ventilation (ie, in- justable mandibular custom mouthpiece, from 3.27 mm2
creased oxygen saturation and removal of carbon diox- at 0 mm, to 8.45 mm 2 at 2 mm, 17.73 mm 2 at 4 mm,
ide), then there could consequently be an improvement 24.45 mm2 at 6 mm, and 35.82 mm2 at 8 mm. This re-
in lactate levels. The authors found that with 24 partici- search suggests that the positioning of the mouthpiece will
pants, there was improvement in lactate levels after 30 min- impact the degree of airway opening, with greater movement
utes of running on a treadmill at 85% of maximal heart rate of mandible in a forward position resulting in a greater open-
(4.01 mmol/L with mouthpiece vs 4.92 mmol/L without ing of the velopharynx. With the findings of previous stud-
mouthpiece).12 ies as well as those in the authors’ laboratory, the hypothesis

10 Compendium—Volume 30 (Special Issue 2)

Garner and McDivitt

of this study is that there will be increased airway opening
and a decrease in lactate levels with the use of a mouthpiece. 30

25
Mouthpiece
METHODS 20

Millimeters
No Mouthpiece
For this pilot study the authors recruited 10 participants to 15
determine if there were differences in airway openings with 10
the use of a mouthpiece and if there were differences in lac- 5
tate levels after 30 minutes of running. The mouthpiece
0
used was a boil and bite upper mouthpiece which had a Width Diameter

greater bite opening distal vs proximal (EDGE, Bite Tech Figure 1 Mean values of oropharynx width and diameter
Inc, Minneapolis, MN). Participants were 18–21 years old, with and without a mouthpiece.
male, and from The Citadel. Each participant completed a
computed tomography scan (i-CAT 3D Dental Imaging
3.0
System, Imaging Sciences International, Hatfield, PA) with

Lactate levels (mmol/L)
2.5
and without a mouthpiece, and the mean oropharynx area
Mouthpiece
was measured in each. Participants then completed two 2.0
No Mouthpiece
30 minute runs on the treadmill at 75%–85% of their 1.5

maximum heart rate, and lactate levels were assessed at 0, 1.0

15, and 30 minutes of the run (Accutrend Lactate Ana- 0.5
lyzer, Sports Resource Group, Inc, Minneapolis, MN). Par- 0
ticipants were randomly assigned a mouthpiece during each Mean of Participants (N = 10)

running trial and were required to refrain from exercising Figure 2 Mean lactate levels after 30 minutes of running at
the day before and the day of testing. If participants failed 75%–85% of maximum heart rate.
to cooperate, they were asked to return on a subsequent day
when compliance was met. oral appliance. Kyung et al14 also found reduced apnea-
hypopnea indices, reducing the average index from 44.9 to
RESULTS 10.9 with an oral appliance.
The results of this study displayed a significant increase in Research continues to elucidate the degree of forward
mean width value of the oropharynx at 28.27 mm with the movement which would be most beneficial. In the research
mouthpiece vs 25.93 mm without the mouthpiece (P = .029) by Zhao and colleagues17 there was a range of improvement
(Figure 1). In addition, the mean value of the diameter was in the airway opening for participants: as the mandible was
increased with a mouthpiece vs without a mouthpiece moved to a more forward position, the opening of the air-
(12.17 mm vs 11.21 mm, P = .096) (Figure 1). As previous way increased. It should also be noted that a specific mouth-
studies had suggested, the difference in lactate levels from piece was used for this present study. This particular
pre- to post-exercise was lowered with the mouthpiece vs mouthpiece offered minimal obstruction for the partici-
without the mouthpiece, though not at the level of signif- pants as they ran, yet was also designed to bring the man-
icance (1.86 mmol/L with mouthpiece vs 2.72 mmol/L dible to a forward position. The mouthpiece was easy to
without mouthpiece) (Figure 2). use and mold to participants, who noticed no impairment
in their breathing patterns during use. Further research to
DISCUSSION understand how different mouthpieces could affect the air-
There is a plethora of research to suggest that the upper airway openings is warranted. Such studies should focus on
way of patients with sleep apnea is improved with a custom- measuring the movement of the mandible with the use of a
fit oral device, due specifically to the forward movement of mouthpiece and how this may affect airway openings in
the mandible.13-18 Ryan and colleagues18 found improve- healthy participants.
ment in the cross-sectional area of the velopharynx and in The results of the study suggest that the use of a mouthpiece
the apnea index with the use of a mandibular advancement increases airway openings in these healthy participants and


Research Update—Lactate Levels

that the use of a mouthpiece while exercising may improve exercise intensity, the glycolytic pathway is highly utilized to
lactate levels. While previous studies with sleep apnea popu- meet energy needs. The end product of this pathway is the
lations indicated improvements in airway openings with production of lactic acid. Lactic acid is broken down into
the use of a mouthpiece, there were limited data on a lactate and hydrogen ions, and it is this increase of hydro-
younger, healthy population (age 21 +/- 1.1 years). This gen ions that is negatively associated with metabolic proc-
study, however, is similar in a study by Gao and col- esses, leading to fatigue.19-20 Thus, any mechanism which
leagues16 which took magnetic images of 14 healthy Japa- elicits lowered hydrogen levels resulting from lactic acid
nese men (age 27.7 +/- 1.9 years). Gao et al16 saw improve- should increase an athlete’s time to fatigue. For example, if
ments in airway opening with a custom-fit oral device that the pathways used during exercise rely more on oxygen,
was specifically designed to move the mandible in a more then lactate levels will be lowered. Yet understanding this
forward position. Their study found significant improve- link between lowered lactate levels and increased airway
ments in the velopharynx (P = .0006) and the oropharynx openings is a complex issue needing further investigation.12
(P = .0258), while the current study noted a significant im- Previous studies have noted that an improvement in
provement in the oropharynx width (P = .029). breathing work rates leads to improved exercise time be-
Because of the financial costs of obtaining 2 CT scans cause of reduced oxygen uptake and ventilation.21-22 Spe-
for each participant, this study was limited in the number cifically, if breathing mechanics are improved, then there is
of participants. In addition, this was designed as a pilot a decreased need for oxygen and blood flow by the respira-
study to determine: 1) if there were changes in airway tory muscles which typically require approximately 10% of
openings with a mouthpiece in healthy participants; and the oxygen needs during strenuous exercise. Less blood
2) if this could translate into lowered lactate levels. The flow to the respiratory muscles suggests an increase of
results suggest there may be a link, which could be one pos- blood flow to the exercising skeletal muscles, which would
sible physiological explanation for performance improve- prolong time to fatigue. Specifically, Harms and colleagues
ment with a mouthpiece. found that when respiratory muscle work was decreased
It may be surmised that the lack of significant differ- (via a proportional-assist ventilator), time to exercise ex-
ences in lactate levels in this study may be because of the haustion was increased in 76% of the trials by an average
low number of subjects, even though the trend was lower of 1.3 minutes (+/-0.4 minutes).22
lactate levels with the mouthpiece vs no mouthpiece. As Improvement in respiratory muscle function may not
the authors’ previous study suggested (N = 24), lactate lev- be the only mechanism that occurs during mouthpiece
els were significantly lower with a mouthpiece vs without a use. An interesting study by Kilding and colleagues23 exam-
mouthpiece after 30 minutes of running on a treadmill ined response time of oxygen kinetics in endurance runners
(4.01 mmol/L mouthpiece vs 4.92 mmol/L no mouth- (N = 36) to understand its possible effect on a 5 kilometer
piece) (Figure 3). time trial. An important finding from their study was that
Research has consistently noted the correlation between a faster phase II oxygen uptake kinetic response at the on-
exercise fatigue and higher lactate levels. As one increases set of moderate intensity exercise resulted in faster 5 kilo-
meter performance. Thus, they concluded that those runners
who had a shorter oxygen deficit at the onset of exercise (as
6
indicated by shortened phase II response) could increase
Lactate levels (mmol/L)

5
Mouthpiece
time to exhaustion, as indicated by the better 5 kilometer
4 performance. Kilding cited previous work by Casaburi and
No Mouthpiece
3 colleagues24 stating a decrease in oxygen deficit at the onset
2 of exercise could result in decreased lactate production,
1 which could potentially improve endurance performance.
0 This present study suggests mechanisms by which lactate
Mean of Participants (N = 24) production may be improved with increased airway open-
Figure 3 Mean lactate levels after 30 minutes of running at ings, thereby improving oxygen kinetics such as lowered
85% of maximum heart rate. oxygen deficit and/or improved breathing work rates.


Garner and McDivitt

CONCLUSION 9. Francis KT, Brasher J. Physiological effects of wearing mouth-
This study found that the use of a mouthpiece significant- guards. Br J Sports Med. 1991;25(4):227-231.
ly improves airway openings in participants as compared 10.Ugalde V, Breslin EH, Walsh SA, et al. Pursed lips breathing
with these same participants who do not wear the mouth- improves ventilation in myotonic muscular dystrophy. Arch
piece. In addition, lactate levels are improved when partici- Phys Med Rehabil. 2000;81(4):472-478.
pants wear the mouthpiece vs when they do not wear the 11.Tiep BL. Pursed lips breathing—easing does it. J Cardiopulm
mouthpiece. One explanation for the decrease in lactate Rehabil Prev. 2007;27(4):245-246.
levels may be an improvement in oxygen kinetics at the 12.Garner DP, McDivitt E. The effects of mouthpiece use on sa-
livary cortisol and lactate levels during exercise. MSSE Suppl.
onset of exercise or improvement in breathing work rates
In press.
which may be prompted by enhanced airway openings with
13.Trenouth MJ, Timms DJ. Relationship of the functional oro-
the use of a mouthpiece. Previous research in the field of
pharynx to craniofacial morphology. Angle Orthod. 1999;69
mouthpiece use and its effect on human performance sug-
(5):419-423.
gests that mouthpieces improve performance. However,
14.Kyung SH, Park YC, Pae EK. Obstructive sleep apnea patients
these studies have been unable to elucidate the possible phys-
with the oral appliance experience pharyngeal size and shape
iological mechanisms for this improvement. This research
changes in three dimensions. Angle Orthod. 2005;75(1):15-22.
is novel in the area of human movement because it suggests 15.Gale DJ, Sawyer RH, Woodcock A, et al. Do oral appliances
a possible physiological explanation for the improvement in enlarge the airway in patients with obstructive sleep apnea? A
performance as noted by athletes. Further studies should focus prospective computerized tomographic study. Eur J Orthod.
on the reasons for these improvements, noting differences in 2000;22(2):159-168.
jaw morphology and airway dynamics for individuals who 16.Gao X, Otsuka R, Ono T, et al. Effect of titrated mandibular
may benefit from a mouthpiece during exercise and sport. advancement and jaw opening on the upper airway in nonap-
neic men: a magnetic resonance imaging and cephalometric
DISCLOSURE study. Am J Orthod Dentofacial Orthop. 2004;125(2):191-199.
Dr. Garner has received an honorarium from Bite Tech Inc. 17.Zhao X, Liu Y, Gao Y. Three-dimensional upper-airway changes
associated with various amounts of mandibular advancement
REFERENCES in awake apnea patients. Am J Orthod Dentofacial Orthop. 2008;
1. Hughston JC. Prevention of dental injuries in sports. Am J Sports 133(5):661-668.
Med. 1980;8(2):61-62. 18.Ryan CF, Love LL, Peat D, et al. Mandibular advancement oral
2. Glendor U. Aetiology and risk factors related to traumatic den- appliance therapy for obstructive sleep apnoea: effect on awake
tal injuries—a review of the literature. Dent Traumatol. 2009; caliber of the velopharynx. Thorax. 1999;54(11):972-977.
25(1):19-31. 19.Green HJ. Neuromuscular aspects of fatigue. Can J Sport Sci.
3. ADA Council on Access, Prevention and Interprofessional Re- 1987;12(3):7S-19S.
lations; and ADA Council on Scientific Affairs. Using mouth- 20.Westerblad, H, Lee JA, Lännergren J, Allen DG. Cellular mech-
guards to reduce the incidence and severity of sports-related oral anisms of fatigue in skeletal muscle. Am J Physiol. 1991;261
injuries. J Am Dent Assoc. 2006;137(12):1712-1720. (2 pt 1): C195-C209.
4. Bureau of Dental Education, American Dental Association. Eval- 21.Harms CA, Wetter T, McClaran SR, et al. Effect of respiratory
uation of mouth protectors used by high school football players. muscle work on cardiac output and its distribution during max-
J Am Dent Assoc. 1964;68:430-442. imal exercise. J Appl Physiol. 1998;85(2):09-618.
5. Klossner D, ed. 2008-2009 NCAA Sports Medicine Handbook. 22.Harms CA, Wetter TJ, St Croiz CM, et al. Effect of respiratory
19th ed. Indianapolis, IN: NCAA; 2008:94-95. muscle work on exercise performance. J Appl Physiol. 2000;89
6. Smith S. Muscular strength correlated to jaw posture and the tem- (1):131-138.
poromandibular joint. N Y State Dent J. 1978;44(7):278-285. 23.Kilding AE, Winter EM, Fysh M. Moderate-domain pulmo-
7. Smith SD. Adjusting mouthguards kinesiologically in profes- nary oxygen uptake kinetics and endurance running perform-
sional football players. N Y State Dent J. 1982;48(5):298-301. ance. J Sports Sci. 2006;24(9):1013-1022.
8. Garabee WF. Craniomandibular orthopedics and athletic per- 24.Casaburi R, Storer TW, Ben-Dov I, Wasserman K. Effect of en-
formance in the long distance runner: a three year study. Basal durance training on possible determinants of VO2 during heavy
Facts. 1981;4(3):77-81. exercise. J Appl Physiol. 1987;62(1):199-207.


RESEARCH UPDATE

Effects of Mouthpiece Use
on Auditory and Visual Reaction Time
in College Males and Females
Dena P. Garner, PhD;1 and Jenni Miskimin, MS2

Abstract: Studies in exercise science have suggested that the use of a mouthpiece can improve performance, and these
improvements may be linked to an enhancement in temporomandibular joint (TMJ) positioning. Studies have suggested
that by improving TMJ positioning, there is improved blood flow in the area of the TMJ. Changes in TMJ positioning may
be improved with an oral device. The purpose of this study was to determine if there were improvements in auditory
and visual reaction time with the use of a boil and bite mouthpiece. Using a BIOPAC system, study participants (N = 34)
were asked to respond to an auditory signal during 40 trials. In the visual reaction time test, participants (N = 13) were
assessed on how quickly they responded to a computer cue for a total of 30 trials. Auditory results showed a significant
improvement with the use of a mouthpiece (241.44 ms) vs without a mouthpiece (249.94 ms). Visual results showed that
participants performed slightly better with the mouthpiece (285.55 ms) vs without the mouthpiece (287.55 ms). These
findings suggest that the use of mouthpiece positively affects visual and auditory reaction time, which is a vital aspect
to optimal sport and exercise performance. Future studies should continue to shed light on possible reasons for the
improvements in auditory and visual reaction time with the use of a mouthpeice. In addition, future studies should further
illuminate what, if any, connection these improvements have with enhanced TMJ positioning.

R
eaction time is the period that occurs between a times in people with advanced fencing skills, thereby explain-
stimulus and the initiation of muscle response1 ing improved performance.2
and can be assessed as simple reaction time, Many studies in exercise science have suggested that the use
choice reaction time, and discriminate reaction time.1 Sig- of a mouthpiece can improve performance, which may be relat-
nals to any sensory system in a variety of populations can ed to an enhancement in temporomandibular joint position-
be ascertained in any of the above situations. For exam- ing. Without proper temporomandibular joint positioning,
ple, Borysiuk2 evaluated reaction and movement time with nerves and arteries within the joint may become occluded,
tactile, acoustic, and visual stimuli in advanced and novice resulting in strain in nearby tissues, thereby reducing blood
fencers. He found that the advanced fencers had a signif- flow.3-7 By neutralizing the temporomandibular joint with a
icantly improved reaction time with the visual (P < .057) mouthpiece, patients have reported to their dentists reduced
and the tactile (P < .029) stimuli, with no significant differ- pain in the jaw, head, and neck areas, along with increased phys-
ences in the acoustic stimuli between novice and advanced ical strength. This improvement in strength may be linked to
fencers. However, the mean reaction and movement times improved blood flow and oxygen kinetics associated with re-
with all three stimuli were lower in experienced fencers vs the duced stress in the temporomandibular joint, thereby produc-
beginners. Borysiuk found fencing training improved reaction ing improved blood flow to the exercising skeletal muscles.8-10

1Assistant Professor, Department of Health, Exercise and Sport Science, The Citadel, Charleston, South Carolina

2ACSM Health and Fitness Specialist, Boeing Activity Center, The Boeing Company, Everett, Washington


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