Since the 1980s, elite athletes have used a clinical measure called heart rate variability (HRV) to help assess their fatigue, recovery and readiness to compete, but up until 4 years ago, no user friendly, affordable version was available to recreational athletes and sportspeople. This presentation will cover the stages of bringing HRV out of the lab and onto the smartphone, including making the measurement itself simple and convenient, and the evolution of a user interface that helps users decide when they should train for best effect but also discover lifestyle factors that have a major influence on their performance and overall health.
Shock. Also known as the alarm stage, stage one is a healthy body's response to a new stressor. During this stage:HRV decreasesAfferent (towards the brain) signals cause an efferent (outward) effect on the nervous system, hormonal system, and motor neurons.The body reacts with increased sympathetic toneIncreased output of central stress hormones (CRH and ACTH)Increased adrenal output of epinephrine, norepinephrine and cortisolOverreaching. Known as the resistance stage in the G.A.S. Stage two occurs in response to an imbalance between training stress and recovery.Decreased Beta 2 Adrenoreceptor density reduces adrenal response to the central stress hormone ACTH (corticotropin)CNS responds to decreased adrenal response by increasing central stress hormone outputSympathetic tone during stress (exercise) increasesParasympathetic tone during recovery increasesHRV increases due to increased anti-inflammatory parasympathetic responseDecreased turnover of contractile proteins (i.e., slower recovery)Cortisol and other stress hormone levels remain elevatedChronic Stress. This is overtraining, or the G.A.S. exhaustion phase. Stage three occurs when the body continually fails to adapt to chronic stress.CNS shuts down production of central stress hormonesAdrenals remain resistant to the central stress hormone ACTHSympathetic response is impairedHRV remains elevated due to chronically increased parasympathetic responseIncreased baseline cortisolDecreased diurnal cortisol variationDecreased heart rate dipping at nightDecreased testosterone and other anabolic markersPsychological symptoms of "burnout"Depressed protein synthesis (slow recovery to muscle damage)Depressed immune functionIncreased systemic inflammationSupercompensation or Recovery. This is the de-load phase. If you haven't slipped into stage three overtraining, you should only need about a week for this. Heavy exhaustion can take months for full recovery.HRV decreases back to baseline (Baseline likely increases if the training block focused on aerobic improvements)Cortisol levels decrease back to resting levels with possible improvementDiurnal cortisol variation increasesCNS increases central stress hormone response to acute stressorsAdrenals regain Beta 2 Adrenoreceptor density and sensitivity to central hormonesInflammation is mitigated
Ideally, an individual has a powerful, sympathetic response to an acute stressor (like a competition), along with an equally powerful parasympathetic response when it comes time to rest and recover, whether that's on days off from training, de-load periods, or even breaks betweenThe difference between your good run days and your bad ones are determined largely by the status of your nervous system. Just as you stress a muscle in training in order to force it to adapt and become stronger, your nervous system is being stressed, recovering and attaining a new level of strength.The cycle between stress and recovery matters to your muscles and it's a crucial factor in the health of your nervous system as well. There's a fine line between the right amount of stress, sufficient recovery, and going too far.How do we know where we are in that continuum? What can we do to ensure that we have more good days in the gym than bad?