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New Tech in The World of Strength and Conditioning

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Part 1 of a two-part review of the recent Paul Longo SI.com article. This part focuses on the use of heart rate and sleep data and what it tells the coaching staff about how an athlete is recovering.

Matt Cashore-USA TODAY Sports

An interesting article was posted on SI.com last Thursday, detailing the high-tech approach Strength and Conditioning Coordinator Paul Longo has taken to maximize results for ND's student-athletes.  The article talks about how technology has enhanced performance monitoring in the two realms of an athlete's off-field life: in the gym and at home.  This part of the review will focus on the at home advances and the next will focus on the advances in the gym.

Starting this summer, ND football players, under the direction of Longo, will begin using the Basis tracker, described as such in the article:

When one of Notre Dame's players wears the device, the strength and conditioning staff will be able to track the amount of sleep the player gets, the quality of that sleep, his heart rate upon waking and other variables. The data may offer clues as to why a player is sluggish or not recovering well from workouts, be it stress or over-training. Those clues may inform an adjusted plan to keep the player sharper and healthier. Or they may prompt Longo and his staff to lecture a player on better habits. Either way there is objective evidence at Longo's disposal. The interpretation is the art of it, but the numbers don't lie.

So why do trainers want to know all of this extra information?  The simple answer is that while each human body responds to stress in the same general fashion, the magnitude and quality of that response varies from person to person.  As such, two athletes of similar body type and size could perform exactly the same workout with exactly the same resistance yet one may recover in a matter of hours while the other recovers in a matter of days.  By gathering data pertaining to an athlete's recovery, trainers can now tailor a program that leads to gains, not deterioration.

The Stress Response

The stress response in humans is divided into two categories.  The first is the immediate "fight, flight, or freeze" response.  This reaction to stress is mediated by a division of the nervous called the autonomic nervous system, over which the brain exerts only unconscious control.  These nerves secrete norepinephrine, a precursor to epinephrine (also known as adrenaline), that does everything needed to respond to a threat including increasing the cardiac output, opening up the air passages, constricting the blood vessels to increase blood pressure, and dilating the pupils to let in more light.  This is a phenomenon we've all experienced, and as I'm sure we can all recall, it subsides within a few minutes.  For completeness sake there is another half to the autonomic nervous system that does the opposite of everything I just listed, but the details are not relevant for this discussion.

The second category of the stress response is the long-term response mediated by hormones from the adrenal glands.  The major players here are cortisol and epinephrine.  Cortisol is the primary stress hormone in the body and is exclusively catabolic i.e. it promotes the breakdown of otherwise healthy tissue.  When released, cortisol causes the breakdown of muscle protein and fat so that both can be used to make glucose to fuel the brain and the rest of the body.  In addition, cortisol inhibits the immune response consequently increasing susceptibility to illness. Finally, cortisol increases the blood vessels' ability to respond to epinephrine and norepinephrine, thus causing greater narrowing of the vessels, leading to an increased blood pressure, which in turn places more strain on the heart.  Epinephrine does everything in the "fight or flight" response, except that it acts over the course of hours not minutes.

As a general rule, the body produces a spike of cortisol in the morning, and the levels decrease throughout the day.  Variation between individuals becomes a factor because the amount of stress needed to stimulate the release of cortisol is different for everyone, as is the amount of cortisol released in response to stressful situations.  In aggregate, this is what ND's athletic trainers are trying to identify in each athlete by measuring heart rate and other indicators of stress in order to put that information to work in the player's best interest. If the player is under physiological stress when not actively working out, it could be an indicator that he is not responding well to a particular regimen and changes need to be made.

Sleep

Sleep is good.  We all need it, despite what professors or bosses seem to believe.  Sleep is our body's way of shutting down for repairs.  Sleep is also a really complex process that is far from being completely understood so this section will be brief.  Sleep is critical for athletes in particular for two reasons.  First, it is the best time for muscle to be repaired and built-up.  It's an old saying that muscles are not built in the gym, but in the kitchen.  While that might give you the courage to choke down that 10th rubbery chicken breast of the week, it's not exactly accurate.  Muscles are made in bed when you're asleep.  Second, sleep is good for the mind too.  As we sleep, neural connections made during the day are strengthened and streamlined.  For athletes, the "muscle memory" gained in practice gets crystallized into defined neural pathways during sleep.

As a final consideration, not all sleep is considered equal.  Sleep consists of four stages (plus REM sleep which is not discussed here) with stage 1 being the lightest and stage 4 the deepest.  As we sleep, we progress through all 4 stages.  Some people, however, cannot pass into the deeper stages of sleep and instead remain in the light stages.  This can be due to stress or sleep apnea or countless other sleep disturbances.  The consequence is that the restorative and reparative qualities of sleep only manifest in the deeper stages of sleep.  As such, a person who only experiences the lighter sleep stages will wake up tired and their body will be in a state of general disrepair.  Of course, after one night's short sleep the damage is pretty minimal.  Over time, however, the fatigue and disrepair accumulate increasing the stress on the body and thus increasing the sleep disturbance in a vicious cycle. Thus, an athlete can work all day in the gym, the film room, and on the practice field and have it all be for naught if he does not get adequate sleep.

Conclusion

As we learn more and more about the physiology of exercise, there is going to be an increased demand to make that theoretical knowledge applicable to athletes, soldiers, and the populace at large.  I find it very encouraging that the Irish are willing to expend the resources to make this knowledge available to their student-athletes.  Ultimately, the staff is trying to remove the mystery from training.  If an athlete is struggling, they have a means of pinpointing the problem and correcting it.  As always, feel free to post any questions in the comments and I'll try to answer them as best I can.