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Case Study: Heart Rate Variability

Heart Rate Variability and High School: A Case Study Using HRV Guided Training to Improve Recovery and Performance for High School Athletes

By: Coach Armond Willis

Willis Performance Training

Over the past two years I have been privileged to work literally with hundreds of athletes and create specific athletic programs and make them better athletes.

One of the biggest keys to really maximizing athletic potential is creating exact programs at the right time to elicit the best responses in each individual athlete.

As a dedicated strength and conditioning coach, it is important to focus more on the long term performance enhancement, hence why I am adamant in the word program.

Yes Programs are broken down in to single sessions, but collectively these sessions have to advance the athlete to the intended goal, whether strength, speed, coordination, power etc.

However regardless of what the goal is, intensity changes according to the athlete. The key is knowing when and how to adjust.

Regardless of what the intended program may be for the week, things happen throughout the day that can change the session.

Specifically at the high school level, different stressors can affect the athlete’s level of readiness to train or practice. Factors range from diet, exercise, stress, dealing with academic pressures, and sleep.

These are often time overlooked criteria that can not only have a detrimental effect on overall performance and recovery, but quite possibly when recognized can help prevent injury by minimizing overtraining.

My Introduction To Heart Rate Variability

A few months ago I was introduced in depth on HRV at a strength and conditioning clinic where I met with one of the Head Sport Scientist at The University of Alabama (yes the national Champions), Dr. Michael Esco.

Through his in depth studies using collegiate athletes as subjects, more light is being shed on correlations between athlete recovery, and fluctuations on HRV due to outside “stressors” including but not limited to practices, conditioning, academics, and other physiological and psychological stresses.

The basic premise is that the body’s autonomic nervous system responds to these stressors in unique ways, causing a constant shift between the 2 branches of the Autonomic Nervous System called the Parasympathetic and Sympathetic Branch which we will cover briefly in a later part.

The most significant takeaway is that the biofeedback provided through monitoring the HRV in athletes provides an opportunity to reduce injury, minimize fatigue when necessary, guide training, peak performance, and promote overall body awareness.

And in working with both elite high school, collegiate, even the everyday person, it peaked my interest as a potential tool to use not only to better monitor athletes and regular clients physical states, but also really specify training programs by implementing the right training parameters at the right times based on periodization principles.

This has sparked 3 months of my very own research and experimentation.

HRV: What is It?

Heart Rate Variability is the measurement of time between heart beats (not to be confused with Heart Rate which is just heart beats per minute).

HRV is closely linked to Autonomic Nervous System dynamics, and specifically reflective of both the Parasympathetic and Sympathetic branches of the Autonomic Nervous System.

Autonomic Nervous System

The ANS is responsible for a lot of processes that occur in your body automatically. It involves a dynamic relationship between a network of nerves, muscles, glands, blood vessels, and more that not only control performance but keeps you alive!

The ANS affects blood sugar, adrenaline, digestion, pupil dilation, and much more.

It has 2 main branches: The Sympathetic Nervous System (SNS) and Parasympathetic Nervous System (PNS).

The Sympathetic Nervous System is also known as the fight or flight branch. Indications of this state include elevated blood pressure, increased heart rate, dilated pupils, and can cause you to sweat among other things.

The Parasympathetic Nervous System, also termed the rest and digest system, plays a huge role in digestion, lowering blood pressure, lowering heart rate, but most importantly in relation to this article muscle repair and recovery.

In simple terms, you want to be more leaning towards a parasympathetic state vs a sympathetic one, however stressors will often cause the body to be in a sympathetic state and that is normal and why also you want to have a strong SNS. The temporary disturbance is healthy for athletes in training.

It is a constant back and forth between the two and the variation in nervous system states is how we are able to actually measure HRV.

Injury and the “Tie in” to High School Athletes

Athletes are always being introduced to various training loads, whether from practice, training, conditioning, games etc.

Sometimes these exposures to loads supersede their tolerance thresholds. As a result, adaptations to training decreases, and overall performance is compromised.

When an athlete drives themselves beyond their physiological limits, fatigue accumulates at a more rapid rate…and the greater the fatigue level, the greater the negative training effects such as decreased strength and power, and more significantly a lower rate of recovery.

It should be noted that outside stressors such as work and life in general can increase with fatigue.

The Force Generating Deficit

Fatigue overtime can inhibit an athlete’s force generating capacity and cause an inability to maintain required forces for practices, weight training, even games.

After a certain level of fatigue, firing rates in force producing skeletal muscle decreases (with studies showing a decrease of up to 80 percent after 30 seconds), and negatively affect muscle recruitment.

The rate in which neurons signal muscles to fire and contract is heavily dependent on the state of the nervous system. And if the nervous system is fatigued or suppressed, firing rates are slowed down.
This research directly debunks the old school train of thought of working until exhaustion every single session as firing frequency decreased with more repetitions that were performed.

As muscle contractions progress, reserves become more depleted, resulting in more relaxation of motor units and lower frequency of muscle contractions.

Fatigue is the ultimate proponent of inhibited central nervous system behavior.

Sufficient time and recovery is needed for the nervous system to properly regenerate and produce necessary forces with quality for extended periods of time.

It is worth noting that training among fatigue is necessary to an extent in order to create a mental resiliency come time for competition. However it is the excessive doses in which this is practiced that can affect peaking during competition.

Back to HRV

Throughout my coaching years, more and more injuries have become prevalent among high school athletes and their daily routines.

The majority of these injuries are more so from overuse and lack of recovery.

In some instance, athletes have mandatory weight room classes where they lift at near maximal loads on a weekly basis, and this is compounded with sport practices that can involve a high volume of running as well as academic loads, insufficient diets, and various other lifestyle stressors.

Besides being able to coach technique properly and implement training loads, coaches need to be able to recognize when an athlete is physiologically and psychologically fatigued.

And using HRV to monitor an athlete’s state and readiness to take on external stressors such as practices and heavy lifting is a simple, and non-invasive approach that offers invaluable feedback to help create the best programs possible.

The bottom line is the majority of current high school training one size fits all programs and the lack of recognition of when an athlete truly needs a break and “run hard lift heavy” all the time mentality creates more opportunity for injury.

And my purpose for piloting an HRV program with High School Athletes was to help determine optimal times to train and recover, and the below data from a 2 month HRV monitoring using a varsity High School Lacrosse athlete supports the use.

I wanted to get to the bottom of things and actually have quantifiable data that would support change in training programs at the high school level and better my very own understanding and programming.

Case Study:

Grade: 11th
Sport: Lacrosse
Position: Middy

Goal: Increased Size, Strength, Speed, Recovery

This past year, this specific athlete under our training program has been able to put on over 15 pounds of muscle and decrease his 40 time from a high 4.9 to a 4.7, placing in top speeds at a few of his showcases in the north east.

The HRV reading process:

Using a Bluetooth heart rate strap, every morning the athlete wakes up, and takes a morning read. After every single one of his reads the athlete then receives a score on his Readiness for the day.

The sensor records his heart rate for a full minute to 5 minutes and calculates the RR Intervals (time between heart beats), and he receives a score and a detailed analysis of the read.

It will tell whether or not he is in sympathetic (elevated heart rate) state or parasympathetic (recovery) state.

Again, not necessarily bad to be in a sympathetic state, but too many days in that state CAN indicate lack of recovery.

The charts below show readings over several weeks’ time.



The above data segment shows the reading results from December 4 2017 to January 13 2018. The empty spaces between the bars indicate the days where were no readings done. In order to receive “scores”, a baseline has to be established. This requires that at least a week of readings are done before being able to receive a score. Reading must be done around the same

It is important to note that results are highly specific to the individual, so when a baseline is established, it is unique to THAT individual. Thus, when looking at and analyzing baseline changes, it is best to compare to that specific athlete’s scores over time.

A higher HRV score over time is indicative of better recovery from training loads and lifestyle stressors. Consistently lower HRV scores can indicate a lack of recovery or signs of over training.

The reading procedure works as such: The athlete wakes up and first thing in the morning, they strap on any compatible blue tooth heart rate monitor and just lay down while a signal is sent to the Elite HRV app that we use.  After a minute, the program analyzes the heart beats and provides a reading as shown on the below image.

A baseline reading is provided and the athlete is able to get a read for the day letting him know their overall “readiness”.


A Closer Look:

Here we have a slightly closer look at readings that originated in early December. The yellow scores indicate days where he may not have been fully recovered and average readiness scores that hovered around 5-6 (on a 10 point scale).

Not coincidentally, these yellow scores were right around when finals and exams were, and as the athlete indicated he was up late studying and stressing over finals, on top of having to participate in over the top team workouts, really stressing him physically.

As finals ended and Christmas break began, there were no school practices and exams were completed. He was able to get more rest and deal with less stress. During this time he was able to come in to our facility for his training sessions.


From this above view we can see the same information in a different charted segment. Here, Readiness Score, ANS Balance, HRV Score, and HRV CV (average of weekly variance, are delineated by column.

In the ANS column, S=sympathetic and PS=Parasympathetic

The yellow areas we can clearly see he was in a predominant Sympathetic state during the week and week prior to exams and heavy practices.

The days and week following, he was able to “get back into the green”.

Implications for Program Design

Programs are normally designed anywhere from a 3-6 week cycles, however because we commonly work with high school athletes who have separate “training classes” and practices at their schools, programs and sessions are never written in stone.

If an athlete comes in to our facility during a day where they “maxed out” at school, then we normally adjust on the spot so not to overload muscles and joints that were taxed during school or practice sessions.

In the particular case of this athlete, we looked at and analyzed his readings to increase or reduce intensity during session.

Days where he came in and he “scored” low, then we limited intensity, focused on auxiliary exercise and a cardio based strength circuit to help facilitate recovery. (Sample Recovery workout Card)


The goal was to bring his score back up after recovery days like this and from there implement more intense sessions after a sufficient recovery.

However, it is worth noting firstly that EVERY athlete responds to stressors differently and their work capacities vary, but overtime their tolerance should be improving if the right training parameters are implemented at the right times (periodization).

With that said, a “low score” was not always translated as doing absolutely no kind of intensity at all. Occasional low scores would be normal as intense training disturbs the body’s homeostasis, so a low score just means that the body is trying to adapt to the increased intensity.

Overtime, the athlete will adjust and will not be as “disturbed” physiologically from the same training stresses.



The “concern” comes when scores are consistently low, or Sympathetic dominant, which could be indications of overtraining, and a means for rest (more on this in the conclusion).


As seen here on his chart, we were able to increase his scores after adjusting his training on top of finals coming to an end.

Further to the right, we see consistent lower scores. These occurred right around when school and classes began and his preseason practices with the school Lacrosse team began. The empty spaces between readings were days that he forgot or was not able to take his readings.


 Final Results:

This in house experiment is still ongoing. Currently this athlete suffered an injury during a tournament and has not bene able to consistently do his reads. However, the implications were evident that HRV and recovery are definitely effected by the athlete’s workloads both in sport, training, and lifestyle.

We were however able to successfully increase size, strength, and speed. Even though we were able to see improvement in overall HRV scores in a short time, more time is needed to really be able to quantify his ability to recover from various stressors.

The fact that size, speed, and strength were enhanced is an indication that recovery was also improved as recovery is necessary in order to enhance these performance variables.


Performance. Training. Practice. Stress. Sleep. Diet. Mood.

All of these factor into to how well an athlete recovers and adapts to loads taken on. At the high school level, specifically for a highly competitive sport like lacrosse, the demands can far outweigh the body’s supply to cope with them.

In this singular case, we were able to somewhat gauge noninvasively the physiological state of recovery of this athlete and couple it with his daily life and see the effects that it had both physically and mentally.

With this insight our team could better create or adjust training plans to not only better adapt, but also know when to dial back or increase intensity at the right times and not just go off of a rigid program.

My initial reason behind launching this program was because I wanted better physical insight on the state of the athlete and better gauge fatigue levels as it relates to injury and overtraining.

There were just too many injuries happening as a result of training, whether acute or overuse, and being able to measure and visually see fatigue, we could recognize that change needs to occur in current school training regimens and practice because they can ultimately affect long-term health.

It is clear that programs should be adjusted according to the state of the athlete, but occasionally school programs are put together with the intent of overworking just to get the athlete “in shape”, when all it could be doing is the reverse.

As mentioned earlier, the importance of the nervous system and the contractile properties of muscle make a significant difference on efficiency. If an athlete is not recovered and or fatigued, then count on the fact they will not adapt as fast because the nervous system is overworked.

Overtraining is common in high school. Couple this with adolescent habits of subpar dieting, up and down sleep habits, “stressful” academics, and sport demands and we now have growing opportunity for injury.

The intention here is to get better insight from the athlete, recognize when overreaching is beginning to occur, find potential reasons why, and create the right training environment to overcome.

Our HRV guided training program takes a global approach using key insight to enhance performance, whether remotely, in person, or both, and maximize overall fitness and readiness.

This program is a great solution for a parent concerned about their child’s workloads and does not want them to burnout, and also a great program for competitive high school athlete really looking for a custom program specific to their needs that can be executed in conjunction with their schedule.

Every day is a learning process, and the more we are able to learn, the better we can specify the right programs at the right times.