This week is Part Two of my Load Monitoring Series. Last week I talked about the importance of monitoring load as an athlete and the differences between internal and external load. External load is a little simpler to understand and grasp whereas monitoring internal load (which has recently become more popular) is a little bit more difficult. This week I'm going to talk specifically about internal load, two key methods of internal load monitoring, and how to monitor internal and external load simultaneously.
For a brief recap, internal load is defined as the "relative and psychological stress imposed" on the body as a reflection of the external load that has been placed/undertaken. Two of the most popular ways to monitor internal load are resting heart rate variability and sleep (quality and quantity)... let's talk about these more specifically.
- Resting Heart Rate Variability: rHRV is the variation in the timing of heart beats. High or low rHRV indicates high or low control from the autonomic nervous system. rHRV is a great metric to measure physiological stress on the body. In general a high resting rHRV (relative to one's self) is better. High resting rHRV values indicate the body's ability to tolerate stressors and recover well from activity. Wearable devices such as Biostrap and Whoop or downloadable apps such as EliteHRV or HRV4Training can be easy ways to measure rHRV in the mornings. Individuals can also monitor Resting Heart Rate, but rHRV is preferred due to it being the most precise predictor of Autonomic Nervous System activity and also takes into account cardiorespiratory strain. Resting Heart Rate is limited to measuring cardiovascular strain and activity.
- Sleep: Monitoring sleep quality and quantity help with early detection to avoid detrimental decreases in performance and health. Many wearable devices (as well as downloadable apps onu your phone) such as Garmin, Fitbit, Biostrap, Whoop, etc allow athletes to track their sleep patterns nightly. This consists of time in bed, time asleep, sleep latency (amount of time to fall asleep), sleep cycles, disturbances and sleep stages (awake, light, REM and deep sleep). Many of the devices previously mentioned will take all of these metrics into account and then assign a sleep score, or quality once you wake up and your sleep in processed. This sleep score/quality contributes significantly to recovery and can also help you to determine your workout/external load for the day.
How to Monitor
In order to make the most of monitoring internal load, we want to monitor it in correspondence with external load.
For monitoring internal load, the Traffic Light metaphor is pretty commonly used when interpreting data. When you see high values and scores, you're likely well rested and ready to take on a big day of training, consider this your green light. If you see slightly decreased scores (ex. yellow light- likely from a previous hard day) consider taking a lighter day, or incorporating an upcoming easy/rest day if you have another big day of training planned. If you experience significantly decreased scores (red light- likely from poor/lack of sleep or consecutive hard training days) consider taking a day off. Monitoring resting Heart Rate Variability and sleep quality/quantity is a good reflection of internal training load in accordance to external loads and stressors. When you put this metaphor into action you can maximize your training on rested days, avoid injury/illness/overtraining, and make the most of your training program.
Whoop is currently leading the external and internal load monitoring market. I've been monitoring internal training load via different wearable devices over the past year, and Whoop is the current device that I am utilizing. Whoop makes a wearable device that is designed to be worn 24/7 and targeted towards serious athletes. Whoop has done an exceptional job of not only creating a device to capture the data, but also creating algorithms and models (backed by numerous white papers and studies) to tell you what to do with that data and how to act. These are some of my favorite metrics and screens to look at and keep in mind with the Whoop app.
- Daily Strain vs Recovery: Monitoring daily strain (external load) in comparison with recovery (internal load) is a great tool to make sure you are resting at appropriate times and not accumulating excess fatigue which can lead to injury, illness or over-training (and help avoid under-training). Pictured below, is a week of my daily strain compared to my recovery. I consistently have high strain and in order to progress as an athlete that needs to be accompanied by appropriate rest. This week (Saturday to Friday) consisted of 18.5 hours on the bike, and 3 hours of strength work. In order to avoid injury, illness or over-training these weeks need to have recovery days built in.
- Sleep Hours vs Need: One thing I have learned is that we need a lot more sleep that we expect and on average you lose an hour of sleep per night while awake (just because you go to bed at 11pm and wake up and 7am doesn't mean you got 8 hours of sleep). A good way to ensure that you are making the most of your sleep is by having good quality (sleep hygiene: cold temperature, no screens before bed, no alcohol or caffeine within 2 hours of bed). Matching high external training loads and strain with high quality and quantity of sleep are one key to success as an athlete.
The recent popularization of load monitoring has been a massive benefit to athletes and coaches across sport. Monitoring internal and external load can help athletes and coaches get the most out of training plans; train hard at appropriate times, rest at appropriate times and reap the benefits of listening to the body and how it is recovering and adapting to exercise. Load monitoring is something any athlete, regardless of skill level, should consider paying attention to.
References: Monitoring training load to understand fatigue in athletes. Shona L. Hanson. 2014. Australian Institute of Sport. DOI 10.1007/s40279-014-0253-z
Heart rate variability vs. heart rate. Jason Moore. June 24 2016. HRV Course.