How long should I train? How hard should I train? How often should I train and what will the consequences of my training be in terms of successful performance gains or inevitable signs of fatigue. These are important questions an athlete must ask themselves during every phase of training and planning. The summation of these questions is: what training load am I placing on my body, and how much do I need for optimal development? Training load simply stated is the cumulative amount of stress placed on an individual from a single or multiple training sessions over a given period of time; and is represented as a product of two factors: 1) training duration and 2) training intensity. Perhaps, the most widely cited model to address training load in a practical sense is Eric Banisters training impulse or TRIMP model (1991). The model applies training intensity and training duration metrics to assess training load in terms of both performance and fatigue. It is evident that both duration and intensity are relevant and should be monitored. I would recommend a review by Shona Halson (2014), for more insight into all the possible metrics, and a series of papers by Peter Hofmann on the relevant effect of varying both intensity and or duration on training load (2017, 2022). Duration and intensity are both measurable parameters. While by no means, less relevant and often under evaluated (see the 2022 paper by Birnbaumer, Hofmann et al.), duration is generally a much more straightforward measure. Deciding the number of minutes or hours to train can of course be challenging, but the metrics are simple – seconds, minutes, hours. Intensity on the other hand is not as straight forward. It is self-evident that intensity effects performance and fatigue. Simple evaluation of a power or speed duration curve illustrates the non-linearity of the relationship, and thereby the effect of both intensity and duration on performance and fatigue. But how should you measure intensity? A general split can be made using either internal or external metrics. External meaning physical output, for example power or speed. Internal meaning physiological work or input to generate a physical output, for example heart rate or ventilation, or as per subject of this article muscle oxygenation (SmO₂). External metrics are objective and extremely useful. They are the measurement that defines success. To clarify, the winner of a running race is the athlete who can run the fastest for the duration of the event – cover the distance in the shortest amount of time. In other words, speed is the defining performance metric. However, the problem with external metrics is that the human body does not function like a machine, and performance can vary significantly from day-to-day, or between environments. This is true for competition, but also for daily training. If I define my training intensity solely on external metrics, for example watts using my power meter, it will function irrespective of my individual physiological state today. My 200-watt intensity ride will always demand 200 watts, but my internal load may vary significantly when attempting to generate the same 200 watts. Coupling this very important external load metric with an individual internal load metric can help us understand our performance (the external load) and potential fatigue. An internal load, understood in context to external load, will optimise intensity control and thereby training load.

The goal of training is to improve performance. This typically involves skirting a very thin line between maximizing performance and overtraining. However, training isn’t the only stress that our bodies undergo throughout the day. Stress can present itself through things like work, home, relationships, and pretty much every other aspect of life. And a huge challenge when training for high performance is balancing stress and workload with proper recovery. There have been many attempts to monitor all stress levels, to get an idea of how hard to push the body during a training session, and while things like heart rate, and power output, seem to do a decent job at monitoring training stress, there is still a general lack of guidelines of when to terminate a workout early based on these factors. Monitoring skeletal muscle oxygenation (SmO2) offers a more objective means of monitoring how the muscle is responding to the stress of training. Arguably, one of the largest benefits of monitoring SmO2 during workouts is the ability to autoregulate workouts. While this is an extremely powerful tool to monitor the acute effects of exercise and tailor workouts to an individuals’ physiology. It’s been shown that heart rate at the same power output improves over time, the highest maintainable power output during an endurance event increases and VO2max increases with proper training, yet, very little has been done to monitor how training effects SmO2. In the next few posts I want to walk through a case study to detail changes to an athletes’ physiology over the course of 5 weeks of training. This first post will detail the set-up and give proper background information, the second post will look at the acute effects of each workout, and the final post will detail the patterns of change throughout the 5 weeks.

Scientists and coaches have long been searching for the perfect interval workout that pushes the athlete hard enough to elicit a specific adaptation while keeping them healthy enough to continue to train consistently. Such studies have resulted in the creation of guidelines for set and rep schemes for both strength and endurance training aimed at targeting specific adaptations. While this research has gleaned many generalizable rules, these rules have a tendency to fall apart when applied purely on an individual basis. Even something as simple as hypertrophy training (3-5 sets of 8-12 reps) does not always elicit the mass gain it promises. Speaking from experience, it’s extremely frustrating to complete prescribed workouts, with what seems like adequate stimulus, without gaining the benefits that are touted.

Injuries are one of the major causes of stagnation or lack of progress during training. I am sure many of you have been there, you are working very hard towards your next big goal race, then, during one of your major training sessions you feel the start of a dull ache in the front of your knee. Your first thought is “Oh it’s nothing, just a little soreness from all the hard work I have been putting in.” The next day you can barely walk without shooting pain from your knee to your hip. You take a day off, rest, ice, and foam roll, and next thing you know it’s been three weeks of no concerted training. The next time you complete a solid training session you feel as if you lost ALL of your progress. Any athlete who has trained for an extended period of time has experienced the pain and disappointment of an overuse injury. For those of you who have experienced this the main recommendation from most coaches, trainers, or doctors, is to get more rest and don’t push yourself as hard. Essentially, you need to recover harder and smarter. While I believe that proper rest and recovery is EXTREMELY important to longevity in any athletic pursuit, I don’t think it’s the only piece of the puzzle, especially if you continually get injuries only occurring on one side of the body. The prediction of an overuse injury is almost impossible and it’s extremely challenging to identify how or why these types of injuries occur. While I have written a lot about using Moxy to dictate training I want to start to explore how Moxy could be used to identify unilateral differences in muscle oxygenation, and how this could be used to prevent or potentially identify weaknesses that could cause overuse injuries.

Functional threshold power (FTP) tests have been used by cyclists to determine the highest sustainable power a rider can maintain for rides/races lasting anywhere from 30-90 minutes. Detailed - here - FTP is determined by either 90 or 95% of the power maintained for an 8 or 20 minute all out ride, respectively.

In the last blog post, I detailed my adventure through the back country of Utah, in the Behind the Rocks 30k. I explained the training leading up to the race, as well as the race itself, which left me begging for mercy with bilateral hamstring cramps 3 miles from the finish line. During the race, I was wearing a heart rate monitor, and Moxy monitor while also tracking speed, elevation, and running dynamics. In this post I want to explore the biometric data that was collected throughout the race to see if there were any indicators that cramps or decreases in performance were immanent. 

We often talk about identifying physiologic limiters with Moxy.  We can determine if an athlete is limited by oxygen delivery or oxygen utilization and we can further discern if a supply limitation is due to the cardiac or the pulmonary system.

Denis Šketako is a Slovenian triathlete that Moxy has recently begun sponsoring. He has been using Moxy with his trainer, Sašo Rupnik, for the past two years. Here is a short email interview with Denis that tells us a little bit more about him and how Moxy fits into his training.

Denis also made a video that shows how he uses Moxy, which you can check out here.  

1. How did you get interested in the sport of Triathlon, and at what distances do you compete?

I have been training for basketball at local club for 14 years, but I couldn’t see the opportunity for being a professional athlete in that environment, so I decided to find new challenges. Working as a lifeguard for a couple of years, I learned to swim pretty well. I also started with some recreational cycling. One day, the word “Ironman” randomly came to my attention, and I just couldn’t get it out of my mind. I got beaten by the curiosity and decided to give it a go. In 2011, I finished my first Ironman at the age of 21 in 10h 20min, and last year I finished it in 8h 27min.

There are many variations of Triathlon competitions, depending on the length of each discipline. I find my best performance at long distances, i.e. a full Ironman: 3.8 km swim + 180 km bike + 42 km run. To prepare for these races, I sometimes also compete in a half-distance Ironman called Ironman 70.3.