A well-designed training program will expose athletes to a range of stresses, all of which will induce fatigue and adaptations to that stress to differing degrees. Without an objective measure of the stress being imposed on the athlete, or their response to that stress, coaches and sports scientists are unable to quantify the true effectiveness of their interventions.
The consequences of failing to correctly measure those loads can be under- or overloading of athletes, which can lead to increased risk of injury, illness, and sub-optimal performance levels. So how can practitioners measure the load being placed on their athletes? More importantly, how can they use information to derive meaningful insights to help address performance questions and support the work of coaching staff?
MEASURING INTERNAL AND EXTERNAL LOAD
At a basic level, external load can be characterised as the work completed by an athlete independent of his or her internal characteristics. In terms of Catapult wearable technology, measures which we think of as locomotive (e.g. distance covered, average velocity, number of sprints, etc.) and mechanical (e.g. Player Load) are all measures of external load.
Internal load refers to the physiological stresses placed on an athlete during a bout of work. An example of an internal load measure is heart rate, and heart rate-based indicators such as Heart Rate Exertion (also known as Training Impulse or TRIMP).
While external load is important in quantifying athlete capacity and work completed, internal load is also critical in measuring training load and assessing subsequent adaptation. As both internal and external load measures inform our understanding of the athlete’s training load, a combination of both is essential for an effective monitoring program.