Brief Overview of Functional Overreaching, Non-Functional Overreaching, and Overtraining Syndrome
Before we begin a discussion on markers of functional overreaching, it is imperative that we have a discussion about the continuum of fatigue so that we understand the different stages of fatigue. There is a wide range of normal fatigue that occurs from regular endurance training, and then there is a state of functional overreaching (which is positive and somewhat essential to the training process), and then non-functional overreaching and overtraining syndrome (both of which are detrimental to training, performance, and potentially health).
So let’s start with someone that is sedentary and does not exercise at all or very minimally. This person that leads a relatively physically inactive lifestyle may carry minimal to no residual fatigue and physiological stress. A dedicated endurance athlete who trains regularly may be carrying around a healthy amount of physiological fatigue and stress on a daily basis. An athlete who pushes their body very hard for a brief period of time, but with adequate recovery between training sessions and training weeks, may begin to carry too much fatigue, putting them in a state of functional overreaching with noticeable performance decrements. This state is considered potentially positive, should the right amount of rest and de-loading occur in the realm of 5-7 days once this state is achieved, as when the athlete recovers, they can usually achieve a state of higher overall performance and fitness (also called ‘super-compensation’). If the athlete, however, continues to push themself, their fatigue and stress levels continue to build to the point where they are in a state of non-functional overreaching, performance starts to decline significantly, and health may be impacted. If the athlete continues to maintain their usual training habits while in a state of functional overreaching, they may eventually exceed their body’s capacity to handle stress and the body then breaks down. This is known as overtraining syndrome, and it carries with it significantly reduced performance and serious health consequences. Full-blown overtraining syndrome can take months or years to recover from! The figure below depicts the continuum of fatigue to better put these terms into visual context.
It is important to note that there is a VERY distinct difference between functional overreaching and non-functional overreaching and overtraining syndrome. Most research and many coaches focus on identifying symptoms of non-functional overreaching and overtraining syndrome, but it is also important to identify when an athlete might be in a state of functional overreaching so that the appropriate rest can be planned. Functional overreaching is a physiologically beneficial state only if the appropriate recovery period is programmed into one’s training. Typically, an athlete might purposefully achieve a state of functional overreaching right before a taper into a key race as, after the taper, they will super compensate and be in a greater state of fitness than before the functional overreaching period. An athlete might also go away on a training camp and purposefully push their body to the limit for a few weeks to gain a big early season boost in fitness. However, this training camp is usually followed up with a week or two of recovery and much less training volume and intensity. So, identifying this physiologic state can be useful for coaches and athletes alike. Let’s take a look at some research in the following section that sheds some light on potential markers that may be indicative of functional overreaching.
What Does the Research Support as Potential Markers of Functional Overreaching?
Roete and colleagues published a systematic review in 2021 that aimed to identify key indicators of functional overreaching across the available research on the topic. In total, they included 12 relevant research studies in order to determine markers of functional overreaching. They found that the following markers were associated with a state of functional overreaching in trained and professional endurance athletes (comprised of cyclists, runners, and triathletes):
A reduction in peak power output when performing a maximal effort
A lower achievable maximum heart rate (HR)
A faster 60-second HR recovery after stopping an exercise effort
A reduction in average power output and average submaximal HR during a time trial effort
Higher rating of perceived exertion (RPE) at submaximal efforts
It is also important to mention the markers that were NOT associated with a state of functional overreaching, including:
Heart Rate Reserve (HRR)
What is quite interesting with the above findings is that some of these markers can also be a sign of improved physiological fitness (i.e., faster HR recovery, lower submaximal HR during a time trial effort). Therefore, it has been proposed that utilizing multiple markers including fitness markers in conjunction with RPE and the overall mood and energy level of the athlete be taken into account when aiming to determine the status of functional overreaching.
For example, if an athlete achieves a lower HR during a submaximal training effort during a session, this alone is not enough to be indicative of functional overreaching because the athlete might have seen a fitness improvement indicative by a lower HR and a higher pace or power output during the effort. However, if an athlete has been consistently showing a depressed HR during training sessions alongside a higher RPE during those sessions and is feeling a lack of energy and motivation alongside their training, this may be indicative of a functional overreaching state, or at least a state of chronic fatigue that warrants a week of recovery.
Keep in mind, it is very important to not confuse functional overreaching with non-functional overreaching or full-blown overtraining syndrome. The latter states usually present with some ill health effects in conjunction with poor physical performance, including sleep disturbances, depressed mood, changes in weight or appetite, chronic underlying muscular soreness or poor recovery, greater frequency of illness, etc. Functional overreaching is not associated with any ill health effects or symptoms and just presents as a mild state of fatigue alongside a static or very slightly depressed physical performance level.
Being able to identify a state of functional overreaching as a coach or self-coached athlete can be very useful as it can help aid in the programming of planned recovery. Typically, functional overreaching comes from a phase of elevated training volume and/or training intensity for the purpose of improving overall fitness in the long-term. It is a state that an athlete does not want to be in chronically, but rather a state that can planned for multiple times in a season as long as appropriate recovery follows the training block. Knowing the difference between functional overreaching and non-functional overreaching and overtraining syndrome is important, and the markers identified in recent research mentioned herein can be useful in identifying a state of functional overreaching and differentiating it from full-blown overtraining syndrome.
Roete AJ, Elferink-Gemser MT, Otter RT, Stoter IK, Lamberts RP. A systematic review on markers of functional overreaching in endurance athletes. International journal of sports physiology and performance. 2021 Jun 8;16(8):1065-73.
Happy training and racing!
-Ryan Eckert, MS, CSCS
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