Chasing Fitness While Managing Fatigue
Published by
Benjamin Gheen
on
An Overview of the Fitness Fatigue Model
What is fitness? How does fitness impact fatigue?
In exercise science, fitness describes our capacity to do physical work. However, our capacity is not static but rather dynamic and can change over time with appropriate ‘doses’ of exercise. Each ‘dose’ of exercise can increase both fitness and fatigue. Fatigue, in this context, is the amount of exhaustion inability to continue exercising at a given intensity, the degree of difficulty associated with the exercise being performed (e.g. Squats with 100kg for 10 reps). We can think of fatigue in several different contexts; a) acute fatigue from recent exercise, b) residual fatigue accumulated over a period of time that has not dissipated from recovery yet, c) localized fatigue within the target muscles after a bout of exercise, d) systemic fatigue (aka ‘central’ fatigue or ‘global’ fatigue) accumulated over a period of time, and even e) mental fatigue to describe our level of cognitive exhaustion. But regardless of the context we apply the term, fatigue is generated in proportion to the quantity of exercise and intensity of such exercise being performed. To better understand the dynamic relationship that exists between exercise, fitness, and fatigue, we can turn to the Fitness-Fatigue Model.
As we exercise, our fitness and fatigue elevate. Luckily, fatigue dissipates much faster than fitness with adequate recovery. Recovery, being that time dependent umbrella term for a complex restorative process for the body. As such, allocating some amount of time towards recovery is beneficial to reduce fatigue, enabling us to better express our fitness through performance. Performance we will define as a fluctuating expression of fitness on any given day, minus fatigue.
Performance = Fitness – Fatigue
How much time should we dedicate towards recovery?
Well, our body’s performance and recovery status are impacted by a variety of internal and external factors such as sleep, nutrition, life stress, hormones, and other environmental factors. But, hopefully, with adequate recovery fatigue should decrease substantially allowing you the opportunity to express improvements in your fitness via your performance on a given day.
Assuming normal adaptations to training occur, your performance should generally increase over time with each training session despite regular fluctuations on a given day.
But, remember fitness is dynamic in nature and with more training stimulus, eg. ‘doses’ of training, further increases in fitness can occur. Cue progressive overload, the concept of gradual increases in training stimulus over time.
Hopefully, your training program accounts for progressive overload with one or more variables. ‘Conventional’ methods of progressive overload include such variables as volume or intensity thereby increasing the amount of work performed (e.g. # of reps and/or sets) or increasing the degree of effort (e.g. percentage of one rep max). However, one may consider manipulating less ‘conventional’ variables like the range of motion, movement quality, or velocity. In either case, we need to keep in mind that progressive overload only works if you are relatively proficient in the movement being performed. Otherwise, the increases in strength are attributable to neuromuscular adaptations and not attributable to hypertrophy.
As your fitness level advances to that of an experienced lifter, the application of progressive overload becomes increasingly relevant to facilitate further progress. By applying progressive overload to your training, we can expect residual fatigue to accumulate. If residual fatigue exceeds recovery and the increases in fitness, your performance will begin to be negatively impacted entering into a state of overreaching. This degree of overload is required to drive adaptation in experienced lifters but comes at a large fatigue cost.
As high levels of fatigue accumulate from progressively overloading, a strategy to balance the overload and recovery appropriately becomes more critical. When progressive overload and recovery are balanced appropriately, overreaching should lead to increases in performance. This is referred to as functional overreaching.
When progressive overload and recovery are unbalanced, performance may remain stagnate or even regress. Referred to non-functional overreaching, the acute suppression of performance that does not lead to a net improvement in fitness, a signal of overtraining.
The accumulated fatigue has gotten so high it is preventing you from training with sufficient quality to increase or even maintain your current level of fitness. Thankfully, overtraining rarely occurs in resistance training and requires a longer period of time to reach. Overtraining also requires a longer period of time to resolve than a simple taper or deload, as one might expect.
So how do we strike a balance between progressive overload and fatigue so we can actually improve fitness and performance? Sounds like we need a strategy that enables us to improve our fitness while managing fatigue so we can express new levels of fitness through performance over time. Enter periodization, the intentional manipulation of training variables (e.g. volume, intensity, frequency, etc.) over time to achieve specific goals. Simply put, periodization is a more thoughtful approach to training in hopes of improving progress while managing fatigue and recovery. Utilizing periodization helps to avoid falling into a state of overtraining, a state of heightened fatigue hindering one’s performance and stalling or even diminishing fitness. Thankfully overtraining is rare, more common among physique and performance athletes during a competitive season but less common during the offseason and amongst recreational athletes. Physical symptoms of overtraining include continuous muscle soreness, pain sensations as well as clinical and/or endocrinological disturbances following prolonged non-functional overreaching and under-recovery. Periodization can help to adjust training variables in a cyclical fashion across training periods to strategically promote your fitness and keep progressing while managing fatigue and allowing adequate recovery.
Citations
Halson, S.L. Monitoring Training Load to Understand Fatigue in Athletes. Sports Med 44 (Suppl 2), 139–147 (2014). https://doi.org/10.1007/s40279-014-0253-z
Kellmann, M. and colleagues Recovery and Performance in Sport: Consensus Statement International Journal of Sports Physiology and Performance 2018 vol 13 240-245 https://journals.humankinetics.com/view/journals/ijspp/13/2/article-p240.xml?content=contributor-notes
Functional and Nonfunctional Overreaching and Overtraining NSCA National Strength and Conditioning Association June 2017 https://www.nsca.com/education/articles/kinetic-select/functional-and-nonfunctional-overreaching-and-overtraining/
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