Fatigue comes in many forms. In the sports realm, we commonly see acute fatigue that occurs in responses to intense training or competition. Or, we can see chronic fatigue that occurs due to insufficient recovery or poor manipulation of training loads over time.
Simply put, technique changes in the presence of fatigue. As a simple example, observe how a lineman’s three point stance changes throughout a long series in football. Observe how change of direction technique deteriorates in during a rugby match after several repeated sprint efforts. It’s no surprise that the majority of injuries are likely to occur in the second half of matches as acute fatigue accumulates and at the second half of the season as chronic fatigue accumulates. Over three consecutive seasons following an amateur Rugby League squad, Gabett (2000) found that “Significantly more injuries occurred in the latter stages of the season with most injuries sustained in the second half of matches’.
Playing in a fatigued state is a necessary component of most team sports. As coaches we aim to minimize fatigue by developing high levels of conditioning in our players. A high level of “sport specific” fitness will help mitigate fatigue which would obviously preserve technique and thus minimize injury risk.
A growing area of concern in the sports training world is the use of “Extreme Conditioning Protocols” (ECP). This type of training may include Crossfit style work-outs, metabolic conditioning and so forth. ECP training can be characterized as performing high repetitions with moderate loads with minimal rest periods. An emphasis is placed on training density; doing as much work as possible in as short a time as possible. Without question, there is a high risk of injury involved with performing exercise in a fatigued state, particularly with compound barbell movements and Olympic lifts. Such a strategy may be effective at improving conditioning and/or body composition, but the risks must be seriously considered.
A new study out of UCONN (Hooper et al. 2014) examined changes in squat technique during a simulated ECP workout in resistance-trained male and female college-aged subjects. The workout involved performing the squat, bench press and deadlift exercise with 75% of 1RM for descending sets (set 1 = 10 reps, set 2 = 9 reps, set 3 = 8 reps, etc.) until the last set of 1 rep. The subjects were told to complete the workout as fast as possible, and their time was recorded. The researchers found squat technique changes resulted in greater forward trunk lean resulting in a higher shear force on the spine and changes in knee angle (squat depth).Women were more sensitive to technique changes than men. The researchers note that the deviations in squat technique increase the risk of injury.
Conditioning practices should be designed where injury risk is minimized. This involves appropriate planned progression where technical abilities are challenged, but maintained in the presence of fatigue. ECP’s and torturous interval sessions at the end of practice are probably a risk not worth taking.
Gabbett, T. J. (2000). Incidence, site, and nature of injuries in amateur rugby league over three consecutive seasons. British Journal of Sports Medicine,34(2), 98-103.
Hooper et al. (2014) Effects of fatigue from resistance training on barbell back squat biomechanics. Journal of Strength and Conditioning Research, 28(4): 1127-1134.