The Effects of the Pre-Fatigue Method of Brain Endurance Training on Physical Endurance Performance

Introduction: Mental fatigue (MF) impairs endurance exercise performance (Van Cutsem et al., 2017). Brain endurance training (BET) – engaging in mentally demanding cognitive tasks concurrently during exercise – can develop resilience to MF and improve physical performance compared to physical training alone (Dallaway et al., 2017; Marcora et al., 2015,).

The pre-fatigue method of BET proposes that engaging in mentally demanding cognitive tasks prior to physical training can induce a state of MF, increasing ratings of perceived exertion (RPE) during the subsequent physical training. It has been hypothesized that MF impairs physical performance via the anterior cingulate cortex (ACC), as it is activated by both exercise and complex cognitive tasks. It remains to be determined if physical and mental tasks that activate the ACC have overlapping or additive effects on performance.

Aim: To examine if pre-fatigue BET enhances endurance performance over identical physical training and to explore the underlying mechanisms.

Methods: Pre/Post testing: 24 participants completed a rhythmic handgrip task requiring generation of as much force as possible, by squeezing a dynomometer once a second for 300 s. This was performed on its own and followed 1200 s of a 2-back memory/attention task. Cardiac activity (ECG), electromyographic (EMG) forearm activity, pre-frontal cerebral haemodynamic (near infrared spectroscopy), and force were recorded continuously.

Training: Participants (randomized to a Control or BET group) completed 5 weeks of training (20 sessions) comprised of submaximal hand contractions, once a second, until reaching a force target relative to maximum voluntary contraction. In addition, the BET group completed cognitive tasks (2-back, word incongruence Stroop) for 1200 s prior to the physical training.

Measures of motivation, physical and mental exertion, mental fatigue and mood were collected via self-report throughout.

Results: Averaged across the 2 physical tasks, handgrip endurance performance improved (p.05) more following pre-fatigue BET (24.2%) than physical training alone (12.5%). The BET group showed higher prefrontal oxygenation at post-testing (p.05) but the same RPE, motivation, cardiac and EMG activity compared to controls.

Discussion: Our findings demonstrate that sub-maximal physical handgrip training in a state of MF (pre-fatigue BET) improves endurance performance over the identical physical training alone.

References:

Dallaway et al. (2020) JSAMS 10.1016/j.jsams.2020.10.008

Van Cutsem et al. (2017). Sports Medicine, doi:10.1007/s40279-016-0672-0

Marcora et al. (2015). ACSM Annual meeting. San Diego.