Neuromuscular fatigue during high-intensity intermittent exercise in individuals with intellectual disability.
Adults with ID fatigue faster during short, hard bursts because their neural drive drops quickly—give longer rests and keep sets brief.
01Research in Context
What this study did
Borji et al. (2013) put adults with mild intellectual disability on a bike. They did ten hard six-second sprints with short rests.
Force sensors and EMG checked how fast leg muscles tired versus a control group.
What they found
Adults with ID started weaker and lost force faster. Their nerves could not keep the muscles fully turned on.
The authors call this 'neural activation deficit'—the signal from brain to muscle fades early.
How this fits with other research
Zafeiridis et al. (2010) saw the opposite pattern: men with ID got tired more slowly, not faster. The key difference is work length. Andreas used thirty-second bouts; Rihab used six-second bouts. Short bursts expose weak neural drive, long ones reveal slow energy use.
Borji et al. (2014) later showed the same adults could only activate about seventy percent of their quad strength even when fresh. That follow-up gives the mechanism behind the 2013 fatigue spike.
Andrews et al. (2024) ran a six-month sprint program with older adults with ID. Performance went up even though the 2013 lab test said sprints should exhaust them fast. Training builds bigger recovery windows and stronger muscles, offsetting the neural gap.
Why it matters
High-intensity intervals still work for clients with ID, but you must guard against early neural fade. Insert longer rests—at least two minutes—after every five- to ten-second burst. Watch for dropped knee height or slower pedal speed; those are early signs the neural signal is slipping. Pair the work with strength days so the muscle that can be activated grows stronger.
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02At a glance
03Original abstract
This study examined neuromuscular fatigue after high-intensity intermittent exercise in 10 men with mild intellectual disability (ID) in comparison with 10 controls. Both groups performed three maximal voluntary contractions (MVC) of knee extension with 5 min in-between. The highest level achieved was selected as reference MVC. The fatiguing exercise consists of five sets with a maximal number of flexion-extension cycles at 80% of the one maximal repetition (1RM) for the right leg at 90° with 90 s rest interval between sets. The MVC was tested again after the last set. Peak force and electromyography (EMG) signals were measured during the MVC tests. Root Mean Square (RMS) and Median Frequency (MF) were calculated. Neuromuscular efficiency (NME) was calculated as the ratio of peak force to the RMS. Before exercise, individuals with ID had a lower MVC (p<0.05) and a lower RMS (p<0.05). No significant difference between groups in MF and NME. After exercise, MVC decreases significantly in both groups (p<0.001). Individuals with ID have greater force decline (p<0.001 vs. p<0.01). RMS decreased significantly (p<0.001) whereas the NME increased significantly (p<0.05) in individuals with ID, but both remained unchanged in controls. The MF decreased significantly in both groups (p<0.001). In conclusion, individuals with ID presented a lower peak force than individuals without ID. After a high-intensity intermittent exercise, individuals with ID demonstrated a greater force decline caused by neural activation failure. When rehabilitation and sport train ID individuals, they should consider this nervous system weakness.
Research in developmental disabilities, 2013 · doi:10.1016/j.ridd.2013.09.025