Muscle fatigue during intermittent exercise in individuals with mental retardation.

Zafeiridis et al. (2010) asked adults with mild–moderate intellectual disability to pedal hard for short bursts, rest, then repeat. The team measured leg strength, lactate, and how fast the riders tired.

They compared the group to adults without disability who did the same stop-and-go workout in the lab.

The riders with ID started weaker and made less lactate. Their power dropped more slowly, so they looked less tired even when the set ended.

In plain words, the usual red-face-and-burn feeling arrived late, so they could keep going longer than you might expect.

Borji et al. (2013) ran almost the same lab test and saw the opposite: adults with ID fatigued faster, not slower. The difference is the lens. Andreas watched whole-body power drop; Rihab watched nerve-to-muscle signal drop. Same legs, two clocks.

Bigham et al. (2013) add another piece. They showed the heart-rate and blood-pressure surge you count on mid-workout is blunted in ID. Less surge means less lactate, matching Andreas’ numbers.

Borji et al. (2014) then proved the brain is part of the problem: adults with ID could only switch on about 80 % of their muscle at will. Put together, the picture is clear—expect both slower burn and faster nerve fade; plan for both.

When you run bike or rowing intervals, don’t stop just because the client looks fresh. Use longer work bouts or more reps before rest, then build in extra recovery time when the neural drop finally shows. Pair this with short heart-rate checks; if the beat barely climbs, you are still in the safe zone.