Aerobic Capacity Determines Habitual Walking Acceleration, Not Electromyography-Indicated Relative Effort

Objective: Habitual walking is important for health and can be measured with accelerometry, but accelerometry does not measure physiological effort relative to capacity. We compared accelerometer-measured absolute intensity electromyography (EMG)-measured muscle activity between people low versus excellent aerobic fitness levels during their habitual walking. Methods: Forty volunteers (19 women; age 49.3 ± 17.1 years, body mass index 24.0 2.6 kg/m 2 ; peak oxygen uptake 40.3 12.5 ml/kg/min) wore EMG-shorts a hip-worn accelerometer simultaneously 11.6 2.2 hr on 1.7 1.1 days. Continuous gait bouts of at least 5-min duration were identified based acceleration mean amplitude deviation (MAD, in milli gravitational acceleration, mg) EMG amplitude, normalized maximal isometric knee extension flexion (EMG, percentage voluntary contraction EMG). Peak was treadmill strength leg press (leg max). MAD age- sex-specific groups (low-average, good, excellent) linear models. Results: During (4.1 4.1 bouts/day, 0.9 1.0 min/bout), the low-average fit participants had an approximately 28% lower (245 64.3 both good (313 68.1 mg, p < .05), same (13.1% 8.42% EMG, = .10). Absolute, mass, skeletal (but max) positively associated independent sex ( .01), there no associations EMG. Conclusions: People capacity habitually walk intensity, stimulus lower-extremity muscles similar those This should considered when measuring prescribing health.