A 10-mg dose of amiloride increases time to failure during blood-flow-restricted plantar flexion in healthy adults without influencing blood pressure.

Amiloride has been shown to inhibit acid-sensing ion channels (ASICs), which contribute to ischemia-related muscle pain during exercise. The purpose of this study was to determine if a single oral dose of amiloride would improve exercise tolerance and attenuate blood pressure during blood-flow-restricted (BFR) exercise in healthy adults. Ten subjects (4 females) performed isometric plantar flexion exercise with BFR (30% maximal voluntary contraction) after ingesting either a 10-mg dose of amiloride or a volume-matched placebo (random order). Time to failure, time-tension index (TTI), and perceived pain (visual analog scale) were compared between the amiloride and placebo trials. Mean blood pressure, heart rate, blood pressure index (BPI), and BPI normalized to TTI (BPInorm) were also compared between trials using both time-matched (TM50 and TM100) and effort-matched (T50 and T100) comparisons. Time to failure (+69.4 ± 63.2 s, P < 0.01) and TTI (+1,441 ± 633 kg·s, P = 0.02) were both significantly increased in the amiloride trial compared with placebo, despite no increase in pain (+0.4 ± 1.7 cm, P = 0.46). In contrast, amiloride had no significant influence on the mean blood pressure or heart rate responses, nor were there any significant differences in BPI or BPInorm between trials when matched for time (all P ≥ 0.13). When matched for effort, BPI was significantly greater in the amiloride trial (+5,300 ± 1,798 mmHg·s, P = 0.01), likely owing to an increase in total exercise duration. In conclusion, a 10-mg oral dose of amiloride appears to significantly improve the tolerance to BFR exercise in healthy adults without influencing blood pressure responses.

Increasing the Pleasure and Enjoyment of Exercise: A Novel Resistance-Training Protocol.

This study was designed to test the effect of an increasing- (UP) or decreasing-intensity (DOWN) resistance-training (RT) protocol on the pleasure and enjoyment of RT. The participants (N = 40; mean age = 35.0 ± 9.2 years) completed two RT sessions comprising 3 × 10 repetitions of six exercises. In the UP condition, load progressively increased from 55% to 75% of 1-repetition maximum, while in the DOWN condition, this pattern was reversed (i.e., 75-55% 1-repetition maximum). The DOWN condition resulted in more overall pleasure compared with UP and a slope of increasing pleasure, while the UP condition resulted in decreasing pleasure. Enjoyment of RT, postexercise pleasure, and remembered pleasure were all significantly greater for DOWN compared with UP (all ps > .01). These findings suggest that decreasing RT intensity throughout an exercise bout can elicit a positive slope of pleasure and enhance affective evaluations of exercise.