Abstract
We investigated the acute neuromuscular and stress responses to three different high-intensity interval training sessions in young (age 19.5 ± 1.3 years) and older (age 65.7 ± 2.8 years) women. Cycling exercise comprised either 6 × 5 s or 3 × 30 s all-out, or 3 × 60 s submaximal, efforts each performed 5 weeks apart in randomized order. Peak and average power was higher in young than in older women and was largest during the 6 × 5 s strategy in both groups (p < 0.05). The decrease in the ratio of torques evoked by 20 and 100 Hz electrical stimulation, representing low-frequency fatigue, was more evident after the 3 × 30 and 3 × 60 s than the 6 × 5 s bout in both groups and was larger in young than in older women (p < 0.05). Both groups preferred 6 × 5 s cycling for further training. In conclusion, in young women, very low volume (6 × 5 s) all-out exercise induces significant physiological stress and seems to be an effective means of training. For older women, longer exercise sessions (3 × 60 s) are more stressful than shorter ones but are still tolerable psychologically.
Highlights
Reduced physical activity in older adults is associated with increased risk of disease and mortality [1, 2], and it is well established that exercise training reduces the risk of disease and disability [3]
Body weight and body mass index were significantly greater in the older women, but lean body mass did not differ between groups (p > 0.05, Table 1)
VO2 peak and peak power attained during the progressive cycling were significantly higher in the young women
Summary
Reduced physical activity in older adults is associated with increased risk of disease and mortality [1, 2], and it is well established that exercise training reduces the risk of disease and disability [3]. HIIT sessions are typically short (15–300 s), intense (70–100% of maximum) bursts of activity interspaced with 1–5 min of rest [9] This training differs from traditional endurance training that involves prolonged and continuous exercise supplied mainly by aerobic energy system [10, 11]. There is little agreement on the extent to which the benefits of HIIT can be attributed to the exercise intensity alone among the other load variables [12, 13]. Training at both moderate to high (70–80%) and near-maximal (>90%)
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