These findings demonstrate that brief, intense exercise is a time efficient means for improving CVD risk factors in adolescents.

The effects of inspiratory muscle (IM) warm-up on the maximum dynamic IM function and the maximum repetitions of 20-m shuttle run (Ex) in the Yo-Yo intermittent recovery test were examined. Ten men were recruited to perform identical IM function test and exercise test in three different trials randomly. The control trial was without IM warm-up while the placebo and experimental trials were with IM warm-up by performing two sets of 30 breaths with inspiratory pressure-threshold load equivalent to 15% (IMW(P)) and 40% (IMW) maximum inspiratory mouth pressure, respectively. In IMW, maximum dynamic IM functions including the maximal inspiratory pressure at zero flow (P0) and maximal rate of P0 development (MRPD) were increased compared with control values (P < 0.05). The Ex was also augmented [mean (SD)] [19.5% (12.6)] while the slope of the linear relationship of the increase in rating of perceived breathlessness for every 4th exercise interval (RPB/4i) was reduced (P < 0.05). In IMW(P), although increase in Ex and reduction in RPB/4i were occurred concomitantly in some subjects, the differences in Ex, RPB/4i and dynamic IM functions between control and IMW(P) trials were not statistically significant. For the changes (Delta) in parameters in IMW and IMW(P) (n = 20), negative correlations were found between Delta RPB/4i and Delta Ex (r = -0.92), DeltaP0 and Delta RPB/4i (r = -0.48), and Delta MRPD and Delta RPB/4i (r = -0.54). Such findings suggested that the specific IM warm-up in IMW may entail reduction in breathlessness sensation, partly attributable to the enhancement of dynamic IM functions, in subsequent exhaustive intermittent run and, in turn, improve the exercise tolerance.

Visceral fat loss in response to four‐cycle ergometer training regimens with explicit differences in exercise intensity and modality was compared. Fifty‐nine obese young women (body fat percentage ≥ 30%) were randomized to a 12‐week intervention consisting of either all‐out sprint interval training (SITall‐out, n = 11); supramaximal SIT (SIT120, 120% trueV˙O2peak, n = 12); high‐intensity interval training (HIIT90, 90% trueV˙O2peak, n = 12), moderate‐intensity continuous training (MICT, 60% trueV˙O2peak, n = 11), or no training (CON, n = 13). The total work done per training session in SIT120, HIIT90, and MICT was confined to 200 kJ, while it was deliberately lower in SITall‐out. The abdominal visceral fat area (AVFA) was measured through computed tomography scans. The whole‐body and regional fat mass were assessed through dual‐energy X‐ray absorptiometry. Pre‐, post‐, and 3‐hour post‐exercise serum growth hormone (GH), and epinephrine (EPI) were measured during selected training sessions. Following the intervention, similar reductions in whole‐body and regional fat mass were found in all intervention groups, while the reductions in AVFA resulting from SITall‐out, SIT120, and HIIT90 (>15 cm2) were greater in comparison with MICT (<3.5 cm2, P < .05). The AVFA reductions among the SITs and HIIT groups were similar, and it was concomitant with the similar exercise‐induced releases of serum GH and EPI. CON variables were unchanged. These findings suggest that visceral fat loss induced by interval training at or above 90% trueV˙O2peak appeared unresponsive to the change in training intensity. Nonetheless, SITall‐out is still the most time‐efficient strategy among the four exercise‐training regimes for controlling visceral obesity.

The purpose of this study was to evaluate the interactive effects of exercise duration and intensity on the elevation of serum cardiac troponin T (cTnT) in trained adolescent athletes following prolonged exercise in a laboratory-based setting. Thirteen male adolescent runners (mean age 14.8+/-1.6 year) performed two 45-min and two 90-min constant-load treadmill runs with intensities set at the running speeds that corresponded to either 80% or 100% ventilatory threshold (Th(vent)): 80%Th(vent)45 min, 80%Th(vent)90 min, 100%Th(vent)45 min and 100%Th(vent)90 min. Serum cTnT was assessed pre and post exercise. In the 100%Th(vent)45 min trial, the post-exercise serum cTnT level [(Median) 0.015 ng x ml(-1); (Range)<0.01-0.375 ng x ml(-1)] was greater than that of the 80%Th(vent)45 min (undetectable cTnT) and 80%Th(vent)90 min (detectable cTnT in two subjects, 0.021 and 0.133 ng x ml(-1)) trials (P<0.01). The serum cTnT level was further increased in the 100%Th(vent)90 min trial [(Median) 0.063 ng x ml(-1); (Range)<0.01-0.417 ng x ml(-1)] when the treadmill run was sustained for an additional 45 min (P<0.05). Similar changes were observed in the cTnT positive rate in subjects. These findings suggest that exercise duration and intensity are essential factors in eliciting cTnT release interactively following an endurance exercise. Nevertheless, exercise intensity compared to duration appears to cause a more pronounced increase in cTnT levels.

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