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This study examined the impact of a 4-week school-based sprint interval training program on cardiorespiratoryfitness (CRF), daily physical activity (PA) behavior, and cardiometabolic risk (CMR) outcomes in adolescents. Methods: A totalof 56 adolescents (22 females) were allocated to either an intervention (n = 22; 17.0 [0.3] y) or control group (n = 30; 16.8 [0.5] y).Intervention group performed 5 to 6, 30 second “all out” running sprints, interspersed with 30-second rest intervals, 3 times perweek, for 4 consecutive weeks, whereas control group performed their normal physical education lessons. CRF was estimatedfrom the 20-m multistage fitness test and PA behavior was determined using accelerometry. Fasting blood samples were obtainedto measure biochemical markers of CMR. Results: Significant group × time interactions were observed for CRF (5.03 [1.66 to8.40]; P < .001; d = 0.95), sedentary time (136.15 [91.91 to 180.39]; P = .004; d = 1.8), moderate PA (57.20 [32.17 to 82.23];P < .001; d = 1.5), vigorous PA (5.40 [4.22 to 6.57]; P < .001; d = 1.2), fasting insulin (0.37 [−0.48 to 1.21]; P = .01;d = 1.0), homeostasis model of assessment-insulin resistance (0.26 [0.15 to 0.42]; P < .001; d = 0.9), and clustered CMR score(0.22 [−0.05 to 0.68]; P < .001; d = 10.63). Conclusion: Findings of this study indicate that 4 weeks of school-based sprintinterval training improves CRF, improves PA profiles, and maintains CMR in adolescents during the school term.

This study examined the impact of a 4-week school-based sprint interval training program on cardiorespiratoryfitness (CRF), daily physical activity (PA) behavior, and cardiometabolic risk (CMR) outcomes in adolescents. Methods: A totalof 56 adolescents (22 females) were allocated to either an intervention (n = 22; 17.0 [0.3] y) or control group (n = 30; 16.8 [0.5] y).Intervention group performed 5 to 6, 30 second “all out” running sprints, interspersed with 30-second rest intervals, 3 times perweek, for 4 consecutive weeks, whereas control group performed their normal physical education lessons. CRF was estimatedfrom the 20-m multistage fitness test and PA behavior was determined using accelerometry. Fasting blood samples were obtainedto measure biochemical markers of CMR. Results: Significant group × time interactions were observed for CRF (5.03 [1.66 to8.40]; P < .001; d = 0.95), sedentary time (136.15 [91.91 to 180.39]; P = .004; d = 1.8), moderate PA (57.20 [32.17 to 82.23];P < .001; d = 1.5), vigorous PA (5.40 [4.22 to 6.57]; P < .001; d = 1.2), fasting insulin (0.37 [−0.48 to 1.21]; P = .01;d = 1.0), homeostasis model of assessment-insulin resistance (0.26 [0.15 to 0.42]; P < .001; d = 0.9), and clustered CMR score(0.22 [−0.05 to 0.68]; P < .001; d = 10.63). Conclusion: Findings of this study indicate that 4 weeks of school-based sprintinterval training improves CRF, improves PA profiles, and maintains CMR in adolescents during the school term.

Introduction: Advancing age in men is associated with a progressive decline in serum testosterone (T) and interactions between exercise, aging and androgen status are poorly understood. The primary aim of this study was to establish the influence of lifelong training history on serum T, cortisol (C) and sex hormone binding globulin (SHBG) in aging men. A secondary aim was to determine the agreement between serum and salivary measurement of steroid hormones in ageing men. Methods: Serum and salivary steroid hormones (serum C, T and SHBG, and salivary measures of C and T) were determined and compared between two distinct groups; lifelong exercising males (LE [n = 20], 60.4 ± 4.7 year) and age matched lifelong sedentary individuals (SED [n = 28], 62.5 ± 5.3 years). Results: T-test revealed a lack of significant differences for serum C or SHBG between LE and SED, while Mann-Whitney U revealed a lack of differences in total T (TT), bioavailable T (bio-T) or free testosterone (free-T). Further, salivary T (sal-T) did not correlate with serum markers of T in LE, SED, or when pooled (r = 0.040; p > 0.05). Conclusions: Findings from this investigation suggested that resting levels of serum T and calculated free-T was unable to distinguish between diverse lifelong training histories in aging men. Further, sal-T was not an appropriate indicator of serum T and calculated free-T values in older males and considerable caution should be exercised when interpreting sal-T measurements in aging males.

Due to its noninvasive, convenient, and practical nature, salivary testosterone (sal-T) and cortisol (sal-C) are frequently used in a clinical and applied setting. However, few studies report biological and analytical error and even fewer report the ‘critical difference’ which is the change required before a true biological difference can be claimed. It was hypothesized that (a) exercise would result in a statistically significant change in sal-C and sal-T and (b) the exercise-induced change would be within the critical difference for both salivary hormones. In study 1, we calculated the critical difference of sal-T and sal-C of 18 healthy adult males aged 23.2 ± 3.0 years every 60 min in a seated position over a 12-h period (08:00–20:00 hours [study 1]). As proof-of-concept, sal-C and sal-T was also obtained pre and at 5 and 60 min post a maximal exercise protocols in a separate group of 17 healthy males (aged 20.1 ± 2.8 years [study 2]). The critical difference of sal-T calculated as 90 %. For sal-C, the critical difference was 148 % (study 1). Maximal exercise was associated with a statistically significant (p < 0.05) changes in sal-T and sal-C. However, these changes were all within the critical difference range. Results from this investigation indicate that a large magnitude of change for sal-C and sal-T is required before a biologically significant mean change can be claimed. Studies utilizing sal-T and sal-C should appreciate the critical difference of these measures and assess the biological significance of any statistical changes.