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High intensity interval training (HIIT) is known to be an effective exercise training regimen to improve energy substrate metabolism and insulin sensitivity. However, the underlying mechanisms of improvement in insulin sensitivity due to HIIT have not yet been fully clarified. C1q/TNF-related protein (CTRP) 1 and CTRP9, which are adiponectin paralogs and novel adipokines, have favorable effects on energy substrate metabolism and insulin sensitivity. The purpose of this study was to investigate the effects of a single bout of HIIT on CTRP1 and CTRP9 secretions in healthy men. Eight healthy male subjects (mean ± standard error: age, 23.4 ± 1.1 years; height, 172.1 ± 1.7 cm; body mass, 68.0 ± 2.0 kg; BMI, 22.9 ± 0.5 kg/m2) participated in this study. They performed a single bout of HIIT consisted of four 30-s maximal cycling bouts with 4-min rest between bouts using a cycle ergometer. Blood samples were collected before the exercise, at 0 (immediately after the exercise), 15, 30, and 120 min after the single bout of HIIT. Serum CTRP1, CTRP9, and high-molecular-weight (HMW) adiponectin concentrations were measured using enzyme-linked immunosolvent assay kits. CTRP1 concentration significantly increased at 120 min after the HIIT. CTRP9 concentration also significantly increased immediately after the single bout of HIIT. In contrast, there were no significant differences in HMW adiponectin concentration before and after the acute HIIT. These findings suggest that a single bout of HIIT may stimulate CTRP1 and CTRP9 secretions in healthy men.

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All‐out sprint interval training (SIT) is speculated to be an effective and time‐efficient training regimen to improve the performance of aerobic and anaerobic exercises. SIT under hypoxia causes greater improvements in anaerobic exercise performance compared with that under normoxia. The change in oxygen concentration may affect SIT‐induced performance adaptations. In this study, we aimed to investigate the effects of all‐out SIT under hyperoxia on the performance of aerobic and anaerobic exercises. Eighteen college male athletes were randomly assigned to either the normoxic sprint interval training (NST, n = 9) or hyperoxic (60% oxygen) sprint interval training (HST, n = 9) group and performed 3‐week SIT (six sessions) consisting of four to six 30‐sec all‐out cycling sessions with 4‐min passive rest. They performed maximal graded exercise, submaximal exercise, 90‐sec maximal exercise, and acute SIT tests on a cycle ergometer before and after the 3‐week intervention to evaluate the performance of aerobic and anaerobic exercises. Maximal oxygen uptake significantly improved in both groups. However, blood lactate curve during submaximal exercise test significantly improved only in the HST group. The accumulated oxygen deficit (AOD) during 90‐sec maximal exercise test significantly increased only in the NST group. The average values of mean power outputs over four bouts during the acute SIT test significantly improved only in the NST group. These findings suggest that all‐out SIT might induce greater improvement in aerobic exercise performance (blood lactate curve) but impair SIT‐induced enhancements in anaerobic exercise performance (AOD and mean power output).

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