Mammals have circadian clocks, which consist of the central clock in the suprachiasmatic nucleus and the peripheral clocks in the peripheral tissues. The effect of exercise on phase of peripheral clocks have been reported in rodents but not in humans. Continuous sampling is necessary to assess the phase of the circadian rhythm of peripheral clock gene expressions. It has been assumed that the expression of the genes in leukocyte may be “an accessible window to the multiorgan transcriptome.” The present study aimed to examine whether exercise affects the level and phase of clock gene expression in human leukocytes. Eleven young men participated in three trials, in which they performed a single bout of exercise at 60% V̇o2max for 1 h beginning either at 0700 (morning exercise) or 1600 (afternoon exercise) or no exercise (control). Blood samples were collected at 0600, 0900, 1200, 1500, 1800, 2100, and 2300 and at 0600 the next morning, to assess diurnal changes of clock gene expression in leukocytes. Brain and muscle ARNT-like protein 1 ( Bmal1) expression level increased after morning and afternoon exercise, and Cryptochrome 1 ( Cry1) expression level increased after morning exercise. Compared with control trial, acrophase of Bmal1 expression tended to be earlier in morning exercise trial and later in afternoon exercise trial. Acrophase of Cry1 expression was earlier in morning exercise trial but not affected by afternoon exercise. Circadian locomotor output cycles kaput ( Clock), Period 1–3 ( Per1–3), and Cry2 expression levels and those acrophases were not affected by exercise. The present results suggest a potential role of a single bout of exercise to modify peripheral clocks in humans. NEW & NOTEWORTHY The present study showed that a single bout of exercise affected peripheral clock gene expression in human leukocytes and the effect of exercise depended on when it was performed. Brain and muscle ARNT-like protein 1 ( Bmal1) expression was increased after exercises performed in the morning and afternoon. Cryptochrome 1 ( Cry1) expression was also increased after the morning exercise. The effect of exercise on acrophase of Bmal1 depended on the time of the exercise: advanced after morning exercise and delayed after afternoon exercise.
PurposeIndividual variations in response of C-reactive protein (CRP) to acute strenuous exercise are less well known. The purpose of this study was to investigate the relationship between running economy and systemic inflammation following a marathon.Materials and methodsSixteen college recreational runners participated in this study. To measure maximal oxygen uptake and running economy, the treadmill running test was performed 1–2 weeks before the marathon race. Running economy was defined as oxygen cost (mL/kg/km) at submaximal running. CRP and muscle damage markers (creatine kinase and lactate dehydrogenase) were measured before and 1, 2, and 3 days after the race.ResultsAll subjects completed the race in 4 hours 7 minutes 43 seconds±44 minute 29 seconds [mean±SD]. The marathon running significantly increased CRP and muscle damage markers. The levels of inflammation and muscle damage peaked after 1 day and remained high throughout the 3-day recovery period compared to that before the race. Spearman correlation analysis showed that the change in CRP level was significantly positively correlated with oxygen cost (r=0.619, P=0.011) but not maximal oxygen uptake. There was no significant relationship in responses between muscle damage markers and CRP.ConclusionThese findings suggest that running economy is related to postmarathon race CRP response. Further study to clarify the cause of the relationship and clinical significance of transient increase in CRP is necessary.
This study aimed to elucidate the effects of exercise intensity on stretch-shortening cycle (SSC) function of the lower limbs after cycling. Ten male triathletes performed a cycling graded test to determine the ventilatory threshold (VT) and two hopping-cycling (30 min of cycling at 90 or 110% VT)-hopping tests. The two hopping-cycling-hopping tests performed in random order. Power output (PO), heart rate (HR) and rate of perceived exertion (RPE) were monitored throughout the 30-min cycling. Blood lactate concentrations (BLa) were measured in order to assess metabolic stress. The SSC function was calculated as the ratio of the jump height to the time spent in contact with the ground (reactive strength index [RSI]). PO, HR and RPE values during cycling at 110%VT was higher than at 90%VT (p < 0.01). BLa value after the cycling at 110%VT was higher than at 90%VT (90%VT: 2.4±1.0 vs. 110%VT: 5.9±2.8 mmol/ L, p < 0.01). Regardless of the cycling exercise intensity, the RSI significantly decreased after the cycling exercise (p < 0.01). The RSI remained decreased at 15 min after the cycling exercise (p < 0.05). These results demonstrated that the SSC function decreased after cycling. Exercise intensity during cycling is likely to have no effect on the decrease in SSC function.
Takahashi, K, Shirai, Y, and Nabekura, Y. Stretch-shortening cycle function of lower limbs after cycling in triathletes. J Strength Cond Res 36(9): 2610–2614, 2022—Impaired cardiorespiratory response and changes in biomechanical variables occur when running after cycling relative to isolated running. Nevertheless, little is known about the causes of these changes or the training to prevent them. This study aimed (a) to determine whether stretch-shortening cycle (SSC) function decreases after cycling exercise and (b) to determine whether the decreases in SSC function are related to brick training. Eleven male university triathletes performed hopping tests to measure SSC function before and after cycling (30 minutes of cycling at 110% ventilatory threshold). Stretch-shortening cycle function was calculated as the ratio of the jump height to the time spent in contact with the ground (reactive strength index [RSI]). Brick training was evaluated by the total experience of brick training. The RSI significantly decreased after the cycling exercise (−10.7%; p < 0.01), but changes in RSI after cycling did not significantly correlate with the total experience of brick training, despite a large effect size (p < 0.10; r = 0.62). These results suggest that SSC function decreases after cycling and that brick training is potentially useful for inhibiting decreases in SSC function after cycling.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.