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Background: This study examined the effects of a single all-out bout of 30-s sprint-cycle performed daily for 5 consecutive days per week for 6 weeks, on aerobic fitness, muscle strength and metabolic-health markers in physically active young males and females., Methods: Healthy, physically active 20-28 year olds, were randomly assigned to either experimental (EXP, N = 11) or non-training control (CON, N = 8) group. With supervision, the EXP group performed one bout of 30-s sprint-cycle daily, Mondays to Fridays over 6 weeks, while CON group continued with their usual lifestyle. The followings were measured at pre- and post-intervention: maximal aerobic power, peak torque of knee extensors and flexors at velocities 30° s -1 and 300° s -1 , resting heart rate, resting blood pressure, body fat percentage, fasting lipid profile, fasting blood glucose, and fasting insulin levels., Results: There were no significant improvements in the EXP group for all the measured variables (all P > 0.05); except for significant interaction effects in peak torque of knee extensors at 30° s -1 (P = 0.044) and low-density lipoprotein-cholesterol (P = 0.046). Post hoc test indicate that CON group showed decline in their low-density lipo-proteins levels (P = 0.024)., Conclusion: Six weeks of one all-out bout of 30-s sprint-cycle per day, for 5 consecutive days per week, was ineffective in improving cardiovascular fitness, maximal strength, and most health markers in physically active young adults. The present results when combined with the previous literature suggest that there is a possibility of a minimum threshold for a number of sprint-cycle bouts needed to be performed before any form of cardio-metabolic-health benefit is accrued., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Purpose: To determine whether carbohydrate mouth rinsing would improve endurance running performance of tropical natives in a warm-humid (30 °C and 70% relative humidity) environment., Method: Twelve endurance male runners [age 25 ± 3 years; peak aerobic capacity ([Formula: see text]O 2peak ) 57.6 ± 3.6 mL . kg -1 . min -1 ] completed three time-to-exhaustion (TTE) trials at ~ 70% [Formula: see text]O 2peak while swilling 25 ml of a 6% carbohydrate (CHO) or taste-matched placebo (PLA) as well as no mouth rinse performed in the control (CON) trial., Results: TTE performance was significantly longer in both CHO and PLA trials when compared with the CON trial (54.7 ± 5.4 and 53.6 ± 5.1 vs. 48.4 ± 3.6 min, respectively; p < 0.001 and p = 0.012, respectively), but was not significantly different between CHO and PLA trials (p = 1.000). The rating of perceived exertion was not different between the CHO and PLA trials, however, was significantly affected when compared to the CON trial (p < 0.001). A similar effect was observed for perceived arousal level between the CHO and PLA trials to the CON trial. Core temperature, mean skin temperature and skin blood flow were not significantly different between the three trials (all p > 0.05). Similarly, plasma lactate and glucose as well as exercise heart rate were not influenced by the trials., Conclusions: The present study demonstrates that mouth rinsing, whether carbohydrate or placebo, provides an ergogenic benefit to running endurance when compared to CON in a heat stress environment. Nevertheless, the results do not support the notion that rinsing a carbohydrate solution provides a greater advantage as previously described among non-heat acclimated individuals within a temperate condition., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Purpose: This study investigated whether regular precooling would help to maintain day-to-day training intensity and improve 20-km cycling time trial (TT) performed in the heat. Twenty males cycled for 10 day × 60 min at perceived exertion equivalent to 15 in the heat (35 °C, 50% relative humidity), preceded by no cooling (CON, n = 10) or 30-min water immersion at 22 °C (PRECOOL, n = 10)., Methods: 19 participants (n = 9 and 10 for CON and PRECOOL, respectively) completed heat stress tests (25-min at 60% [Formula: see text] and 20-km TT) before and after heat acclimation., Results: Changes in mean power output (∆MPO, P = 0.024) and heart rate (∆HR, P = 0.029) during heat acclimation were lower for CON (∆MPO - 2.6 ± 8.1%, ∆HR - 7 ± 7 bpm), compared with PRECOOL (∆MPO + 2.9 ± 6.6%, ∆HR - 1 ± 8 bpm). HR during constant-paced cycling was decreased from the pre-acclimation test in both groups (P < 0.001). Only PRECOOL demonstrated lower rectal temperature (T re ) during constant-paced cycling (P = 0.002) and lower T re threshold for sweating (P = 0.042). However, skin perfusion and total sweat output did not change in either CON or PRECOOL (all P > 0.05). MPO (P = 0.016) and finish time (P = 0.013) for the 20-km TT were improved in PRECOOL but did not change in CON (P = 0.052 for MPO, P = 0.140 for finish time)., Conclusion: Precooling maintains day-to-day training intensity and does not appear to attenuate adaptation to training in the heat.

Purpose: This study examined the effects of combined cooling and lower body heat maintenance during half-time on second-half intermittent sprint performances., Methods: In a repeated measures design, nine males completed four intermittent cycling trials (32.1 ± 0.3 °C and 55.3 ± 3.7% relative humidity), with either one of the following half-time recovery interventions; mixed-method cooling (ice vest, ice slushy and hand cooling; COOL), lower body passive heating (HEAT), combined HEAT and COOL (COMB) and control (CON). Peak and mean power output (PPO and MPO), rectal (T re ), estimated muscle (T es-Mus ) and skin (T SK ) temperatures were monitored throughout exercise., Results: During half-time, the decrease in T re was substantially greater in COOL and COMB compared with CON and HEAT, whereas declines in T es-Mus within HEAT and COMB were substantially attenuated compared with CON and COOL. The decrease in T SK was most pronounced in COOL compared with CON, HEAT and COMB. During second-half, COMB and HEAT resulted in a larger decrease in PPO and MPO during the initial stages of the second-half when compared to CON. In addition, COOL resulted in an attenuated decrease in PPO and MPO compared to COMB in the latter stages of second-half., Conclusion: The maintenance of T es-Mus following half-time was detrimental to prolonged intermittent sprint performance in the heat, even when used together with cooling.

Purpose: To examine the effect of carbohydrate (CHO) mouth rinsing on endurance running responses and performance in dehydrated individuals., Methods: In a double blind, randomised crossover design, 12 well-trained male runners completed 4 running time to exhaustion (TTE) trials at a speed equivalent to 70% of VO 2peak in a thermoneutral condition. Throughout each run, participants mouth rinsed and expectorated every 15 min either 25 mL of 6% CHO or a placebo (PLA) solution for 10 s. The four TTEs consisted of two trials in the euhydrated (EU-CHO and EU-PLA) and two trials in the dehydrated (DY-CHO and DY-PLA) state. Prior to each TTE run, participants were dehydrated via exercise and allowed a passive rest period during which they were fed and either rehydrated equivalent to their body mass deficit (i.e., EU trials) or ingested only 50 mL of water (DY trials)., Results: CHO mouth rinsing significantly improved TTE performance in the DY compared to the EU trials (78.2 ± 4.3 vs. 76.9 ± 3.8 min, P = 0.02). The arousal level of the runners was significantly higher in the DY compared to the EU trials (P = 0.02). There was no significant difference among trials in heart rate, plasma glucose and lactate, and psychological measures., Conclusions: CHO mouth rinsing enhanced running performance significantly more when participants were dehydrated vs. euhydrated due to the greater sensitivity of oral receptors related to thirst and central mediated activation. These results show that level of dehydration alters the effect of brain perception with presence of CHO.

Laser class sailors have to hike out, i.e. hook their feet under the toe straps near the centreline of the boat and hold their upper bodies over the edge of the boat, to counteract the heeling forces generated by the sails. To identify the parameters that are associated with maximal hiking performance, this cross-sectional observational study measures various knee extensor and hip flexor muscle performance characteristics in 55 Laser sailors and correlates each with the area-under-the-curve hiking moment over 3 min of hiking on a hiking dynamometer (HM180). Our results showed that higher body mass and HM180 were significantly associated with better race scores (Spearman's rho = - 0.69 and - 0.62, respectively, both P < 0.01) in male sailors who participated in the National Inter-School Laser competition. Body mass (Pearson's correlation coefficient, r > or = 0.95, P < 0.01 in both males and females), maximum voluntary isometric strength of the quadriceps (r > or = 0.80, P < 0.01 in both males and females), and 3-RM knee extension strength (r > or = 0.80, P < 0.01 in both males and females) were associated with a higher HM180. The correlations between height, abdominal muscle endurance (crunches), explosive lower body strength (vertical jumps), cycling time-to-exhaustion, quadriceps strength endurance, or isometric quadriceps endurance with incremental loads (bucket test), and HM180 were weaker (r < 0.60). HM180 may be a useful performance indicator for Laser racing. Since strength measures correlated well with HM180, greater emphasis should be placed on developing maximum strength in the quadriceps to improve maximal hiking performance.