This study aimed to explore a valid test protocol for measuring VO 2max in healthy untrained male Wistar rats of different ages and quantifying the exercise intensity (%VO 2max) of running under different treadmill grades and speeds. The test protocols and %VO 2max will provide a reference for the design of exercise intensity. We tested male Wistar rats aged 4 weeks, 10 weeks, 10 months and 16 months old with three test protocols (Procedure 1 [P1], 2 [P2] and 3 [P3]) for each age group to quantify VO 2max. We analysed VO 2max , respiratory exchange ratio and test duration to determine an optimal test protocol of VO 2max for different age groups. We used the optimal test protocol to explore the changes in age-related VO 2max. Finally, %VO 2max of running under different treadmill speeds and grades was quantified. VO 2max of Wistar rats decreased significantly after the age of 4 weeks (p < 0.05). The optimum VO 2max can be induced by personalised protocols for different ages. In 4-week-old Wistar rats, the highest VO 2max values were attained by P1 (104.4 ± 6.9 mL • kg −1 • min −1 , p = 0.032). The highest VO 2max value (84.7 ± 3.7 mL • kg −1 • min −1 , p = 0.037) of 8-week-old Wistar rats was attained in P2. In 10-month-old Wistar rats, the highest VO 2max value was obtained in P3 (63.3 ± 1.7 mL • kg −1 • min −1). This work could be used as a reference for assessing aerobic capacity in studies on exercise intervention with untrained male Wistar rats. However, the %VO 2max measurements at various treadmill speeds and grades only apply to untrained male Wistar rats. Cardiorespiratory fitness (CRF) reflects the integrated ability to transport oxygen from the atmosphere to the mitochondria for performing large-muscle, dynamic, and moderate-to-vigorous intensity exercises for prolonged time periods. CRF is directly related to the integrated function of numerous systems, including the nervous, respiratory, cardiovascular and musculoskeletal systems 1-2. CRF is considered a reflection of total body health. Low CRF is associated with a high risk of cardiovascular diseases, all-cause mortality and various types of cancer 3-5. Hence, the American Heart Association (2016) regarded CRF as a new clinical vital sign with equal importance as the heart rate, blood pressure, respiration and body temperature 1. CRF can be measured directly, expressed as maximal oxygen consumption (VO 2max) or estimated from the peak work rate achieved on a treadmill, a cycle ergometer or through non-exercise algorithms 6. VO 2max is the criterion measure of CRF 2. In sports science, VO 2max has been used extensively to evaluate CRF and quantify exercise intensity for general populations and professional athletes 7,8. Exercise intensity is a critical factor for people to achieve beneficial effects from physical activities. Such intensity is usually determined by VO 2max in the experimental design of sports science; thus, an objective and reliable test protocol should be formulated for VO 2max measurement 9. At present, VO 2max measurement and assess...
We investigated whether single or combined methods of pre-cooling could affect high-intensity exercise performance in a hot environment. Seven male athletes were subjected to four experimental conditions for 30 min in a randomised order. The four experimental conditions were: 1) wearing a vest cooled to a temperature of 4 ℃ (Vest), 2) consuming a beverage cooled to a temperature of 4 ℃ (Beverage), 3) simultaneous usage of vest and consumption of beverage (Mix), and 4) the control trial without pre-cooling (CON). Following those experimental conditions, they exercised at a speed of 80% VO2max until exhaustion in the heat (38.1 ± 0.6 ℃, 55.3 ± 0.3% RH). Heart rate (HR), rectal temperature (Tcore), skin temperature (Tskin), sweat loss (SL), urine specific gravity (USG), levels of sodium (Na+) and potassium (K+), rating of perceived exertion (RPE), thermal sensation (TS), and levels of blood lactic acid ([Bla]) were monitored. Performance was improved using the mixed pre-cooling strategy (648.43 ± 77.53 s, p = 0.016) compared to CON (509.14 ± 54.57 s). Tcore after pre-cooling was not different (Mix: 37.01 ± 0.27 ℃, Vest: 37.19 ± 0.33 ℃, Beverage: 37.03 ± 0.35 ℃) in all cooling conditions compared to those of CON (37.31 ±0.29 ℃). A similar Tcore values was achieved at exhaustion in all trials (from 38.10 ℃ to 39.00 ℃). No difference in the level of USG was observed between the conditions. Our findings suggest that pre-cooling with a combination of cold vest usage and cold fluid intake can improve performance in the heat.
Context Among sports-recovery methods, cold-water immersion (CWI), contrast-water therapy (CWT), and whole-body cryotherapy (WBC) have been applied widely to enhance recovery after strenuous exercise. However, the different timing effects in exercise-induced muscle damage (EIMD) after these recovery protocols remain unknown. Objective To compare the effects of CWI, CWT, and WBC on the timing-sequence recovery of EIMD through different indicator responses. Design Crossover study. Setting Laboratory. Patients or Other Participants Twelve male middle- and long-distance runners from the Beijing Sport University (age = 21.00 ± 0.95 years). Intervention(s) Participants were treated with different recovery methods (control [CON], CWI, CWT, WBC) immediately postexercise and at 24, 48, and 72 hours postexercise. Main Outcome Measure(s) We measured perceived sensation using a visual analog scale (VAS), plasma creatine kinase (CK) activity, plasma C-reactive protein (CRP) activity, and vertical-jump height (VJH) pre-exercise, immediately postexercise, and at 1, 24, 48, 72, and 96 hours postexercise. Results For the VAS score and CK activity, WBC exhibited better timing-sequence recovery effects than CON and CWI (P < .05), but the CWT demonstrated better effects than CON (P < .05). The CRP activity was lower after WBC than after the other interventions (P < .05). The VJH was lower after WBC than after CON and CWI (P < .05). Conclusions The WBC positively affected VAS, CK, CRP, and VJH associated with EIMD. The CWT and CWI also showed positive effects. However, for the activity and timing-sequence effect, CWT had weaker effects than WBC.
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