Garnacho-Castaño, MV, Albesa-Albiol, L, Serra-Payá, N, Gomis Bataller, M, Pleguezuelos Cobo, E, Guirao Cano, L, Guodemar-Pérez, J, Carbonell, T, Domínguez, R, and Maté-Muñoz, JL. Oxygen uptake slow component and the efficiency of resistance exercises. J Strength Cond Res 35(4): 1014–1022, 2021—This study aimed to evaluate oxygen uptake slow component (V̇o 2sc) and mechanical economy/efficiency in half squat (HS) exercise during constant-load tests conducted at lactate threshold (LT) intensity. Nineteen healthy young men completed 3 HS exercise tests separated by 48-hour rest periods: 1 repetition maximum (1RM), incremental-load HS test to establish the %1RM corresponding to the LT, and constant-load HS test at the LT. During the last test, cardiorespiratory, lactate, and mechanical responses were monitored. Fatigue in the lower limbs was assessed before and after the constant-load test using a countermovement jump test. A slight and sustained increase of the V̇o 2sc and energy expended (EE) was observed (p < 0.001). In blood lactate, no differences were observed between set 3 to set 21 (p > 0.05). A slight and sustained decrease of half squat efficiency and gross mechanical efficiency (GME) was detected (p < 0.001). Significant inverse correlations were observed between V̇o 2 and GME (r = −0.93, p < 0.001). Inverse correlations were detected between EE and GME (r = −0.94, p < 0.001). Significant losses were observed in jump height ability and in mean power output (p < 0.001) in response to the constant-load HS test. In conclusion, V̇o 2sc and EE tended to rise slowly during constant-load HS exercise testing. This slight increase was associated with lowered efficiency throughout constant-load test and a decrease in jump capacity after testing. These findings would allow to elucidate the underlying fatigue mechanisms produced by resistance exercises in a constant-load test at LT intensity.

Introduction There is a lack of information regarding the slow component of oxygen uptake (VO 2 sc) and efficiency/economy in resistance exercises despite the crucial role played in endurance performance. Purpose this study aimed to compare the VO 2 sc, efficiency/economy, metabolic, cardiorespiratory responses, rating of perceived effort and mechanical fatigue between cycling and half-squat (HS) exercises during a constant-load test at lactate threshold (LT 1 ) intensity. Methods Twenty-one healthy men were randomly assigned in a crossover design to perform cycle-ergometer or HS tests. The order of the two cycle ergometer tests was an incremental test for determining load-intensity in watts (W) at LT 1 , followed by a constant-load test at the LT 1 intensity. For the three HS tests, the order was a 1RM test to determine the load (kg) corresponding to the 1RM percentages to be used during the second test, incremental HS exercise to establish the load (kg) at the LT 1 intensity, and finally, a constant-load HS test at the LT 1 intensity. A rest period of 48 h between each test was established. During the HS and cycle-ergometer constant-load tests, cardiorespiratory and metabolic responses were recorded. Lower limbs fatigue was determined by a jump test before and after the constant-load tests. Results A significant exercise mode × time interaction effect was detected in VO 2 , heart rate, energy expenditure (EE), gross efficiency (GE), and economy ( p < 0.05). A significant and sustained VO 2 raise was confirmed in HS exercise ( p < 0.05) and a steady-state VO 2 was revealed in cycle-ergometer. A higher GE and economy were obtained in HS test than in cycle-ergometer exercise ( p < 0.001). In both exercises, a non-significant decrease was observed in GE and economy ( p > 0.05). Lower limbs fatigue was only detected after constant-load HS test. Conclusion Although the VO 2 , heart rate and EE responses were higher in cycling exercise, the constant-load HS test induced a greater VO 2 sc and EE raise than the cycling test in a predominantly aerobic metabolism. These results could explain a decrease observed in jump performance only after HS test. GE and economy could benefit from the eccentric phase of the HS exercise.

There is a lack of evidence about the ventilatory efficiency in resistance exercises despite the key role played in endurance exercises. This study aimed to compare the cardiorespiratory, metabolic responses and ventilatory efficiency between half-squat (HS) and cycle ergometer exercises during a constant-load test at the lactate threshold (LT) intensity. Eighteen healthy male participants were randomly assigned in a crossover design to carry out HS or cycle ergometer tests. For the three HS tests, a one repetition maximum (1RM) test was performed first to determine the load (kg) corresponding to the 1RM percentages. In the second test, the incremental HS exercise was carried out to establish the load (kg) at the LT intensity. Finally, a constant-load HS test was performed at the LT intensity. The first cycle ergometer test was incremental loading to determine the intensity in watts corresponding to the LT, followed by a constant-load test at the LT intensity. A recovery time of 48 hours between each test was established. During both constant-load test, cardiorespiratory and metabolic responses were monitored. A significant exercise mode x time interaction effect was only detected in oxygen uptake (VO 2 ), heart rate, and blood lactate (p < 0.001). No differences were found between the two types of exercise in ventilatory efficiency (p >0.05). Ventilation (VE) and carbon dioxide were highly correlated (p <0.001) in the cycle ergometer (r = 0.892) and HS (r = 0.915) exercises. In the VO 2 efficiency slope (OUES), similarly significant and high correlations (p <0.001) were found between VO 2 and log 10 VE in the cycle ergometer (r = 0.875) and in the HS (r = 0.853) exercise. Although the cardioventilatory responses were greater in the cycle ergometer test as compared to HS exercise, ventilatory efficiency was very similar between the two exercise modalities in a predominantly aerobic metabolism.

The assessment of ventilatory efficiency is critical to understanding the matching of ventilation (VE) and perfusion in the lungs during exercise. This study aimed to establish a causal physiological relationship between ventilatory efficiency and resistance exercise performance after beetroot juice (BJ) intake. Eleven well-trained males performed a resistance exercise test after drinking 140 mL of BJ (~12.8 mmol NO3−) or a placebo (PL). Ventilatory efficiency was assessed by the VE•VCO2−1 slope, the oxygen uptake efficiency slope and the partial pressure of end-tidal carbon dioxide (PetCO2). The two experimental conditions were controlled using a randomized, double-blind crossover design. The resistance exercise test involved repeating the same routine twice, which consisted of wall ball shots plus a full squat (FS) with a 3 min rest or without a rest between the two exercises. A higher weight lifted was detected in the FS exercise after BJ intake compared with the PL during the first routine (p = 0.004). BJ improved the VE•VCO2−1 slope and the PetCO2 during the FS exercise in the first routine and at rest (p < 0.05). BJ intake improved the VE•VCO2−1 slope and the PetCO2 coinciding with the resistance exercise performance. The ergogenic effect of BJ could be induced under aerobic conditions at rest.

The main objective of this study was to identify the relationship between performance parameters and the probability that a team will win or lose during regular season games. A retrospective observational study of a professional rugby team with thirty players and sixteen regular season games was conducted. Analyzes included the following metrics: open play carries, winline success, gainline failure, good pass, average pass, bad pass, good kick, average kick, bad kick, effective ruck, ruck ineffective, dominant tackle, neutral tackle, passive tackle, assisted tackle, missed tackle, defender in position, good offload, kick fielded, kick fielded unsuccessful, loose ball, interception, turnover made, line break, yellow card , red card, penalty awarded, try scored, injury, player out, player on, successful kick at goal, missed kick at goal, lineout, lineout won, scrum, scrum won, return to play, ruck speed and tackle completion. No single parameter could be directly related to profit or loss. However, four parameters when pooled could be associated with winning during the analyzed season (r = 0.897, r2 = 0.805, adjusted r = 0.635, p < 0.05): win-line success (p < 0.002), effective ruck (p<0.009), dominant tackle (p<0.018) and assisted tackle (p<0.029). In this specific context, coaches and professionals should pay more attention to these specific actions to improve team performance. Keywords: performance, breakdown, gain, ruck, tackle