Effect of acute exposure to moderate altitude on muscle power: hypobaric hypoxia vs. normobaric hypoxia.

When ascending to a higher altitude, changes in air density and oxygen levels affect the way in which explosive actions are executed. This study was designed to compare the effects of acute exposure to real or simulated moderate hypoxia on the dynamics of the force-velocity relationship observed in bench press exercise. Twenty-eight combat sports athletes were assigned to two groups and assessed on two separate occasions: G1 (n = 17) in conditions of normoxia (N1) and hypobaric hypoxia (HH) and G2 (n = 11) in conditions of normoxia (N2) and normobaric hypoxia (NH). Individual and complete force-velocity relationships in bench press were determined on each assessment day. For each exercise repetition, we obtained the mean and peak velocity and power shown by the athletes. Maximum power (Pmax) was recorded as the highest P(mean) obtained across the complete force-velocity curve. Our findings indicate a significantly higher absolute load linked to P(max) (∼ 3%) and maximal strength (1 RM) (∼ 6%) in G1 attributable to the climb to altitude (P<0.05). We also observed a stimulating effect of natural hypoxia on P(mean) and P(peak) in the middle-high part of the curve (≥ 60 kg; P<0.01) and a 7.8% mean increase in barbell displacement velocity (P<0.001). No changes in any of the variables examined were observed in G2. According to these data, we can state that acute exposure to natural moderate altitude as opposed to simulated normobaric hypoxia leads to gains in 1 RM, movement velocity and power during the execution of a force-velocity curve in bench press.

The effect of lactate concentration on the handgrip strength during judo bouts.

Judo is a combat sport in which the athletes attempt to hold and control their adversary through gripping techniques (kumi-kata) to apply opportune throwing techniques (nage-waza). Twelve male judo athletes, representing national teams, were recruited to investigate the changes in the maximal isometric strength in both hands before (pre) and after (post) 4 judo bouts and its relationship with the maximal blood lactic acid concentration. The subjects performed a maximal isometric contraction with each hand immediately before and after each bout. A blood sample was taken at 1, 3, and 14 minutes after each bout, and the lactic acid concentration was determined. An overall effect of the successive bouts on the maximal isometric handgrip strength of prebouts was observed for both hands (p < 0.05) but not in that of postbouts (p > 0.05). The dominant hand showed an overall decrease in the maximal isometric strength because of the bout, with the decrease being significant for the first, third, and fourth bouts (p < 0.05). The nondominant hand only showed a significant decrease in the first prebout and postbout (p < 0.05). We observed an inverse relationship between the maximal isometric handgrip strength of postbouts and maximum lactic acid concentration (Lacmax), and between the maximal isometric handgrip strength of postbouts and the lactic acid concentration at minute 14 of the recovery period (Lac14) (p < 0.05). These results show that successive judo bouts significantly reduce the maximal isometric strength of both hands and may suggest that fatigue of each hand depends on different factors. An enhanced understanding of the behavior of the isometric handgrip strength, and the factors that affect grip fatigue during judo bouts in the dominant and nondominant hands, can aid coaches in developing optimal training and exercise interventions that are aimed at mitigating decreases in the capacity of judo athletes to perform a grip.