Effect of Acute Exposure to Moderate Altitude on Muscle Power: Hypobaric Hypoxia vs. Normobaric Hypoxia
December
Effect of Acute Exposure to Moderate Altitude on Muscle Power: Hypobaric Hypoxia vs. Normobaric Hypoxia
Bele n Feriche 0 3 4
Amador Garca-Ramos 0 3 4
Carmen Caldero n-Soto 1 3 4
Franchek 3 4
Drobnic 2 3 4
Juan G. Bonitch- Go ngora 0 3 4
Pedro A. Galilea 2 3 4
Joan Riera 2 3 4
Paulino 3 4
0 Department of Physical Education and Sport, University of Granada , Granada , Spain,
1 High Performance Centre of Sierra Nevada, High Sport Council , Granada , Spain,
2 Department of Sport Physiology, Grup d'Investigacio en el Rendiment i la Salut de l'Esportista d'Alt Nivell Esportiu del Centre D'Alt Rendiment, High Sport Council , Barcelona , Spain
3 Funding: This study has been supported by a Grant from the Ministry of education, culture and Sport of Spain, Reference 14/UPB10/07. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript
4 Editor: John Calvert, Emory University , United States of America
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 (n517) in conditions of normoxia (N1) and hypobaric hypoxia (HH) and G2 (n511) 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 Pmean obtained across the complete force-velocity curve. Our findings indicate a significantly higher absolute load linked to Pmax (,3%) and maximal strength (1RM) (,6%) in G1 attributable to the climb to altitude (P,0.05). We also observed a stimulating effect of natural hypoxia on Pmean and Ppeak 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 1RM, movement velocity and power during the execution of a force-velocity curve in bench press.
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During ascent to higher altitude, the partial pressure of oxygen (O2) in the air
gradually diminishes and this reduces the arterial partial pressure of O2 leading to
tissue hypoxia [1]. It is known that endurance performance is compromised at
hypoxic enviroments and mean reductions in VO2max of 6% per 1000 m of ascent
have been described [2]. For short-duration high-intensity activities lasting less
than 1 min, the predominant energy source is phosphorylation and non-oxidative
production of ATP [3]. Given that explosive performance is not aerobic
dependent, short-explosive actions should not be impaired by altitude. In fact, it
was observed during the Mexico City Olympics Games in 1968 (at 2240 m) in
sprint events [4].
Peronnet et al. [4] proposed that air density decrement at altitude (,3%
reduction for each 305 m rise [5]) diminish the energy cost of running at high
velocities without impairing energy availability. The reduction in external
resistance to movement [6] and/or the modified muscle recruitment pattern due
to increased anaerobic metabolism [7, 8], could be related to this reduced energy
cost and thus improve performance in rapid actions such as throws, jumps or
blows [5, 6]. However, strength and resistance training at altitude have been
scarcely addressed in the scientific literature. Some studies have related the severe
hypoxia of high altitude (.5500 m) to muscle deterioration and reduced
muscular function [9, 10] and power [11], including a loss of up to 15% lean mass
[12], along with a reduced strength gain (26.4%) compared to that produced in
conditions of normoxia for the same training exercise [13].
In contrast, the effect of exposure to a real moderate altitude (20003000 m asl)
on muscle power has not yet been adequately addressed, despite this being the
altitude most athletes select for training. Recently, Scott et al. did not find an effect
of moderate and high acute simulated hypoxic stimulus (fraction of inspired
oxygen [FiO2] of 0.16 and 0.13) during a resistance high intensity in back squat
and dead lift exercises on force and power measurements [14]. Conversely,
Chirosa et al. [15] reported an improvement in the force-velocity curve for half
back squat in 5 recreational athletes after rapidly ascending to an altitude of
2320 m. Using the load at which maximum power was achieved in normoxia, in
acute moderate hypoxia, 4% gains in velocity and 7% gains in power were
produced (P,0.0 (...truncated)