Author(s): ROUSSE, Y., CHABLOZ, E., SLAWINSKI, J., BROCHERIE, F., MILLET, P.G., Institution: INSEP, Country: FRANCE, Abstract-ID: 2357

INTRODUCTION:
At the Mexico City Olympics, ~3% of Beamon’s long jump record [1] and ~2–3% sprint/jump gains were due to altitude reducing air density and drag [2]. In this context, several studies have examined hypoxia’s effect on the force–velocity (F–V) profile.
Feriche et al. [3] reported that real altitude (2320 m, hypobaric hypoxia) improved mean power and velocity, whereas equivalent normobaric hypoxia did not. Surprisingly, these gains occurred only at high loads (60–90 kg), where air density has the least impact. The authors suggested that these improvements could result from hypoxia per se, via increased recruitment of type-II muscle fibres, motor units and neuromuscular excitability. Although it is known that severe hypoxia (HH) (>3500 m) leads to mechanical alteration during high-intensity exercise not seen in moderate hypoxia (LH) (<2000 m) [4], the influence of hypoxia severity on F–V profile remains unknown.
Therefore, this study aimed to examine the impact of different levels of normobaric hypoxia severity on the F–V relationship.
METHODS:
Using a single-blind design, 17 healthy trained participants (14 men, 3 women; 23.8±1.6 yr; 75.5±10.3 kg; 183±8 cm) completed three F–V profiling bench press test in normoxic control (CON, FiO₂ = 20.9%), low (LH, 2000 m, FiO₂ = 16.9%) and high normobaric hypoxia (HH, 3800 m, FiO₂ = 13.1%) in randomised order. After a standardised warm-up, heart rate and peripheral oxygen saturation (SpO₂) were measured. One-repetition maximum (1-RM) test was determined, followed by maximal-effort at six relative loads (0–80% 1-RM) to characterise the F–V profile. Maximal velocity, force, and power were recorded with an accelerometer (Myotest® Pro) on the bar.
RESULTS:
The quality of the F–V relationships was controlled using mean R² (0.97–0.98) and the range covered (79%) for each condition (CON, LH, and HH).
SpO₂ was significantly lower only in HH (87.1±5.4%) compared to CON (95.8±1.8%) (p < .001) and LH (94.0±1.7%) (p = 0.004).
No significant differences were observed between the three conditions for F–V profile variables, with only trivial percentage differences between CON and LH/HH in theoretical maximal force (−0.0% and +0.7%), theoretical maximal velocity (+2.4% and +1.2%) and theoretical maximal power (+1.7% and +1.0%).
CONCLUSION:
The severity of acute normobaric hypoxia exposure did not influence the bench press F–V profile. These results confirm that the gains in velocity and power under hypobaric hypoxia are likely induced by the reduced air density and not hypoxia per se in such short-duration exercise. By showing that the relationship between force and velocity remain unchanged, this study has practical application for resistance training in hypoxia usually performed in severe normobaric hypoxia [5].
REFERENCES
1. Frohlich C, 1985, American Journal of Physics; 2. Hamlin MJ, 2015, Int J Sports Physiol Perform; 3. Feriche B, 2014, PLOS ONE; 4. Brocherie F, 2016, Med Sci Sports Exerc; 5. Scott BR, 2014, Sports Med.