Introduction
Volume oxygen maximum (VO2max) is the maximum rate at which oxygen can be utilized by the body during strenuous exercise. It is a measure of physical fitness and athletic performance. Lactate accumulation during exercise occurs when anaerobic metabolism predominates. Exercise of sufficient intensity is known to stimulate Beta Endorphin release from the central nervous system. There is a difference of opinion among researchers on the intensity of exercise needed to cause this release and the role of lactate. The use of anabolic steroids is increasing globally particularly among bodybuilders hypothesized to affect body systems.
Aim
To determine the effect of VO2max on the circulatory lactate and beta-endorphins levels and assess the correlation between the two parameters in male bodybuilders using anabolic steroids, non-users and non-bodybuilders.
Materials and Methods
This cross-sectional study was conducted at the exercise physiology laboratory at the Postgraduate medical institute, Pakistan. The study involved 30 healthy male subjects within (20 to 30 years) recruited through convenience non-probability sampling. The study population included 3 groups: Group I (non-bodybuilders), Group II (bodybuilders not using anabolic steroids), and Group III (bodybuilders using anabolic steroids). All participants underwent a graded exercise test on cardiopulmonary exercise testing (CPET) equipment up till exhaustion for VO2max assessment. Blood sampling was done pre and post-exercise (80% of VO2max) to measure blood lactate and beta-endorphin levels. Data was analyzed by SPSS version 23. Paired t-test, ANOVA and Pearson were applied. p-value <0.05 taken statistically significant.
Results
Bodybuilders achieved a significantly higher VO2max as compared to non-bodybuilders (43.4 ± 4.2ml/min/kg, 35.4 ± 4.8 ; p <0.001) respectively. Anabolic steroids using bodybuilders showed a significantly lower VO2max compared to non-users (38 ± 3.1ml/min/kg, 43.4±4.2 ml/min/kg ; p = 0.016) respectively. No statistically significant difference was seen in the respiratory exchange ratio among groups both at rest (0.9 ± 0.1 , 0.8 ± 0.1, 0.83 ± 0.1 ; p = 0.148) and at max (1.2 ± 0.1 , 1.1 ± 0.1 , 1.1± 0.1 ; p = 0.097). Minute ventilation showed a non-significant difference between the three study groups( 98.6 ± 38.2 , 121.6 ± 18.2 , 109 ± 15.3 ; p = 0.103) . Blood lactate and beta-endorphin levels increased significantly in all the three study groups at an exercise intensity of 80% of VO2max (p <0.001). A non-significant difference in blood lactate levels was found between anabolic steroids using bodybuilders and non-users (3.75 ± 0.3 , 4.00 ± 0.6 ; p = 0.756).  Beta-endorphin levels were found to be significantly lower in anabolic steroid users than in non-users (26.4±10.0 , 40.4±12.8 ; p = 0.029). There was a significant positive correlation found between blood lactate and beta-endorphin levels post-exercise, r (28) = 0.31, p = 0.05.
Conclusion:
Exercise intensity of 80% of VO2max is sufficient for the significant increase in blood lactate and beta-endorphin levels in bodybuilders using anabolic steroids, non-users and non-bodybuilders. Exogenous steroid intake blunts the release of exercise-induced beta-endorphins. Acidosis caused by lactate accumulation is likely to contribute to an increase in beta-endorphins.