Efeitos agudos da ocitocina intranasal sobre respostas hormonais, neuromusculares e indicadores de recuperação em atletas do Powerlifting Paralímpico

Abstract

The neuropeptide oxytocin, involved in stress regulation, energy metabolism, and social responses, has been studied as a potential physiological modulator of training responses. The aim of this study was to investigate the acute effects of intranasal oxytocin administration on hormonal, neuromuscular, biochemical, and thermal responses associated with performance and recovery after a strength training session in Paralympic Powerlifting athletes. The study was conducted over 3 weeks and adopted a single-subject, double-blind, randomized, placebo-controlled design with 11 para-athletes. The experimental sessions were spaced one week apart. Before each training session, participants self-administered an intranasal spray containing either a placebo or oxytocin (24 IU). Immediately afterward, pre-tests of dynamic strength (45% of 1RM) were initiated, along with blood samples for hormone levels (total and free testosterone, cortisol), muscle damage (CK, LDH, AST, and ALT), and skin temperature measurements in the main muscles involved in the motor gesture of the sport. A training protocol of 5 sets of 5 repetitions with a load of 80% of 1RM was used, during which the dynamic strength test was performed. The tests were repeated immediately after training, and again at 24 and 48 hours post-training. The dynamic strength variables measured included average propulsive speed, maximum speed, and power. The results showed that, under oxytocin conditions, there was a significant reduction in cortisol from pre- to post-workout (9.52 ± 3.57 vs. 6.48 ± 2.07 µg/dL; p = 0.002) and recovery after 24h (p = 0.039). In the placebo group, cortisol also decreased (p = 0.011), but with a less stable pattern. In submaximal strength variables (45% of 1RM), oxytocin preserved post-workout power (613.73 W vs. 481.82 W; p = 0.024) and VMax (1.38 m/s vs. 1.31 m/s; p = 0.040), demonstrating greater fatigue tolerance. Under maximum load (80% of 1RM), oxytocin showed superior performance in series 4 in VMax (0.73 m/s vs. 0.61 m/s; p = 0.030) and power (564.55 W vs. 457.55 W; p = 0.030). In muscle damage markers, a faster reduction in LDH was observed at 24h and 48h post-training with oxytocin (356.64 ± 67.14 vs. 409.64 ± 86.52 U/L; p = 0.005 and 328.55 ± 60.58 vs. 393.82 ± 72.54 U/L; p = 0.001, respectively), in addition to smaller elevations in CK. Thermography showed that the use of oxytocin attenuated prolonged increases in skin temperature, especially in the triceps brachii (31.20 ± 1.06°C vs. 32.52 ± 1.17°C; p = 0.003) and external pectoralis major (32.50 ± 2.10°C vs. 33.42 ± 1.46°C; p = 0.017), suggesting less peripheral overload. Under the conditions analyzed, we can conclude that acute intranasal oxytocin administration may act as a multifactorial modulator of training responses, promoting hormonal balance, preservation of strength and power, reduction of muscle damage, and improvement of thermal recovery.