性別差異與咖啡因攝取在有或無延遲性肌肉酸痛下對等長收縮肌力與肌肉疲勞的效應

PURPOSE: Exploring the gender effect in acute caffeine ingestion on maximal isometric muscle contraction and muscle fatigue with or without delayed onset of muscle soreness. METHODS: Two separate experiments both with randomized, double-blind crossover design were conducted. One is to investigate whether gender effect exists in caffeine ingestion on isometric strength and muscle fatigue, and the second is to find whether caffeine ingestion to attenuate the force loss during delayed onset of muscle soreness is influenced by gender. Both experiments were to recruit 24 (12 females & 12 males) college athletes. In the first experiment, all subjects (age: 20.04 ± 1.55 years, BMI: 21.89 ± 2.16 kg/m2) ingested caffeine (6 mg/kg BW) or placebo 1 hour before performing maximal voluntary isometric contractions (MVIC) and submaximal muscle fatigue (Tlim) test. In the second experiment, all subjects (age: 21.08 ± 2.45 years, BMI: 22.13 ± 1.87 kg/m2 ) ingested caffeine (6 mg/kg BW) or placebo 24 and 48 hours following downhill running. To determine effects of caffeine ingestion on force loss during delayed onset of muscle soreness, MVIC and Tlim tests were conducted before the ingestion and one hour after the ingestion. Peripheral blood was collected before each MVIC test and analyzed for K+, Ca2+, norepinephrine, and creatine kinase. RESULT：Whatever with or without DOMS, there were no significance differences on gender and ingestion interaction in MVIC, Tlim, K+, Ca2+, norepinephrine, and creatine kinase. After caffeine ingestion’s MVIC (with DOMS: 11% , without DOMS: 271.25 ± 58.36 Nm) were all significant higher than placebo (with DOMS: -1.97%, without DOMS: 258.71±57.81 Nm) (p＜.05). Without DOMS, after caffeine ingestion’s Tlim and Ca2+ were all higher than placebo [Caffeine: Tlim (87.13 ± 19.56 sec), Ca2+ (2.6%) vs. placebo: Tlim (78.67 ± 15.30 sec), Ca2+ (0.33%) (p＜.05)]. Male was lower than female in muscle pain index with caffeine ingestion ( Male: -18.2% vs. female: -7.7%) (p＜.05), and caffeine ingestion was also lower than placebo (Caffeine: -12.9%, placebo: 3.35%) (p＜.05). CONCLUSION: Caffeine could improve anaerobic muscle strength and endurance performance, but there are no gender differences. The mechanism of anaerobic performance improvement might be related to Ca2+ releasing. In addition, caffeine can reduce muscle pain during DOMS, and which is more beneficial on male than female.