This study aimed to identify the acute effects of caffeinated chewing gum (CAF) on bicycle motocross (BMX) time-trial (TT) performance. In a randomized, placebo-controlled, double-blind cross-over design, 14 male BMX riders (age = 20.0 ± 3.3 years; height = 1.78 ± 0.04 m; body mass = 72 ± 4 kg), consumed either (300 mg; 4.2 ± 0.2 mg/kg) caffeinated (300 mg caffeine, 6 g sugars) or a placebo (0 mg caffeine, 0 g sugars) gum, and undertook three BMX TTs. Repeated-measure analysis revealed that CAF has a large ergogenic effect on TT time, F(1, 14) = 33.570, p = .001, ${\mathrm{\eta }}_{\mathrm{p}}^2=.71$; −1.5% ± 0.4 compared with the placebo. Peak power and maximal power to weight ratio also increased significantly compared with the placebo condition, F(1, 14) = 54.666, p = .001, ${\mathrm{\eta }}_{\mathrm{p}}^2=.79$; +3.5% ± 0.6, and F(1, 14) = 57.399, p = .001, ${\mathrm{\eta }}_{\mathrm{p}}^2=.80$; +3% ± 0.3, respectively. Rating of perceived exertion was significantly lower F(1, 14) = 25.020, p = .001, ${\mathrm{\eta }}_{\mathrm{p}}^2=.64$ in CAF (6.6 ± 1.3) compared with the placebo (7.2 ± 1.7). Administering a moderate dose (300 mg) of CAF could improve TT time by enhancing power and reducing the perception of exertion. BMX coaches and riders may consider consuming CAF before a BMX race to improve performance and reduce rating of perceived exertion.

本研究旨在确定含咖啡因口香糖 (CAF) 对自行车越野赛 (BMX) 计时赛 (TT) 表现的急性影响。在一项随机、安慰剂对照、双盲交叉设计中，14 名男性 BMX 骑手（年龄 = 20.0 ± 3.3 岁；身高 = 1.78 ± 0.04 m；体重 = 72 ± 4 kg）服用（300 mg； 4.2 ± 0.2 毫克/公斤）含咖啡因（300 毫克咖啡因，6 克糖）或安慰剂（0 毫克咖啡因，0 克糖）口香糖，并进行了 3 次 BMX TT。重复测量分析表明，CAF 对 TT 时间有很大的增力作用，F (1, 14) = 33.570，p  = .001，${\mathrm{\eta }}_{\mathrm{p}}^2=.71$; 与安慰剂相比-1.5% ± 0.4。与安慰剂条件相比，峰值功率和最大功率重量比也显着增加，F (1, 14) = 54.666，p  = .001，${\mathrm{\eta }}_{\mathrm{p}}^2=.79$; +3.5% ± 0.6，且F (1, 14) = 57.399，p  = .001，${\mathrm{\eta }}_{\mathrm{p}}^2=.80$; 分别为+3%±0.3。感知用力等级显着降低F (1, 14) = 25.020, p  = .001,${\mathrm{\eta }}_{\mathrm{p}}^2=.64$与安慰剂 (7.2 ± 1.7) 相比，CAF (6.6 ± 1.3) 。施用中等剂量（300 mg）的 CAF 可以通过增强力量和减少用力感觉来改善 TT 时间。BMX 教练和骑手可以考虑在 BMX 比赛前服用 CAF，以提高表现并降低感知用力程度。