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Lori M. Keys, Matthew A. Chatlaong, Daphney M. Stanford, Matthew B. Jessee. University of Mississippi, University, MS.

BACKGROUND: Training with 2 x 20s cycling sprints improves cardiorespiratory fitness but reducing this to 1 sprint does not. It is unclear if fatigue induced by the first sprint might lead to greater cardiovascular demand in the second sprint. PURPOSE: Characterize power production and cardiovascular responses to 1- and 2 - 20s maximal cycling sprints. METHODS: In a single lab visit, 43 participants completed 2 x 20 second maximal “Wingate” leg cycling sprints (5 min rest between) with no warm-up or cool-down. Peak and mean power for each sprint (S1 = sprint 1, S2 = sprint 2), were determined by Lode ergometer software. Heart rate (HR) was measured via telemetry and analyzed at baseline, during S1 and S2, in minutes 1 (M1), 3 (M3), and 5 (M5) of recovery after each sprint, and at 10- (M10) and 15- (M15) minutes post-exercise. Mean HR was averaged over windows of 1-min at baseline, 20s during S1 and S2, and for 30s at M1, M3, M5, M10, and M15. Peak HR was the highest value during each window. Bayesian paired t tests were used to compare peak and mean power between sprints. Bayesian rmANOVA were used to compare mean and peak HR between time points. BF10 = likelihood of alternative vs. null. Results are mean±SD. RESULTS: Mean power (W) was higher for S1 (577.7±171.8) than S2 (543.2±159.4, BF10=2101.2). Peak power (W) was also higher for S1 (935.3±326.5) than S2 (882.4±208.4, BF10=57.3). Mean HR (bpm) increased from baseline (89.1±15.3) and did not return by M10 (108.0±18.6, BF10=526390.3) or M15 (106.2±18.1, BF10=245115.2). Comparing mean HR during the sprints, S2 (129.4±18.0) was higher than S1 (119.2±18.8, BF10=100615.6). Peak HR (bpm) during S2 (149.5±20.0) was higher than S1 (143.9±22.3, BF10=28.3). Comparing the recovery from each sprint, mean HR was higher at S2M1 (152.1±21.9) vs S1M1 (144.7±23.3, BF10=1051.7), S2M3 (123.2±21.5) vs S1M3 (110.7±21.1, BF10=6.919e+7), and S2M5 (115.4±21.0) vs S1M5 (107.1±20.8, BF10=351.8). Peak HR followed the same pattern, being higher at S2M1 (158.4±20.8) vs S1M1 (154.2±23.4, BF10=11.0), S2M3 (129.7±19.8) vs S1M3 (118.6±20.0, BF10=1.938e+11), and S2M5 (120.6±19.8) vs S1M5 (114.1±18.9, BF10=22.4). CONCLUSION: The lower power production in sprint 2 suggests a robust, fatiguing stimulus was induced by sprint 1. This may have led to a cumulative increase in cardiovascular demand, as heart rate responses were also substantially higher after the second sprint than the first.

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