Effects of 2% Dehydration on Lactate Concentration during Constant-Load Cycling

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The lactate [La] threshold can predict endurance performance potential. Dehydration may alter [La] threshold. This study examined effects of dehydration on [La] response during constant load cycling. Recreationally fit (VO2 peak = 48.7 ± 5.2 ml•kg-1•min-1) male participants (n=9) completed 2 x 40 min constant-load cycling trials; euhydrated (HYD) and following previous evening passive (water bath) dehydration (2% body weight, DEH) (HYD and DEH counterbalanced). [La], heart rate (HR), 10 point Omni Ratings of Perceived Exertion (RPE) and rectal temperature (Trec) were measured following warm-up and at 10, 20, 30, and 40 min. Before cycling, urine specific gravity (USG) was measured and participants estimated Perceived Recovery Status (PRS). USG DEH (1.027 ± 0.004) was significantly greater than HYD (1.013 ± 0.007). After warm-up, [La] was significantly greater (all time points) for DEH (~4.1 mmol•L-1) vs. HYD (~3.5 mmol•L-1) with similar results for HR (DEH: ~167, HYD: ~158 b•min-1). For DEH, RPE was significantly greater (~1 unit) at 20, 30, and 40 min, and Trec was significantly greater at 30 and 40 min (~0.4°C). DEH (vs. HYD) also resulted in significantly different resting HR (93 ± 6, vs. 85 ± 7 b•min-1), significantly greater Session RPE (7.7 ± 1.1 vs. 5.3 ± 1.1), and significantly lower subjective feelings of recovery (PRS = 6.4 ± 2.9, vs. 9.0 ± 1.5). Current results indicate systematic changes in [La] and associated physiological responses result from previous day dehydration. Hydration status should be a concern in paradigms where [La] assessment is utilized.

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