Five-Kilometer Time Trial Reliability of a Nonmotorized Treadmill and Comparison of Physiological and Perceptual Responses vs. a Motorized Treadmill.

Waldman, HS, Heatherly, AJ, Waddell, AF, Krings, BM, and O'Neal, EK. Five-kilometer time trial reliability of a nonmotorized treadmill and comparison of physiological and perceptual responses vs. a motorized treadmill. J Strength Cond Res 32(5): 1455-1461, 2018-This study examined the reliability of running performance across 3 nonmotorized treadmill (NMT) 5-km time trials (TTs) and physiological, gait, and perceptual differences at a 5-km pace for both NMT and motorized treadmills (MTs). Ten male runners experienced in road racing who had never run on an NMT completed 3 TT to establish personal best 5-km pace. In a later session, participants ran at this pace for 5 minutes on the NMT while metabolic, gait, and perceptual measures were recorded and then ran at outdoor 5-km personal best pace on an MT at 1% grade (counter-balanced crossover design). Intraclass correlation (ICC = 0.95) between the TT1 and TT2 was strong but improved between TT2 and TT3 (ICC = 0.99) with considerable reduction in variability. Nonmotorized treadmill resulted in a 24% slower pace (10.6 ± 1.5 vs. 13.9 ± 2.6 km·h; p < 0.001), shorter stride length (1.02 ± 0.10 vs. 1.27 ± 0.18 m; p < 0.001), and decreased cadence (175 ± 12 vs. 181 ± 13 steps per·minute; p = 0.01). However, V[Combining Dot Above]O2, respiratory exchange ratio (RER), lactate concentration, and heart rate did not differ between modalities (NMT = 3.4 ± 0.4 L·min, 0.96 ± 0.04, 6.9 ± 3.7 mmol, 172 ± 10 b·min; MT = 3.4 ± 0.5 L·min, 0.96 ± 0.04, 5.7 ± 3.4 mmol, 170 ± 10 b·min). rate of perceived exertion (RPE) for legs, breathing, and overall did not differ between treadmill types. A familiarization session should be included for TT using NMT. Other than gait and pace characteristics similar responses were elicited by both treadmills when running at 5-km pace. However, with these considerations, NMT TT of 4-km might be more appropriate in matching MT 5-km TT duration without altering physiological responses significantly.

Effects of Hypohydration on Repeated 40-yd Sprint Performance.

This study examined the effects of hypohydration on repeated 40-yd sprint performance. Anaerobically fit current and former Division II male athletes (n = 12) completed 2 bouts of 10 × 40-yd sprints followed by an agility test, dehydrated (∼3% body weight [DT]), or hydrated trial (HT). Statistical analysis of group means indicated that hypohydration had little effect on sprint times for either the first (DT= 5.38 ± 0.37; HT = 5.35 ± 0.34) or second (DT = 5.47 ± 0.39; HT = 5.42 ± 0.39) bout of 10 sprints with only sprint number 2, 5, and 6 of bout 2 reaching statistical significance. However, when individual sprint performance was considered, a greater effect was seen. In all, 83% (10 of 12) of subjects experienced a meaningful change (≥0.1 seconds) (positive or negative) in mean sprint time (DT vs. HT) for one or more bout of 10 sprints. Ratings of perceived exertion was significantly higher (∼1 unit on a 10 point scale) for DT in all sprints during bout 1 and the first 2 sprints of bout 2. These results indicate that the effect of hypohydration on repeated sprint performance varies among individuals. Some improved performance with hypohydration, while others experienced detrimental effects. Hypohydration also resulted in a particularly notable negative impact on perceptual measures of exertion even when performance was similar.

Hydration profile and sweat loss perception of male and female division II basketball players during practice.

Hydration affects multiple aspects of basketball performance, but few investigations have examined the hydration profiles of collegiate basketball players. We examined multiday prepractice hydration status of 11 male and 11 female NCAA (National Collegiate Athletic Association) Division II basketball players' sweat losses, fluid intake, and how accurately players estimated their sweat losses. Urine-specific gravity (USG) was spontaneously assessed before 2 practices. Sweat losses and fluid intakes were measured during a conditioning practice (CP) and sport-specific practice (SP). After practices, players filled 1,030 ml practice bottles to estimate their sweat losses. Urine-specific gravity between practices exhibited a moderate correlation (r = 0.54; p = 0.012) and were consistently high (17% of samples = USG >1.030) with no difference in mean USG between men (1.026 ± 0.004) and women (1.022 ± 0.008). Athletes' estimations of their sweat loss volumes between CP and the longer SP were strongly correlated (r = 0.88; p < 0.001). Estimation error was high (absolute error for both practices = 71 ± 52%) and error direction varied greatly within men. Women consistently underestimated sweat losses by 63 ± 28% and 65 ± 20% during CP and SP. Sweat losses during SP equaled 2,471 ± 495 ml and 1,910 ± 441 ml for men and women, respectively, but high practice fluid intake limited body mass losses to 1.1 ± 0.6% by the end of practice. It is plausible that hypohydration is related to poor conceptualization of sweat losses. Simulating the methodology of this study could help identify chronically hypohydrated athletes and be used to educate on between-practice fluid needs.