Justin A. Kraft

Heart Rate and Perceived Exertion During Self-selected Intensities for Exergaming Compared to Traditional Exercise in College-age Participants

Kraft, JA, Russell, WD, Bowman, TA, Selsor III, CW, and Foster, GD. Heart rate and perceived exertion during self-selected intensities for exergaming compared to traditional exercise in college-age participants. J Strength Cond Res 25(6): 1736-1742, 2011—Exergames may be useful for promoting physical activity in younger populations. Heart rate (HRs) responses and rating of perceived exertion (RPE) at self-selected intensities were compared in college-age participants during 2 modes of exergame activity vs. traditional exercise. Thirty-seven participants (men: 20, women: 17) completed 3 30-minute self-selected intensity trials: (a) video game interactive bicycle ergometer (GB) (CatEye GB300), (b) interactive video dance game (Dance Dance Revolution [DDR]), and (c) traditional cycle ergometer (CE) while watching television. Mean HR, peak HR (PkHR), and minutes above target HR (THR) were significantly higher for GB (144 ± 22 b·min−1 [57% HR reserve (HRR)], 161 ± 23 b·min−1, and 22.5 ± 11.1 minutes) than for DDR (119 ± 16 b·min−1 [37% HRR], 138 ± 20 b·min−1, and 11.2 ± 11.9 minutes) or for CE (126 ± 20 b·min−1 [42% HRR], 144 ± 24 b·min−1, and 14.2 ± 12.6 minutes). The RPE was significantly higher for GB (4.2 ± 1.5) and CE (3.8 ± 1.2) than for DDR (2.7 ± 1.3). Recovery HR (RecHR) (15 minutes postexercise) was significantly higher for GB (91 ± 14 b·min−1) than for DDR (80 ± 11 b·min−1) and neared significance vs. CE (84 ± 14 b·min−1, p = 0.059). No difference in PkHR, RecHR, or minutes above THR was observed between DDR and CE. Session RPE was significantly higher for GB (4.6 ± 1.7) and CE (4.1 ± 1.6) than for DDR (2.8 ± 1.5). All modes elicited extended proportions of time above THR; GB: 75%, DDR: 37%, and CE: 47%. Results support that exergames are capable of eliciting physiological responses necessary for fitness improvements. Practitioners might consider exergames as periodic activity options for clients needing motivation to be regularly active.

The Influence of Hydration on Anaerobic Performance: A Review.

This review examines the influence of dehydration on muscular strength and endurance and on single and repeated anaerobic sprint bouts. Describing hydration effects on anaerobic performance is difficult because various exercise modes are dominated by anaerobic energy pathways, but still contain inherent physiological differences. The critical level of water deficit (∼ 3–4%; mode dependent) affecting anaerobic performance is larger than the deficit (∼ 2%) impairing endurance performance. A critical performance-duration component (> 30 s) may also exist. Moderate dehydration (> 3% body weight; precise threshold depends on work/recovery ratio) impairs repeated anaerobic bouts, which place an increased demand on aerobic metabolism. Interactions between dehydration level, dehydration mode, testing mode, performance duration, and work/recovery ratio during repeated bouts make the dehydration thresh-old influencing anaerobic performance mode dependent.

Session ratings of perceived exertion responses during resistance training bouts equated for total work but differing in work rate.

Abstract Kraft, JA, Green, JM, and Thompson, KR. Session ratings of perceived exertion responses during resistance training bouts equated for total work but differing in work rate. J Strength Cond Res 28(2): 540–545, 2014—Session ratings of perceived exertion (SRPE) during resistance training may be influenced by specific exercise parameters. The purpose of this study was to examine the influence of work rate (total work per unit time) and recording time on SRPE. Participants performed 3 exercise bouts of bench press, lat pull-down, overhead press, upright row, triceps extension, and biceps curl at 60% of predetermined 1 repetition maximum according to these protocols: (a) 3 sets × 8 repetitions (reps) × 1.5 minutes of recovery, (b) 3 sets × 8 reps × 3 minutes of recovery, and (c) 2 sets × 12 reps × 3 minutes of recovery. Session ratings of perceived exertion for the 3 × 8 × 1.5-minute recovery (5.3 ± 1.8) and 2 × 12 × 3-minute recovery trials (6.2 ± 1.7) were significantly greater vs. 3 × 8 × 3-minute recovery trial (4.2 ± 1.8). The difference approached significance between work rate–matched protocols (p = 0.08). No difference was observed between SRPE at 15 minutes (5.1 ± 1.8) vs. 30 minutes (5.2 ± 1.9) post exercise. Post-set in-task ratings of perceived exertion were higher for the 2 × 12 × 3-minute recovery trial (5.9 ± 1.4) vs. 3 × 8 × 1.5-minute recovery trial (4.8 ± 1.2) and 3 × 8 × 3-minute recovery trial (4.0 ± 1.6). The difference approached significance (p = 0.07) for the 3 × 8 × 3-minute recovery trial vs. 3 × 8 × 1.5-minute recovery trial. Session ratings of perceived exertion responded to changes in work rate with no significant difference at matched work rates, indicating that SRPE is responsive to training load. Results indicated that more proximal monitoring (15 minutes post exercise) yielded reliable estimates of SRPE increasing the practical utility of the measure.

Effects of Heat Exposure and 3% Dehydration Achieved Via Hot Water Immersion on Repeated Cycle Sprint Performance

Kraft, JA, Green, JM, Bishop, PA, Richardson, MT, Neggers, YH, and Leeper, JD. Effects of heat exposure and 3% dehydration achieved via hot water immersion on repeated cycle sprint performance. J Strength Cond Res 25(3): 778-786, 2011-This study examined effects of heat exposure with and without dehydration on repeated anaerobic cycling. Males (n = 10) completed 3 trials: control (CT), water-bath heat exposure (∼39°C) to 3% dehydration (with fluid replacement) (HE), and similar heat exposure to 3% dehydration (DEHY). Hematocrit increased significantly from pre to postheat immersion in both HE and DEHY. Participants performed 6 × 15s cycle sprints (30s active recovery). Mean Power (MP) was significantly lower vs. CT (596 ± 66 W) for DEHY (569 ± 72 W), and the difference approached significance for HE (582 ± 76 W, p = 0.07). Peak Power (PP) was significantly lower vs. CT (900 ± 117 W) for HE (870 ± 128 W) and approached significance for DEHY (857 ± 145 W, p = 0.07). Postsprint ratings of perceived exertion was higher during DEHY (6.4 ± 2.0) and HE (6.3 ± 1.6) than CT (5.7 ± 2.1). Combined heat and dehydration impaired MP and PP (decrements greatest in later bouts) with HE performance intermediate to CT and DEHY.

Work distribution influences session ratings of perceived exertion response during resistance exercise matched for total volume.

Abstract Kraft, JA, Green, JM, and Gast, TM. Work distribution influences session ratings of perceived exertion response during resistance exercise matched for total volume. J Strength Cond Res 28(7): 2042–2046, 2014—Session ratings of perceived exertion (SRPE) are sensitive to changes in total work volume and work rate during resistance training. This study examined the influence of work distribution (varied load, set, and repetitions [reps]) on SRPE in 2 resistance exercise trials matched for total work volume (sets × reps × percentage of 1 repetition maximum [% 1RM]) and work rate (total work volume/time). Participants completed a low load/high rep (LLHR) trial (2 sets × 12 reps × 3-minute recovery at ∼60% 1RM) and a high load/low rep (HLLR) trial (3 sets × 6 reps × 1.5-minute recovery at ∼80% 1RM) of the bench press, lat pull-down, overhead press, upright row, triceps extension, and biceps curl. A 2-minute recovery separated each exercise in both trials. Session ratings of perceived exertion and recovery heart rate (HR) were recorded 20 minutes after exercise. Preset and postset RPE and HR were higher for HLLR vs. LLHR (3.1 ± 1.6; 104 ± 15 b·min−1 vs. 2.1 ± 1.3; 98 ± 10 b·min−1) and (5.5 ± 0.9; 139 ± 14 b·min−1 vs. 4.4 ± 0.9; 131 ± 12 b·min−1), respectively. Session RPE was higher for HLLR (5.7 ± 1.4) vs. LLHR (4.3 ± 1.4) with no difference in recovery HR. Session ratings of perceived exertion was greater with higher load despite matched total volumes and work rates. Higher preset acute RPE and HR in HLLR may indicate differences in recovery between sets. Higher postset acute RPE and HR in HLLR indicated increased difficulty of individual sets in HLLR, which likely contributed to SRPE differences. Practitioners can be confident that SRPE accurately reflects changes in training load when the number of sets, reps, and loads are altered within routine training.

Influence of Experience Level on Physical Activity During Interactive Video Gaming

BACKGROUND The ability of interactive video games (IVGs) to individualize physical demands influences their viability as a physical activity option. This study examined the influence of experience level on activity levels and affect resulting from playing a martial arts IVG. METHODS Twenty participants completed 3 15-minute trials: (1) walking, (2) IVG with no previous experience (INEXP), and (3) IVG activity after 2 hours of practice (EXP) during which heart rate (HR), step counts, metabolic equivalents of task (METs), ratings of perceived exertion (RPE), session RPE, and affect (positive/negative affect, enjoyment) were measured. RESULTS Mean HR was lower during walking (107 ± 18 bpm) than during INEXP (131 ± 25 bpm) and EXP (120 ± 20 bpm). Peak HR and session RPE were lower for walking than for INEXP and EXP. No difference in mean HR was observed between IVG conditions, but peak HR and session RPE were lower for EXP than for INEXP. Walking resulted in greater postactivity reduction of negative affect; however, the IVG conditions were perceived as more enjoyable. CONCLUSIONS Although the current IVG provided a greater exercise stimulus than walking, results suggest that user movements become more efficient with greater IVG experience and that exercise outcomes may decrease as a result.