Robert L. Herron

Ambient Air Cooling for Concealed Soft Body Armor in a Hot Environment

Concealed soft body armor inhibits convective and evaporative heat loss and increases heat storage, especially in hot environments. One option to potentially mitigate heat storage is to promote airflow under the soft body armor. The purpose of this study was to evaluate the effect of ambient air induction (∼100 liters per minute) on heat strain while wearing concealed soft body armor in a hot environment (wet bulb globe temperature = 30°C). A counter-balanced, repeated measures protocol was performed with nine healthy male volunteers. Participants were fitted with either a traditional or modified Level II concealed soft body armor. Participants performed cycles of 12 min of walking (1.25 liters per minute) and 3 min of arm curls (0.6 liters per minute) for a total of 60 min. Two-way repeated measures ANOVA was used to assess the mean differences in physiological measures (rectal temperature, heart rate, micro-environment [temperature and relative humidity]). Post hoc Bonferroni analysis and paired samples t-tests (alpha = 0.01) were conducted on omnibus significant findings. Perceptual measures (perceived exertion, thermal comfort) were analyzed using Wilcoxon Signed Ranks Tests. Modification led to an improvement in perceived exertion at 45 min (MOD: 10 ± 1; CON: 11 ± 2; p ≤ 0.001) and 60 min (MOD: 10 ± 2; CON: 12 ± 2; p ≤ 0.001) and a reduction in micro-environment temperature in MOD (1.0 ± 0.2°C, p = 0.03) compared to CON. Modification did not attenuate change in rectal temperature or heart rate (p < 0.01) during 60-min work bout. Change in rectal temperature approached significance between MOD and CON at the end of the work bout (MOD: 0.4 ± 0.2°C; CON: 0.7 ± 0.3°C; p = 0.048). The slope of rectal temperature was significantly greater (p = 0.04) under CON compared to MOD. These data suggest that air induction may provide small benefits while wearing concealed soft body armor, though improvements are needed to lessen physiological strain.

The Effect of Intermittent Arm and Shoulder Cooling on Baseball Pitching Velocity

Abstract Bishop, SH, Herron, RL, Ryan, GA, Katica, CP, and Bishop, PA. The effect of intermittent arm and shoulder cooling on baseball pitching velocity. J Strength Cond Res 30(4): 1027–1032, 2016—The throwing arm of a baseball pitcher is subjected to high stress as a result of the repetitive activity of pitching. Intermittent cryotherapy may facilitate recovery from this repeated high stress, but few researchers have investigated cryotherapys efficacy in an ecologically valid setting. This study investigated the effects of intermittent cryotherapy on pitching velocity and subjective measures of recovery and exertion in a simulated baseball game. Trained college-aged male baseball pitchers (n = 8) threw 12 pitches (1 pitch every 20 seconds) per inning for 5 total innings during a simulated pitching start. Between each inning, pitchers received shoulder and arm cooling (AC) or, on a separate occasion, no cooling (NC). All sessions took place in a temperate environment (18.3 ± 2.8° C; 49 ± 4% relative humidity). Pitch speeds were averaged for each participant each inning and overall for 5 innings. Perceived exertion (rating of perceived exertion [RPE]) was recorded at the end of each simulated inning. Perceived recovery (perceived recovery scale [PRS]) was recorded after treatment between each inning. Mean pitching velocity for all-innings combined was higher (p = 0.04) for shoulder and elbow cooling (AC) (31.2 ± 2.1 m·s−1) than for no cooling (NC) (30.6 ± 2.1 m·s−1). Average pitch speed was significantly higher in the fourth (p = <0.01) and fifth (p = 0.02) innings in AC trial (31.3 ± 2 m·s−1 for both innings) compared with NC trial (30.0 ± 2.22 m·s−1 and 30.4 ± 1.99 m·s−1, for the fourth and fifth innings, respectively. AC resulted in a significantly lower RPE (p ⩽ 0.01) and improved PRS (p ⩽ 0.01) compared with NC. Intermittent cryotherapy attenuated velocity loss in baseball pitching, decreased RPE, and facilitated subjective recovery during a 5-inning simulated game.

Impact of upper body precooling during warm-up on subsequent time trial paced cycling in the heat

OBJECTIVES The purpose of this study was to test the hypothesis that cooling the upper body during a warm-up enhances performance during a subsequent 16.1-km simulated cycling time trial in a hot environment. DESIGN Counterbalanced, repeated measures design. METHODS Eight trained, male cyclists (peak oxygen uptake=57.8±5.0mLkg-1min-1) completed two simulated 16.1-km time trials in a hot environment (35.0±0.5°C, 43.8±2.0% relative humidity) each separated by 72h. Treatments were counterbalanced; participants warmed up for 20min while either wearing head and neck ice wraps and an ice vest (COOLING) or no cooling apparatus (CONTROL). RESULTS Following the warm-up mean skin temperature (T¯sk), mean body temperature (T¯b) and rating of thermal comfort were significantly lower than baseline following the COOLING trial (all P<0.05); however, rectal temperature was unaffected (P=0.35). Because the effects of precooling on T¯sk and T¯b were not sustained during exercise, values for COOLING and CONTROL were not different throughout the time trial (P=0.38). Nonetheless, time to completion was significantly faster following the COOLING intervention when compared to the CONTROL (29.3±3.6min, vs. 30.3±3.1min; P=0.04). CONCLUSIONS These data suggest that in short distance time trials in hot conditions cyclists may benefit from utilizing a cooling modality during the warm-up.

Acute Metabolic and Enjoyment Responses of Three Walking Protocols

Encouraging physical activity is a key component of public health. The purpose of this study was to test the hypothesis that interval walking would produce higher oxygen uptake (VO2) and similar enjoyment responses during and following exercise compared to continuous walking. Ten healthy adults (4 women, 6 men; mean age = 24 ± 5 years) completed the following 3 walking bouts in counterbalanced order and equated for total volume (90 MET·min): 1) 30 min of low-moderate continuous walking (3 METs; ~ 4.8 km/h), 2) 24 min and 24 s of interval walking (IW1) with cycles of 30 s:60 s of high-moderate (5 METs; ~ 6.4 km/h):low-moderate intensities, and 3) 26 min and 20 s of interval walking (IW2) with cycles of 30 s:120 s of high-moderate:low-moderate intensities. Accumulated O2 uptake during exercise was higher during IW2 (28,232 ± 2,782 mL) compared to IW1 (26,561 ± 2,685 mL; p = 0.03) and continuous walking (24,500 ± 2,427 mL; p = 0.001), and higher during IW1 than during continuous walking (p = 0.001). EPOC over 20 min was higher after IW1 (1,268 ± 117 mL O2) compared to continuous walking (892 ± 73 mL; p = 0.04); the 2 interval walking protocols were not different (IW2: 1,174 ± 178 mL; p > 0.05). Exercise enjoyment before, during, and after exercise did not differ among the walking protocols (all p > 0.05). Interval walking elicited greater VO2 and EPOC in shorter total durations of exercise compared to continuous walking of a similar enjoyment and volume.

Acetylsalicylic acid does not alter thermo-effector responses during mild whole-body passive heat stress in young men

Abstract Acetylsalicylic acid (ASA), aspirin, exerts potent systemic effects that may interfere with normal thermo-effector responses. We investigated the influence of commonly ingested ASA doses on measures of skin blood flow (SkBF) and local sweat rate (SR) during whole-body, passive heat stress. Seven male participants completed counter-balanced trials to compare ASA treatments (single dose 325 mg or 4 consecutive days 81 mg (4-d 81 mg)) to control (no ASA). Laser-Doppler flowmetry provided an index of SkBF. A ventilated capsule measured local sweat rate via capacitance hygrometry. Mean body temperature () was increased by 1 °C above baseline using a water-perfused suit. was similar at the onset of cutaneous vasodilation among trials. Cutaneous vascular conductance, expressed as a percentage change from baseline, was not different among trials. Additionally, at the onset of local SR and SR sensitivity did not differ among trials. While ASA has previously been shown to influence SkBF during heat stress, it is possible our cohort’s relatively young age may have contributed to our dissimilar results.