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This study compared physiological responses and total work tolerance time following forearm submersion (FS) or leg submersion (LS) in cool water, after performing work in a hot environment while wearing fire fighting protective clothing (FPC). Participants walked at 3.5 mph on a treadmill in a hot environment (WBGT 32.8 ± 0.9°C) until a rectal temperature (T(rec)) of 38.5°C was reached. Participants were then subjected to one of two peripheral cooling interventions, in a counterbalanced order. Forearms or lower legs were submerged in water (16.9 ± 0.8°C) for a total of 20 min, followed by a work tolerance trial. Results indicated no significant difference (p = 0.052) between work tolerance time (LS = 21.36 ± 5.35 min vs. FS = 16.27 ± 5.56 min). Similarly, there was no significant difference for T(rec) (p = 0.65), heart rate (HR) (p = 0.79), mean skin temperature (T(sk)) (p = 0.68), and rating of perceived exertion (RPE) (p = 0.54). However, LS ratings of thermal comfort (RTC) at Minute 14 (p = 0.03) were significantly lower for LS (10 ± 1) vs. FS (12 ± 1). Results indicate little difference between FS and LS for physiological measures. Despite a lack of statistical significance a 5-min (24%) increase was found during the work tolerance time following LS.

Athletes with spinal cord injury often experience high heat storage due to reduced sweating capacity below the spinal injury. Spray bottle (SB) may be used to apply mist for evaporative cooling during breaks in competitions. This study examined the efficacy of SB during rest breaks. Seven participants, four female and three males, (mean +/- SD age 24 +/- 4.1 year, weight 56.2 +/- 7.0 kg, upper-body VO(2) peak 2.4 +/- 0.6 l/min) volunteered for the study. Participants were paraplegic athletes (T3-T12/L1) with both complete and incomplete lesions. Participants arm-cranked using a ramp protocol in an environment of 21 +/- 1.5 degrees C and 55 +/- 3% rh once using a SB during 1-min rest between 7-min stages of increasing intensity and once without the SB (CON). Mean total work was similar (p = 0.86) for the SB and CON (2495.7 +/- 914.6 vs. 2407.1 +/- 982.3 kJ, respectively). Likewise, the mean work times were similar between trials (27 +/- 6 and 26 +/- 7 min for SB and CON, respectively). Furthermore, there were no significant differences detected between trials for skin temperature, rectal temperature, esophageal temperature (p > 0.05). There were no statistically significant differences detected between trials for RPE (p > 0.05). In conclusion, the application of artificial sweat via SB was ineffective in attenuating the onset of uncompensable heat strain during high-intensity arm exercise in a comfortable environment.

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 cryotherapy's 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) than for no cooling (NC) (30.6 ± 2.1 m·s). 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 for both innings) compared with NC trial (30.0 ± 2.22 m·s and 30.4 ± 1.99 m·s, 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.

Previous research has studied the impact of Level II concealed soft body armor (SBA) on the augmentation of heat storage in a hot environment simulating a typical summer day in the southeastern United States (wet bulb globe temperature [WBGT] = 30°C) and noted a significant difference between macro- and micro-WBGTs. The purpose of this study was to characterize the microclimate (micro-WBGT) under a concealed Level II SBA during 60 min of moderately intense work at two separate macro-WBGTs (26°C and 30°C), and to establish WBGT corrections to allow prediction of heat strain in an individual wearing a concealed Level II SBA. A single trial was performed with nine volunteers (27 ± 4 years) outfitted with a simulated standard law enforcement uniform and a traditional concealed Level II SBA, in a moderately warm environment (WBGT = 26°C). Each participant performed cycles of 12 min of walking (1.25 L · min(-1)) and 3 min of arm curls (14.3 kg, 0.6 L · min(-1)) with a 5 min rest after every other cycle, for a total of 60 minutes. This trial was compared to an identical previously completed 60-min work bout at 30°C. A two-way repeated measures ANOVA with Post hoc Bonferroni and paired samples t-test analysis was conducted. A greater difference between macro- micro-WBGTs existed at 26°C compared to the 30°C macro-WBGT. Under these conditions, a moderate work in Level II SBA requires a WBGT correction of 8.9°C and 6.2°C at macro-WBGTs of 26°C and 30°C, respectively. A modified simple linear regression prediction model was established for mean Micro-WBGT for each macro-WBGTs after the plateau point at the 30 min mark. The derivation regressions at 26°C (R(2) = 0.99), and 30°C (R(2) = 0.99) indicate that micro-WBGT could be predicted for each 15 minutes time at both macro-WBGTs tested for individuals doing moderate intensity (300 Kcals · hr(-1)) work wearing concealed Level II SBA.

Cardiovascular (CV) drift, the progressive increase in heart rate (HR) and decrease in stroke volume (SV) during constant rate, moderate intensity exercise, is related to reduced maximal oxygen uptake (V O 2max ) during heat stress. Once it has already occurred, it is unknown whether the detrimental effects of CV drift on V O 2max can be reversed. This study tested the hypothesis that fan cooling after CV drift has occurred attenuates decrements in V O 2max associated with CV drift. Eight men completed a control graded exercise test (GXT) in 22°C to measure V O 2max . Then on separate, counterbalanced occasions, they completed one 15-min (15MIN) and two 45-min bouts (45NF and 45FAN) of cycling in 35°C, 40% RH at 60% V O 2max , each immediately followed by a GXT to measure V O 2max . For one of the 45-min trials (45FAN), fan airflow (4.5 m/s) was directed at participants beginning~5 min before the GXT and continuing throughout the remainder of exercise. The purpose of the separate 15-and 45-min trials was to measure V O 2max during the same time interval that CV drift occurred. HR increased (13.8% and 11.4%) and SV decreased (14.4% and 14.1%) for 45NF and 45FAN, respectively; trials were not different (all P > 0.05). Despite a decrease in mean skin temperature of~1°C with fan use, V O 2max decreased similarly between conditions (17% vs. 15% for 45NF and 45FAN, P = 0.54). Fan cooling after CV drift was insufficient to reverse the negative consequences of CV drift on V O 2max after prolonged exercise 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.

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