Heart rate provides an index of the degree of circulatory strain during exercise. Essentials hoodie depicts the mean heart rates during RBL, seated recovery, and treadmill walking for all uniform conditions. Although these values tended to be lowest during CON and highest during FULL, heart rate was not different (between uniforms) during the first 30 minutes of treadmill exercise as a result of large SDs (Figure 5). However, at the 40th minute of exercise, heart rate for both the PART (171 ± 9; P = .04, d = 1.27) and FULL (181 ± 9; P = .003, d = 1.99) conditions was greater than for the CON condition (156 ± 14). The final heart rate represented the point of exhaustion, a different exercise duration for each uniform condition, and near-maximal heart rates. The final heart rate was less for the CON condition (164 ± 14 beats/min) than for the PART (178 ± 8 beats/min; P = .012, d = 0.92) or FULL (180 ± 13 beats/min; P = .04, d = 1.41) conditions; the PART and FULL conditions were not different at any time point.

Heart rate responses (mean ± SD) during repetitive box lifting (RBL), recovery, and treadmill walking while wearing 3 clothing types (N = 10). Statistical significance is described in the “Results” section. Data points depict only those segments with 5 or more participants.

Table 5 presents systolic and diastolic blood pressures for the 3 phases of the experimental protocol. The ANOVA detected a main effect of time for systolic (F2,48 = 15.80, P < .001) and diastolic (F2,48 = 11.70, P < .001) pressures. Although the between-uniforms blood pressure comparisons were not different for diastolic (F2,24 = 2.12, P = .14) pressure, a between-uniforms trend was detected for systolic pressure (main effect, F2,24 = 2.71, P = .09).

Systolic and Diastolic Blood Pressures (mm Hg) at 3 Time Points (Mean ± SD), N = 9

When the hematologic factors were analyzed in samples collected pre-RBL and immediately after the end of treadmill walking, we found no between-uniforms differences for plasma lactate, glucose, or osmolality or for percentage change in plasma volume (Table 6).

We evaluated the differential effects of 2 football uniform configurations and control clothing on thermal, cardiovascular, hematologic, and perceptual responses during an 80-minute exercise protocol in a hot environment. Although some researchers6,7,9,11 have evaluated football uniforms, their experimental protocols make interpretation of data and comparison of uniform components difficult. Two laboratory studies have provided information about this matter. In one study,11 investigators observed 8 college-aged men while they walked on a motor-driven treadmill at 35% of their maximal aerobic power (V?o2max). Using numerous combinations of air temperature (range, 29°C–39°C) and relative humidity (range, 15%–65%), the investigators sought to identify the environmental conditions at which uncompensable heat stress occurred (ie, esophageal temperature did not reach a plateau during constant-rate exercise). Their participants wore either practice uniforms or full game uniforms, and these uniforms were compared with control clothing from a previous study. The American College of Sports Medicine1 used these data to develop guidelines for wearing uniforms in hot environments, but they acknowledged that additional controlled experiments were needed.

In the other relevant laboratory study,9 investigators evaluated the energy cost of a simulated football practice (28°C, 55% relative humidity, 55% V?o2max) involving 49.5 minutes of intermittent exercise plus 2 minutes of