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Seasonal differences in the performance and physiology of participants in a physically demanding military road march
Author(s) -
Tharion William J,
Buller Mark J,
Karis Anthony J,
Yokota Miyo,
Hoyt Reed W
Publication year - 2011
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.25.1_supplement.1053.10
Subject(s) - mile , zoology , relative humidity , demography , mathematics , chemistry , medicine , biology , meteorology , physics , astronomy , sociology
Purpose To compare the performance and physiological responses of participants in U.S. Army Ranger Training Brigade (RTB) Spring (SP), Summer (SUM) and Winter (W) classes qualifying road marches. Marches should be equally challenging across seasons. Methods 83 males (SP: n = 28; SUM: n = 25; W: n = 25) who were age: 25 ± 4 yrs; wt: 81 ± 9 kg; ht: 177 ± 6 cm; % body fat 15 ± 4%; 2‐mile run time: 12:56 ± 0:53 (mean ± SD) participated. March distances: SP and W = 12 mi (~19.3 km); SUM = 8 mi (~12.9 km). Heart rates (HR), core temperatures (T c ) and paces were measured. Marches were held at night; environmental conditions: SP = 17.2 to 21.0°C T air ; 53 to 75% relative humidity (RH); 0 to 2.1 m/s wind speed (WS); SUM = 24.4 to 25.0°C T air ; 82 to 89% RH; 2.1 to 3.1 m/s WS; W = −4.4°C to −6.2°C T air ;, 51% to 60% RH, and 0 to 2.1 m/s WS. Participants in the SP class carried significantly more wt (SP: 34.1 ± 1.9 kg, SUM: 31.6 ± 1.2 kg, W: 30.8 ± 1.6 kg). Results The pace of the SP (15:35 ± 0:45 min/mile) class was significantly slower than the SUM (14:57 ± 0:58 min/mile) or W (14:46 ± 1:19 min/mile). Individual characteristics did not differ between classes. HR ( p < 0.05) and T c ( p < 0.02) at pre‐, mid‐ and post‐march showed significant interaction effects for Time (pre, mid, post) and Class (SP, SUM, W). For HR, SUM began with the lowest HR pre‐march (101 ± 24 bpm) and had the highest HR post‐march (141 ± 15 bpm). For T c , SUM showed the greatest increase in T c by mid‐march (Pre: 37.3° ± 0.5°C Mid: 38.6° ± 0.5°C). All three classes had a plateau in T c from mid‐march to post‐march. Conclusion The RTB goal of equally challenging training was not met. The shorter SUM march distance ensured SUM and W marches were similar, but the SP march, in warm weather with heavier loads, was most challenging.