Search

Alemany, JA, Pierce, JR, Bornstein, DB, Grier, TL, Jones, BH, and Glover, SH. Comprehensive physical activity assessment during U.S. Army Basic Combat Training. J Strength Cond Res XX(X): 000-000, 2021-Physical activity (PA) volume, intensity, and qualitative contextual information regarding activity type and loads carried are limited during U.S. Army Basic Combat Training (BCT). The purpose of this study was to characterize daily (05:00-20:00 hours) PA during BCT using a comprehensive approach. During 2 10-week BCT cycles (n = 40 trainees per cycle), pedometers, accelerometers, and direct observation were used to estimate daily step count, PA volume, and intensity. Physical activity intensity was categorized by metabolic equivalents (METs) such as "sedentary" (1-2 METs), "light" (2-3 METs), "moderate" (3-6 METs), or "vigorous" (≥6 METs). Daily PA data were analyzed longitudinally using linear mixed models, with significance set at p ≤ 0.05. The mean daily step count was 13,459 ± 4,376 steps, and the mean daily accelerometer-assessed PA volume and intensity were as follows: sedentary: 505 ± 98 minutes, light: 190 ± 78 minutes, moderate: 168 ± 51 minutes, and vigorous: 14 ± 14 minutes, with no differences between cycles for all measures (p > 0.50). Cumulative time on feet (∼50%) and sitting (20-25%) accounted for most daily activity types during both cycles. Trainees, on average, carried between 3 and 9 kg, and ≥9 kg, for 60% and 10% of the monitored day, respectively. Basic Combat Training's physical demands are high, where trainees achieved 1.7 to 2.7 times greater daily ambulation and 6 times the recommended weekly moderate-to-vigorous PA compared with civilian counterparts and performed weight-bearing load carriage for nearly half of the day. Basic Combat Training-associated PA may increase injury risk among trainees unaccustomed to arduous PA and exercise. Implementing national PA policies to improve physical fitness and facilitate acclimatization to BCT's high physical demands could reduce public health burdens and military nonreadiness.

AB Introduction: The pulsatile secretion pattern of growth hormone (GH) is an important parameter of GH action at peripheral tissues, and more information is needed on how exercise impacts GH secretion. This study hypothesized that both aerobic and resistance exercise would exhibit dose-response relationships with respect to exercise duration and 20-h postexercise GH secretion. Methods: Eight healthy men randomly completed five separate conditions: 1) control (no exercise; CON), 2) a moderate-duration (1-h) aerobic exercise session (MA), 3) a long-duration (2-h) aerobic exercise session (LA), 4) a moderate-duration (1-h) resistance exercise session (MR), and 5) a long-duration (2-h) resistance exercise session (LR). Exercise intensity, diet, sleep, and physical activity were strictly controlled during each condition, and blood was sampled postexercise every 20 min for 20 h, and GH secretion parameters were analyzed via cluster and deconvolution analyses. Results: Only the 2-h aerobic exercise bout resulted in a significant amplification of GH secretion as evidenced by increases in GH burst peak amplitude (~100%), basal GH secretion rate (~127%), total GH basal secretion (~120%), total pulsatile secretion (~88%), and total GH secretion (~89%) over the control (i.e., no exercise) condition. GH secretions for the resistance exercise conditions were not different from control. Conclusions: The fact that the 2-h aerobic exercise condition resulted in higher energy expenditure than the other exercise conditions could offer a partial explanation for the greater GH amplification because of the metabolic effects that GH exerts in stimulating postexercise lipolysis. We conclude that extending the duration of aerobic exercise, but not resistance exercise, from 1- to 2-h significantly amplifies GH secretion during a 20-h period.

Various physical demands are placed on soldiers, whose effectiveness and survivability depend on their combat-specific physical fitness. Because sport training programs involving weight-based training have proven effective, this study examined the value of such a program for short-term military training using combat-relevant tests. A male weight-based training (WBT) group (n = 15; mean +/- SD: 27.0 +/- 4.7 years, 173.8 +/- 5.8 cm, 80.9 +/- 12.7 kg) performed full-body weight-based training workouts, 3.2-km runs, interval training, agility training, and progressively loaded 8-km backpack hikes. A male Army Standardized Physical Training (SPT) group (n = 17; mean +/- SD: 29.0 +/- 4.6 years, 179.7 +/- 8.2 cm, 84.5 +/- 10.4 kg) followed the new Army Standardized Physical Training program of stretching, varied calisthenics, movement drills, sprint intervals, shuttle running, and distance runs. Both groups exercised for 1.5 hours a day, 5 days a week for 8 weeks. The following training-induced changes were statistically significant (P0.05) for both training groups: 3.2-km run or walk with 32-kg load (minutes), 24.5 +/- 3.2 to 21.0 +/- 2.8 (SPT) and 24.9 +/- 2.8 to 21.1 +/- 2.2 (WBT); 400-m run with 18-kg load (seconds), 94.5 +/- 14.2 to 84.4 +/- 11.9 (SPT) and 100.1 +/- 16.1 to 84.0 +/- 8.4 (WBT); obstacle course with 18-kg load (seconds), 73.3 +/- 10.1 to 61.6 +/- 7.7 (SPT) and 66.8 +/- 10.0 to 60.1 +/- 8.7 (WBT); 5 30-m sprints to prone (seconds), 63.5 +/- 4.8 to 59.8 +/- 4.1 (SPT) and 60.4 +/- 4.2 to 58.9 +/- 2.7 (WBT); and 80-kg casualty rescue from 50 m (seconds), 65.8 +/- 40.0 to 42.1 +/- 9.9 (SPT) and 57.6 +/- 22.0 to 44.2 +/- 8.8 (WBT). Of these tests, only the obstacle course showed significant difference in improvement between the two training groups. Thus, for short-term (i.e., 8-week) training of relatively untrained men, the Army's new Standardized Physical Training program and a weight-based training experimental program can produce similar, significant, and meaningful improvements in military physical performance. Further research would be needed to determine whether weight-based training provides an advantage over a longer training period.

The purpose of this investigation was to determine the test-retest reliability and coefficient of variation of 2 novel physical performance tests. Ten healthy men (22.0 +/- 3.0 years, 87.0 +/- 8.0 kg, 20.0 +/- 5.0% body fat) performed 30 continuous and dynamic jump squats (JS) and bench throws (BT) on 4 separate occasions. The movements were performed under loaded conditions utilizing 30% of subject's predetermined 1 repetition maximum in the back squat and bench press. Mean power (MP; W), peak power (PP; W), mean velocity (MV; m.s(-1)), peak velocity (PV; m.s(-1)), and total work (TW; J) were assessed using a ballistic measurement system (Innervations Inc., Muncie, IN). Data were analyzed using repeated measures analysis of variance with Duncan's post hoc test when mean differences were p < or = 0.05. Intraclass correlation coefficient (ICC) and within-subject coefficient of variation (CV%) were also calculated. All values are presented as mean +/- SE. BT variables were statistically similar across the 4 sessions: MP (350.0 +/- 13.9 W), PP (431.4 +/- 18.5 W) MV (1.6 +/- 0.03 m.s(-1)), PV (2.0 +/- 0.03 m.s(-1)), and TW (199.1 +/- 7.2 J). For JS, session 3 PP (1,669.8 +/- 111.2 W) was significantly greater vs. sessions 1, 2, and 4 (1,601.2 +/- 58.4 W). Session 4 MP (1,403.2 +/- 88.6 W) and MV (1.9 +/- 0.1 m.s(-1)) for JS were significantly lower during sessions 1, 2, and 3 (MP: 1,479.4.5 +/- 44.8 W, MV: 2.0 +/- 0.05 m.s(-1)). TW (834.7 +/- 24.3 J) and PV (2.2 +/- 0.04 m.s(-1)) were statistically similar during all sessions for JS. The CVs ranged from 3.0 to 7.6% for the BT and 3.2 to 5.7% for the JS. ICCs for MP, PP, MV, PV, and TW were 0.92, 0.95, 0.94, 0.91, and 0.95, respectively, during BT. ICCs during JS for MP, PP, MV, PV, and TW were 0.96, 0.98, 0.94, 0.94, and 0.89, respectively. The results of the current study support the use of a 30 continuous and dynamic BT protocol as a reliable upper-body physical performance test, which can be administered with minimal practice. Slightly greater variability for JS was observed, although the test had high reliability.