Thirty-five healthy men were matched and randomly assigned to one of four training groups that performed high-intensity strength and endurance training (C; n = 9), upper body only high-intensity strength and endurance training (UC; n = 9), high-intensity endurance training (E; n = 8), or high-intensity strength training (ST; n = 9). The C and ST groups significantly increased one-repetition maximum strength for all exercises (P < 0.05). Only the C, UC, and E groups demonstrated significant increases in treadmill maximal oxygen consumption. The ST group showed significant increases in power output. Hormonal responses to treadmill exercise demonstrated a differential response to the different training programs, indicating that the underlying physiological milieu differed with the training program. Significant changes in muscle fiber areas were as follows: types I, IIa, and IIc increased in the ST group; types I and IIc decreased in the E group; type IIa increased in the C group; and there were no changes in the UC group. Significant shifts in percentage from type IIb to type IIa were observed in all training groups, with the greatest shift in the groups in which resistance trained the thigh musculature. This investigation indicates that the combination of strength and endurance training results in an attenuation of the performance improvements and physiological adaptations typical of single-mode training.

ripheral blood concentrations of testosterone in males FLECK. Hormonal and growth factor responses to heavy resist-(9, 13, 19, 29). Furthermore, it has been suggested that ance exercise protocols. J. Appl, Physiol. 69(4): 1442-1450, training may influence resting values of testosterone (14-1990.-To examine endogenous anabolic hormone and growth training m a i lun ingivale t estosterone (14-factor responses to various heavy resistance exercise protocols 16). Limited data also indicate that human growth hor-(HREPs), nine male subjects performed each of six randomly mone may increase in response to an acute bout of assigned HREPs, which consisted of identically ordered exer-resistance exercise (25, 29, 33). VanHelder et al. (33) cises carefully designed to control for load [5 vs. 10 repetitions have demonstrated that human growth hormone elevamaximum (RM)], rest period length (1 vs. 3 min), and total tions may be dependent on specific exercise characteriswork effects. Serum human growth hormone (hGH), testoster-tics such as the load utilized and frequency of lifting one (T), somatomedin-C (SM-C), glucose, and whole blood exercise. To our knowledge, no data exist regarding solactate (HLa) concentrations were determined preexercise, matomedin-C responses to heavy resistance exercise promidexercise (i.e., after 4 of 8 exercises), and at 0, 5, 15, 30, 60, tocols. The purpose of this investigation was to deter-90, and 120 min postexercise. All HREPs produced significant mine the impact of load, rest period length, and total (P < 0.05) temporal increases in serum T concentrations, min te ima toftload, rest p rod th andmtota although the magnitude and time point of occurrence above work on serum testosterone, human growth hormone, resting values varied across HREPs. No differences were ob-and somatomedin-C response patterns during and after served for T when integrated areas under the curve (AUCs) different heavy resistance exercise protocols. were compared. Although not all HREPs produced increases in serum hGH, the highest responses were observed consequent METHODS to the H10/1 exercise protocol (high total work, 1 min rest, 10-RM load) for both temporal and time integrated (AUC) reNine healthy male subjects gave informed written consponses. The pattern of SM-C increases varied among HREPs sent to participate in this investigation. The physical and did not consistently follow hGH changes. Whereas tem-characteristics of the subjects were the following: age, poral changes were observed, no integrated time (A T "-) differ-24.66 ± 4.27 (SD) yr; height, 178.41 ± 7.77 cm; body ences between exercise protocols occurred. These data indicate that the release patterns (temporal or time integrated) observed mass, 81.08 l 12.03 kg; maximal oxygen consumption, are complex functions of the type of HREPs utilized and the 54.17 ±4.63 ml.kg-min-; and body fat 1596+4.18%. physiological mechanisms involved with determining periph-All subjects had recreational experience with resistance era] circulatory concentrations (e.g., clearance ...

This study reviews historical and biomedical aspects of soldier load carriage. Before the 18th century, foot soldiers seldom carried more than 15 kg while on the march, but loads have progressively risen since then. This load increase is presumably due to the weight of weapons and equipment that incorporate new technologies to increase protection, firepower, communications, and mobility. Research shows that locating the load center of mass as close as possible to the body center of mass results in the lowest energy cost and tends to keep the body in an upright position similar to unloaded walking. Loads carried on other parts of the body result in higher energy expenditures: each kilogram added to the foot increases energy expenditure 7% to 10%; each kilogram added to the thigh increases energy expenditure 4%. Hip belts on rucksacks should be used whenever possible as they reduce pressure on the shoulders and increase comfort. Low or mid-back load placement might be preferable on uneven terrain but high load placement may be best for even terrain. In some tactical situations, combat load carts can be used, and these can considerably reduce energy expenditure and improve performance. Physical training that includes aerobic exercise, resistance training targeted at specific muscle groups, and regular road marching can considerably improve road marching speed and efficiency. The energy cost of walking with backpack loads increases progressively with increases in weight carried, body mass, walking speed, or grade; type of terrain also influences energy cost. Predictive equations have been developed, but these may not be accurate for prolonged load carriage. Common injuries associated with prolonged load carriage include foot blisters, stress fractures, back strains, metatarsalgia, rucksack palsy, and knee pain. Load carriage can be facilitated by lightening loads, improving load distribution, optimizing load-carriage equipment, and taking preventive action to reduce the incidence of injury.

The SJ equation is a slightly more accurate equation than that derived from CMJ data. This equation should be used in the determination of peak power in place of the formulas developed by both Harman et al. and Lewis. Separate equations for males and females are unnecessary.

To examine endogenous anabolic hormonal responses to two different types of heavy resistance exercise protocols (HREPs), eight male and eight female subjects performed two randomly assigned protocols (i.e. P-1 and P-2) on separate days. Each protocol consisted of eight identically ordered exercises carefully designed to control for load, rest period length, and total work (J) effects. P-1 utilized a 5 RM load, 3-min rest periods and had lower total work than P-2. P-2 utilized a 10 RM load, 1-min rest periods and had a higher total work than P-1. Whole blood lactate and serum glucose, human growth hormone (hGH), testosterone (T), and somatomedin-C [SM-C] (i.e. insulin-like growth factor 1, IGF-1) were determined pre-exercise, mid-exercise (i.e. after 4 of the 8 exercises), and at 0, 5, 15, 30, and 60 min post-exercise. Males demonstrated significant (p less than 0.05) increases above rest in serum T values, and all serum concentrations were greater than corresponding female values. Growth hormone increases in both males and females following the P-2 HREP were significantly greater at all time points than corresponding P-1 values. Females exhibited significantly higher pre-exercise hGH levels compared to males. The P-1 exercise protocol did not result in any hGH increases in females. SM-C demonstrated random significant increases above rest in both males and females in response to both HREPs.(ABSTRACT TRUNCATED AT 250 WORDS)

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