Acute and chronic hormonal responses induced by exercise and/or training have .... rifle with a sling, and combat gear), approximately 19.2% of body weight.
MILITARY MEDICINE, 175, 4:273, 2010
Effects of Basic Training on Acute Physiological Responses to a Combat Loaded Run Test LTCOL Matti Santtila, MSc*; Keijo Häkkinen, PhD†; William J Kraemer, PhD‡; Heikki Kyröläinen, PhD†§ ABSTRACT The purpose of the study was to examine the effects of an 8-week basic training (BT) with added strength training (ST) or endurance training (ET) on both the performance of a 3K-combat loaded run test and the acute neuromuscular and hormonal responses. All training groups improved ( p < 0.001) their run-test times: ST by 12.4%, ET by 11.6%, and normal training (NT) by 10.2%. Significant acute decreases were observed in maximal isometric force of leg extensors ( p < 0.01–0.05) in all subject groups following the run. Increases were observed in acute testosterone responses ( p < 0.001) after the test in all groups both at pre- and post-training. However, ET and NT demonstrated lower ( p < 0.001–0.05) acute post-training serum cortisol responses than ST. In conclusion, the present results indicate that within a demanding BT, the added training for ET and especially ST may be compromised in their adaptation potential due to interference from the demands of BT.
INTRODUCTION Military training and field exercises consist of many different challenging tasks such as prolonged physical activity and lifting or carrying heavy loads that require high endurance and/ or strength capacities.1,2 Nindl et al.3 have shown that higher physical fitness levels in soldiers can offset the detraining that can occur with harder military training and combat operations. Therefore, military basic training has as one of its fundamental tenets, improving physical fitness. In fact, in a study by Sharp et al.4 they observed that a 9-month military operation in Afghanistan caused a significant decrease only in the U.S. Army soldier’s aerobic performance and upper body anaerobic power possibly due to the low training frequency during the operation and resulting detraining.5 In that study by Sharp et al.,4 they examined a wide array of tests including body composition measurements, lifting strength measured by an incremental lifting machine, lower and upper body explosive power measurements (vertical jump, medicine ball put), and aerobic capacity measurement. One type of field test, which taxes both the aerobic and strength capabilities of a soldier, is the loaded running or marching test.2,3 Typically load tests reflect heavier demands and a lighter combat loaded run test has not been used to evaluate physical training programs in the military. Such tests would reflect some of the operational demands in combat field operations. The effects of combined strength and endurance training have been shown to enhance heavy 2-mile load carriage performance more than strength or endurance training alone.2 *Personnel Division of Defence Command, Finnish Defence Forces, P. O. Box 919, 00131 Helsinki, Finland. †Department of Biology of Physical Activity, University of Jyväskylä, P. O. Box 35 (VIV), 40014 Jyväskylä, Finland. ‡Department of Physiology and Neurobiology, University of Connecticut, Storrs, Connecticut 06269. §Department of Biology of Physical Activity, University of Jyväskylä and National Defence University, P. O. Box 7, 00861 Helsinki, Finland.
A field-specific run test with a combat load will allow the evaluation of the various physical training programs of its performance and changes in physiological stress responses (e.g., hormonal responses). Testosterone (TES) and cortisol (COR) have been used as primary hormonal markers representing the predominance of anabolic and catabolic activity, respectively. Acute and chronic hormonal responses induced by exercise and/or training have been widely reported.6 It has been shown that strength training can induce acute and in some cases chronic changes in total serum TES, COR, and immunoreactive growth hormone (GH), which are strongly related to volume, intensity, and duration of exercise session.6,7,8 Changes in the resting and acute responses to an exercise protocol with training can provide insights into the physiological mechanisms involved with the stress adaptations of the exercise training protocol.6 Endurance exercise usually induces acute increases in serum TES, GH, insulin-like growth factor-1 (IGF-1), and COR.8 However, endurance exercise of a prolonged duration (>2 h) can lead to acute decrease in TES.9 With endurance training no changes or decreases are observed in serum basal TES, IGF-1, GH, or COR.6,10 Nindl et al.3 have additionally demonstrated that 8 weeks of intensive military training caused chronic increases in COR and decreases in TES concentrations. These changes were associated with energy deficit and losses in fat and fat-free mass. The endurance part of concurrent endurance and strength training could, however, induce a more catabolic response and therefore, may interfere with strength development.11 Although concurrent endurance and strength training has not been shown to reduce TES, a significant increase has been observed in serum COR level.8 In the present study, we evaluated the effects of different basic training protocols using a new 3K-combat loaded running field test to evaluate soldiers’ field running performance corresponding to operational combat loaded requirements. Therefore, the primary purpose of the present study was to investigate the effects of three different 8-week basic training
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Combat Loaded Run Test
courses: normal basic training (NT), basic training with added strength training (ST), or basic training with added endurance training (ET) on a novel 3K-combat run test. A secondary purpose was to examine the acute neuromuscular force production capabilities and hormonal responses to the 3K-combat run test before and after basic training. METHODS Subjects A total of 72 male conscripts volunteered for the study after passing the medical examination and were randomly assigned to one of three training groups: NT (n = 24); ST (n = 24), or ET (n = 24). However, after group assignment, there were nine dropouts (four in the ET group, three in the ST group, and two in the NT group) due to cessation of military service for mental health reasons, sick leave of over 14 days, missing information from training diaries, or a change of garrison. The mean age of the subjects was 19.2 ± 0.9 years, height 1.79 ± 0.06 m, initial body mass 73.8 ± 12.4 kg, and body mass index 23.0 ± 3.8. No significant initial differences between the groups were observed with respect to age, height, body mass, muscle strength, aerobic capacity, or physical activity. Subjects were carefully informed about the design of the study with special information given on possible risks and discomfort that might occur, and subsequently they signed an informed consent document before the study. This study was conducted according to the Declaration of Helsinki 1975 and was approved by the Ethical Committee of the Central Finland Health Care District and the University of Jyväskylä, Finland.
subjects trained with loads of 30–50% or 60–70% of one repetition maximum (1 RM) for 2–3 sets and 10–15 or 20–40 repetitions (muscle endurance), during weeks 4 and 5 with loads of 60–80% of 1 RM for 2–4 sets and 6–10 repetitions (hypertrophy cycle), and finally during weeks 6 to 8 with loads of 80–100% for 5–7 sets and 1–6 repetitions (maximal strength/ power cycle). Additionally, explosive strength training was also performed during the last training cycle. The ET group had three additional endurance sessions a week with a duration of 60–90 min with a total of 51 h, which included nordic walking, walking, running, bicycling, and some other endurance exercises. The training intensity was mainly aerobic (50–70% of maximal heart rate). The NT group served as a control group and trained according to the basic training standard program. The SRPT program of NT consisted of endurance-type sport activities such as ballgames and muscle fitness exercises for a total of 33 h. Experimental Testing 3K-Combat Loaded Run Test
A 3-kilometer field running test with maximal effort was performed twice on the same cross-country track while carrying the 14.2-kg combat load (battle dress, running shoes, rifle with a sling, and combat gear), approximately 19.2% of body weight. All subjects were instructed to complete the test in the shortest possible time. Heart rate (HR) was recorded continuously using heart rate monitors (Suunto T6, Suunto, Vantaa, Finland). Blood samples, maximal isometric force of leg extensors, and maximal hand grip were assessed before and after the 3K-combat run test. Aerobic Capacity
Experimental Design The duration of the present study (BT season) was 8 weeks, including a total of 300 h of military training. The subjects were tested during the first and ninth service weeks before and after the training period using the identical protocols. The detailed description of the training program has been published earlier.12 The BT standard program for all groups consisted of combat simulations and marching with a load of 15–25 kg including clothing, as well as marksmanship training, material handling, general military and theoretical education, skill training, and sport-related physical training (SRPT). SRPT refers to running, nordic walking (using walking poles), walking, cycling, strength training, ball games, orienteering, and other sport activities. The SRPT program during basic training of each group differed with regard to specific training sessions. The SRPT program of the ST group contained three strength training sessions a week with a duration of 60–90 min for a total of 44 h. A whole body linear periodized strength-training program consisted of gym and circuit training and each training session always included two exercises for leg extensor muscles. During the first 3 weeks of preparatory training, the
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Peak oxygen uptake was measured using the bicycle ergometer (Ergoline GmbH, Ergoline, Germany). Oxygen uptake (VO2 peak) was measured continuously using an automated gas analysis system (SensorMedics, Yorba Linda, California). The detailed description of the protocol has been reported earlier.12 The pretest for the loaded run and VO2 peak tests were performed during the first training week and the post-test during the ninth training week, respectively. Blood Analyses
Blood samples were obtained from the antecubital vein. Serum total immunoreactive classical 21 kDa (191 aa) growth hormone (GH) was analyzed (1235 WallacAutoDelfia, Wallac Oy, Turku, Finland) using time-resolved fluoroimmunoassay (Auto-DelfiahGH, Wallac Oy, Turku, Finland). The sensitivity and intra-assay variance for this assay was up to
