Changes in physical performance, body composition and physical training during military operations: systematic review and meta-analysis.

Systematic review and meta-analysis applying PRISMA guidelines with a PICOS format was constructed to provide an overview of changes in physical performance, body composition and physical training in soldiers during prolonged (≥ 3 months) military operations. Twenty-four studies out of the screened 4431 records filled the inclusion criteria. A small decrease in endurance performance was the most consistent finding (Hedge's g [g] - 0.21, 95% CI - 0.01 to - 0.41) while small overall increases in maximal strength of the lower (g 0.33, 95% CI 0.16-0.50) and upper body (g 0.33, 95% CI 0.19-0.46) were observed. In addition, small increases in strength endurance (push-up, g 0.34, 95% CI 0.15-0.52; sit-up g 0.26, 95% CI 0.07-0.44) were observed. The overall changes in body composition were trivial. Heterogeneity in the outcome variables varied mainly between low to moderate. Large inter-individual variations were observed in physical training volume, including decrements especially in endurance training frequency and volume. A reduction in total training load was often associated with negative changes in body composition and physical performance according to the principle of training specificity. Individuals with higher initial fitness level were more susceptible to decrements in their physical performance during operation.

Greater levels of cardiorespiratory and muscular fitness are associated with low stress and high mental resources in normal but not overweight men.

BACKGROUND: The aim of the present study was to investigate how cardio respiratory (CRF) and muscular fitness (MF) together with leisure-time physical activity (LTPA) influence stress symptoms and mental resources among normal-weight and overweight men, because it is not known how body weight affects this association. METHODS: In a cross-sectional study, 824 men (mean ± SD: age 25 ± 5 y, weight 81 ± 13 kg, BMI 25 ± 4 kg/m(2)) underwent CRF and MF tests and completed LTPA and stress questionnaires. For the analysis, the subjects were divided into BMI groups (normal vs. overweight) and CRF / MF / LTPA (low, moderate, high) tertiles. RESULTS: Normal-weight men with low CRF reported 12 % (p = 0.001) more stress symptoms (SS) compared to normal-weight men with moderate CRF, and 13 % (p = 0.004) more SS compared to normal-weight men with high CRF. Normal-weight men with low MF reported 13 % (p = 0.001) higher SS compared to normal-weight men with moderate MF and 16 % (p = 0.002) more SS compared to men with high MF. Among overweight men, there were no significant differences in SS or mental resources (MR) between the low, moderate and high CRF and MF tertiles. Overweight men with high CRF experienced 8 % (p = 0.039) more SS compared to normal-weight participants with high CRF when age, tobacco and alcohol use, MF and LTPA were considered as covariates (p = 0.014). CONCLUSION: Higher CRF and MF are associated with lower stress and higher mental resources in normal-weight men, but in overweight men, these relationships may differ.

Maximal strength, muscular endurance and inflammatory biomarkers in young adult men.

The aim was to study associations of maximal strength and muscular endurance with inflammatory biomarkers independent of cardiorespiratory fitness in those with and without abdominal obesity. 686 young healthy men participated (25±5 years). Maximal strength was measured via isometric testing using dynamo-meters to determine maximal strength index. Muscular endurance index consisted of push-ups, sit-ups and repeated squats. An indirect cycle ergometer test until exhaustion was used to estimate maximal aerobic capacity (VO2max). Participants were stratified according to those with (>102 cm) and those without abdominal obesity (<102 cm) based on waist circumference. Inflammatory factors (C-reactive protein, interleukin-6 and tumour necrosis factor alpha) were analysed from serum samples. Maximal strength and muscular endurance were inversely associated with IL-6 in those with (ß=-0.49, -0.39, respectively) (p<0.05) and in those without abdominal obesity (ß=-0.08, -0.14, respectively) (p<0.05) adjusted for smoking and cardio-respiratory fitness. After adjusting for smoking and cardiorespiratory fitness, maximal strength and muscular endurance were inversely associated with CRP only in those without abdominal obesity (ß=-0.11, -0.26, respectively) (p<0.05). This cross-sectional study demonstrated that muscular fitness is inversely associated with C-reactive protein and IL-6 concentrations in young adult men independent of cardiorespi-ratory fitness.

Physical fitness and volume of leisure time physical activity relate with low stress and high mental resources in young men.

AIM: There is limited evidence available regarding the relationship between physical fitness, especially muscular fitness, and the mental well-being among young healthy men. Therefore, the aim of the present study was to investigate the impact of measured cardiovascular and muscle fitness and self reported leisure time physical activity (LTPA) on outcomes of stress and mental resources in Finnish young men. METHODS: In a cross-sectional study, 831 men (mean age 25 y) underwent cardiovascular and muscle fitness test and completed LTPA and Occupational Stress Questionnaires (OSQ). For analysis, the subjects were divided to LTPA, CVF and MFI tertiles. RESULTS: The group with low LTPA reported 6% and 13% more stress (ANCOVA using age, body mass index, smoking and alcohol use as covariates, P<0.05 in both) and 6% and 12% (P<0.05 in both) less mental resources than the moderate and high LTPA groups, respectively. The group having low cardiovascular fitness experienced 8% and 9% (P<0.001 in both) more stress and 7% and 7% (P<0.05 in both) less mental resources than moderate and high cardiovascular fitness groups. The low muscle fitness index (MFI) group reported 7% (P<0.01) less mental resources than those with moderate MFI and 8% (P<0.001) more stress and 8% (P<0.001) less mental resources than those with high MFI. CONCLUSION: Both good aerobic and muscular fitness together with high LTPA are associated with low stress and high mental resources.

Associations of maximal strength and muscular endurance with cardiovascular risk factors.

The aim was to study the associations of maximal strength and muscular endurance with single and clustered cardiovascular risk factors. Muscular endurance, maximal strength, cardiorespiratory fitness and waist circumference were measured in 686 young men (25±5 years). Cardiovascular risk factors (plasma glucose, serum high- and low-density lipoprotein cholesterol, triglycerides, blood pressure) were determined. The risk factors were transformed to z-scores and the mean of values formed clustered cardiovascular risk factor. Muscular endurance was inversely associated with triglycerides, s-LDL-cholesterol, glucose and blood pressure (ß=-0.09 to - 0.23, p<0.05), and positively with s-HDL cholesterol (ß=0.17, p<0.001) independent of cardiorespiratory fitness. Muscular endurance was negatively associated with the clustered cardiovascular risk factor independent of cardiorespiratory fitness (ß=-0.26, p<0.05), whereas maximal strength was not associated with any of the cardiovascular risk factors or the clustered cardiovascular risk factor independent of cardiorespiratory fitness. Furthermore, cardiorespiratory fitness was inversely associated with triglycerides, s-LDL-cholesterol and the clustered cardiovascular risk factor (ß=-0.14 to - 0.24, p<0.005), as well as positively with s-HDL cholesterol (ß=0.11, p<0.05) independent of muscular fitness. This cross-sectional study demonstrated that in young men muscular endurance and cardiorespiratory fitness were independently associated with the clustering of cardiovascular risk factors, whereas maximal strength was not.

Both poor cardiorespiratory and weak muscle fitness are related to a high concentration of oxidized low-density lipoprotein lipids.

Good physical fitness is associated with favorable serum lipids. Oxidized low-density lipoprotein (ox-LDL) could be even more atherogenic than serum lipids. We studied the association of ox-LDL and serum lipids with physical fitness. Healthy young (mean age 25 years) men (n=846) underwent maximal oxygen uptake (VO(2max)) and muscle fitness index (MFI) tests and completed a leisure-time physical activity (LTPA) questionnaire. Age (ANCOVA1), age+waist circumference+systolic blood pressure+fasting blood glucose+smoking (ANCOVA3) were used as covariates. The groups with the lowest VO(2max), MFI and LTPA had 23%, 16% and 8% higher concentrations of ox-LDL than the groups with the highest VO(2max) (P<0.0001), MFI (P=0.022) and LTPA (P=0.039) groups, respectively. Subjects with poor fitness (low VO(2max) or low MFI) or low LTPA had elevated levels of ox-LDL/high-density lipoprotein (HDL)-cholesterol, total cholesterol, LDL-cholesterol, triglycerides and a low level of HDL-cholesterol (ANCOVA1, in all, P<0.05). Furthermore, low VO(2max) is associated with a high level of ox-LDL/HDL-cholesterol and triglycerides, and with a low level of HDL-cholesterol (ANCOVA3, in all, P<0.05). Also, subjects with low LTPA had a high ratio of ox-LDL/HDL-cholesterol (ANCOVA1, P=0.001). In conclusion, both poor fitness (both low VO(2max) and low MFI) and low LTPA are associated with a higher concentration of ox-LDL lipids and serum lipids, which may indicate a higher risk for atherosclerosis.

Aerobic fitness, energy balance, and body mass index are associated with training load assessed by activity energy expenditure.

The present study examined whether activity energy expenditure related to body mass (AEE/kg) is associated with maximal aerobic fitness (VO(2max)), energy balance, and body mass index (BMI) during the 2 hardest weeks of the military basic training season (BT). An additional purpose was to study the accuracy of the pre-filled food diary energy intake. Energy expenditure (EE) with doubly labeled water, energy intake (EI), energy balance, and mis-recording was measured from 24 male conscripts with varying VO(2max). AEE/kg was calculated as (EE x 0.9-measured basal metabolic rate)/body mass. The reported EI was lower (P<0.001) than EE (15.48 MJ/day) and mis-recording of the pre-filled diary was -20%. The negative energy balance (-6+/-26%) was non-significant; however, the variation was high. The subjects with a low VO(2max), a high BMI, and a negative energy balance were vulnerable to low AEE/kg. However, in the multivariate regression analysis only BMI remained in the model, explaining 33% of the variation in AEE/kg. During wintertime BT, AEE/kg is affected by energy balance, VO(2max), and BMI. From these three factors, overweight limits high-level training the most. Furthermore, an optimal energy balance facilitates physical performance and enables high training loads to be sustained during the BT season.

Waist circumference and BMI are independently associated with the variation of cardio-respiratory and neuromuscular fitness in young adult men.

OBJECTIVE: To test two hypotheses: (1) cardiorespiratory (CRF) and neuromuscular (NMF) fitness is associated with body mass index (BMI) and waist circumference (WC), independent of each other and of leisure-time physical activity; (2) individuals with high CRF and NMF have lower WC for a given BMI, compared with those with low CRF and NMF. DESIGN: Cross-sectional study. SETTING: Men participating in refresher training organized by the Finnish Defence Forces. PARTICIPANTS: A total of 951 men (mean age 29.1, s.d. 4.2 years; BMI 25.3 kg/m(2), s.d. 3.8; WC 91, s.d. 11 cm). MAIN OUTCOME MEASURES: Body mass index, WC, maximal oxygen uptake (VO(2)max), height of vertical jump, number of push-ups and sit-ups during a 1-min test, static back extension endurance, isometric grip strength, self-reported leisure-time vigorous physical activity. Multiple linear regressions were used to explain the variation in fitness. RESULTS: Waist circumference had significant (P<0.001) negative association with all test results (standardized beta coefficients from -0.23 to -0.77), except for grip strength. Body mass index had significant negative association with VO(2)max (-0.12; P<0.05), but positive association (P<0.01) with grip strength (0.28), vertical jump (0.21) and push-ups (0.55). For a given BMI, the estimated WC was highest among those with the poorest results for VO(2)max, vertical jump, sit-ups and push-ups. CONCLUSIONS: Despite stronger isometric grip strength, the functional muscle fitness of the upper body, trunk and lower extremities is impaired in individuals with abdominal obesity. Although the known loss of CRF is a serious consequence of obesity, the deterioration of NMF deserves increased attention.