Physical fitness and activity in Home Guard soldiers

Physical fitness is an important attribute in soldiers because military work may be physically demanding. Existing literature has primarily described fitness and activity levels in full-time soldiers, while reserve soldiers are less frequently investigated. To be able to measure and interpret data on physical fitness in a good way, it is important to know the reliability and validity of the measurement tools. Such method comparison studies are therefore needed.

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Place: NIH. Prøveforelesning:

Formal title

Physical Fitness and Physical Activity in Norwegian Home Guard Soldiers – a cross-sectional and method comparison study

Formal

The main aim of this thesis is to describe physical fitness and physical activity in a nationally representative sample of Norwegian Home Guard (HG) soldiers. An additional aim is to investigate the reliability and validity of an aerobic fitness test (20 meter Shuttle Run Test) and different field methods for body composition (body
fat) assessments.

Description

This project includes three studies: a method comparison study of the 20 m SRT, a method comparison study of body composition field methods, and a cross-sectional study of physical fitness and physical activity in HG soldiers.

The method comparison study of the 20 m SRT included 38 male HG soldiers and 28 cadets. Test–retest reliability was analyzed from two repeated trials conducted on the HG soldiers. Validity was analyzed from comparisons between running performance in the 20 m SRT and direct measurements of maximal oxygen uptake (VO2max). A new VO2max prediction equation was generated from the HG soldiers' data. This equation (together with previously published equations) was cross-validated on the cadets.

The method comparison study of body composition field methods included 65 male and female cadets, soldiers and officers. Reliability and validity were investigated for two types of bioelectrical impedance analysis (BIA, single- and multi-frequency), skinfold measurements, and a combination of single BIA and skinfold measurements. Dual-energy X-ray absorptiometry (DXA) analysis was used as the criterion measure when investigating validity. Reliability and validity of several body fat prediction equations was evaluated.

The cross-sectional study on physical fitness and physical activity in HG soldiers was conducted on 799 male HG soldiers from five HG districts and 38 troops. Aerobic capacity, body composition and anthropometrics were measured during HG military training. Physical activity was objectively measured with an activity-monitor during HG military training and the succeeding civilian week.

Result

The 20 m SRT produced a test–retest reliability intraclass correlation coefficient (ICC) of 0.95 and a 95 % limits of agreement (LoA) of ± 3.1 mL/kg/min. Pearson correlation between estimated V̇O2max from the 20 m SRT and directly measured V̇O2max was r = 0.82 and r = 0.69 in HG soldiers and cadets, respectively. The corresponding LoA were ± 7.2 and ± 6.2 m/kg/min, respectively. A discrepancy of up to 23 % for mean estimated V̇O2max was demonstrated among previously published 20 m SRT equations. The 20 m SRT appears to be a sufficiently reliable test for practical use in the military. The 20 m SRT may estimate V̇O2max accurately on group level, but a relatively large measurement error should be accounted for at the individual level.

Test–retest ICC for estimated percent body fat from skinfold and BIA was typically ≥ 0.95, while test–retest LoA were normally between ± 1─3 body fat percentage points. Estimated percent body fat from skinfold and BIA typically correlated to DXA with a Pearson r ≈ 0.80─0.90. The LoA varied from 3.5─8.0 body fat percentage points, dependent on method, equation, and gender. No single body composition field method stood out as clearly more reliable and valid than the other methods. Many equations seem reliable for general use in the military – yet, a relatively large measurement error must be accounted for at the individual level when predicting percent body fat. Moreover, reliability and validity varied substantially among some of the body composition equations.

Mean 20 m SRT run performance in Norwegian HG soldiers was 70 shuttles, which corresponds to a V̇O2max of approximately 50 mL/kg/min. Mean body mass index, waist circumference and body fat were 26.1 kg/m2, 94.0 cm and 19.7 %, respectively. The HG soldiers spent significantly more time in moderate intensity physical activity during HG training compared to civilian life, but less time in vigorous and very vigorous physical activity. Two out of three HG soldiers reached commonly recommended values for aerobic fitness, body composition and anthropometrics. Thus, the majority of the HG soldiers seem to have a sufficient physical capacity to carry out the pre-planned jobs designated for HG soldiers. Increased focus on physical fitness and physical activity could still be valuable to physically prepare HG soldiers for more unforeseen tasks with possibly higher demands than observed during HG training.

Four papers are published from this study:
Aandstad A, Holme I, Berntsen S, Anderssen SA. Validity and reliability of the 20 meter shuttle run test in military personnel. Mil Med. 2011 May;176(5):513-8. https://www.ncbi.nlm.nih.gov/pubmed/21634295

Aandstad A, Holtberget K, Hageberg R, Holme I, Anderssen SA. Validity and reliability of bioelectrical impedance analysis and skinfold thickness in predicting body fat in military personnel.Mil Med. 2014 Feb;179(2):208-17. https://www.ncbi.nlm.nih.gov/pubmed/24491619

Aandstad A, Hageberg R, Holme IM, Anderssen SA. Anthropometrics, body composition, and aerobic fitness in Norwegian home guard personnel. J Strength Cond Res. 2014 Nov;28(11):3206-14. https://www.ncbi.nlm.nih.gov/pubmed/24832972

Aandstad A, Hageberg R, Holme IM, Anderssen SA. Objectively Measured Physical Activity in Home Guard Soldiers During Military Service and Civilian Life. Mil Med. 2016 Jul;181(7):693-700. https://www.ncbi.nlm.nih.gov/pubmed/27391624

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