Changes in Maximum Muscle Strength and Rapid Muscle Force Characteristics after Long-Term Special Support and Reconnaissance Missions: A Preliminary Report

Christensen, Peter Bondo; Jacobsen, O. H.; Thorlund, Jonas Bloch; Madsen, Thomas O.; Møller, Carsten; Jensen, Claus Hjorth; Suetta, Charlotte; Aagaard, Per

doi:10.7205/milmed.173.9.889

Cited by 15 publications

(21 citation statements)

References 17 publications

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“…Subsequently, after 3 h of light activity and nourishment, the post2 test was conducted. During the entire 8‐day period, a relatively high degree of combat stress/threat was maintained (Christensen et al, 2008). To ensure that changes did not occur due to dehydration or malnutrition, the subjects received 3 liters of water and a standardized field ration per day (3564 kcal, protein 84 g, carbohydrates 547 g and fat 116 g).…”

Section: Methodsmentioning

confidence: 99%

“…However, during Special Support and Reconnaissance (SSR) missions, Special Forces soldiers experience extreme conditions with 8-12 days of muscle unloading (i.e. lying prone 24 h/day with restricted space for movement) in rough weather and often with limited nutrition (Christensen et al, 2008). Muscle unloading has been studied previously during space travel, bed rest or by lower limb casting to investigate the effect of immobilization on muscle mechanical function.…”

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confidence: 99%

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Changes in muscle strength and morphology after muscle unloading in Special Forces missions

Thorlund

Jakobsen

Madsen

et al. 2011

Scandinavian Med Sci Sports

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The purpose of the present study was to determine the changes in maximal muscle strength, rapid force capacity, jumping performance and muscle morphology following a Special Forces military operation involving 8 days of muscle unloading. Nine male Special Forces soldiers were tested before (pre) and immediately after (post1) an 8-day simulated special support and reconnaissance (SSR) mission and after 3 h of active recovery (post2). Maximal muscle strength (MVC) and rate of force development (RFD) were measured along with maximal counter movement jump height (JH). Muscle biopsies were obtained from the vastus lateralis at pre and post1. Acute reductions were found in MVC (11%), JH (10%) and RFD (17-22%) after 8 days of muscle unloading (post1) (P≤0.05). Type IIX fiber type area% increased (P≤0.05) at post1 together with a tendency toward increased type IIX fiber type % (P=0.09) and decreased type I fiber type % (P=0.06), suggesting a transition toward a less fatigue-resistant fiber-type profile. In conclusion, short-term unloading during SSR missions led to marked reductions in mechanical muscle function and functional performance, which may be partly explained by the changes in muscle morphology. Future studies should identify intervention strategies to counter-act the observed impairments.

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Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

Changes in muscle strength and morphology after muscle unloading in Special Forces missions

Thorlund

Jakobsen

Madsen

et al. 2011

Scandinavian Med Sci Sports

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“…Consumption of the rations was not monitored. At the end of the 8‐day period, subjects were not allowed to carry any of their equipment and were driven while lying prone to the testing facility, where the muscle biopsy sampling and strength testing were immediately performed (Christensen et al., ).…”

Section: Methodsmentioning

confidence: 99%

“…Adequate physical capacity is critical for soldiers engaging in military operations. During special support and reconnaissance (SSR) missions, Special Forces soldiers may face extreme conditions with 1–2 weeks of immobilization (prone position 24 h/day with restricted movement space) often with limited nutrition and in harsh weather conditions (Christensen et al., ), which impair muscle strength, rate of force development, and functional performance (Thorlund et al., ). These impairments are likely to endanger the life of soldiers, as sufficient muscle mass and strength are crucial in combat or rapid acute evacuation situations.…”

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confidence: 99%

Alterations in molecular muscle mass regulators after 8 days immobilizing Special Forces mission

Jespersen

Mikkelsen

Nedergaard

et al. 2014

Scandinavian Med Sci Sports

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In military operations, declined physical capacity can endanger the life of soldiers. During special support and reconnaissance (SSR) missions, Special Forces soldiers sustain 1-2 weeks full-body horizontal immobilization, which impairs muscle strength and performance. Adequate muscle mass and strength are necessary in combat or evacuation situations, which prompt for improved understanding of muscle mass modulation during SSR missions. To explore the molecular regulation of myofiber size during a simulated SSR operation, nine male Special Forces soldiers were biopsied in m. vastus lateralis pre and post 8 days immobilizing restricted prone position. After immobilization, total mammalian target of rapamycin protein was reduced by 42% (P < 0.05), whereas total and phosphorylated protein levels of Akt, ribosomal protein S6k, 4E-BP1, and glycogen synthase kinase3β were unchanged. Messenger RNA (mRNA) levels of the atrogenes forkhead box O3 (FoxO3), atrogin1, and muscle ring finger protein1 (MuRF1) increased by 36%, 53%, and 71% (P < 0.01), MuRF1 protein by 51% (P = 0.05), whereas FoxO1 and peroxisome proliferator-activated receptor γ coactivator-1 β mRNAs decreased by 29% and 40% (P < 0.01). In conclusion, occupational immobilization in Special Forces soldiers led to modulations in molecular muscle mass regulators during 8 days prone SSR mission, which likely contribute to muscle loss observed in such operations. The present data expand our knowledge of human muscle mass regulation during short-term immobilization.

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“…Moreover, they have to deal with stressors common to combat operations (e.g., energy deficit, sleep deprivation, and sustained load carriage). Studies on students participating in military training courses and sustained operations exercises lasting 3.5 to 64 days have reported weight losses ranging from 3 to 16% of initial body mass (88)(89)(90)(91)(92)(93)(94)(95)(96)(97). More importantly, LBM accounted for, on average, over 50% of the total mass lost, which highlights the disparity between military personnel and their civilian counterparts, who experience similar reductions in total body mass with generally no appreciable decrement in LBM (98,99).…”

Section: Future Directions and Conclusionmentioning

confidence: 99%

Optimized dietary strategies to protect skeletal muscle mass during periods of unavoidable energy deficit

2014

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Interactions between dietary protein and energy balance on the regulation of human skeletal muscle protein turnover are not well described. A dietary protein intake above the recommended dietary allowance during energy balance typically enhances nitrogen retention and up-regulates muscle protein synthesis, which in turn may promote positive protein balance and skeletal muscle accretion. Recent studies show that during energy deficit, muscle protein synthesis is down-regulated with concomitant increases in ubiquitin proteasome-mediated muscle proteolysis and nitrogen excretion, reflecting the loss of skeletal muscle mass. However, consuming high-protein diets (1.6-2.4 g/kg per day), or high-quality, protein-based meals (15-30 g whey) during energy deficit attenuates intracellular proteolysis, restores muscle protein synthesis, and mitigates skeletal muscle loss. These findings are particularly important for physically active, normal-weight individuals because attenuating the extent to which skeletal muscle mass is lost during energy deficit could prevent decrements in performance, reduce injury risk, and facilitate recovery. This article reviews the relationship between energy status, protein intake, and muscle protein turnover, and explores future research directives designed to protect skeletal muscle mass in physically active, normal-weight adults.

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Changes in Maximum Muscle Strength and Rapid Muscle Force Characteristics after Long-Term Special Support and Reconnaissance Missions: A Preliminary Report

Abstract: Eight days of immobilization during a covert SSR mission by Special Forces soldiers led to substantial decrements in maximal muscle force and especially in rapid muscle force capacity. This may negatively influence the ability for rapid exfiltration and redeployment, respectively.

Cited by 15 publications

References 17 publications

Changes in muscle strength and morphology after muscle unloading in Special Forces missions

Changes in muscle strength and morphology after muscle unloading in Special Forces missions

Alterations in molecular muscle mass regulators after 8 days immobilizing Special Forces mission

Optimized dietary strategies to protect skeletal muscle mass during periods of unavoidable energy deficit

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