Dataset Information

Metabolic, cardiovascular, neuromuscular and perceptual responses to repeated military-specific load carriage treadmill simulations.

ABSTRACT: Bouts of military load carriage are rarely completed in isolation; however, limited research has investigated the physiological responses to repeated load carriage tasks. Twelve civilian men (age, 28 ± 8 years; stature, 185.6 ± 5.8 cm; body mass 84.3 ± 11.1 kg and maximal oxygen uptake, 51.5 ± 6.4 mL·kg^-1 min^-1) attended the laboratory on two occasions to undertake a familiarisation and an experimental session. Following their familiarisation session, participants completed three bouts of a fast load carriage protocol (FLCP; ∼65 min), carrying 25 kg, interspersed with a 65-min recovery period. Physiological strain (oxygen uptake [V̇O₂] and heart rate [HR]) was assessed during the FLCP bouts, and physical performance assessments (weighted counter-movement jump [wCMJ], maximal isometric voluntary contraction of the quadriceps [MIVC] and seated medicine ball throw [SMBT]) was measured pre and post each FLCP bout. A main effect for bout and measurement time was evident for V̇O₂ and HR (both p < 0.001 and Ѡ² = 0.103-0.816). There was no likely change in SMBT distance (p = 0.201 and Ѡ² = 0.004), but MIVC peak force reduced by approximately 25% across measurement points (p < 0.001 and Ѡ² = 0.133). A mean percentage change of approximately -12% from initial values was also evident for peak wCMJ height (p = 0.001 and Ѡ² = 0.028). Collectively, these data demonstrate that repeated FLCP bouts result in an elevated physiological strain for each successive bout, along with a substantial reduction in lower body power (wCMJ and MIVC). Therefore, future research should investigate possible mitigation strategies to maintain role-related capability.

SUBMITTER: Vine CAJ

PROVIDER: S-EPMC11295085 | biostudies-literature | 2024 Aug

REPOSITORIES: biostudies-literature

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Metabolic, cardiovascular, neuromuscular and perceptual responses to repeated military-specific load carriage treadmill simulations.

Vine Christopher A J CAJ Coakley Sarah L SL Blacker Sam D SD Runswick Oliver R OR Myers Stephen D SD

European journal of sport science 20240617 8

Bouts of military load carriage are rarely completed in isolation; however, limited research has investigated the physiological responses to repeated load carriage tasks. Twelve civilian men (age, 28 ± 8 years; stature, 185.6 ± 5.8 cm; body mass 84.3 ± 11.1 kg and maximal oxygen uptake, 51.5 ± 6.4 mL·kg<sup>-1</sup> min<sup>-1</sup>) attended the laboratory on two occasions to undertake a familiarisation and an experimental session. Following their familiarisation session, participants completed ...[more]

PMID: 38886977

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Project description:UnlabelledTrekking and military missions generally consist of carrying heavy loads for extreme durations. These factors have been separately shown to be sources of neuromuscular (NM) fatigue and locomotor alterations. However, the question of their combined effects remains unresolved, and addressing this issue required a representative context.PurposeThe aim was to investigate the effects of extreme-duration heavy load carriage on NM function and walking characteristics.MethodsTen experienced infantrymen performed a 21-h simulated military mission (SMM) in a middle-mountain environment with equipment weighing ∼27 kg during battles and ∼43 kg during marches. NM function was evaluated for knee extensors (KE) and plantar flexors (PF) pre- and immediately post-SMM using isometric maximal voluntary contraction (MVC) measurement, neural electrical stimulation and surface EMG. The twitch-interpolation method was used to assess central fatigue. Peripheral changes were examined by stimulating the muscle in the relaxed state. The energy cost, mechanical work and spatio-temporal pattern of walking were also evaluated pre-/post-SMM on an instrumented treadmill in three equipment conditions: Sportswear, Battle and March.ResultsAfter the SMM, MVC declined by -10.2±3.6% for KE (P<0.01) and -10.7±16.1% for PF (P = 0.06). The origin of fatigue was essentially peripheral for both muscle groups. A trend toward low-frequency fatigue was detected for KE (5.5%, P = 0.08). These moderate NM alterations were concomitant with a large increase in perceived fatigue from pre- (rating of 8.3±2.2) to post-SMM (15.9±2.1, P<0.01). The SMM-related fatigue did not alter walking energetics or mechanics, and the different equipment carried on the treadmill did not interact with this fatigue either.Conclusionthis study reports the first data on physiological and biomechanical consequences of extreme-duration heavy load carriage. Unexpectedly, NM function alterations due to the 21-h SMM were moderate and did not alter walking characteristics.Clinical trial registrationName: Effect of prolonged military exercises with high load carriage on neuromuscular fatigue and physiological/biomechanical responses. Number: NCT01127191.

Project description:We examined the effects of repeated sprint training (RST) session volume on acute physiological, neuromuscular, perceptual and performance outcomes. In a randomised, counterbalanced, and crossover design, 14 healthy and trained male and female athletes (age: 23 ± 3 years) completed two sets of 10 × 40 m (10 × 40), 5 × 40 m (5 × 40), 10 × 20 m (10 × 20) and 5 × 20 m (5 × 20) sprints with 30 s rest between repetitions and 3 min rest between sets for all protocols. Average and peak heart rate, average oxygen consumption (VO2), time >90% of maximal oxygen consumption (VO2max), differential ratings of perceived exertion (RPE), session-RPE training load (sRPE-TL), percentage sprint decrement (Sdec), acceleration load and distance >90% of maximal sprint speed were recorded during each session. Neuromuscular performance (i.e. countermovement jump, lower-limb stiffness and isometric hamstring strength) were measured post-session, 24 h, and 48 h and compared to pre-session. A univariate analysis of variance was used to compare within- and between-protocol differences. To aid data interpretation, all effects were expressed as an effect size and accompanied by probability values (pMET). The 10 × 40 protocol induced the greatest training load compared to all other protocols (pMET < 0.05), including moderate to very large differences in breathlessness RPE, large differences in Sdec and time >90% VO2max and very large differences in sRPE-TL. The 5 × 20 protocol induced the lowest training load compared to all other protocols (pMET < 0.05), including moderate to large differences in sRPE-TL and leg muscle RPE. Heart rate, VO2, sRPE-TL, leg muscle RPE and Sdec were similar between 5 × 40 and 10 × 20 (pMET < 0.05), but the acceleration load was greater for 10 × 20 when compared to 5 × 40 (pMET < 0.001), and this difference was large. Changes in neuromuscular performance across all timepoints and all protocols were unclear. Larger session volumes increase the demands of RST and by manipulating volume, sprint distance and the number of repetitions, practitioners can alter the internal and external training load.

Project description:Discomfort during load carriage is a major issue for activities using backpacks (e.g. infantry maneuvers, children carrying school supplies, or outdoor sports). It is currently unclear which mechanical parameters are responsible for subjectively perceived discomfort. The aim of this study was to identify objectively measured mechanical predictors of discomfort during load carriage. We compared twelve different configurations of a typical load carriage system, a commercially available backpack with a hip belt. The pressure distribution under the hip belt and the shoulder strap, as well as the tensile force in the strap and the relative motion of the backpack were measured. Multiple linear regression analyses were conducted to investigate possible predictors of discomfort. The results demonstrate that static peak pressure, or alternatively, static strap force is a significant (p<0.001) predictor of discomfort during load carriage in the shoulder and hip region, accounting for 85% or more of the variation in discomfort. As an additional finding, we discovered that the regression coefficients of these predictors are significantly smaller for the hip than for the shoulder region. As static peak pressure is measured directly on the body, it is less dependent on the type of load carriage system than static strap force. Therefore, static peak pressure is well suited as a generally applicable, objective mechanical parameter for the optimization of load carriage system design. Alternatively, when limited to load carriage systems of the type backpack with hip belt, static strap force is the most valuable predictor of discomfort. The regionally differing regression coefficients of both predictors imply that the hip region is significantly more tolerant than the shoulder region. In order to minimize discomfort, users should be encouraged to shift load from the shoulders to the hip region wherever possible, at the same time likely decreasing the risk of low back pain or injury.

Dataset Information

Metabolic, cardiovascular, neuromuscular and perceptual responses to repeated military-specific load carriage treadmill simulations.

Publications

Metabolic, cardiovascular, neuromuscular and perceptual responses to repeated military-specific load carriage treadmill simulations.

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