Training-Induced Acute Neuromuscular Responses to Military Specific Test during a Six-Month Military Operation.

Kai Pihlainen,Jani P Vaara,Jani Raitanen,Joonas Helén,Taija Finni,Arto J Pesola,Heikki Kyröläinen,Tommi Ojanen,Keijo Häkkinen,Matti Santtila

doi:10.3390/ijerph18010215

Abstract

Limited data are available regarding strength and endurance training adaptations to occupational physical performance during deployment. This study assessed acute training-induced changes in neuromuscular (electromyography; EMG) and metabolic (blood lactate, BLa) responses during a high-intensity military simulation test (MST), performed in the beginning (PRE) and at the end (POST) of a six-month crisis-management operation. MST time shortened (145 ± 21 vs. 129 ± 16 s, −10 ± 7%, p < 0.001) during the operation. Normalized muscle activity increased from PRE to POST in the hamstring muscles by 87 ± 146% (116 ± 52 vs. 195 ± 139%EMGMVC, p < 0.001) and in the quadriceps by 54 ± 81% (26 ± 8 vs. 40 ± 20%EMGMVC, p < 0.001). In addition, higher acute BLa values were measured after MST during POST. Changes in BLa and EMG suggested an increased neural input and metabolic rate during POST MST, likely leading to faster performance times at the end of the operation. High EMG values throughout the different phases of MST suggested that despite the anaerobic nature of the test, the soldiers were able to maintain their voluntary muscle activation level until the end of the test. This indicates only limited neural fatigue during the two-minute high-intensity military specific performance. While learning effect may explain some part of the improvement in the MST performance times, combined strength and endurance training three times per week may improve neuromuscular performance in occupationally relevant tasks.

Highlights

EMG amplitude of quadriceps femoris (QF) increased by 10% in the MVC measurement
The military simulation test (MST) performance was improved by 10% (145 ± 21 vs. 129 ± 16 s, ps < 0.001)
Combined strength and endurance training performed on average, three times per week during the deployment, likely increased the activation of the thigh muscles, and resulted in improved occupational performance of soldiers, assessed with MST. This would be expected, since our prior study showed that 66% of the variance in the MST time was explained by explosive strength of the lower extremities, muscle mass, endurance running performance, and muscle endurance of the upper extremity extensor muscles [13]

Summary

Introduction

Several duties performed during military operations such as patrolling in combat gear and material handling tasks are physically demanding [1,2]. Maintenance of physical performance may be challenged during deployments due to increased environmental and operative demands, mental and physical stress, as well as limited access and time to train [3,4]. Several studies have reported decreases in aerobic fitness after prolonged (>nine months) military deployments [5,6,7,8]. Neuromuscular performance may be attenuated within a few weeks of detraining [9]. Deterioration of physical fitness may have a negative impact on occupational performance and combat readiness during sustained military operations.

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