"The effect of motion and inversion on neuromuscular and cardiovascular systems"

Abstract

The purpose of the study was to analyze the effect of inversion with wave motion on the functioning of cardiovascular and neuromuscular systems. Cardiovascular system was assessed by measuring the heart rate response and neuromuscular system was analyzed by measuring maximum voluntary contraction (MVC) force and electromyography (EMG). Force production and electromyographic (EMG) activity for elbow flexors and knee extensors were measured along with muscle activation of trunk and abdominal muscles. Heart rate was measured before and after each experimental procedure. All the parameters were tested in upright and inverted seated position with wave motions. Both positions were combined with 3 sets (pitch, roll and random, all combined with heave) wave motions and were selected randomly. Pitch, roll and heave are types of wave motion, where random was combining all the three types of wave motion together. Each experimental procedure lasted I minute and subjects performed two isometric MVCs for the right elbow flexors and right knee extensors at beginning and at the end of one minute. Results showed that wave motion induced significantly less knee extension MVC force (Pitch = 8%; Roll = 13.4%; Random = 13.5%, P < 0.0001) and significant less elbow flexors MVC force (Pitch = 21.1 %; Roll = 26.7%; Random = 25.1 %, p < 0.000 I). A main effect for time showed that there was a significant drop in EMG activity with the second MVC (compared to first MVC) for vastus lateralis (15.4 %, p = .0024). biceps brachii (11.7 %, p = 05). lower abdominal structure (LAS) and external obliques muscles (12.5 %. p = .034). A significant increase in heart rate (18.1 %.p=.OOOI)wasseenpostexperimentalproceduresin upright seated position compared to before the start of the procedure. The results were evaluated by keeping position, time and wave motion as factors. Tlie aforementioned results suggest significant neuromuscular impairments and heart rate responses with wave motion and inversion combined over time. The results of this study provide both basic physiological mechanisms and applications to life threatening situations such as submerged helicopters subjected to wave motions as well as overturned vehicles among other situations.