Muscle tissue oxygenation, pressure, electrical, and mechanical responses during dynamic and static voluntary contractions

Abstract

Dynamic muscle contractions have been shown to cause greater energy turnover and fatigue than static contractions performed at a corresponding force level. Therefore, we hypothesized that: (1) electro- (EMG) and mechanomyography (MMG), intramuscular pressure (IMP), and reduction in muscle oxygen tension (rTO(2)) would be larger during dynamic (DYN) than intermittent static (IST) low force contractions; and that (2) oxygen tension would remain lower in the resting periods subsequent to DYN as compared to those following IST. Eight subjects performed elbow flexions with identical time-tension products: (1) DYN as a 20 degrees elbow movement of 2 s concentric and 2 s eccentric followed by a 4 s rest; and (2) IST with a 4 s contraction followed by a 4 s rest. Each session was performed for 1 min at 10 and 20% of the maximal voluntary contraction (MVC). The force, bipolar surface EMG, MMG, IMP, rTO(2) were measured simultaneously from the biceps brachii, and the data presented as the mean values together with the standard error of the means. Comparison of the corresponding time periods showed the EMG(rms) and MMG(rms) values to be larger during DYN than IST (concentric phase: DYN vs IST were 14.2 vs 9.4, and 22.0 vs 15.9%(max)-EMG(rms); eccentric phase: in DYN, the MMG was approximately 1.5 and approximately 2.0-fold IST at 10 and 20%MVC, respectively). In contrast, the IMP of the concentric phase in DYN was lower than in IST (2.3 vs 29.5 and 10.9 vs 42.0 mmHg at 10 and 20%MVC, respectively), and a similar picture was seen for the eccentric phase. However, no differences were seen in rTO(2) in either the contraction or the rest periods. In a prolonged rest period (8 s) after the sessions, DYN but not IST showed rTO(2) above baseline level. In conclusion, rTO(2) in DYN and IST were similar in spite of major differences in the MMG and EMG responses of the muscle during contraction periods. This may relate to the surprisingly lower IMP in DYN than IST.

Optimal Elbow Angle for MMG Signal Classification of Biceps Brachii during Dynamic Fatiguing Contraction

“…The accelerometer was placed on the muscle belly of the biceps Brachii, without covering the end plate zone or getting too close to the musculotendinous region [24]. A flexible electrogoniometer (Biometrics Ltd.) was placed on the lateral side of the arm to measure the elbow angle and arm oscillations.…”

Work-related musculoskeletal disorders in sonographers: a review of causes and types of injury and best practices for reducing injury risk

“…Research has shown that work can be maintained for several hours per day without symptoms of fatigue if the force exerted does not exceed approximately 10% of the maximum force of the muscle involved. [18][19][20] When the frequency and duration of loading exceeds the ability of the muscles and tendons to adapt, inflammation occurs, followed by degeneration, microtears, and scar formation. 15,18 Muscles and tendons are designed to stretch and to be used regularly; therefore, an important injury prevention strategy is movement.…”

Effects of dynamic and static handgrip exercises on hand and wrist volume

“…During repetitive dynamic contraction, arterial blood Xow continuously increases during the relaxation phase after each contraction (Bystrom and Kilbom 1990), thereby accumulating a larger amount of arterial blood volume. Also, it has been demonstrated that intramuscular pressure response is smaller during dynamic contraction than intermittent static contraction, indicating that blood Xow is larger during dynamic contraction than intermittent static contraction (Vedsted et al 2006). In addition, increases in cardiac output are larger during dynamic handgrip exercise than during static handgrip exercise (Lewis et al 1985).…”

“…To compare static and dynamic handgrip exercises, the index of identical time-tension products was used. The identical accumulation of force development over a given period of time is a standard method when comparing dynamic and static exercises (Vedsted et al 2006). Both dynamic and static handgrip exercises consisted of six sets of 30-s contractions with 10-s rest intervals between exercise bouts.…”