Upper-limb surface electro-myography at maximum supination and pronation torques: the effect of elbow and forearm angle

Abstract

Forearm pronation and supination, and increased muscular activity in the wrist extensors have been both linked separately to work-related injuries of the upper limb, especially humeral epicondylitis. However, there is a lack of information on forearm torque strength at ranges of elbow and forearm angles typical of industrial tasks. There is a need for strength data on forearm torques at different upper limb angles need to be investigated. Such study should also include the measurement of muscular activity for the prime torque muscles and also other muscles at possible risk of injury due to high exertion levels during tasks requiring forearm torques.Twenty-four male subjects participated in the study that involved maximum forearm torque exertions for the right arm, in the pronation and supination directions, and at four elbow and three forearm rotation angles. Surface EMG (SEMG) was used to evaluate the muscular activity of the pronator teres (PT), pronator quadratus (PQ), biceps brachi (BB), brachioradialis (BR), mid deltoid (DT) and the extensor carpi radialis brevis (ECRB) during maximum torque exertions. Repeated measures ANOVA indicated that both direction and forearm angle had a significant effect on the maximum torques (p<0.05) while elbow angle and the interactions were highly significant (p<0.001). The results revealed that supination torques were stronger overall with a mean maximum value of 16.2 Nm recorded for the forearm 75% prone. Mean maximum pronation torque was recorded as 13.1 Nm for a neutral forearm with the elbow flexed 45 0 . The data also indicated that forearm angle had a greater effect on supination torque than pronation torque. Supination torques were stronger for the mid range of elbow flexion, but pronation torques increased with increasing elbow extension. The strength profiles for the maximum torque exertions were reflected in the EMG changes in the prime supinators and pronators. In addition, the EMG data expressed as the percentage of MaximumVoluntary Electrical activity (MVE), revealed high muscular activity in the ECRB for both 3 supination (26-43% MVE) and pronation torques (17-55% MVE). The results suggest that the ECRB acts as a stabiliser to the forearm flexors for gripping during pronation torques depending on forearm angle, but acts as a prime mover in wrist extension for supination torques with little effect of elbow and forearm angle. This indicates a direct link between forearm rotations against resistance and high muscular activity in the wrist extensors, thereby increasing stress on the forearm musculo-skeletal system, especially the lateral epicondyle.4

Effect of Elbow Flexion, Forearm Rotation and Upper Arm Abduction on MVC Grip and Grip Endurance Time

“…Then, the participant was asked again to press up to maximum grip after a minimum recovery time of 2 min or until he felt no discomfort. The recovery time was set according to O'Sullivan and Gallwey [30] and Mukhopadhyay et al [29]. The greater of the two was recorded as the MVC grip for that particular treatment condition for the participant.…”

“…Moreover, they did not investigate the effect on endurance time, which is most important in tool and work design. Therefore, for the present study, three levels of upper arm abduction (0°, 45° and 90°) in combination with three levels of elbow flexion (45°, 90° and 135°) (in line with Mukhopadhyay et al) and three levels of forearm rotation (0° and 60° in prone and supine) (in line with Kattel et al [1] and O'Sullivan and Gallwey [30]) were chosen. In this study, 0° forearm rotation was the position of the forearm, while the wrist was in the plan formed by the axis of the forearm and upper arm.…”

A Robotic Platform to Assess, Guide and Perturb Rat Forelimb Movements

“…No scientific literature was found reporting the maximum pronation and supination torques of the rat forelimb. These values were determined based on the study of O'Sullivan and Gallwey which examined pronation and supination torques in human male subjects (O'Sullivan and Gallwey 2002), and downscaled with respect to the mass of the rat, assuming a proportional relationship between mass and achievable torque according to the laws of similitude. This resulted in a 49mNm maximum pronation and 61mNm maximum supination torques estimation.…”

New Assessment of Forearm Strength: Reliability and Validity

“…The elbow has often been set in a position of 90°flexion (Gordon, Pardo, Johnson, King, & Miller, 2004;Shigeyama et al, 1997), a position found to maximize supination strength (O'Sullivan & Gallwey, 2002) because the position optimizes the moment arm of the biceps. Pronation strength was strongest in 45°elbow flexion (O'Sullivan & Gallwey, 2002). The position of the forearm has also been found to affect forearm strength and muscle activity.…”

“…The position of the forearm has also been found to affect forearm strength and muscle activity. On the one hand, strength has been greatest when the relevant muscles were lengthened (i.e., supination torque was greatest in a pronated forearm position and vice versa; Matsuoka et al, 2006;O'Sullivan & Gallwey, 2002). On the other hand, forearm muscle activation as measured with electromyography has been greater when the muscle was in the shortened position (i.e., supination activation was greatest in the supinated position; Gordon et al, 2004).…”