Isometric axial rotation of the trunk in the neutral posture

Abstract

The purpose of this study was to measure the torque, the magnitude of the electromyogram (EMG) signal and the phase relationship of 14 muscles during trunk axial rotation. Fifty normal healthy volunteers (27 males and 23 females) with no lower-back injury participated in the study. The subjects were seated in an upright position in the axial rotation tester (AROT) after applying surface electrodes bilaterally to the following muscles: pectoralis major, rectus abdominis, external oblique, internal oblique, latissimus dorsi, and erector spinae at T10 and L3. They were stabilized from the hip down, and the shoulder harness of the AROT was applied to their shoulders. These subjects performed maximal isometric axial rotations to the left and right in a random order. The torque and 14 channels of EMG were monitored, and their magnitude, slope of the increase in magnitude, and timing of the anticipation and onset activity were determined. The results revealed that the females produced 65% of the torque of their male counterparts. The pattern and magnitude of EMG in performing these tasks were significantly different between males and females (P<0.01). Males generated the greatest activity in their ipsilateral latissimus dorsi followed by their contralateral external oblique muscles. In the females, maximal EMG activity was observed in their contralateral pectoralis muscle. Thus, under the current experimental conditions, the females employed a different muscle recruitment strategy compared to the males. Each muscle involved in axial rotation was significantly different from the other (P < 0.01). The timing pattern for these activities was inconsistent, implying that there is no fixed-order phasic recruitment of the torso muscles during maximal isometric axial rotation.

Relationship between side medicine-ball throw performance and physical ability for male and female athletes

“…The magnitude of the torque (Table 2) and ratio between males and females that was 100:62 in the present study during IMTRT was similar to a previous study (Kumar et al 2001) in which the ratio between males and females was 100:65. With respect to the relationship between isometric strength and dynamic performance, a number of studies reported these relationships (Mero et al 1981;Stone et al 2003b;Young et al 1995;Murphy and Wilson 1996;Viitasalo et al 1981).…”

“…It is likely that these strength relations in females aVected the contributing factors to S-MBT and FS-MBT. Kumar et al (2001) reported that females use the contralateral pectoralis muscles to generate rotary torque to compensate for a weakness in abdominal and back muscles, while males recruit the external oblique and latissimus dorsi muscles. Based on this report, it is possible that females could not similarly recruit their trunk rotator muscles during S-MBT and FS-MBT tests.…”

“…Kaneko et al (1989Kaneko et al ( , 1990 reported that the value of isometric maximal trunk rotation torque of javelin throwers was superior to that of normal young males in the right rotation, which is contrary to the throwing rotation for right-handed males. Kumar et al (2001) revealed that the females showed a diVerent EMG pattern compared to the males during isometric maximal trunk rotation.…”

Postural Muscle Tone in the Body Axis of Healthy Humans

“…The average T max of the neck muscles has been estimated at 15 Nm in males and 6 Nm in females (Vasavada et al 1998). The average T max of the trunk muscles has been estimated at 97 Nm in standing males and 60 Nm in females (Kumar and Panjabi 1995;Kumar et al 2001;McGill and Hoodless 1990;Ng et al, 2001;Perez and Nussbaum 2002). Finally, the average T max of internal hip rotation has been estimated to be 60% of that of the trunk in males and 65% in females (Stoll et al 2000).…”

Trunk Muscle Activity in Two-Leg Standing to One-Leg Standing in Healthy Elderly Adults

“…OI has been reported to be active with ipsilateral trunk rotation [18][19][20][21][22][23] . Though the stronger activity is o b s e r v e d i n r e s e a r c h u s i n g a t hi n n e e d l e electromyograph in the lower region of the OI in the inside, there is no difference in the direction of rotation in the intermediate place.…”