Effect of Shoulder Position on Scapular Muscle Activity during Scapular Protraction

Purpose@#This study was to evaluate several tasks performed at a high intensity in terms of their ability to elicit EMG activity in the serratus anterior by comparing the EMG activities of the serratus anterior, upper trapezius, and lower trapezius muscles during six tasks combined shoulder flexion with rotation. @*Methods@#Fifteen healthy males were recruited to this study. Each subject was instructed to assume a sitting position without back support and asked to flex (90° or 120°) the right shoulder and protract the scapula in the sagittal plane with maximal external rotation; to assume a neutral position; or to internally rotate the glenohumeral joint. The EMG data were collected from the serratus anterior (SA), upper trapezius (UT), and lower trapezius (LT) muscles were normalized to maximum voluntary isometric contraction. The UT/LT and UT/SA muscle activity ratios in each task were assessed by calculating the surface EMG. Data were analyzed by two-way repeated-measures analysis of variance, with the level of significance set at p<0.05. @*Results@#The results of this study, shoulder flexion with external rotation resulted in low upper trapezius/serratus anterior and upper trapezius/lower trapezius ratios and a relatively high level of serratus anterior activation. @*Conclusion@#Shoulder flexion with external rotation used herein may be considered as important for clinical interventions aimed at selectively increasing SA strengthen and clinical selection of exercises for improving glenohumeral joint and scapulothoracic control.

Effect of Shoulder Abduction Angles on EMG Activity of the Abdominal Muscles during Single Leg Holding on the Foam Roller

Purpose@#This study examined the electromyography (EMG) activity of the abdominal muscles and the ratio of the oblique abdominal muscle activity to the rectus abdominis muscle during a single-leg holding position with isometric shoulder abduction (SLHISA) in the supine position on a foam roller. @*Methods@#Nineteen healthy males were recruited to the study. Each subject was asked to lay on a round foam roller and perform single-leg (nondominant) holding with contralateral shoulder abduction to one of three angles (45°, 90°, or 135°) in random order. The surface EMG signals of the bilateral rectus abdominis (RA), external oblique abdominis (EO), and combined internal oblique abdominis (IO) and transverse abdominis (TrA) muscle were collected during the tasks. The EO/RA and (IO & TrA)/RA ratios were determined using surface EMG. One way repeated measure ANOVA with three SLHISAs was used to assess the significant abdominal muscle EMG activity and the ratio of the oblique abdominal muscles activity to the RA muscle. The statistical significance level was p<0.05. @*Results@#The results were as follows. The SLHISA 135° showed significantly higher EMG activity of both RAs, left EO, and right IO & TrA muscles (p<0.05). The right EO and left IO and TrA muscles/RA were significantly different among the SLHISA angles. The SLHISA 45° showed a significantly greater ratio of right EO/RA and left IO & TrA/RA (p<0.05). @*Conclusion@#SLHISA on a foam roller is useful for lumbopelvic stabilization exercise by increasing the activity and recruiting a specific pattern of the oblique abdominal muscle.

Effect of Shoulder Position on Scapular Muscle Activity during Scapular Protraction

Purpose@#This study was to evaluate several tasks performed at a high intensity in terms of their ability to elicit EMG activity in the serratus anterior by comparing the EMG activities of the serratus anterior, upper trapezius, and lower trapezius muscles during six tasks combined shoulder flexion with rotation. @*Methods@#Fifteen healthy males were recruited to this study. Each subject was instructed to assume a sitting position without back support and asked to flex (90° or 120°) the right shoulder and protract the scapula in the sagittal plane with maximal external rotation; to assume a neutral position; or to internally rotate the glenohumeral joint. The EMG data were collected from the serratus anterior (SA), upper trapezius (UT), and lower trapezius (LT) muscles were normalized to maximum voluntary isometric contraction. The UT/LT and UT/SA muscle activity ratios in each task were assessed by calculating the surface EMG. Data were analyzed by two-way repeated-measures analysis of variance, with the level of significance set at p<0.05. @*Results@#The results of this study, shoulder flexion with external rotation resulted in low upper trapezius/serratus anterior and upper trapezius/lower trapezius ratios and a relatively high level of serratus anterior activation. @*Conclusion@#Shoulder flexion with external rotation used herein may be considered as important for clinical interventions aimed at selectively increasing SA strengthen and clinical selection of exercises for improving glenohumeral joint and scapulothoracic control.

Effect of Shoulder Abduction Angles on EMG Activity of the Abdominal Muscles during Single Leg Holding on the Foam Roller

Purpose@#This study examined the electromyography (EMG) activity of the abdominal muscles and the ratio of the oblique abdominal muscle activity to the rectus abdominis muscle during a single-leg holding position with isometric shoulder abduction (SLHISA) in the supine position on a foam roller. @*Methods@#Nineteen healthy males were recruited to the study. Each subject was asked to lay on a round foam roller and perform single-leg (nondominant) holding with contralateral shoulder abduction to one of three angles (45°, 90°, or 135°) in random order. The surface EMG signals of the bilateral rectus abdominis (RA), external oblique abdominis (EO), and combined internal oblique abdominis (IO) and transverse abdominis (TrA) muscle were collected during the tasks. The EO/RA and (IO & TrA)/RA ratios were determined using surface EMG. One way repeated measure ANOVA with three SLHISAs was used to assess the significant abdominal muscle EMG activity and the ratio of the oblique abdominal muscles activity to the RA muscle. The statistical significance level was p<0.05. @*Results@#The results were as follows. The SLHISA 135° showed significantly higher EMG activity of both RAs, left EO, and right IO & TrA muscles (p<0.05). The right EO and left IO and TrA muscles/RA were significantly different among the SLHISA angles. The SLHISA 45° showed a significantly greater ratio of right EO/RA and left IO & TrA/RA (p<0.05). @*Conclusion@#SLHISA on a foam roller is useful for lumbopelvic stabilization exercise by increasing the activity and recruiting a specific pattern of the oblique abdominal muscle.