The aim of this study was to evaluate the acute effect of the use of stable and unstable surfaces on electromyography (EMG) activity and coactivation of the scapular and upper-limb muscles during the push-up plus (with full protraction of the scapula). Muscle activation of anterior deltoid (AD), posterior deltoid (PD), pectoralis major, biceps brachii (BB), triceps brachii (TB), upper trapezius (UT), middle trapezius (MT), lower trapezius (LT), and serratus anterior (SA) levels and coactivation index were determined by surface EMG in 20 young men during push-up plus performed on a stable and unstable condition (2 unstable devices applied to hands and feet). The paired t test and Cohen d were used for statistical analysis. The results showed that during the execution of the push-up plus on the unstable surface an increased EMG activity of the scapular stabilizing muscles (SA, MT, and LT) was observed, while AD and PD muscles showed a decrease. During exercise execution on the unstable surface there was a higher index of coactivation of the scapular muscles (SA-MT and UT-LT pairs). No significant differences were observed in TB-BB and AD-PD pairs. These results suggest that the push-up-plus exercise associated with unstable surfaces produced greater EMG activity levels and coactivation index of the scapular stabilizing muscle. On the other hand, the use of an unstable surface does not promote the same effect for the shoulder muscles.

No abstract

Scapular dyskinesis is the term used to describe changes in the positioning or movement of the scapula. Such dysfunction is associated with changes in the activation of the scapular muscles. However, the influence of the axial muscles on the scapular muscles activity of subjects with scapular dyskinesis is unknown. This study aimed to compare the electromyography (EMG) activity of periscapular muscles and its correlation with the external oblique muscle during the execution of push-up performed in different surfaces, in volunteers with and without scapular dyskinesis. Thirty-six men, divided in two groups (control and dyskinesis), performed push-up on stable and unstable surface. The EMG activity of serratus anterior (SA_5th and SA_7th fibers), upper (UT) and lower (LT) trapezius, external oblique (EO) was recorded during execution of each task condition. Statistical analyzes were performed using two way ANOVA repeated measures and Pearson correlation. It was observed effect of interaction between factors, being evidenced increased activity of UT, SA_7th and OE for the control group and decreased activity of SA_5th, SA_7th and EO for dyskinesis group during execution of push-up on unstable surface. In both groups positive correlations (r > 0.47) were observed between EMG activity of SA and EO. In the exercises tested, there seems to be an anatomical and functional relationship between the SA and EO muscles. The use of the unstable surface promotes increased neuromuscular demand, but the neuromuscular strategies appear to differ between groups.

Context: Stretching intensity is an important variable that can be manipulated with flexibility training. However, there is a lack of evidence regarding this variable and its prescription in stretching programs. Objective: To investigate the effects of 12 weeks of knee flexor static stretching at different intensities on joint and muscle mechanical properties. Design: A randomized clinical trial. Setting: Laboratory. Participants: A total of 14 untrained men were allocated into the low- or high-intensity group. Main Outcome Measures: Assessments were performed before, at 6 week, and after intervention (12 wk) for biceps femoris long head architecture (resting fascicle length and angle), knee maximal range of motion (ROM) at the beginning and maximal discomfort angle, knee maximal tolerated passive torque, joint passive stiffness, viscoelastic stress relaxation, knee passive torque at a given angle, and affective responses to training. Results: No significant differences were observed between groups for any variable. ROM at the beginning and maximal discomfort angle increased at 6 and 12 weeks, respectively. ROM significantly increased with the initial angle of discomfort (P < .001, effect size = 1.38) over the pretest measures by 13.4% and 14.6% at the 6- and 12-week assessments, respectively, and significantly improved with the maximal discomfort angle (P < .001, effect size = 1.25) by 15.6% and 18.8% from the pretest to the 6- and 12-week assessments, respectively. No significant effects were seen for muscle architecture and affective responses. Initial viscoelastic relaxation for the low-intensity group was lower than ending viscoelastic relaxation. Conclusion: These results suggest that stretching with either low or high discomfort intensities are effective in increasing joint maximal ROM, and that does not impact on ROM, stiffness, fascicle angle and length, or affective response differences.

Objective: To evaluate the effects of 24 weeks of strength training on stable (ST) and unstable surfaces (UST) on the functional mobility, balance, and concern about falling in healthy older adults, younger than 70. Design: A single-center randomized clinical trial.Participants: Sixty-four older adults (58 females and 6 males; 68 years) were randomized into control, ST, or UST groups. Interventions: Both ST and UST intervention groups received a core muscle, upper, and lower limb moderate-intensity strength exercises using stable and unstable surfaces. The classes were performed three times per week over a 24-week period. The control group did not receive any type of active intervention. Measurements: The primary outcome measures were the dynamic balance (Berg Balance Scale (BBS)) and functional mobility (timed up and go (TUG) test). The secondary outcomes included the sitting and rising test (SRT) and Falls Efficacy Scale-International (FESI) scores. Results: There was a significant improvement in balance performance (BBS = +4 points) after 24 weeks of both ST (+1.22; 95% CI, −0.19 to 2.63) and UST (+2.26; 95% CI, 0.83-3.70) compared with the control group. Additionally, compared with the control, only UST experienced functional mobility gains (TUG = −2.44; 95% CI, −4.41 to −0.48; SRT = +1.12; 95% CI, 0.08-2.17) and decreased concern about falling (FESI = −4.41; 95% CI, −9.30 to −0.27). Conclusion: Long-term ST with and without unstable devices was effective to improve dynamic balance in older adults. Furthermore, the effects of UST were extended to functional mobility gains and reduced concern about falling. K E Y W O R D Sexercise, instability, resistance training