Muscle Activation Rate Variations During Pull-ups: Post-training Assessment Using An Innovative Assisting Device

PURPOSE: For college students with limited pull-up capacity, performing assisted pull-ups can be a good way for them to develop requisite pulling strength. Traditional pull-up assisting methods often alter posture or prove cumbersome. To this end, researchers introduced a new device which is not only easy to operate, but also make performers stay standing posture during training. This study aims to assess the efficacy of an 8-weeks strength training program utilizing the proposed pull-up assisting device in enhancing maximum pull-up repetitions among students, and to investigate potential differences in muscle activation between pretest and posttest sessions. METHODS: 47 male participants (age = 19.3 ± 1.5 years, height = 176.35 ± 5.40 cm, weight = 67.7 ± 8.8) were recruited and divided into 2 groups. Group 1 accepted an intervention of 8 weeks by the assisting device, Group 2 was set as a contrast group without any intervention. EMG signals of 8 muscles on the dominant side were examined: brachioradialis(BR), biceps brachii(BB), Posterior deltoid(PD), pectoralis major(PM), infraspinatus(IPS), latissimus dorsi(LD), erector spinae (ES) , and external oblique(EO). Inter-group differences were assessed using Mann-Whitney U test, while within-group variations were examined through the Wilcoxon signed-rank test. RESULTS: No significant difference were observed between pretests of group1 and group2 , as well as between the pretest and posttest of group2 . However, a significant difference existed between the pretest and posttest group 1 ( 3 (2-6) vs. 8(4-16), P < 0.001). Muscle contribution rate were not normal distribution data in PM, LD and EO of group1, and PM, LSP, EO of group 2, therefore, Wilcoxon test were used for them and paired t-test were used for others. Significant difference was found in BR( 21.30% ± 7.41% vs. 17.83% ± 3.30%, P < 0.05), PD(12.98% ± 5.84% vs. 19.13% ± 7.03%, P < 0.05) and PM(8.47% (10.17%-15.02%) vs. 6.57%(7.36%-9.76%), P < 0.01) of group 1 and ES(0.0564 ± 10.0268 vs. 0.0386 ± 0.0137, p < 0.05) of group 2. CONCLUSIONS: Intervention with this novel pull-up assisting device significantly improved student’s maximum repetitions and PD activation, indicated that inadequate pulling strength of shoulder may be one of the greatest factors that hinder students from performing the pull-up.