Variations in upper limb and trunk muscles activation during isometric exercises with or without exertion of control

Abstract

BACKGROUND: Muscle activation during isometric contraction can be changed using an external-focus instruction method. OBJECTIVE: To explore and compare the activity of eight upper limb and trunk muscles during isometric chest squeeze exercises, performed in the same posture with and without the exertion of control to avoid crushing an object. METHODS: Muscle activation by an isometric chest squeeze with 45∘ shoulder abduction and forearm pronation was examined. Isometric chest squeeze exercises were performed while holding objects with maximum pressure, and with exerted control to avoid crushing the object Muscle activation was measured by surface electromyography. RESULTS: During the exercises performed while exerting control to avoid crushing the object the lower trapezius (p< 0.001) and latissimus dorsi (p= 0.03) showed significantly higher activity. During the exercises performed without control, the upper trapezius, serratus anterior, and pectoralis major showed significantly higher activity (p= 0.016, p< 0.001, p< 0.001, respectively). CONCLUSIONS: This novel isometric exercise can increase the scapular muscles in the intermediate range of the glenohumeral joint. Therefore, it may assist in improving sport performance, in preventing injuries and in rehabilitation following musculoskeletal injuries.

Trunk muscle activation in side plank exercises with and without external-focus instruction

“…In this study, a side plank exercise was performed using a paper balloon while exerting control not to crush the item. In a previous study, Murofushi et al demonstrated externally focused instruction while exerting control to avoid crushing an item maintaining a static position and holding a soft paper balloon during a chest squeeze exercise [8]. This method significantly activated the LT without involving any complicated movement.…”

“…Furthermore agonist and antagonist muscle cocontractions were found between LT and UT, Lat and PM. The greater the force exerted by the agonist muscles, the more the appropriate amount of contraction of the antagonist muscle is required to maintain the posture and joint angle [8]. Previous studies have reported that a collection of trunk muscles work synchronously to maintain and stabilize posture [18].…”

“…Data were rectified and smoothed using a root-mean-square algorithm with a 50-ms time reference. This experimental test followed the previous research method, Murofushi et al [8], not set for comparing muscle activation levels between the muscles. Rather, an amplitude comparison was made between signals from a given muscle between the two exercise tasks performed by an individual in the same period, under the same experimental conditions, and without altering the EMG electrodes [15,16].…”

“…muscles. It is thought that adding external-focus instruction to the side plank exercise, which increases the activity of the trunk muscles [9], can induce a cocontraction and further increase the activity of the trunk muscles [8,9]. However, no reports have examined how the activity of upper limb and trunk muscles changes when external-focus instruction is added to the side plank exercise using a paper balloon Also, no reports examine activation on the unsupported side during the side plank when external-focus instruction is added.…”

Influence of an Upper Limb Isometric Task in Perceived and Performance Fatigability of Elderly Subjects: A Quasi-Experimental Study

“…Considering that the elderly population continues to increase [ 27 ], health maintenance and physical independence in this population is a global goal [ 28 ]. Fatigue and pain are the major symptoms in this population [ 5 ], and isometric activity can be an important strategy for recreational, sports, and rehabilitation plans to improve health, fitness, and functional performance, since its benefits include improved joint stability (without joint movement), lower blood pressure [ 29 , 30 ] and decreased overall pain [ 31 ].…”