Increased hip adductor activation during sit-to-stand improves muscle activation timing and rising-up mechanics in individuals with hemiparesis

I wouldn't be able to stand at all with a ball between my legs, my body twisting and pushoff from my right hand would  prevent that.  If a survivor can do this they are a complete outlier.

Increased hip adductor activation during sit-to-stand improves muscle activation timing and rising-up mechanics in individuals with hemiparesis

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https://doi.org/10.1016/j.jelekin.2022.102741Get rights and content

Abstract

Long sit-to-stand (STS) time has been identified as a feature of impaired functional mobility. The changes in biomechanics of STS performance with simultaneous hip adductor contraction have not been studied, which may limit indications for use of hip adductor activation during STS training.

Ten individuals with hemiplegia (mean age 61.8 years, injury time 29.8±15.2 months) performed the STS with and without squeezing a ball between two legs. The joint moments, ground reaction force (GRF), chair reaction force and movement durations and temporal index of electromyography were calculated from the control condition for comparison with those from the ball squeezing condition.

Under the squeeze condition, reduced peak vertical GRF during the ascension phase with increased loading rate was observed in the nonparetic limb, and the peak knee extensor moment occurred earlier in the paretic. Earlier activation of tibialis anterior and gluteus maximus, and gluteus medius were found in squeeze STS.

Squeezing a ball between limbs during STS increased the contraction timing of tibialis anterior, gluteus maximus, gluteus medius, and soleus as well as a more symmetric rising mechanics encourage the use of squeezing a ball between limbs during STS for individuals with hemiparesis.

Introduction

Long sit-to-stand (STS) time has been identified as a feature of impaired functional mobility (Boukadida et al., 2015, Faria et al., 2010, Pollock et al., 2014) and a risk factor for falls in individuals with stroke (Cheng et al., 1998). Peak vertical ground reaction force (GRF) on the paretic side is lower in individuals with hemiparesis than in those without hemiparesis (Brière et al., 2010, Cheng, Liaw, 1998, Roy et al., 2006). Asymmetrical weight bearing following a stroke may be associated with the inaccurate perception of weight distribution (Brière, Lauzière, 2010, Brière et al., 2013). Peak joint moment in the paretic limbs is low in patients with stroke, leading to asymmetrical joint moment (Lomaglio and Eng, 2005, Roy et al., 2007). Electromyography (EMG) studies have suggested that muscle activation timing plays a crucial role in neuromuscular control when rising from a chair (Cheng et al., 2004, Silva et al., 2013). Individuals with hemiparesis exhibit substantial coactivation of antagonistic muscles, which may result in insufficient joint torque at the ankle (Neckel et al., 2006). This may also be associated with high fall risk in individuals with hemiparesis during their engagement in functional activities. In patients with stroke, this coactivation may lead to abnormal muscle activation patterns during STS.

The movement characteristics of STS have been investigated empirically. The determinants of successful STS have been categorised into three groups: strategy related, chair related, and person related [e.g. changing foot position (Blache et al., 2014, Kawagoe et al., 2000, Khemlani et al., 1999) and seat height (Blache, Pairot de Fontenay, 2014, Kuo et al., 2010)]. Squeezing a therapeutic ball between the knees may enable individuals with hemiparesis to rise from a chair with relatively symmetrical movement (Granacher et al., 2013, Hwang et al., 2017, Jang et al., 2013). However, to the best of our knowledge, the mechanisms by which hip adductor contraction affects STS in this population warrants exploration. A 2012 study of healthy young adults found that a combination of hip adductor activation and other workout programmes effectively improved trunk muscle activation (Na et al., 2012). Other studies have reported that hip adductor contraction promotes gluteus medius (GMed) and vastus lateralis activity during squat exercises (Coqueiro et al., 2005, Felício et al., 2011). This may be attributed to the pelvis stabilising effect of this movement and its contribution to the control of the internal rotation of the femur (Mascal et al., 2003, McCrory et al., 2004, Nyland et al., 2004). Although the benefits of hip movement training in various types of exercise have been documented (Jung and Chung, 2017, Lee et al., 2015), relevant studies on individuals with hemiparesis are scant.

Joint moment and chair reaction force (CRF) should be considered, as well as movement duration, GRF, and EMG, in the evaluation of the biomechanical changes in the lower limb joints during hip adductor training. The present study investigated whether the GRF, joint moment, and EMG variables could predict knee loading asymmetries (using vertical GRF calculations) in individuals with poststroke hemiplegia during STS at a self-selected pace under control (Figure 1A) and squeeze (Figure 1B) conditions. The efficacy of hip adductor activation during STS was also evaluated on the basis of biomechanical indices. The following hypotheses were considered: (1) Hip adductor contraction during STS under the ball squeezing condition would facilitate pelvic and hip muscle contraction and thus enhance hip joint stability, and (2) Hip adductor activation would enhance STS efficiency and mechanics through the improvement of muscle activation timing and symmetrical GRF and joint moments in individuals with hemiparesis.

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