Unveiling the benefits of stretch-shortening cycle exercise for children with obstetric brachial plexus injury: a clinical trial assessing muscle strength, bone mineral density, and functional capacity

BACKGROUND: Obstetric brachial plexus injury (OBPI) is associated with several temporary or permanent impairments including muscle weakness/atrophy and retarded bone accrual, which negatively affect upper extremity functionality. Thus, to remedy these impairments, improved and unequivocally effective intervention strategies are required. AIM: To evaluate the effectiveness of a 12-week stretch-shortening cycle exercise (SSC-Ex) program on muscle strength, bone mineral density, and upper extremity function in a convenience sample of children with OBPI. DESIGN: A prospective, dual-group randomized controlled trial with the outcome assessor being blinded to the treatment allocation. POPULATION: Fifty-six children with a confirmed diagnosis of the upper-arm type of OBPI (i.e. categorized as level I [C5/C6 injury] or II [C5/C6/C7 injury] per Narakas classification system) and aged between 10 and 16 years were randomly allocated to either the SSC-Ex group (N.=28) or the control group (N.=28). METHODS: The SSC-Ex group participants underwent a supervised SSC-Ex regimen for ~35 minutes, twice/week (with 2-day recovery intervals at minimum) over 12 consecutive weeks (totaling 24 sessions), while the control received the standard exercises (equated for the training volume, frequency, and duration). The primary outcomes included an assessment of muscle strength – specifically, shoulder flexors, abductors, external rotators, elbow flexors, and extensors – as well as the bone mineralization of the humerus, radius, and ulna. Functional performance was considered as a secondary outcome. These measures were undertaken both pre- and post-intervention. RESULTS: The SSC-Ex group exhibited favorable pre-to-post improvement in muscle strength measures (P<0.05; η²_partial ranged between 0.11 and 0.17), bone mineralization variables (P<0.05; η²_partial ranged between 0.13 and 0.21), and functional performance (P=0.006; η²_partial=0.13) when compared with the control group. CONCLUSIONS: The SSC-Ex showed promise in enhancing strength, bone mineralization, and functional capacity in children with OBPI. CLINICAL REHABILITATION IMPACT: The SSC-Ex can be a beneficial component of the rehabilitation program for children with OBPI. Physical rehabilitation specialists might opt for such a training paradigm to improve several aspects of motor functions, bone mineral properties, and upper extremity function based on empirical evidence.