Alterations in neuromuscular function in girls with generalized joint hypermobility

Area of Science:

• Biomechanics
• Neuromuscular Physiology
• Musculoskeletal Health

Background:

• Generalized Joint Hypermobility (GJH) is linked to a higher incidence of joint pain.
• Understanding the neuromuscular adaptations in GJH is crucial for managing associated pain.

Purpose of the Study:

• To investigate differences in neuromuscular performance and muscle activation strategies between girls with and without GJH.
• To explore potential compensatory mechanisms in GJH.

Main Methods:

• Participants: Girls with GJH and non-GJH (NGJH) controls.
• Tasks: Isometric knee flexions and extensions at various angles and submaximal contractions, plus explosive isometric knee flexions.
• Measurements: Electromyography (EMG) of knee flexor and extensor muscles, torque development.

Main Results:

• Girls with GJH exhibited a 53% faster early rate of torque development compared to NGJH girls.
• Reduced hamstring activation was observed in girls with GJH, while knee extensor and calf muscle activation remained similar between groups.
• Higher flexion-extension and medial-lateral co-activation ratios were noted in girls with GJH during knee flexions.

Conclusions:

• GJH is associated with an enhanced capacity for rapid force generation, possibly a motor adaptation to joint laxity.
• Increased medial muscle activation in GJH suggests greater medial knee joint compression.
• Elevated co-activation ratios in GJH may stem from diminished hamstring agonist drive, indicating altered neuromuscular control strategies.