The key role of physical activity against the neuromuscular deterioration in patients with Parkinson's disease

Aim: Decreased muscle strength has been frequently observed in individuals with Parkinson's disease (PD). However, this condition is still poorly examined in physically active patients. This study compared quadriceps (Q) maximal force, and the contribution of central and peripheral components of force production during a maximal isometric task between physically active PD and healthy individuals. In addition, the correlation between force determinants and energy expenditure indices were investigated. Methods: Maximal voluntary contraction (MVC), resting twitch force (RT), pennation angle (Θp), physiological cross-sectional area (PCSA), and Q volume were assessed in 10 physically-active PD and 10 healthy control (CTRL) individuals matched for age, sex, and daily energy expenditure (DEE) profile. Results: No significant differences were observed between PD and CTRL in MVC (142±85; 142±47 N m), Q volume (1469±379; 1466±522 cm3 ), PCSA (206±54; 205±71 cm2 ), Θp (14±7; 13±3 rad) and voluntary muscle specific torque [MVC/PCSA (67±35; 66±19 N m cm-2 )]. Daily calories and MVC correlated (r=0.56, p=0.0099). However, PD displayed lower maximal voluntary activation (MVA) (85±7; 95±5 %), rate of torque development (RTD) in the 0-0.05 s (110±70; 447±461 N m s-1 ) and the 0.05-0.1 s (156±135; 437±371 N m s-1 ) epochs of MVCs, whereas RT normalised for PCSA was higher (35±14; 20±6 N m cm-2 ). Conclusion: Physically active PDs show a preserved strength of the lower limb. This resulted by increasing skeletal muscle contractility, which counterbalances neuromuscular deterioration, likely due to their moderate level of physical activity.