Relationships between muscle size, strength, and physical activity in adults with muscular dystrophy

Abstract

BackgroundMuscular dystrophy (MD) is characterized by progressive muscle wasting and weakness, yet few comparisons to non‐MD controls (CTRL) of muscle strength and size in this adult population exist. Physical activity (PA) is promoted to maintain health and muscle strength within MD; however, PA reporting in adults with MD is limited to recall data, and its impact on muscle strength is seldom explored.MethodsThis study included 76 participants: 16 non‐MD (CTRL, mean age 35.4), 15 Duchenne MD (DMD, mean age 24.2), 18 Becker's MD (BMD, mean age 42.4), 13 limb‐girdle MD (LGMD, mean age 43.1), and 14 facioscapulohumeral MD (mean age 47.7). Body fat (%) and lean body mass (LBM) were measured using bioelectrical‐impedance. Gastrocnemius medialis (GM) anatomical cross‐sectional area (ACSA) was determined using B‐mode ultrasound. Isometric maximal voluntary contraction (MVC) was assessed during plantar flexion (PFMVC) and knee extension (KEMVC). PA was measured for seven continuous days using triaxial accelerometry and was expressed as daily average minutes being physically active (TPAmins) or average daily percentage of waking hours being sedentary (sedentary behaviour). Additionally, 10 m walk time was assessed.ResultsMuscular dystrophy groups had 34–46% higher body fat (%) than CTRL. DMD showed differences in LBM with 21–28% less LBM than all other groups. PFMVC and KEMVC were 36–75% and 24–92% lower, respectively, in MD groups than CTRL. GM ACSA was 47% and 39% larger in BMD and LGMD, respectively, compared with CTRL. PFMVC was associated with GM ACSA in DMD (P = 0.026, R = 0.429) and CTRL (P = 0.015, R = 0.553). MD groups were 14–38% more sedentary than CTRL groups, while DMD were more sedentary than BMD (14%), LGMD (8%), and facioscapulohumeral MD (14%). Sedentary behaviour was associated with LBM in DMD participants (P = 0.021, R = −0.446). TPAmins was associated with KEMVC (P = 0.020, R = 0.540) in BMD participants, while TPAmins was also the best predictor of 10 m walk time (P < 0.001, R 2 = 0.540) in ambulant MD, revealed by multiple linear regression.ConclusionsQuantified muscle weakness and impaired 10 m walking time is reported in adults with MD. Muscle weakness and 10 m walk time were associated with lower levels of TPA in adults with MD. Higher levels of sedentary behaviour were associated with reduced LBM in DMD. These findings suggest a need for investigations into patterns of PA behaviour, and relevant interventions to reduce sedentary behaviour and encourage PA in adults with MD regardless of impairment severity.

Quality of life in adults with muscular dystrophy

“…Knee extension maximal voluntary contraction (KEMVC) torque was measured using methods replicative to Quantitative Muscular Assessment, as is commonly used in dystrophic studies [27, 44], for which a full description and reliability data have been reported previously [11]. Below is an overview of the measurement of KEMVC.…”

“…LGMD and FSHD are classically characterised by local weakness consistent with their names [9, 10]. Irrespective of condition, all MDs typically present with declining muscle strength and eventual loss of ambulation [11], which are likely to reduce independence, and the self-perception of physical function [12]. The loss of muscle strength and function is commonly seen as a defining feature of MD, despite however, QoL reported as typically lower in adults with MD [13–17], the impact on perceived QoL through objectively methods of muscle strength remain unreported in adults with MD [18].…”

“…By comparison, loss of muscle strength has previously been correlated with QoL in children with DMD [18]. More broadly in MD, a loss of muscle strength limits the ability to walk and perform functional tasks [11, 27], which are both facets contributing to QoL. In addition, increased BMI has been reported previously in adults with MD [11, 28], and shown to impact not only function [29], but also effect psychological wellbeing in overweight individuals [30].…”

“…More broadly in MD, a loss of muscle strength limits the ability to walk and perform functional tasks [11, 27], which are both facets contributing to QoL. In addition, increased BMI has been reported previously in adults with MD [11, 28], and shown to impact not only function [29], but also effect psychological wellbeing in overweight individuals [30]. Alternatively, psychological aspects such as self-efficacy [31], an individual’s confidence in their ability to overcome problems [32], may provide a greater insight into QoL than physical impairment alone and has been shown to be positively associated with QoL in other clinical conditions [33, 34].…”

Preliminary Evidences of Safety and Efficacy of Flavonoids- and Omega 3-Based Compound for Muscular Dystrophies Treatment: A Randomized Double-Blind Placebo Controlled Pilot Clinical Trial

“…According to these evidences and considering the proximal weakness as clinical hallmarks of DMD, FSHD, and LGMD, our clinical efficacy endpoints included the assessment of endurance by 6MWD (6 min walking distance) in walking patients and dynamometer muscle strength measurement of upper and lower limbs in both walking and wheelchair patients. The parent questionnaire data (EK, Egen Klassifikation; ACTIVLIM, Activity Limitation; ABILHAND, manual ability for adults with upper limb impairments) scales were also used as previously described (45–48). During a 24 weeks period, all patients were administered daily with a dose of either treatment or placebo, which they independently took in.…”