Is overwork weakness relevant in Charcot–Marie–Tooth disease?

Abstract

BackgroundIn overwork weakness (OW), muscles are increasingly weakened by exercise, work or daily activities. Although it is a well-established phenomenon in several neuromuscular disorders, it is debated whether it occurs in Charcot-Marie-Tooth disease (CMT). Dominant limb muscles undergo a heavier overload than non-dominant and therefore if OW occurs we would expect them to become weaker. Four previous studies, comparing dominant and non-dominant hand strength in CMT series employing manual testing or myometry, gave contradictory results. Moreover, none of them examined the behaviour of lower limb muscles. Methods We tested the OW hypothesis in 271 CMT1A adult patients by comparing bilateral intrinsic hand and leg muscle strength with manual testing as well as manual dexterity. Results We found no significant difference between sides for the strength of first dorsal interosseous, abductor pollicis brevis, anterior tibialis and triceps surae. Dominant side muscles did not become weaker than non-dominant with increasing age and disease severity (assessed with the CMT Neuropathy Score); in fact, the dominant triceps surae was slightly stronger than the non-dominant with increasing age and disease severity. Discussion Our data does not support the OW hypothesis and the consequent harmful effect of exercise in patients with CMT1A. Physical activity should be encouraged, and rehabilitation remains the most effective treatment for CMT patients.

Testing overwork weakness in Charcot‐Marie‐tooth disease: Is it true or false?

“…Dexterity has been scarcely investigated. To the best of our knowledge, only 2 studies evaluate dexterity in CMT and they reach opposite conclusions …”

“…To the best of our knowledge, only 2 studies evaluate dexterity in CMT and they reach opposite conclusions. 1,10 So, in conclusion there is no stronger evidence for the presence of OW in literature yet and the topic is open to debate.…”

“…Overwork weakness (OW) refers to a syndrome which causes a permanent weakness of muscles due to excessive exercises, repetitive work or specific daily activities. 1 The first description dates back to a half century ago in post-polio patients. 2,3 After that, OW has been demonstrated in other neuromuscular diseases such as amyotrophic lateral sclerosis, 4 Duchenne and facio-scapulo-humeral dystrophies.…”

“…8 Indeed, both strength measurements showed controversial results, some authors reporting that the non-dominant hand (NDH) is stronger than dominant hand (DH) [9][10][11][12] and other authors stating that DH and NDH have similar strength. 1,11,13 Those who affirm that OW is not present because of both hands are similar, ignore in their discussions the 10% rule. This old rule establishes that grip strength in normal subjects is approximately 10% greater in the DH than in the NDH 14 and this is used by physical therapists as a general guide to set patients goals.…”

Exercise, dominant hand and neurodegeneration

“…The study by Piscosquito et al 5 investigated the hypothesis that dominant limbs may be predominantly affected in 271 patients with CMT1A, by post hoc analyses of large data in Italian–UK ascorbic acid trial for CMT1A. Although this trial failed to show the beneficial effects of ascorbic acid, the study was carefully designed; the dominant side for hand and foot was checked, and bilateral homonymous muscles were tested.…”