Muscular Fatigue, Maximum Strength an Stress Reactions of the Shoulder Musculature in Paraplegics

Abstract

In paraplegic patients, shoulder complaints attributable to muscle dysbalances arising from the particular daily form of exercise are often observed. The goal of therapy is to correct these imbalances through muscular training, whereby eccentric exercise might offer advantages due to lower fatigue with concurrent higher maximum strength. This study therefore examines muscle fatigue, maximum strength, and suitability for paraplegics of eccentric exercise of the shoulder. Muscle fatigue, isokinetic peak torque, and EMG activity were determined eccentric (Ecc) and concentric (Con) in 41 paraplegic subjects (13 early rehabilitants; 16 trained in wheelchair sports; 12 untrained). Serum CK, myoglobin, and subjective pain were collected for one week after exercise. In eccentric exercise, there was less muscle fatigue in all groups. Highest Ecc/Con peak torque ratio was found in trained subjects in all movements, followed by the untrained and the early rehabilitants. EMG-activity was lower in eccentric compared to concentric exercise (Ecc/Con ratio <1). CK and myoglobin concentrations, like pain symptoms, showed a marked increase after exercise. It is concluded that the Ecc/Con strength patterns among paraplegics are altered. Eccentric exercise offers advantages on the basis of lower muscular fatigue independent of training status and lesion time and higher maximum strength with increasing duration of paraplegia and additional athletic training. However, due to structural damage and subjective pain eccentric exercise can only be recommended with reservations in therapy and training.

Assessment of the ability of wheelchair subjects with spinal cord injury to perform a specific protocol of shoulder training: a pilot study

“…Manual wheelchair propulsion requires a pull-push action 38,39 , starting with a flexion movement from a retroflected shoulder position, combined with a low-grade abduction that is converted to adduction during the last part of the push phase, where there is internal rotation to the ends of the movement 39 . The aforementioned movements include concentric and eccentric muscles contractions for the frequent changes between braking and propulsion, that affect shoulder muscular strength and fatigue 17 . Eccentric exercise is considered theoretically beneficial because it requires less muscular fatigue in spite of higher maximum strength and muscle tension [40][41][42] ; additionally, overall metabolic and cardiovascular stress is lower in eccentric than in concentric forms of exercise 41 .…”

“…At the same time, structural musculature damage has been found as result of eccentric exercise, that can be considerably reduced with only a single repeat 43 . Mayer et al 17 examined muscle fatigue, isokinetic peak torque and EMG activity eccentric (ecc) and concentric (conc) in 41 paraplegic subjects (13 early rehabilitants; 16 trained in wheelchair sports; 12 untrained) and they found that in eccentric exercise there was less muscle fatigue in all groups, highest ecc/conc peak torque ratio in trained subjects in all movements, followed by the untrained and early rehabilitants. The authors concluded that although the eccentric exercise requires lower muscle fatigue independent of the training status that induces structural damage and subjective pain, eccentric exercise is recommended with reservations in rehabilitation therapy and training 17 .…”

“…Our protocol included eccentric and concentric exercises performed without apparent difficulties by all the subjects enrolled except for 2 exercises, where the torso-rotation was limited due to the weakness of abdominal and lumbar musculature. Moreover, according to Mayer et al 17 and Kuipers et al 43 , we adviced to perform a single eccentric exercise repeat in case of shoulder complaining during daily home training.…”

“…In the health young population, subjects commonly affected by shoulder dysfunction are overhead sportsmen or workers, in which microtrauma (posterior capsular tighteness and internal impingement) 12,13 or a degenerative process (spur formation, RC thinning) 14,15 underlying the shoulder pathology. The aforementioned pathological conditions are not as well defined in patients with SCI, moreover there are no great literature evidence on muscular imbalance and strength in paraplegic 16,17 , except for recent research articles describing the effects of resistance training on strength and pain in paraplegics 18,19 and isokinetic rotator cuff performance in WC athletes 20 . Isokinetic quantification muscular exercises has been described as a method to understand muscular adaptations during athletic activities in WC users and WC athletes, detemining the influence of WC propulsion and neurological lesion level on peak torque, mean power and the internal/external muscle ratios 20 .…”

Avaliação eletromiográfica de músculos da cintura escapular e braço durante exercícios com carga axial e rotacional

“…More recent studies on the rehabilitation of the pathologies of the upper limbs, especially those related to the articular complex of the shoulder have been searching for the description of the most frequently used exercises according to the level of the electrical activation of the involved musculature (1)(2)(3)(4)(5) . The use of the surface electromyography as the methodology to study the shoulder exercises is justified by the need to know the muscular activity, once for that articular complex, the musculature actuates in a decisive manner to the articular stability, and therefore, to the biomechanics of that region.…”