Central motor drive is increased during voluntary muscle contractions in multiple sclerosis

Ng, Alexander V.; Miller, Robert G.; Kent‐Braun, Jane A.

doi:10.1002/(sici)1097-4598(199710)20:10<1213::aid-mus1>3.0.co;2-f

Cited by 36 publications

(14 citation statements)

References 25 publications

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“…Those with CIS demonstrated greater strength asymmetries in the ankle muscles as well as muscle fatigue compared with the controls, and this indicates that muscle weakness manifests even in the earliest stages of MS. Another study of 9 persons with MS and 11 healthy controls reported that persons with MS had a substantially smaller maximal voluntary contraction of ankle dorsiflexors, measured using a force transducer, compared with controls [18]. This difference in maximal voluntary contraction might be explained by persons with MS requiring greater central motor drive to achieve the same relative force during a maximal muscle contraction as healthy controls [19]. The weakness of lower extremity muscles seems to differ as a function of disability in those with MS. For example, one study compared the peak isometric and isokinetic torque in the knee extensors and flexors between 31 persons with MS who had mild disability and 21 persons with moderate disability [20].…”

Section: Evidence For Physiological Deconditioning In Msmentioning

confidence: 92%

The Importance of Physical Fitness in Multiple Sclerosis

Motl¹

2013

J Nov Physiother

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Multiple Sclerosis (MS) is a common and life-altering neurological disease among adults in the United States and worldwide. This disease has an estimated prevalence of 1 per 1,000 adults in the United States [1] with the majority of cases occurring in women of European descent. The MS pathophysiology initially involves episodic periods of immune-mediated demyelination and transection of axons within the Central Nervous System (CNS). This results in the disruption of saltatory conduction of action potentials along myelinated axonal pathways in the brain, spinal cord, and optic nerves. The MS pathophysiology later transitions into a neurodegenerative disease process, presumably associated with insufficient neurotrophic support, and results in the accumulation of irreversible neurologic disability. The degree and location of axonal and neuronal damage within the CNS result in the heterogeneous expression of symptomatic, functional, and participatory consequences among persons with MS [2]. Such manifestations might be initiated or worsened by physical inactivity and resulting physiological deconditioning.We have previously described a model of physical inactivity, deconditioning, and worsening MS [3,4], and this was based on a similar framework for persons with chronic disease conditions [5] including MS [6]. The model is displayed in figure 1 and indicates that MS onset results in physical inactivity [7,8] that initiates physiological deconditioning (i.e., compromised or reduced physical fitness). This physiological deconditioning, in turn, results in worsening of MS, as indicated by loss of brain structure and function as well as symptomatic (e.g., fatigue) and functional (e.g., walking impairment) manifestations. The worsening of MS results in further physical inactivity and subsequent physiological deconditioning thereby yields a cycle of associations among physical inactivity, deconditioning, and worsening MS that develops over time. This model is important as it conceptualizes the importance of maintaining and improving physical fitness levels in persons with MS. Physical fitness might provide a form of "physiological reserve" that is protective of disease consequences and worsening of MS and this is consistent with other literatures such as cancer [9].To that end, this paper provides a comprehensive review of research on physical fitness in persons with MS. We begin by defining physical fitness and its domains as well as differentiating it from physical activity. We then present research on physiological deconditioning (i.e., detraining that manifests as a reduction in domains of physical work capacity or fitness) in persons with MS as well as evidence on the association between markers of physical fitness and consequences of MS. We lastly review research regarding the effects of exercise training on physical fitness and consequences of MS, and conclude with recently developed exercise recommendations for improving physical fitness. Our goal is the provision of a paper that underscores the (a) importance of p...

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Section: Evidence For Physiological Deconditioning In Msmentioning

confidence: 92%

The Importance of Physical Fitness in Multiple Sclerosis

Motl¹

2013

J Nov Physiother

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“…Changes in the electromyography (EMG) recording can be used to infer changes in neuromuscular recruitment. Using the EMG/Force relationship differences in motor pattern have been shown in MS compared with controls [49]. Essentially the findings from these studies indicate that in MS there is an excessive EMG or central motor drive during sub-maximal muscle contractions with the increased central drive correlated to the disease severity.…”

Section: Muscular Fatigue In Multiple Sclerosismentioning

confidence: 99%

Heat reactions in multiple sclerosis: An overlooked paradigm in the study of comparative fatigue

Marino

2009

International Journal of Hyperthermia

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Multiple sclerosis (MS) is a demyelinating and debilitating disease characterised by a range of symptoms such as motor dysfunction and muscle weakness. A significant MS symptom is heat sensitivity so that exposure to heat will increase body temperature and consequently the appearance of neurological signs. Although some people with MS can undertake exercise, it is thought to be limited by the sensitivity to heat and the subsequent rise in body temperature which occurs. It has been found that central fatigue is a determining factor in muscle activation and performance in normal healthy subjects. However, it is unknown whether thermal strain also induces central fatigue in MS even though muscular fatigue in MS is due mainly to central rather than peripheral factors. This review focuses on the similarities in the manifestation of central fatigue in both MS and healthy subjects with reference to thermal strain and heat reactions.

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“…74,76 Fatigability after exercise: Findings in this area are inconsistent, with greater fatigability found after exercise in one study, 78 but another reported inconsistent fatigability as demonstrated by recovery from exercise 68 and another reported no fatigability during a submaximal exercise protocol. 77 No relationship has been found between fatigue and gait tests. 76 Excessive muscle fatigue found in people with MS has been concluded by some to be from within the muscle itself, with the suggestion that this may be partly due to secondary deconditioning.…”

Section: Muscle Weaknessmentioning

confidence: 96%

“…68,71,75,76 Patients' ankle dorsiflexion was found to be weaker than in controls in one study; 74 however, two studies reported no difference. 73,77 The lack of a clear association between strength and fatigue suggests that they are different phenomena. 74,76 Fatigability after exercise: Findings in this area are inconsistent, with greater fatigability found after exercise in one study, 78 but another reported inconsistent fatigability as demonstrated by recovery from exercise 68 and another reported no fatigability during a submaximal exercise protocol.…”

Section: Muscle Weaknessmentioning

confidence: 99%