Force control during submaximal isometric contractions is associated with walking performance in persons with multiple sclerosis

Davis, Leah A.; Alenazy, Mohammed; Almuklass, Awad M.; Feeney, Daniel; Vieira, Taian; Botter, Alberto; Enoka, Roger M.

doi:10.1152/jn.00085.2020

Cited by 26 publications

(23 citation statements)

References 59 publications

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“…11,12 Two of the most common symptoms in MS are fatigue and difficulties with walking. [13][14][15] The prevalence of fatigue increases with disease progression and eventually becomes a primary concern for up to 80% of the people with MS, 16 irrespective of the MS phenotype. 17,18 Fatigue is typically rated as one of the 2 most disabling symptoms by persons with MS, [19][20][21] but it is difficult to manage clinically as most individuals report that its severity varies within and across days.…”

Section: Introductionmentioning

confidence: 99%

Distinguishing between Fatigue and Fatigability in Multiple Sclerosis

Enoka

Almuklass

Alenazy

et al. 2021

Neurorehabil Neural Repair

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Fatigue is one of the most common debilitating symptoms reported by persons with multiple sclerosis (MS). It reflects feelings of tiredness, lack of energy, low motivation, and difficulty in concentrating. It can be measured at a specific instant in time as a perception that arises from interoceptive networks involved in the regulation of homeostasis. Such ratings indicate the state level of fatigue and likely reflect an inability to correct deviations from a balanced homeostatic state. In contrast, the trait level of fatigue is quantified in terms of work capacity (fatigability), which can be either estimated (perceived fatigability) or measured (objective fatigability). Clinically, fatigue is most often quantified with questionnaires that require respondents to estimate their past capacity to perform several cognitive, physical, and psychosocial tasks. These retrospective estimates provide a measure of perceived fatigability. In contrast, the change in an outcome variable during the actual performance of a task provides an objective measure of fatigability. Perceived and objective fatigability do not assess the same underlying construct. Persons with MS who report elevated trait levels of fatigue exhibit deficits in interoceptive networks (insula and dorsal anterior cingulate cortex), including increased functional connectivity during challenging tasks. The state and trait levels of fatigue reported by an individual can be modulated by reward and pain pathways. Understanding the distinction between fatigue and fatigability is critical for the development of effective strategies to reduce the burden of the symptom for individuals with MS.

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Section: Introductionmentioning

confidence: 99%

Distinguishing between Fatigue and Fatigability in Multiple Sclerosis

Enoka

Almuklass

Alenazy

et al. 2021

Neurorehabil Neural Repair

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“…Patients with multiple sclerosis presented with worse FORCE CoV in the dorsiflexors at 20% MVC, in addition to a reduced walking distance during a 6-minute walk test. In addition, in the patient group an increased time to walk 25 feet was associated with a greater FORCE CoV during submaximal contractions in both muscles (Davis et al, 2020a).…”

mentioning

confidence: 78%

“…Commonly, FORCE CoV has been highlighted as a critical explanatory variable with respect to muscular performance of tasks including walking (Davis et al, 2020a), tremor (Kavanagh et al, 2016; Keogh et al, 2019), and risk of falls in older adults (Carville et al, 2007), with FORCE CoV progressively deteriorating from middle to older age (Piasecki et al, 2021). A recent study by Davis and colleagues examined plantar-flexor and dorsiflexor FORCE CoV at 10 and 20% MVC in individuals who presented with multiple sclerosis and those who did not (Davis et al, 2020a). Patients with multiple sclerosis presented with worse FORCE CoV in the dorsiflexors at 20% MVC, in addition to a reduced walking distance during a 6-minute walk test.…”

Section: Discussionmentioning

confidence: 99%

“…In addition, in the patient group an increased time to walk 25 feet was associated with a greater FORCE CoV during submaximal contractions in both muscles (Davis et al, 2020a). Importantly, a reduced walking distance in the control group was also associated with dorsiflexor FORCE CoV and variation of common input to the plantar flexors during steady contractions (Davis et al, 2020a). Although multiple sclerosis is a neurological disorder impacting both the central and peripheral nervous systems (Davis et al, 2020a), the age-related decline in the neuromuscular system presents with aligned mobility-impairing symptoms which ultimately impact quality of life (Mitchell et al, 2012; Wilkinson et al, 2018).…”

Section: Discussionmentioning

confidence: 99%

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Training induced improvements in knee extensor force accuracy are associated with reduced vastus lateralis motor unit firing variability

Ely

Jones

Inns

et al. 2022

Preprint

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Background: Muscle force output during sustained submaximal isometric contractions fluctuates around an average value and is known to be influenced by variation in motor unit (MU) firing rates. MU firing rate variability seemingly reduces following exercise training interventions, however, much less is known with respect to peripheral MU properties. We therefore investigated whether targeted force accuracy training could lead to improved muscle functional capacity and control, in addition to determining any alterations of individual MU features. Methods: Ten healthy participants (7 females, 3 males, 27+/-6 years, 170+/-8 cm, 69+/-16kg) underwent a 4-week supervised, unilateral, force accuracy training intervention. The coefficient of variation for force (FORCECoV) and sinusoidal wave force tracking accuracy (FORCESinu) were determined at 25% maximal voluntary contraction (MVC) pre- and post-training. Intramuscular electromyography was utilised to record individual MU potentials from the vastus lateralis (VL) muscles at 25% MVC during sustained contractions, pre- and post-training. Results: Knee extensor muscle strength remained unchanged following training, with no improvements in unilateral leg-balance. FORCECoV and FORCESinu significantly improved in only the trained knee extensors by ~13% (p=0.01) and ~30% (p<0.0001) respectively. MU firing rate variability significantly reduced in the trained VL by ~16% (n=8; p=0.001), with no further alterations to MU firing rate or neuromuscular junction transmission instability. Conclusion: Our results suggest muscle force control and tracking accuracy is a trainable characteristic in the knee extensors, which is likely explained by the reduction in MU firing rate variability apparent in the trained limb only.

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“…Different approaches to muscle activation estimation from MU discharge patterns were also developed, including Principal Component Analysis of smoothed MU discharge rates (Negro et al, 2009), NMF of smoothed MU discharge rates (Tanzarella et al, 2021) and Cumulative Spike Train (CST) of identified MUs (Farina et al, 2014). Indeed, studies of simultaneous MU behavior in different muscles are increasing (Héroux et al, 2014;de Souza et al, 2018;Kranjec and Holobar, 2019;Davis et al, 2020;Potočnik et al, 2020;Cohen et al, 2021;Tanzarella et al, 2021). However, to the best of our knowledge, comparisons of MU behavior in a group of simultaneously recorded skeletal muscles of older and young persons are still largely lacking.…”

Section: Introductionmentioning

confidence: 99%

Inter-Person Differences in Isometric Coactivations of Triceps Surae and Tibialis Anterior Decrease in Young, but Not in Older Adults After 14 Days of Bed Rest

et al. 2022

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We examined activation patterns of the gastrocnemius medialis (GM), gastrocnemius lateralis (GL), soleus (SO), and tibialis anterior (TA) muscles in eight older (58.4 ± 3.3 years) and seven young (23.1 ± 2.9 years) participants, before and after 14 days of horizontal bed rest. Visual feedback on the exerted muscle torque was provided to the participants. The discharge patterns of individual motor units (MUs) were studied in three repetitions of isometric plantar flexion at 30 and 60% of Maximum Voluntary Contraction (MVC), before, and 1 day after the 14-day bed rest, respectively. In the GL and GM muscles, the older participants demonstrated higher MU discharge rates than the young, regardless of the contraction level, both before and after the bed rest. In the TA and SO muscles, the differences between the older and young participants were less consistent. Detailed analysis revealed person-specific changes in the MU discharge rates after the bed rest. To quantify the coactivation patterns we calculated the correlation coefficients between the cumulative spike trains of identified MUs from each muscle, and measured the root mean square difference of the correlation coefficients between the trials of the same session (intra-session variability) and between different sessions (inter-session variability) in each participant (intra-person comparison) and across participants (inter-person comparison). In the intra-person comparison, the inter-session variability was higher than the intra-session variability, either before or after the bed rest. At 60% MVC torque, the young demonstrated higher inter-person variability of coactivation than the older participants, but this variability decreased significantly after the bed rest. In older participants, inter-person variability was consistently lower at 60% than at 30% MVC torque. In young participants, inter-person variability became lower at 60% than at 30% MVC torque only after the bed rest. Precaution is required when analyzing the MU discharge and coactivation patterns, as individual persons demonstrate individual adaptations to aging or bed rest.

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Force control during submaximal isometric contractions is associated with walking performance in persons with multiple sclerosis

Cited by 26 publications

References 59 publications

Distinguishing between Fatigue and Fatigability in Multiple Sclerosis

Distinguishing between Fatigue and Fatigability in Multiple Sclerosis

Training induced improvements in knee extensor force accuracy are associated with reduced vastus lateralis motor unit firing variability

Inter-Person Differences in Isometric Coactivations of Triceps Surae and Tibialis Anterior Decrease in Young, but Not in Older Adults After 14 Days of Bed Rest

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