Preliminary effectiveness of a sequential exercise intervention on gait function in ambulant patients with multiple sclerosis — A pilot study

Highlights

• Positive preliminary effect of resistance training on walking performance

• Patients with Multiple Sclerosis had a shorter walking distance, and lower ankle push-off power

• Added effect of the walking-specific endurance training unclear

• Potentially more profound changes in ankle push-off in the less-affected side

• Both the fast-paced 6-minute and self-paced 12-minute walking test may lack construct validity

Abstract

Background

Patients with multiple sclerosis (pwMS) often experience a decline in motor function and performance during prolonged walking, which potentially is associated with reduced ankle push-off power and might be alleviated through structured exercise. The objectives of this pilot study were to assess ankle push-off power and walking performance in pwMS and healthy controls, and the preliminary effectiveness of a sequential exercise program (resistance training followed by walking-specific endurance training) on ankle push-off power and walking performance.

Methods

PwMS (N = 10) with self-reported reduced walking performance and healthy controls (N = 10; at baseline only) underwent 3D gait analysis during a self-paced 12-minute walking test to assess walking performance prior to and following a sequential exercise program. Secondary testing paradigms comprised isometric muscle testing (triceps surae), cardiopulmonary exercise testing and self-report measures.

Findings

PwMS had a shorter 12-minute walking distance, and lower peak ankle push-off power (most-affected leg) in comparison to healthy controls. There was no minute-to-minute decline in walking performance. The 8-week resistance training significantly improved walking distance. In parallel, higher peak and speed-normalized ankle push-off power were found in the less-affected side. No additional changes were found following the walking-specific endurance training phase.

Interpretation

There was no walking-related motor fatigue found during a self-paced 12-minute walking test despite reduced ankle push-off power, and self-reported walking problems. Preliminary effects suggest a positive effect of resistance training on walking performance, potentially associated with increases in ankle push-off power, interestingly, in the less-affected leg. The added effect of the walking-specific endurance training remains unclear.

Introduction

Multiple sclerosis (MS) is considered an immune-mediated progressive disorder of the central nervous system (Compston and Coles, 2008). The clinical complexity and heterogeneity of MS is reflected in the broad range of symptoms found in patients with MS (pwMS), including motor, sensory, brainstem, cerebellar, visual, bowel/bladder, fatigue and cognitive symptoms (Browne et al., 2014; Compston and Coles, 2008). MS is unique in the sense that the (experienced) severity of these symptoms is highly variant between and within pwMS. This is also apparent in the walking performance of pwMS, which is characterized by a progressive decline in motor function, coordination and dual-task performance during a single walking bout (Gutierrez Cruz et al., 2016). Approximately 31% of pwMS showed a decline ≥15% in walking speed following 6 min of fast-paced walking (Leone et al., 2016). It has been suggested that reduced ankle push-off power, more so than ankle dorsiflexion (i.e. toe clearance) for instance, is closely associated with the walking performance of pwMS (Bregman et al., 2012; Cofre Lizama et al., 2016; Kempen et al., 2016). A decline of 30% in ankle push-off power compared to healthy controls has been reported (Huisinga et al., 2013). It is unclear to what extent such a decline is related to a lower comfortable walking speed in pwMS, or the decline in walking performance (Leone et al., 2016). The underlying mechanisms of a reduced ankle push-off power are largely unknown, but may have a central (e.g. neural drive) and peripheral component (e.g. muscle function) (Zijdewind et al., 2016).

Exercise therapy may be a viable treatment option to improve muscular strength, endurance and/or central motor drive and as such regain walking performance (Pearson et al., 2015). A sequential exercise program may have greater benefits (compared to concurrent training) due to the lack of metabolic interference while the frequency and intensity of each training modality (resistance and endurance training) are maintained (Leveritt et al., 1999).

The objective of the present pilot study was to assess i) ankle push-off power and walking performance in pwMS and healthy controls (HC) and ii) the preliminary effectiveness of a sequential exercise program (resistance training followed by walking-specific endurance training) consisting of 8 weeks of resistance training followed by 8 weeks of walking-specific treadmill endurance training on ankle push-off power and walking performance in ambulant pwMS.