Skeletal muscle metabolism after stroke: A comparative study using treadmill and overground walking test

How Does Stroke Affect Skeletal Muscle? State of the Art and Rehabilitation Perspective

Long-term disability caused by stroke is largely due to an impairment of motor function. The functional consequences after stroke are caused by central nervous system adaptations and modifications, but also by the peripheral skeletal muscle changes. The nervous and muscular systems work together and are strictly dependent in their structure and function, through afferent and efferent communication pathways with a reciprocal “modulation.” Knowing how altered interaction between these two important systems can modify the intrinsic properties of muscle tissue is essential in finding the best rehabilitative therapeutic approach. Traditionally, the rehabilitation effort has been oriented toward the treatment of the central nervous system damage with a central approach, overlooking the muscle tissue. However, to ensure greater effectiveness of treatments, it should not be forgotten that muscle can also be a target in the rehabilitation process. The purpose of this review is to summarize the current knowledge about the skeletal muscle changes, directly or indirectly induced by stroke, focusing on the changes induced by the treatments most applied in stroke rehabilitation. The results of this review highlight changes in several muscular features, suggesting specific treatments based on biological knowledge; on the other hand, in standard rehabilitative practice, a realist muscle function evaluation is rarely carried out. We provide some recommendations to improve a comprehensive muscle investigation, a specific rehabilitation approach, and to draw research protocol to solve the remaining conflicting data. Even if a complete multilevel muscular evaluation requires a great effort by a multidisciplinary team to optimize motor recovery after stroke.

The relationship between relative aerobic load, energy cost, and speed of walking in individuals post-stroke

BACKGROUND

Individuals post-stroke walk slower than their able-bodied peers, which limits participation. This might be attributed to neurological impairments, but could also be caused by a mismatch between aerobic capacity and aerobic load of walking leading to an unsustainable relative aerobic load at most economic speed and preference for a lower walking speed.

RESEARCH QUESTION

What is the impact of aerobic capacity and aerobic load of walking on walking ability post-stroke?

METHODS

Forty individuals post-stroke (more impaired N = 21; preferred walking speed (PWS)<0.8 m/s, less impaired N = 19), and 15 able-bodied individuals performed five, 5-minute treadmill walking trials at 70 %, 85 %, 100 %, 115 % and 130 % PWS. Energy expenditure (mlO₂/kg/min) and energy cost (mlO₂/kg/m) were derived from oxygen uptake (V˙O₂). Relative load was defined as energy expenditure divided by peak aerobic capacity (%V˙O₂peak) and by V˙O₂ at ventilatory threshold (%V˙O₂-VT). Relative load and energy cost at PWS were compared with one-way ANOVA's. The effect of speed on these parameters was modeled with Generalized Estimating Equations.

RESULTS

Both more and less impaired individuals post-stroke showed lower PWS than able-bodied controls (0.44 [0.19-0.76] and 1.04 [0.81-1.43] vs 1.36 [0.89-1.53] m/s) and higher relative load at PWS (50.2 ± 14.4 and 51.7 ± 16.8 vs 36.2 ± 7.6 %V˙O₂peak and 101.9 ± 20.5 and 97.0 ± 27.3 vs 64.9 ± 13.8 %V˙O₂-VT). Energy cost at PWS of more impaired (0.30 [.19-1.03] mlO₂/kg/m) was higher than less-impaired (0.19[0.10-0.24] mlO₂/kg/m) and able-bodied (0.15 [0.13-0.18] mlO₂/kg/m). For post-stroke individuals, increasing walking speed above PWS decreased energy cost, but resulted in a relative load above endurance threshold.

SIGNIFICANCE

Individuals post-stroke seem to reduce walking speed to prevent unsustainably high relative aerobic loads at the expense of reduced economy. When aiming to improve walking ability post-stroke, it is important to consider training aerobic capacity.

Brain and Muscle: How Central Nervous System Disorders Can Modify the Skeletal Muscle

It is widely known that nervous and muscular systems work together and that they are strictly dependent in their structure and functions. Consequently, muscles undergo macro and microscopic changes with subsequent alterations after a central nervous system (CNS) disease. Despite this, only a few researchers have addressed the problem of skeletal muscle abnormalities following CNS diseases. The purpose of this review is to summarize the current knowledge on the potential mechanisms responsible for changes in skeletal muscle of patients suffering from some of the most common CSN disorders (Stroke, Multiple Sclerosis, Parkinson’s disease). With this purpose, we analyzed the studies published in the last decade. The published studies show an extreme heterogeneity of the assessment modality and examined population. Furthermore, it is evident that thanks to different evaluation methodologies, it is now possible to implement knowledge on muscle morphology, for a long time limited by the requirement of muscle biopsies. This could be the first step to amplify studies aimed to analyze muscle characteristics in CNS disease and developing rehabilitation protocols to prevent and treat the muscle, often neglected in CNS disease.

Lower limb joint motion and muscle force in treadmill and over-ground exercise

Background

Treadmill exercise is commonly used as an alternative to over-ground walking or running. Increasing evidence indicated the kinetics of treadmill exercise is different from that of over-ground. Biomechanics of treadmill or over-ground exercises have been investigated in terms of energy consumption, ground reaction force, and surface EMG signals. These indexes cannot accurately characterize the musculoskeletal loading, which directly contributes to tissue injuries. This study aimed to quantify the differences of lower limb joint angles and muscle forces in treadmills and over-ground exercises. 10 healthy volunteers were required to walk at 100 and 120 steps/min and run at 140 and 160 steps/min on treadmill and ground. The joint flexion angles were obtained from the motion capture experiments and were used to calculate the muscle forces with an inverse dynamic method.

Results

Hip, knee, and ankle joint motions of treadmill and over-ground conditions were similar in walking, yet different in running. Compared with over-ground running, joint motion ranges in treadmill running were smaller. They were also less affected by stride frequency. Maximum Gastrocnemius force was greater in treadmill walking, yet maximum Rectus femoris and Vastus forces were smaller. Maximum Gastrocnemius and Soleus forces were greater in treadmill running.

Conclusions

Treadmill exercise results in smoother joint kinematics. In terms of muscle force, treadmill exercise requires lower loading on knee extensor, yet higher loading on plantar flexor, especially on Gastrocnemius. The findings and the methodology can provide the basis for rehabilitation therapy customization and sophistic treadmill design.

Electronic supplementary material

The online version of this article (10.1186/s12938-019-0708-4) contains supplementary material, which is available to authorized users.

Senior fitness test; a useful tool to measure physical fitness in persons with acquired brain injury

OBJECTIVES

To evaluate the feasibility and usability of the senior fitness test (SFT) in persons with acquired brain injury (ABI).

METHODS

A pilot cohort design with a convenience sample of persons with ABI was used.

RESULTS

Persons with ABIs (n = 47) were younger than their healthy counterparts (n = 172) were but performed significantly worse on sit to stand, 6-min walk test (6MWT) and 2.45-m up and go. This difference was accentuated in the age groups >60 years of age. Persons with ABIs, divided into subgroups traumatic brain injury (TBI; n = 12) and cerebral insult (CI; n = 35), showed significant differences in leg strength, upper extremity flexibility and walking capacity. Persons with CI were weaker, less flexible in upper and lower extremities, walked shorter distance and were less mobile. CI but not TBI performed significantly worse when compared to healthy elderly persons.

CONCLUSION

This study indicates that SFT is feasible, safe and useful tool for persons with ABI, to evaluate physical capacity, endurance, strength and flexibility. The submaximal test was well tolerated and could be performed by all participants irrespective of age or diagnosis. The distribution of test scores indicates responsiveness to change and no ceiling or floor effects.