A biomechanical cause of low power production during FES cycling of subjects with SCI

Journal of NeuroEngineering and Rehabilitation, 2014 · DOI: 10.1186/1743-0003-11-123 · Published: August 16, 2014

Spinal Cord Injury Neurology Biomechanics

Simple Explanation

The study investigates why individuals with spinal cord injuries (SCI) produce low mechanical power output (PO) during Functional Electrical Stimulation (FES) cycling. The researchers examined the roles of different joints and muscles in power generation and the impact of antagonistic co-contraction during FES cycling. The goal is to understand the biomechanical factors limiting power output in FES cycling, which could lead to improvements in exercise and rehabilitation strategies for individuals with paralysis.

Study Duration

Not specified

Participants

16 subjects with complete spinal cord injury (SCI)

Evidence Level

Not specified

Key Findings

1
The primary power sources were the knee extensors of the quadriceps and the knee flexors of the hamstrings.
2
Two characteristic patterns were found; in 12 subjects most work was generated by the knee extensors in the propulsion phase (83% of total work), while in 4 subjects most work was shared between by the knee extensors (42%) and flexors (44%), respectively during propulsive and recovery phases.
3
Antagonistic activity was generally low due to hamstring weakness and insufficient hamstring mass activation with FES.

Research Summary

The study aimed to investigate the joints and muscles responsible for power generation and the role of antagonist co-contractions during SCI FES cycling to understand the reasons for low power output. The findings revealed two characteristic patterns of power generation, with knee extensors dominating in most subjects, and a balanced contribution from knee extensors and flexors in a smaller group. The results suggest that improving hamstring strength and co-contraction, rather than solely focusing on quadriceps stimulation, is crucial for enhancing biomechanical efficiency in FES cycling for individuals with SCI.

Practical Implications

Training Programs

Clinicians should develop individual training programs to increase strength and fatigue resistance of the hamstrings and glutei muscles.

Stimulation Strategies

Clinicians are advised to use overlapping stimulation ranges.

Future Research

Future work has to investigate whether it is feasible to increase hip flexor contribution using lumbo-sacral root or magnetic stimulation of the iliopsoas muscle.

Study Limitations

1
The electrode placements adopted in the present study for quadriceps (rectus femoris and the three vasti) and hamstrings muscle groups (biceps femoris short and long head, semimembranosus, semitendinosus) stimulation cor- respond to widely used practice
2
The stimulation firing angles used in this study were obtained by measuring individual static pedal force mea- surements [29] at all crank angle positions, and selecting the largest range of stimulation angles that produced positive crank torque for each muscle group
3
The present study focused on the investigation of moment and power patterns evoked in fresh muscles by FES, avoiding decreasing magnitudes and possible change of the pattern shapes caused by fatigue

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