• Burke JR
• Papuga O

• Association of Chiropractic Colleges / congresses

OBJECTIVES: To establish that motor learning occurred during SSC exercises and to determine the effects of orthotic intervention on neuromuscular adaptations and performance gains during motor learning.

METHODS: This study was reviewed and approved by the Institutional Review Board of the New York Chiropractic College. The subjects were 10 physically active, young adults (24 1.5 years; 173 12 cm; 83 20 kg; 6 males and 4 females). Subjects were randomly assigned to perform jumping exercises either with or without their orthotic intervention. The orthotic intervention was the flexible, custom-made orthotics by Foot Levelers, Inc. (Roanoke, VA). The subjects participated in a five-day skill acquisition period and a skill retention session, one week later. All data were pooled to meet the first research goal. A single factor repeated measures ANOVA model was used to analyze the electromyogram amplitudes of the SRR of the medial gastrocnemius, soleus and vastus lateralis muscles and jump height.

RESULTS: Two subjects did not show improvements in jump height performance during the five-day skill acquisition period. These two subjects were excluded from further statistical analyses as the objective of the research was to describe neuromuscular adaptations and performance gains during motor learning. Among the remaining eight subjects, there was a significant improvement in jump height performance of 17% that occurred during the five-day skill acquisition period (F(5,35) = 3.6; p < .05). The improvement in jump height performance was maintained, one week later, to infer motor learning of the drop jump. There were no changes in the electromyogram amplitudes of the SRR of the gastrocnemius, soleus and vastus lateralis muscles accompanying the increase in jump height performance (p > .05). There is a sample size requirement of at least 10 subjects per group to detect significant differences between individuals jumping with or without their orthotic intervention at an adopted power of .80 and alpha level of .05.

DISCUSSION: The increase in jump height performance met our first goal of the research design, which was to establish that motor learning occurred. Facilitation of the SSR did not contribute to increases in jump height performance. Learning-induced changes in the gain of the SSR may account for this finding. Although the current report emphasized the direct measurement of SRR using spike-triggered averaging techniques, electromyogram activities during the preactivation, eccentric, and concentric phases of the drop jump are also being collected in this research study. Thus, neuromuscular adaptations contributing to increases in jump height and changes in the gain of SSR will be addressed. Ten additional healthy young adults are being tested to determine the effects of an orthotic intervention on neuromuscular adaptations and performance gains during motor learning.

A seed money grant from Foot Levelers, Inc. supported this research.

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