Use or lose: A case for normalizing neuromuscular clinical test for body weight in children

Research Objectives: To compare and contrast relationships of contraction- and velocity-specific muscle strength of lower extremity muscles with clinical tests of neuromuscular performance such as lateral step up test (at heights of 0.05 m (LSUT0.05) and 0.15 m (LSUT0.15)) and sit-to-stand (STS) with and without normalization for body weight. Research scientists typically normalize tests of neuromuscular performance for body weight to understand qualitative aspect of neuromuscular performance. However, clinically no normalization of these tests are performed.

Design: Cross-sectional study.

Setting: University laboratory.

Participants: Typically developing children (n=15; male = 40%) 8-13 years of age.

Interventions: Not applicable.

Main Outcome Measures: After a familiarization, Knee extensors and ankle plantarflexors were assessed in random order for concentric (CONC) and eccentric (ECC) muscle strength at 2 different velocities (120°/s and 180°/s) for the knee extensors and ankle plantarflexors on Biodex3 device. We used LSUT0.05, LSUT0.15, and STS to determine neuromuscular performance. We assessed LSUT0.05, LSUT0.15 and STS in random order after familiarization. Maximum counts achieved during testing LSUT0.05, LSUT0.15 and STS were normalized for body mass.

Results: We noted positive spearman correlations for (i) LSUT0.05 and (a) ECC120knee, (b) CONC180ankle (ii), LSUT0.15 and (a) CONC120knee, (b) CONC180knee, and (iii) STS and CONC180ankle (all p < 0.05). However, after adjusting all the measures for body weight, positive spearman correlations were noted for LSUT0.05 and LSUT0.15 with CONC120, CONC180, ECC 120, and ECC180 of the knee and ankle while STS was positively related to CON180knee, ECC120knee, CON120ankle, CON180ankle, and ECC120ankle (all p < 0.05). Most of these relationships remained after adjusting for age, sex, and height.

Conclusions: Adjusting for body mass provides a greater insight on relationships of clinical tests of neuromuscular performance with contraction- and velocity-specific muscle strength of the lower extremity. This knowledge is vital for specific understanding of the role of muscles in clinical tests such as STS and LSUT in children.

Author(s) Disclosures: None