Background/Purpose:

Muscle function can be affected by many chronic disorders of childhood including Juvenile Idiopathic Arthritis (JIA). Whereas the term “muscle strength” is often used to describe muscle function, it does not provide an objective assessment. Instead, the various components of muscle function including muscle force and power need to be measured precisely. Portable ground reaction force plates have been used to assess dynamic muscle function in clinical settings and for clinical studies and this method is commonly referred to as jumping mechanography. While intra-rater reliability has been published, no data is available for inter-rater reliability which is particularly important for multi-centre and longer-term prospective studies. The aim of this study was to determine inter-rater reliability for muscle function assessments using Leonardo^TM Jumping Mechanography.

Methods:

As part of the trans-Canadian, prospective study “Linking Exercise, Activity and Pathophysiology in Juvenile Idiopathic Arthritis (The LEAP Study)”, inter-rater reliability of the Single Two-Legged Jump (S2LJ) and the Multiple One-Legged Jump (M1LJ) on the Leonardo^TMJumping Mechanography was assessed between three raters.

14 healthy subjects were recruited among them 6 adults (3 males, mean age [SD] of 33.2 years[12.42]) and 8 children (3 males, mean age [SD] of 9.0 years[2.27]).

Each participant performed a set of three different jump types, a S2LJ followed by right and left M1LH with each one of three operators. Three trials were completed per jump type and participants had 15 minutes of rest in between jumps.

For the S2LJ, maximum Power was the primary outcome. Efficiency, Maximum Velocity, Maximum Force, Maximum Force and Maximum Height  were also captured. For the M1LH, right and left Maximum Force was the primary outcome.

All of these measures were recorded relative to body weight and as absolute measurements. Reliabilty was determined using the interclass correlation coefficient (ICC) and coefficients of variation (%CV). 

Results:

For the S2LJ, CV and ICC (95% CI) for maximum power were 3.82% and 0.997 (0.992-0.999) respectively for the whole group and 5.09 % and 0.987 (0.958-0.997) for the children only. All other parameters assessed in the S2LJ were in the same range with the maximum variation observed for maximum force with a CV of 5.80% and ICC of 0.997 (0.945-0.992) for all and 6.75% and 0.932 (0.800-0.984) for the children only.

For the M1LH, the CV for maximum force was up to 8.96% and ICC 0.865 (0.704-0.949) for all and 3.69% and 0.851 (0.592-0.965) for the children only. Maximum force relative to body weight showed a maximum CV of 4.04% and ICC of 0.813 (0.615-0.929) in the entire group and 4.24% and 0.752 (0.412-0.938) for the children only.

Conclusion:

Leonardo^TM Jumping Mechanography is a suitable test for objective assessment of muscle function for clinical use and multi-centre trials, with very good inter-rater reliability across multiple parameters of muscle function. We found that maximum force calculation in children may need to be adjusted for body weight to increase accuracy.  This method is currently in use in the LEAP study across Canada.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/inter-rater-reliability-of-jumping-mechanography-in-healthy-children-and-adults/