Author(s): SLUNECKO, M., CSAPO, R., WESSNER, B., Institution: UNIVERSITY OF VIENNA, Country: AUSTRIA, Abstract-ID: 1174

INTRODUCTION:
The 30s chair rise test (30CRT) is a commonly used measure for lower limb muscle function. However, the traditional version, which quantitates the number of chair stands within 30s, has limited reliability and can be influenced by familiarization [1]. An instrumented form of the test that relies on the Leonardo Mechanograph ground reaction force plate (LM) to directly assess force, power, and velocity during the 30s-CRT might improve measurement reproducibility [2]. This study is the first to evaluate the reliability and the presence of learning effects (LE) and fatigue effects (FE) over multiple 30CRTs performed on the LM.
METHODS:
The reliability of the 30CRT on the LM was evaluated in young healthy participants throughout four test sessions organized in two blocks. The first block consisted of 3 test sessions with one trial of the 30CRT each taking place with one rest day in between. The 2nd block consisted of one longer test session on one day, 2-3 weeks after block one. It encompassed four trials of the 30CRT separated by 15 min rest periods. Time- (repetitions [reps] and time per repetition [t_rep]) and force-based (force [F_max], power [P_max], velocity [v_avg]) parameters were recorded and evaluated with the LM software. The three trials of block one and the first trial of block two were analyzed with a repeated measures ANOVA to evaluate the LE. The four consecutive trials of block two were analyzed using a separate repeated measures ANOVA to evaluate the FE. Reliability was assessed by intraclass correlation coefficient (ICC(1)).
RESULTS:
Thirty-four participants (16M/18F, age: 26.0±4.4; BMI: 23.2±4.0 kg/m2) performed 20.6±3.8 reps at baseline. The time-based parameters showed a significant LE (reps: p<0.001, ηp2=0.54; t_rep: p<0.001, ηp2=0.52) with a mean improvement of 20.5% for reps and 16.6% for t_rep from the first to the fourth trial. Apart from a slight improvement of 3.2% for vavg, the force-based parameters did not change significantly over the first four trials (F_max: p=0.16, ηp2=0.05; P_max: p=0.13, ηp2=0.06; v_avg: p=0.03, ηp2=0.10). In the four consecutive trials of block two, further improvements of reps (p<0.001, ηp2=0.60) and t_rep (p<0.001, ηp2=0.55) were observed, as well as a minor drop in vavg (p=0.01, ηp2=0.13). F_max (p=0.13) and P_max (p=0.08) did not change significantly. ICC(1) values over the third and fourth trial, which did not significantly differ in post hoc analyses, ranged between 0.89-0.91 for time- and between 0.91-0.96 for force-based parameters.
CONCLUSION:
Two familiarization trials are recommended for good measurement reproducibility of time-based parameters during the 30CRT in young adults. Force, power, and velocity can be assessed with the LM in a reliable way without familiarization, even while the time-based parameters initially change considerably due to LE.

[1] Rittweger, J., et. al (2004), J Am Geriatr Soc,
[2] Taani, M.H., et. al (2017), Res Gerontol Nurs,