An investigation into the between-day reliability of muscle contractile properties measured using Tensiomyography.

Background and Purpose Tensiomyography (TMG) is reported to measure muscle contractile properties of superficial skeletal muscle. Between day reliability has not been reported for all of the major lower limb muscles in a mixed gender sample of healthy adults. Therefore, the aim of this study was to examine the between-day reliability of muscle contractile properties associated with involuntary contractions of the rectus femoris (RF) and bicep femoris (BF), as measured by TMG. Study Design Within-subject repeated measures study (3 consecutive days) Methods Twenty-four healthy participants (twelve male; twelve females) were recruited to take part in the study over 3 consecutive days. Measurements of muscle contractile properties were obtained on the bicep femoris (BF) and rectus femoris (RF) muscles in the dominant limb. All data were checked for normality using the Shapiro-Wilk test. Pooled intra-class correlation coefficient (ICC), coefficient of variance (CV) and standard error of measurement (SEM) values were generated for the BF and RF for delay time (Td), sustain time (Ts), relaxation time (Tr), contraction time (Tc) maximal displacement (Dm). Additionally, a Bland-Altman analysis was performed for paired data points (day 1 vs 2, 2 vs 3 and 3 vs 1). Identical analyses were then performed on gender sub-groups. Results Good to excellent ICC values (0.68-0.93) were reported for delay time (Td), contraction time (Tc), and maximal displacement (Dm) in BF and RF muscles. Conversely, relaxation time (Tr) and sustain time (Ts) reported low ICC values (-0.10-0.56). Levels of agreement were not significantly different in most pairs of data points across the whole sample and also across males and females (p=>0.05). However, significant differences were detected in the whole sample: day 3 vs day 1 in the Td (p=0.03) and Dm RF (p=0.009); males: BF Td day 1 vs 2 (p=0.04); females: BF day 2 vs 2 (p=0.01), RF Td day 1 vs 2 (p=0.03), RF Ts day 3 vs 1 (p=0.04). Conclusion The Td, Tc, and Dm variables obtained during TMG measurements demonstrate acceptable reliability across 3 consecutive days. The Tr and Ts variables cannot be measured reliably between days using TMG