[Reference values in isometric strength diagnostics : Measurement of core strength values in patients with back pain]. / Referenzwerte in der isometrischen Kraftdiagnostik : Messung von Rumpfkraftwerten bei Patienten mit Rückenschmerzen.

OBJECTIVE: Isometric strength testing is known as a valid and reliable tool in the context of functional diagnostics and quality control for chronic low back pain rehabilitation, but reference values differ markedly between varied assessment devices, depending on their biomechanical lever arm framework. This study aimed to evaluate sex and age-specific isometric peak force reference values of trunk muscle functions in all dimensions using the Myoline® test device (Diers, Schlangenbad, Germany). MATERIAL AND METHODS: In a retrospective cross-sectional study, data of 678 (541 females, 137 males) age-clustered (18-35, 36-50, 51-65 years) low back pain patients (ICD-10: M54) were analyzed referring to their absolute (N) and body weight related (N/kg) isometric maximum peak forces in all spatial dimensions (flexion, extension, rotation, lateral flexion) and the corresponding ratios (M ± SD, 95% CI), accompanied by sex and age-related effect analyses (two-way ANOVA). RESULTS: Male and younger patients were significantly stronger than females and older patients (p < 0.05), but none of the ratios differed significantly between any sex or age cluster (p > 0.05). The flexion/extension ratio showed a 1:2 relation, and the rotation and lateral flexion ratios demonstrated a 1:1 relation, but all ratios varied markedly (30-50%). CONCLUSIONS: The demonstrated data represented a special norm for sex and age clustered low back pain patients assessed with the recent Myoline® test device. The markedly varying peak forces and their ratios underlined the individual diversity and heterogeneous state of functional capacities within low back pain patients.