Isokinetic vs. Hand-Held Dynamometry for Assessing Knee Flexor and Extensor Strength in Athletes: Evaluating a Low-Cost Alternative across the Range of Motion

We explored whether hand-held dynamometry (HHD) could serve as a low-cost, portable alternative for assessing knee flexion and extension strength across the full range of motion. Twelve healthy athletes (7 men, 5 women; aged 21.4-28.5 years) performed maximal concentric (60°/s) and isometric flexion-extension efforts on an isokinetic dynamometer in prone and seated positions. On two separate occasions, peak extension and flexion torque were measured at six knee angles, and values obtained using HHD and isokinetic dynamometry (ISD) were compared at corresponding angles. HHD data demonstrated high reliability at all angles for knee flexion and extension (ICC = 0.812-0.971, p < 0.001). Knee extension torque was similar in HHD and prone ISD isometric measurements at all angles (p > 0.38). Knee flexion torque was similar in HHD and seated ISD isometric measurements at all angles (p ≥ 0.48). The conventional hamstring to quadriceps (H/Q) ratio was similar in HHD and ISD in the seated position for both concentric and isometric measurements (56 ± 11%, 55 ± 8% and 51 ± 10%, respectively, p > 0.792). Angle-specific H/Q ratios from HHD were similar to those obtained by all modes of testing at all knee angles (p > 0.70), except for the knee angle of 10^o, which was the position where the knee was almost extended. The highest H/Q ratios were observed at the knee angles of 10^o and 30^o (p < 0.001). HHD is valid and reliable for assessing knee strength, yielding results comparable to ISD across the range of motion of the knee joint. The findings also emphasize the importance of considering angle-specific H/Q ratios.