Reliability and Validity of the Martin Vigorimeter for Grip Strength Measurement in Korean Adults

Background: Grip strength is important for fine motor skills, and one of the measurement tools for grip strength is the Martin Vigorimeter (MV) dynamometer. Studies on establishing the reliability and validity of the MV in Koreans are limited. We aimed to establish the reliability and validity of the MV for grip strength measurement in healthy Korean adults by comparing it with the Jamar dynamometer, the standard tool used by the American Society of Hand Therapists. Methods: In total, 99 healthy participants (50 men and 49 women) were enrolled. Grip strength was measured using the Jamar dynamometer and MV. Reliability and validity were assessed using the intraclass correlation coefficient (ICC) and minimal detectable change (MDC). The correlation between the measurements of the instruments was analyzed using Pearson's correlation. The effect of hand anthropometry was evaluated, and the conversion equation between the instruments was calculated. Results: MV showed excellent reliability (ICC > 0.90, p < 0.001) and validity with a high correlation (0.7 <= r < 0.9) with the Jamar dynamometer. The MDC was acceptable for detecting minimal clinically important differences (< 19.5%) in both instruments (Jamar: 3.4%-6.7%, MV: 3.8% to 6.3%). The grip strength measured using the MV was independent of hand anthropometry, unlike that using the Jamar dynamometer. Conclusions: This study provides insights into the relationship between the Jamar and MV instruments for measuring grip strength in Koreans. The MV is a viable alternative to the Jamar dynamometer in Koreans, offering not only reproducible and reliable measurements of grip strength but also the advantage of being unaffected by variations in hand anthropometry.