Validity and reliability of handgrip dynamometry in older adults: A comparison of two widely used dynamometers.

BACKGROUND: Among older adults, decreased handgrip strength is associated with greater risk of frailty, and loss of physical function, mobility, lean mass, and overall muscular strength and power. Frailty is also associated with sarcopenia, for which handgrip strength measurement has been recommended for diagnostic purposes. Specific cutoff points for diagnosis have been identified, but use of different devices may affect measurement. Therefore to assess validity and reliability, we compared the two most frequently used devices, the Jamar hydraulic and Smedley spring handgrip dynamometers. METHODS: Sixty-seven older (76.2 ± 0.9 years) men (n = 34) and women (n = 33) completed two trials of handgrip strength measurement on sequential days (T1, T2) using both devices in random order. Intraclass correlations were used to assess test-retest reliability, and Bland-Altman analysis was used to assess validity as the level of agreement between devices. RESULTS: There were significant (p < 0.001) relationships between devices at T1 (r = 0.94) and T2 (r = 0.94) and strong (p < 0.001) intraclass correlations were observed for both devices (Jamar = 0.98; Smedley = 0.96), indicating excellent reliability. However, there were significant differences between devices. Strength measured with Jamar was greater than Smedley at both T1 (27.4 ± 1.4 vs. 23.4 ± 1.1 kg, p < 0.001) and T2 (25.3 ± 1.4 vs. 21.8 ± 1.2 kg, p < 0.001). Bland-Altman analysis confirmed these differences. Subgroup analysis to evaluate the effect of gender and age indicated that in women and old-old (>75 years) participants, differences between devices were closer to zero for both measurements compared to men and young-old (65-75 years) participants. CONCLUSIONS: Our results demonstrate that despite excellent reliability, there is poor agreement between devices, indicating a lack of validity. For use as a diagnostic tool, standardization and device-specific cutoff points for handgrip dynamometry are needed.

Community-Based Survey Exploring Use of the Dietary Supplement Creatine by Adult Non-Athletes.

Creatine is classified as a "sports supplement", but it also has health benefits. The purpose of this study was to assess use of creatine as a dietary supplement in adult non-athletes. Three hundred ninety-nine adults (19-89 years) completed an online survey. Among the respondents, 77% (n = 307) were regularly active, including participation in weightlifting (34%), running (34%), and cycling (21%). Twenty-eight percent (n = 111) reported use of creatine with an average dose of 6.4 ± 4.5 g. Daily creatine use was reported by 45%, and 38% reported using creatine 2-6 times weekly. Primary sources of information about creatine were trainers/coaches (29%), friends/family (32%), and internet (28%). Forty percent (n = 44) of creatine users were female. When compared by age, 46% of young, 32% of midlife, and 6% of old respondents reported creatine use with no differences in dose or frequency. Young and midlife respondents reported primarily trainers/coaches, friends/family, and internet as sources of information about creatine, but old respondents limited their sources to friends/family and fitness magazines. Although creatine is widely used by adult non-athletes who regularly exercise, dietitians and other healthcare providers are not the primary source of information. Fitness trainers can appropriately provide guidance and education regarding safe and effective use of creatine.