Dissertation
Construct validity of grip rate of force development and relaxation in the assessment of muscle weakness in older adults
University of Iowa
Doctor of Philosophy (PhD), University of Iowa
Summer 2020
DOI: 10.17077/etd.005512
Abstract
Background: Age-related decline in muscle function has important health implications; however, there is no agreement on the best clinical practice to screen for declining muscle function. Previous attempts to develop screening methods included maximum grip strength and maximum knee extension strength; however, the former lacks consistent associations with physical function, and the latter requires expensive equipment that often is not readily available. Recently, rate of force development (RFD) has been identified as an important marker of muscle function, specifically explaining neural contributions in the early phase of muscle contraction. Rate of force relaxation (RFR) is also gaining increased attention as a contributor to muscle fatigue and hence muscle function. At this time, the validity and reliability of these measures of the grip using rigorous methodological approaches is not known.
Objective: The aims of this research were to: determine the construct validity of grip RFD and RFR measures in older adults (Aim 1), determine the contribution of these variables to lower body physical function (Aim 2), determine the contribution of these variables to dynamic balance (Aim 3), and determine the contribution of these variables to quantitative ultrasound index (QUI) of the calcaneus.
Methods: Fifty-nine adults (71.1 ± 11.6 years, 49% female, 54% overweight, 90% right-handed, 93% college-educated, 94% White) were recruited to participate in a one-session assessment. Participants’ grip strength, grip RFD, and grip RFR were measured using an electric hand dynamometer. Peak RFD, RFD scaling factor (RFD-SF), Peak RFR, and RFR scaling factor (RFR-SF) were derived from the raw force data. Participants’ lower body performance was measured with the 30-second chair stand test (CST Score) and with 3 consecutive sit-to-stand movements on a ground reaction force plate. Derived variables from the force plate included Leg Power and Rise Time during one single rise. Dynamic balance was assessed from the third sit-to-stand movement on the force plate. Balance measures of foot center of pressure velocity (COP Vel), path length (COP Path) and Sway Index were calculated from the ground reaction force data. QUI of the calcaneus was assessed with a quantitative ultrasonography machine. From the full cohort, 17 participants participated in a 4-week resistance training intervention with two 30-minute long training sessions per week. Grip measures were reassessed each week. For addressing Aim 1, intra-class correlation coefficients (ICC) were used to determine test-retest reliability of grip measures. Pearson correlation coefficients and linear multiple regression models described the associations between grip RFD and lower body performance measures. Linear mixed effects models tested the intervention effects on grip variables. For Aims 2 and 3, and the Exploratory Aim, Pearson correlation coefficients and linear multiple regression models assessed the associations among grip measures, 30-second chair stand test, dynamic balance and bone health, respectively.
Aim 1 Results: ICC of grip measures ranged from 0.80 to 0.97 (95% CI-s from 0.73 to 0.98), indicating excellent test-retest reliability. Peak RFD was associated with CST Score (r = 0.44; p < 0.001), Leg Power (r = 0.48; p < 0.001), and Rise Time (r = -0.33; p < 0.001). RFD-SF was also associated with CST Score (r = 0.29; p < 0.05), but not with Leg Power (r = 0.03; p > 0.05) or Rise Time (r = -0.09; p > 0.05). In the intervention subsample (N = 17), linear mixed effect models revealed that all grip measures increased from baseline, however, improvements were not consistent and ranged from 0.3% to 47%.
Aim 2 Results: Pearson correlations indicated that all grip measures, other than RFR-SF (-0.10; p > 0.05), were associated with CST Score: Peak RFD (r = 0.44; p < 0.001); RFD-SF (r = 0.29; p < 0.05); Peak RFR (-0.42; p < 0.001). However, in linear regression analyses, there were no significant associations between grip measures and CST Score.
Aim 3 Results: Among the balance measurements, only COP Vel was associated with Peak RFD (r = -0.40; p < 0.001) and Peak RFR (r = 0.39; p < 0.001). Multiple linear regression models indicated that both Peak RFD and Peak RFR were significant predictors of COP Vel (Peak RFD: β < 0.001, p < 0.001, R2 = 0.16; Peak RFR: β < 0.001, p < 0.001 R2 = 0.15).
Exploratory Aim Results: No significant associations were observed between grip measures and calcaneus QUI.
Conclusion: Findings suggest that grip Peak RFD and Peak RFR are reliable measures, have moderate agreement with physical function, and are promising predictors of dynamic balance in adults ≥ 55 years. Findings also indicate that RFD and RFR measures can improve with resistance training, however, additional research is warranted to determine the degree of improvement.
Details
- Title: Subtitle
- Construct validity of grip rate of force development and relaxation in the assessment of muscle weakness in older adults
- Creators
- Piroska Boros
- Contributors
- Kara M Whitaker (Advisor)Kathleen F Janz (Committee Member)Clayton R Peterson (Committee Member)Qian Xiao (Committee Member)Steven M Levy (Committee Member)
- Resource Type
- Dissertation
- Degree Awarded
- Doctor of Philosophy (PhD), University of Iowa
- Degree in
- Health and Human Physiology
- Date degree season
- Summer 2020
- Publisher
- University of Iowa
- DOI
- 10.17077/etd.005512
- Number of pages
- xi, 117 pages
- Copyright
- Copyright 2020 Piroska Boros
- Language
- English
- Description illustrations
- illustrations
- Description bibliographic
- Includes bibliographical references (pages 87-95).
- Public Abstract (ETD)
Older adults constitute the fastest growing segment of the U.S. population. Forty-four percent of individuals older than 65 reported one or more limitations in their ability to perform activities of daily living, for example getting up from a chair. Age-related muscle weakness contributes to such limitations, but currently there are no standard tests available to easily screen for those individuals who are at risk of developing muscle weakness. Maximum grip strength has been tested as a tool to screen for muscle weakness; however, it did not consistently explain lower body performance. More recently, researchers have focused on examining the early phases of muscle contraction, including how quickly individuals can develop a critical level of force that is necessary to perform activities of daily living. This rate of force development is largely dependent on neural factors and describes muscle quickness. Force relaxation has also become an assessment of interest for describing muscle fatigue. This research aimed to establish reliability and validity measures of grip force development and force relaxation. Analyses included test-retest reliability, testing the agreement of grip measurements with lower body performance, and testing the responsiveness of grip measures to a strength training intervention. This study also investigated the associations among grip force development, force relaxation, physical function, balance, and heel bone strength.
To meet the study aims, 59 participants (age 55 to 93) completed a series of tests in a laboratory. Tests included grasping a hand grip device several times with varying force levels, repeated stand-ups from a chair at varying seat heights, and a bone assessment test of the left heel bone. From the sample, 17 participants took part in a 4-week strength training intervention with 30-minute training sessions twice a week targeting the larger muscle groups of the body. Grip measures of these participants were retested each week.
Results of the research showed that all grip measures produced consistent values when measurements were repeated. Both force development and force relaxation of the grip indicated medium agreement with lower body performance and balance. No significant associations were seen between any of the grip measures and heel bone. The training intervention improved all grip values; however, large individual differences were observed in the degree of improvement. Based on these findings, grip force development and force relaxation are reliable measures that are associated with important markers of muscle weakness in older adults, but additional research is needed before recommending their use.
- Academic Unit
- Health and Human Physiology
- Record Identifier
- 9983987794902771
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