Examining Additional Aspects of Muscle Function with a Digital Handgrip Dynamometer and Accelerometer in Older Adults: A Pilot Study

Framework for a short muscle function battery using electronic handgrip dynamometry and accelerometry in older adults

BACKGROUND

Electronic handgrip dynamometry and accelerometry enables novel opportunities to collect additional attributes of muscle function beyond just maximal strength, but some muscle function attributes may already be related, which may warrant discerning these attributes into a short muscle function battery (SMFB).

OBJECTIVES

We sought to determine the multivariate relationships between maximal strength, asymmetry, submaximal control, rate of force development, bimanual coordination, fatigability, and contractile steadiness in older adults.

DESIGN

A cross-sectional design was used for this investigation.

SETTING

Laboratory.

PARTICIPANTS

The analytic sample included 121 generally healthy older adults aged 70.7 ± 4.7 years.

MEASUREMENTS

Electronic handgrip dynamometry and accelerometry measured strength, asymmetry, submaximal control, rate of force development, bimanual coordination, fatigability, and contractile steadiness. The handgrip variables were standardized before they were included in a factor analysis. Factors with eigenvalues >1.0 were kept. Items within a factor with a loading |>0.30| were similarly retained.

RESULTS

There were 3 factors retained with eigenvalues of 1.88, 1.56, and 1.10. The first factor (functional strength), which explained 39.9 % of the variance, included strength, submaximal control, and rate of force development. Factor 2 (lateral function), which explained 35.8 % of the variance, included asymmetry and bimanual coordination. The third factor (muscle endurance), which explained 24.3 % of the variance, included fatigability and contractile steadiness.

CONCLUSIONS

Our findings suggest the surfacing of themes in the additional muscle function measures, thereby providing framework for a SMFB. More research is needed for electronic handgrip dynamometry and accelerometry derived muscle function on health before consideration of implementation in clinical practice.

Handgrip strength and asymmetry are associated with lower-body muscle power in older women

BACKGROUND

The difference in strength between hands, as characterized by handgrip asymmetry, has been shown to be significantly associated with several adverse health outcomes. Handgrip strength asymmetry and its relationship with lower-body muscle power in older adults is not well understood. This study aimed to determine if handgrip strength and asymmetry are associated with lower-body muscle power in older women.

METHODS

Twenty active older women (67±5 years) participated in this study. Handgrip contractions were performed with the dominant and non-dominant hand to assess strength measurements of peak force, peak rate of force development (RFD), and RFD at 0-100 (RFD100) and 0-200 (RFD200) ms. Asymmetry ratios were used to determine the severity of differences in handgrip peak force and RFD measurements between the dominant and non-dominant hand. Lower-body peak muscle power was assessed from a vertical jump test.

RESULTS

All handgrip peak force and RFD measurements for the dominant and non-dominant hands were significantly associated with vertical jump peak power (r=0.445-0.547, P=0.013-0.049). Significant correlations were observed between vertical jump peak power and handgrip asymmetry ratios for peak RFD (r=-0.460, P=0.041) and RFD100 (r=-0.591, P=0.006). Multiple regression analysis indicated that handgrip RFD100 asymmetry ratio and RFD200 for the dominant hand were significant predictors of vertical jump peak power, and together, explained 53.9% of its variance.

CONCLUSIONS

These findings suggest that handgrip RFD and asymmetry may be effective measurements at predicting lower-body muscle power in older women.

Observing the Relationship Between Additional Measures of Handgrip Strength and the 6-Minute Push Test in Ambulatory Young Adults

Manual wheelchair users have been shown to have low functional capacity and limited ability to perform activities of daily living. Conventional protocols for assessing physical attributes such as muscle function in this population have unique boundaries such as expensive testing equipment and procedures not specific to wheelchair propulsion. The measurement of muscle function using electronic handgrip dynamometry has shown promise in assessing additional characteristics beyond strength capacity alone. This study aimed to determine the correlations of electronic handgrip dynamometry derived strength, time to peak force generation, fatigability (22.40±10.12%), isometric control, and asymmetry with aerobic capacity in ambulatory young adults. We included 34 recreationally active ambulatory adults aged 23.76±3.57 years. Muscle function was assessed using electronic handgrip dynamometry. Aerobic capacity was examined using the six-minute wheelchair push test (1112.17±92.84ft). Fatigability (22.40±10.12%) showed a significant, near moderate negative correlation (r=-0.345, p<0.05) with push test outcomes, while the correlation with all other measures was not-significant. Our findings show that electronic handgrip dynamometry derived fatigability is related to aerobic capacity in those who use manual wheelchairs. Given the relationships shown in the current study, electronic handgrip dynamometry has promise for assessing functional health in persons with disabilities, which has particular relevance for SCI, and could be used in clinical practice and physical medicine and rehabilitation (PM&R) as a tool to examine functional capacity in applicable populations. However, future research is warranted to assess the concurrent validity of the additional measures of handgrip strength assessing muscle function.

Assessing Additional Characteristics of Muscle Function With Digital Handgrip Dynamometry and Accelerometry: Framework for a Novel Handgrip Strength Protocol

Maximal handgrip strength (HGS) is a convenient and reliable, but incomplete, assessment of muscle function. Although low HGS is a powerful predictor of poor health, several limitations to maximal HGS exist. The predictive value of HGS is restricted because low HGS is associated with a wide range of unspecified health conditions, and other characteristics of muscle function aside from strength capacity are not evaluated. Current HGS protocol guidelines emphasize the ascertainment of maximal force, which is only a single muscle function characteristic. Muscle function is intrinsically multivariable, and assessing other attributes in addition to strength capacity will improve screenings for age-related disabilities and diseases. Digital handgrip dynamometers and accelerometers provide unique opportunities to examine several aspects of muscle function beyond strength capacity, while also maintaining procedural ease. Specifically, digital handgrip dynamometry and accelerometry can assess the rate of force development, submaximal force steadiness, fatigability, and task-specific tremoring. Moreover, HGS protocols can be easily refined to include an examination of strength asymmetry and bilateral strength. Therefore, evaluating muscle function with new HGS technologies and protocols may provide a more comprehensive assessment of muscle function beyond maximal strength, without sacrificing feasibility. This Special Article introduces a novel framework for assessing multiple attributes of muscle function with digital handgrip dynamometry, accelerometry, and refinements to current HGS protocols. Such framework may aid in the discovery of measures that better predict and explain age-related disability, biological aging, and the effects of comorbid diseases that are amenable to interventions. These additional HGS measures may also contribute to our understanding of concepts such as resilience. Using sophisticated HGS technologies that are currently available and modernizing protocols for developing a new muscle function assessment may help transform clinical practice by enhancing screenings that will better identify the onset and progression of the disabling process.

Evaluating Additional Aspects of Muscle Function with a Digital Handgrip Dynamometer and Accelerometer for Cognitive Functioning in Older Adults: A Pilot Study

Handgrip dynamometers are used to assess handgrip strength (HGS), and low HGS is linked to poor cognitive function. Although HGS is a reliable measure of muscle function, it is only measuring maximal grip force. Other aspects of muscle function such as force control, fatigability, and steadiness are unaccounted for in current HGS protocols. This pilot study sought to determine the role of maximal HGS, submaximal HGS force control, HGS fatigability, and HGS neuromuscular steadiness on cognitive function in older adults. Our findings indicate that these additional HGS measurements could factor into detecting poorer cognitive functioning, while also evolving HGS protocols.