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Behavioral and Locomotor Measurements Using an Open Field Activity Monitoring System for Skeletal Muscle Diseases
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Beyond aggregate volume-Accelerometer-derived activity phenotypes reveal a decoupling of lean mass and function: A

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  • 1Department of Physical Education, Capital Normal University, Beijing, China.

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Physical activity patterns, not just volume, impact aging muscle. High activity volume with consolidated sedentary time preserves lean mass but not grip strength, suggesting new sarcopenia guidelines are needed.

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Area of Science:

  • Gerontology and Exercise Physiology
  • Biomedical Data Science
  • Kinesiology

Background:

  • Lean mass preservation is crucial for muscle strength in aging, but aggregate physical activity metrics fail to capture temporal movement patterns.
  • The dissociation between muscle mass and function in older adults necessitates advanced analytical approaches to understand neuromuscular impacts.
  • Unsupervised machine learning can identify distinct physical activity phenotypes to clarify their associations with muscle health.

Purpose of the Study:

  • To investigate the associations between accelerometer-derived physical activity phenotypes and appendicular lean mass versus grip strength in US adults.
  • To compare the explanatory power of phenotype-based models against traditional aggregate volume metrics for muscle mass and function.
  • To determine if specific activity patterns, beyond mere volume, are linked to neuromuscular outcomes in aging populations.

Main Methods:

  • Utilized National Health and Nutrition Examination Survey (NHANES) 2011-2014 data from US adults.
  • Applied K-Means clustering to wrist-accelerometry features (rhythm, fragmentation) to derive activity phenotypes.
  • Employed survey-weighted linear regression to assess associations with appendicular lean mass and grip strength, comparing phenotype models with volume-based models using the Akaike information criterion (AIC).

Main Results:

  • Identified two phenotypes: high-volume/consolidated (HVC) and low-volume/fragmented (LVF).
  • The HVC phenotype was associated with significantly higher appendicular lean mass index, equivalent to five years of age-related decline, but showed no significant advantage in grip strength compared to LVF.
  • Phenotype-based models demonstrated statistical equivalence to traditional volume-based models in explaining outcomes (ΔAIC < 1.0).

Conclusions:

  • Accumulating high physical activity volume through structured patterns is linked to preserved appendicular lean mass in adults.
  • This preservation of lean mass does not necessarily translate to improved grip strength, indicating a dissociation between mass and function.
  • Current sarcopenia guidelines focusing solely on aggregate activity volume may be insufficient; integrating targets for sedentary behavior fragmentation is recommended for comprehensive neuromuscular performance.
  • Consolidated sedentary behavior may compromise neuromuscular performance despite adequate total movement, highlighting the importance of activity patterns.