In healthy young adults, resting mechanical properties of lower limb muscles are significantly associated not only with total body water but, more importantly, with its compartmental distribution, with higher ICW corresponding to greater muscle tone and stiffness, whereas a high ECW proportion is linked to lower values.
Key Findings
Results
Absolute hydration volumes (TBW, ICW, ECW in kilograms) were positively correlated with muscle tone and stiffness across all measured lower limb muscles.
Correlations ranged from weak to high (r ≈ 0.30–0.70, p < 0.001)
Muscles assessed included tibialis anterior, peroneus longus, and gastrocnemius
Sample consisted of 158 healthy adults (97 men, 61 women; mean age 20.8 years)
Pattern was consistent across all muscles and between limbs
Results
Intracellular water (ICW) was the strongest determinant of muscle mechanical properties among the body water compartments.
ICW was identified as the strongest determinant in multiple linear regression models
BW compartments measured using TANITA MC-780 MA multi-frequency body composition analyser
Mechanical properties assessed using MyotonPRO® device
This finding held consistently across all three lower limb muscles examined
Results
Relative extracellular water (ECW expressed as a percentage) showed moderate negative correlations with muscle tone and stiffness.
ECW proportion was negatively correlated with both tone and stiffness measures
The negative associations were described as moderate in magnitude
This bipolar pattern contrasted with the positive associations seen for absolute water volumes
The pattern was consistent across all muscles and between limbs
Results
A consistent bipolar pattern of associations was observed between body water compartments and muscle mechanical properties.
Absolute water volumes (TBW, ICW, ECW in kg) were positively associated with muscle tone and stiffness
Relative ECW (expressed as a percentage) was negatively associated with tone and stiffness
Spearman's rank correlation and multiple linear regression models were used for analysis
The bipolar pattern was consistent across tibialis anterior, peroneus longus, and gastrocnemius muscles
Methods
The study assessed muscle mechanical properties and body water compartments in 158 healthy young adults using non-invasive measurement tools.
Participants included 97 men and 61 women with a mean age of 20.8 years
Body water compartments (TBW, ICW, ECW) were measured with a multi-frequency BIA device (TANITA MC-780 MA)
Muscle mechanical properties including tone and stiffness were measured with MyotonPRO®
Three lower limb muscles were assessed: tibialis anterior, peroneus longus, and gastrocnemius
Sochor M, Mrowiec M, Bączkowicz D. (2026). The association between body water compartments and muscle mechanical properties: A correlational study using bioimpedance and myotonometry.. Clinical nutrition ESPEN. https://doi.org/10.1016/j.clnesp.2026.102927