Submitted on October 16, 2005
Accepted on June 6, 2006
The Changes in Tissue Water Content Measured with Multiple-frequency Bioimpedance and Metabolism Measured with 31P MRS During Progressive Forearm Exercise
Mohan K Raja1, Graydon H Raymer2, Gerald Robert Moran3, Greg Marsh4, and R Terry Thompson2*
1 Medical Biophysics, University of Western Ontario, London, Canada; Division of Imaging Sciences, Lawson Health Research Institute, London, Canada
2 Medical Biophysics, University of Western Ontario, London, Canada; Division of Imaging Sciences, Lawson Health Research Institute, London, Canada; School of Kinesiology, University of Western Ontario, Hamilton, Canada
3 Medical Physics and Applied Radiation Sciences, McMaster University, Hamilton, Canada; Division of Imaging Sciences, Lawson Health Research Institute, London, Canada; Medical Biophysics, University of Western Ontario, London, Canada
4 School of Kinesiology, University of Western Ontario, Hamilton, Canada; Medical Biophysics, University of Western Ontario, London, Canada; Division of Imaging Sciences, Lawson Health Research Institute, London, Canada
* To whom correspondence should be addressed. E-mail: thompson{at}lawsonimaging.ca.
Multiple-frequency bio-impedance analysis (MFBIA) has been used to determine the cellular water composition in the human body. It is non-invasive and has demonstrated good correlations with other invasive measures of tissue water. However the ability of this method to study transient changes in tissue water in specific muscle groups has not been explored. In this study, MFBIA was used to assess changes in forearm intracellular water (ICW), extracellular water (ECW) and total water (TW) in seven healthy volunteers during and after a progressive wrist flexion exercise protocol. In an identical trial, 31P magnetic resonance spectroscopy (31P-MRS) was used to assess changes in intracellular pH and phosphocreatine (PCr). At the completion of exercise, forearm ICW increased 12.6% (SD 0.07, p=0.003), TW increased 10.1% (SD 0.06, p=0.005), and no significant changes were recorded for ECW. A significant correlation was found between the changes in intracellular pH and changes in ICW during exercise (r = -0.84, p=0.018). Using regression analysis, average changes in Pi, PCr and pH were found to predict changes in ICW (R2 = 0.98, p=0.005). In conclusion, MFBIA was sensitive enough to measure transient changes in the exercising forearm muscle. The changes seen were consistent with the hypothesis that intracellular acidification and PCr hydrolysis are important mediators of cellular osmolality and therefore may be responsible for the increased volume of water in the intracellular space that is often recorded following short-term high intensity exercise.
