Water exchange induced by unilateral exercise in active and inactive skeletal muscles

Abstract

Nygren, Anders T., and Lennart Kaijser. Water exchange induced by unilateral exercise in active and inactive skeletal muscles. J Appl Physiol 93: [1716][1717][1718][1719][1720][1721][1722] 2002. First published August 9, 2002; 10.1152/japplphysiol.01117. 2001.-Water exchange was evaluated in active (E-leg) and inactive skeletal muscles by using 1 H-magnetic resonance imaging. Six healthy subjects performed one-legged plantar flexion exercise at low and high workloads. Magnetic resonance imaging measured calf cross-sectional area (CSA), transverse relaxation time (T2), and apparent diffusion capacity (ADC) at rest and during recovery. After high workload, inactive muscle decreased CSA and T2 by 2.1% (P Ͻ 0.05) and 3.1% (P Ͻ 0.05), respectively, and left ADC unchanged. E-leg simultaneously increased CSA, T2, and ADC by 4.2% (P Ͻ 0.001), 15.5% (P Ͻ 0.05), and 12.5% (P Ͻ 0.001), respectively. In conclusion, ADC and T2 correlated highly with muscle volume, indicative of extravascular water displacement closely related to muscle activity and perfusion, which was presumably a combined effect of increased intracellular osmoles and hydrostatic forces as driving forces. A distinguishable muscle temperature release was initially detected in the E-leg after high workload, and the ensuing recovery of ADC and T2 indicated delayed interstitial restitution than restitution of the intracellular compartment. Furthermore, absorption of extravascular water was detected in inactive muscles at contralateral high-intensity exercise.diffusion; magnetic resonance imaging; tissue water; transverse relaxation time MAGNETIC RESONANCE IMAGING (MRI) can be applied on local skeletal muscle regions by analyzing variables pixel by pixel or within multiple local regions, including active as well as less active muscles (31). Therefore, simultaneous evaluation of water exchange in active and inactive muscles during dynamic exercise is valuable to elucidate the signal shift in muscle that is related to exercise and is beneficial to study how different MRI techniques that focus on water displacement relate.The physics of water exchange in the skeletal muscle is highly complex and multifactorial. The magnetic resonance signal has been shown to be multiexponential, which indicates a multicompartmental origin. 1 H-MRI using transverse relaxativity focuses on the intrinsic property of water and its exchange between the different compartments as well as the binding capacity of the water molecule to subcellular structures (11). Most present studies have used a monoexponential transverse relaxativity analysis, although a multiexponential behavior has been described (24). The monoexponential proton transverse relaxation time (T2) of skeletal muscle is known to increase by exercise (6,20). Increased intracellular water content (4, 18) and mechanisms related to aerobic capacity, e.g., net intramuscular accumulation of osmoles (22), are assumed to be the most important factors related to prolonged T2 with exercise. To what degree other factors such as H ϩ , p...

Diffusion tensor imaging of the human calf muscle: distinct changes in fractional anisotropy and mean diffusion due to passive muscle shortening and stretching

“…In the literature, several factors that influence the diffusion properties of a muscle tissue have been discussed: fiber type and composition (7), myofilament lattices (22), temperature (23), and cell volume (24). It seems obvious that the diffusional anisotropy of musculature is the result of physical barriers due to the muscular architecture.…”

“…Nygren and Kaijser (23) hypothesized that changes in ADC due to muscular exercise are probably caused by the rise in temperature of working muscles. Owing to the choice of the static measurement setup in the present study, temperaturerelated effects induced by muscle exercise could be excluded.…”

Evaluation ofT2values and apparent diffusion coefficient of the masseter muscle by clenching

“…1 Recently, diffusion-weighted imaging (DWI) of human skeletal muscle of the extremities has been used for many purposes including evaluating skeletal muscle damage 6 and the changes that accompany contraction. [7][8][9][10] Many studies have examined morphological changes in the masticatory muscles by clenching or jaw opening; however, to our knowledge, there are no previous reports regarding the physiological changes (T 2 time or apparent diffusion coefficient (ADC)) caused by clenching.…”

Reliability of Calf Bioelectrical Impedance Spectroscopy and Magnetic-Resonance-Imaging-Acquired Skeletal Muscle Hydration Measures in Healthy People

“…Several factors can impact the testretest reliability of cBIS-acquired data. These include dayto-day variation in body hydration [23], exercise [21,39], participants' body type, and equations utilized to estimate ECF, ICF, and TW. The reliability of the ECF : ICF may have been affected by the differences in body types of our participants (BMI 25.9 ± 2.8), and differences in offline model fitting (range from 0 to 2) affecting ECF volume calculations of these participants.…”

“…Researchers have used 2 ( 2 : a measure of transverse magnetization signal decay) to investigate the changes in ECF volume or extracellular space ratio following drug-induced myopathy [18], neural damage [19,20], and exercise [21]. Magnetic resonance imaging also provides an apparent diffusion coefficient (ADC), measured by a diffusion-weighted imaging technique, which is sensitive to the hydrodynamic environment of the tissue fluid volume [22].…”