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Abstract: Rhabdomyolysis has sparked new interest in recent years. The causes of rhabdomyolysis include drugs and other toxic agents, infections, physical exertion, crush injury, and muscle diseases (dystrophinopathies and metabolic myopathies). Prompt identification of the pathophysiological mechanism is the key to rapid control of the acute episode and to prevention of recurrences. In this update, we discuss the pathophysiological mechanisms and nosology of rhabdomyolysis, as well as diagnostic investigations, with special emphasis on noninvasive methods. [Copyright &y& Elsevier]

Abstract: Rhabdomyolysis has sparked new interest in recent years. The causes of rhabdomyolysis include drugs and other toxic agents, infections, physical exertion, crush injury, and muscle diseases (dystrophinopathies and metabolic myopathies). Prompt identification of the pathophysiological mechanism is the key to rapid control of the acute episode and to prevention of recurrences. In this update, we discuss the pathophysiological mechanisms and nosology of rhabdomyolysis, as well as diagnostic investigations, with special emphasis on noninvasive methods. [Copyright &y& Elsevier]

Interindividual variations in skeletal muscle metabolism make comparative analyses difficult. In this study, we have addressed the issue of capturing the variability of metabolic performance observed during muscle exercise in humans by using an original method of normalization. Metabolic changes induced by various kinds of exercise were investigated using 31P magnetic resonance spectroscopy (MRS) at 4.7 T in 65 normal subjects (23 women and 42 men) and 12 patients with biopsy-proven muscular disorders. Large variations in the extent of PCr breakdown and intracellular acidosis were recorded among subjects and exercise protocols. For all the data pooled, the amplitude of mechanical performance accounts for 50% of these variations. When scaled to the work output, variations of PCr consumption account for 65% of pH changes through a linear relationship. This linear relationship was substantially improved (90%) when both variables were scaled to the square of work output performed (P1 and P2). By capturing most of the initial interindividual variability (90%), P1 vs. P2 relationship represents an ideal standardization procedure, independent of any anthropometric measurements. This relationship also discloses a significant link between the extent of PCr breakdown and intracellular acidosis regardless of exercise protocol. Moreover, changes in the slope of the P1 vs. P2 regression curve, as measured in old subjects and in selected patients, directly reflect alterations of energy production in muscle. [Copyright &y& Elsevier]

Purpose: Neuromuscular electrostimulation (NMES) leads to a spatially fixed, synchronous, and superficial motor unit recruitment, which could induce muscle damage. Therefore, the extent of muscle damage and its spatial occurrence were expected to be heterogeneous across and along the quadriceps femoris (QF) muscles. The aim of the present study was to characterize muscle spatial heterogeneity in QF damage after a single bout of isometric NMES using multimodal magnetic resonance imaging (MRI). Methods: Twenty-five young healthy males participated in this study. MRI investigations consisted of the assessment of muscle volume, transverse relaxation time (T2), and diffusion tensor imaging (DTI) in muscles positioned near the stimulation electrodes (i.e., vastus lateralis (VL) and vastus medialis (VM)) and muscles located outside the stimulated regions (i.e., vastus intermedius and rectus femoris). These measurements were performed 6 d before, and 2 d and 4 d (D4) after the NMES session. Results: For the muscles placed in direct contact with the stimulation electrodes, volume (VL, +8.5%; VM, +3.8%), T2 (VL, +19.5%; VM, +6.7%) and radial diflusivity (λ3) (VL, + 7.3%; VM, +3.7%) significantly increased at D4. Whereas MRI parameter changes were larger for VL as compared with those for other QF muscles at D4, homogeneous alterations were found along all QF muscles. Conclusions: Isometric NMES induced specific and localized alterations in VL and VM, with heterogeneous damage amplitude among them. Potential effects of unaccustomed intermuscle shear stress during electrically evoked isometric contractions could be a key factor in the spatial occurrence and the extent of damage among QF muscles (especially in VL). The kinetics and extent of MRI changes varied between T2 and diffusion tensor imaging metrics, suggesting the involvement of different physiological processes. [ABSTRACT FROM AUTHOR]