Mesenchymal cells recruited to damaged tissues must circulate through the bloodstream. The absolute numbers of circulating mesenchymal stem cells (cMSCs) in two different models of acute and chronic skeletal muscle injury were determined. cMSCs were present in significantly higher numbers in both models than in healthy controls. These results support the hypothesis that MSCs are mobilised into the bloodstream after skeletal muscle tissue damage. These two models (acute and chronic) would be of value in the search for molecular mediators of mobilisation of MSCs into the circulation.
Muscle biopsy samples were obtained from the gastrocnemius of 26 well-trained runners of widely varying ability. Portions of the sample were analyzed for succinate dehydrogenase (SDH) activity and for muscle fiber composition. VO2 max was determined during uphill treadmill running. Mean values for muscle SDH activity (14.6 U/g), fiber composition (55% slow twitch) and VO 2 max (60.9 ml/kg x min -1) were lower than reported previously for groups of elite and sub-elite runners. The physiological data were consistent with the performance ability of the sample [5 : 12, 11 : 20 and 36 : 40 (min : s) for 1, 2 and 6 miles, respectively]. Within the sample, performance was most strongly related to VO2 max (r = -0.84, -0.87 and -0.88 for 1, 2, and 6 miles). There was little relationship between muscle SDH activity and either performance (r---0.11, -0.14, -0.20 for 1, 2, and 6 miles) or P'O2 max (r = 0.23). The relationship between muscle fiber composition and performance was only modestly strong (r---0.52, -0.54, -0.55 for 1, 2, and 6 miles). The results indicate that the primary determinant of cross-sectional differences in running performance is VO 2 max. Skeletal muscle metabolism apparently contributes little to these cross-sectional differences and may be of much greater importance to variations in performance within an individual.
The muscle protein α-actinin-3 (ACTN3) is normally thought to be expressed in type II muscle fibres and to be necessary for high-power, high-velocity muscle contractions, such as those typically seen in speed/power athletes. The authors report the case of a Spanish elite long jumper (two times Olympian, personal best of 8.26 m) whose genotype for theACTN3gene is577XX(ACTN3 deficient). These data suggest that there might be notable exceptions to the concept thatACTN3is the “gene for speed”.
Circulating mesenchymal cells (cMCs) have a potential for regenerating damaged tissue, e.g., ischaemic myocardium. In patients (age range: 53-76 years) with stable coronary artery disease cMCs were determined before and after dynamic exercise of moderate (< respiratory compensation threshold (RCT)) (n = 9 patients) or high intensity (>RCT) (n = 11). Only high-intensity exercise (i.e., provoking signs of myocardial ischaemia in 3 patients and ventricular extrasystoles in another) induced a significant increase in cMCs (p = 0.009). These results support the hypothesis that intense exercise (near or at the point of myocardial ischaemia) is a potent stimulus for MC mobilisation.
The purpose of this study was to determine if a short-term exercise program (6 weeks) could improve subjective physical appearance ratings. Twenty-five previously sedentary adult men (aged 18-40 years) were randomly assigned to one of 3 training groups: cardiovascular, strength, or control. Subjects participating in an exercise group trained for an average of 34 minutes, 3 times per week. All subjects were pre- and posttested to determine body composition, strength, and cardiovascular fitness. Subjects were also digitally photographed from 4 angles. The photographs were rated by the subjects and by a panel of 6 judges using an analog scale. There was no significant difference in the groups by trials interaction effect for pre- and post-Vo(2)max, percent fat, total lean tissue, percent limb fat, percent trunk fat, lean trunk tissue, or lean limb tissue. The subjects rated themselves higher than the panel, with average scores of 4.74 vs. 3.46, 4.26 vs. 3.10, and 4.61 vs. 3.49 for the cardiovascular, strength, and control groups, respectively (p < 0.05). The men of the panel rated the subjects significantly higher than did the women, with average scores of 4.61 vs. 2.31, 4.13 vs. 2.06, and 4.53 vs. 2.18 for the cardiovascular, resistance, and control groups, respectively (p < 0.05). This study showed that a 6-week training program did not change self-rated or panel-rated appearance scores.
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