Effects of prior exercise on eccentric exercise-induced neutrophilia and enzyme release.

PURPOSE: The purpose of this study was to determine the effects of prior exercise on changes in circulating neutrophils, neutrophil activation, and myocellular enzymes following a standardized bout of eccentric exercise. METHODS: Twenty-four male volunteers were randomized into three groups (N = 8). Group C performed 10 sets of 10 eccentric contractions of the quadriceps muscles with both legs (100% of the concentric IRM). Group D and Group F exercised for 2 h at 56%VO2max on a cycle ergometer followed by a similar bout of eccentric contractions. Group F also received 7.5 mL x kg(-1) of a carbohydrate-electrolyte beverage every 30 min during the submaximal exercise, whereas group D received no fluid. RESULTS: Body weight remained unchanged in groups C and F and decreased in group D by 1.56 +/- 0.34 kg. Ultrastructural Z-Band damage increased three-fold following exercise and remained elevated 3 d after exercise but was not different among groups. Circulating neutrophils were elevated more in group D compared with those in group C immediately after the exercise or rest period, and this difference persisted 3 h after the eccentric exercise. Serum lactoferrin concentrations increased 3.3-fold after exercise in all groups (P < 0.01). Creatine kinase levels (CK) rose in all subjects, with subjects in Group F and D having a significantly greater rise in CK after exercise compared with those in group C. CONCLUSIONS: These data indicate that submaximal exercise followed by a bout of eccentric exercise results in similar amounts of myofibrillar injury with a larger neutrophil response and CK release.

Insulin-like growth factor I in skeletal muscle after weight-lifting exercise in frail elders.

To assess muscle remodeling and functional adaptation to exercise and diet interventions, 26 men and women aged 72-98 yr underwent a vastus lateralis biopsy before and after placebo control condition, and progressive resistance training, multinutrient supplementation, or both. Type II atrophy, Z band, and myofibril damage were present at baseline. Combined weight lifting and nutritional supplementation increased strength by 257 +/- 62% (P = 0.0001) and type II fiber area by 10.1 +/- 9.0% (P = 0.033), with a similar trend for type I fiber area (+12.8 +/- 22.2%). Exercise was associated with a 2. 5-fold increase in neonatal myosin staining (P = 0.0009) and an increase of 491 +/- 137% (P < 0.0001) in IGF-I staining. Ultrastructural damage increased by 141 +/- 59% after exercise training (P = 0.034). Strength increases were largest in those with the greatest increases in myosin, IGF-I, damage, and caloric intake during the trial. Age-related sarcopenia appears largely confined to type II muscle fibers. Frail elders respond robustly to resistance training with musculoskeletal remodeling, and significant increases in muscle area are possible with resistance training in combination with adequate energy intakes.

Acute phase response in exercise. III. Neutrophil and IL-1 beta accumulation in skeletal muscle.

Nine untrained men (22-29 yr) performed 45 min of downhill running (16% incline, 70% of maximum heart rate). Needle biopsies of the vastus lateralis were performed before, 45 min after, and 5 days after exercise. Immunohistochemical staining of muscle cross sections revealed a 135% increase in muscle interleukin-1 beta (IL-1 beta) immediately after and a 250% increase (P < 0.03) 5 days after exercise. Using a rating scale (0-3) for the presence of neutrophils, light microscopic examination showed a significant accumulation of neutrophils in muscle biopsies taken 45 min after and 5 days after exercise [before: 0.5 +/- 0.2, 45 min after: 1.5 +/- 0.3 (P < 0.01), and 5 days after: 1.2 +/- 0.2 (P < 0.04)]. In addition, electron microscopic analysis showed an increase in the percentage of damaged Z-bands relative to total Z-bands [before: 4.8 +/- 3.5%, 45 min after: 32.5 +/- 8.6% (P < 0.05), and 5 days after: 14.1 +/- 3.2%]. Neutrophil accumulation was positively correlated to intracellular Z-band damage (rho = 0.66, P < 0.001). Immunohistochemical staining for IL-1 beta was related to neutrophil accumulation in muscle (rho = 0.38, P < 0.06) and to plasma creatine kinase levels (rho = 0.416, P < 0.04). These data indicate that after eccentric exercise ultrastructural damage to skeletal muscle is associated with neutrophil infiltration and muscle IL-1 beta accumulation.