Biomedical subjects

M P Godard

Publications and source records attributed to M P Godard.

6 recordsLinked to original sources

PubMed2002

Alterations in single muscle fiber calcium sensitivity with resistance training in older women.

The purpose of this investigation was to determine the effects of a 12-week progressive resistance-training program (PRT) on single muscle fiber calcium sensitivity in six older women (73 +/- 2 years). Muscle biopsy samples of the vastus lateralis were obtained pre- and post-PRT. Chemically skinned single muscle fibers ( n=274) were dissected and studied. The experimental sequence for each fiber was the determination of peak maximal isometric tension ( P(o)) at pCa 4.5 (pCa=-log[Ca(2+)]), and then subsequent submaximal activations of the fiber at nine Ca(2+) concentrations (pCa 6.8 to 4.7). Myosin heavy chain (MHC) I fiber (slow-twitch) diameter increased 16% ( P<0.05) with no change in MHC IIa fibers (fast-twitch) pre- to post-PRT, respectively. P(o) in MHC I fibers increased 34% ( P<0.05) as a result of the training with no change in MHC IIa fibers. The mean MHC I Ca(2+) activation threshold (minimal amount of Ca(2+) necessary to induce tension) increased from 6.83 +/- 0.02 to 6.91 +/- 0.01 ( P<0.05), as did the mean half-maximal activation (pCa(50)), 5.51 +/- 0.02 to 5.71 +/- 0.03 ( P<0.05) with PRT. The slope of the Hill plot above ( n(1)) the pCa(50) for MHC I did not change significantly with the PRT. However, the slope of the Hill plot below ( n(2)) the pCa(50) for MHC I demonstrated an increase ( P<0.05) with training. There were no differences with MHC IIa fibers with PRT for any of the variables measured. In conclusion, the results of this investigation indicate that myofibril Ca(2+) sensitivity and activation properties are altered in MHC I, but not MHC IIa fibers with PRT in older women. The alterations in the MHC I Ca(2+) properties appear to have an effect on the mechanisms involved with skeletal muscle adaptability in older women following PRT.

Adaptation, Physiological↗

PubMed2000

An upper arm model for simulated weightlessness.

This investigation examined the effects of 4 weeks of non-dominant arm unloading on the functional and structural characteristics of the triceps brachii muscle of six normo-active college-age males (age: 23 +/- 1 years, height: 176 +/- 4 cm, weight: 76 +/- 6 kg). The primary intention of this study was to determine if arm unloading is an effective analogue for simulating the effects of weightlessness on human skeletal muscle. Subjects were tested 2-3 days preceding unloading in a standard arm sling and following removal of the sling. The sling was worn during waking hours to unload the arm. Subjects were allowed to remove the sling during sleep and bathing. Torque production (Nm) during maximal isometric extension at 90 degrees significantly declined (P < 0.05) in response to unloading (53.93 +/- 5.07 to 47.90 +/- 5.92; 12%). There was no significant change (P > 0.05) in the force-velocity attributes of the triceps over the other measured velocities (1.05, 1.57, 2.09, 3.14, 4.19, 5.24 rad.s-1). Cross-sectional muscle area (CSA) of the upper arm was smaller (44.3 +/- 2.7 to 42.4 +/- 2.5 cm2; 4%) following 4 weeks of unloading (P < 0.05). Histochemical analysis of individual muscle fibres demonstrated reductions in fibre CSA of 27 and 18% for type I and type II fibres, respectively. However, these changes were not statistically significant. Electrophoretic analysis of muscle samples revealed a significant increase (40 +/- 7 to 58 +/- 4%, pre- and post-, respectively) in myosin heavy chain (MHC) type II isoforms following unloading. Reductions in type I MHC isoform composition failed to reach statistical significance (P < 0.08). Amplitude of the integrated electromyographic (IEMG) signal during maximal isometric contraction of the long head of the triceps decreased by 21% in response to the 4-week unloading period (P < 0.05). The changes in triceps, muscle structure and function found with arm unloading are similar in magnitude and direction to data obtained from humans following exposure to real and simulated weightlessness. These findings demonstrate that arm unloading produces some of the effects seen in response to weightlessness in muscles of the upper arm and provides potential for an additional model to simulate the effects of microgravity on human skeletal muscle.

Adult↗

PubMed2000

Beta-hydroxy-beta-methylbutyrate ingestion, Part I: effects on strength and fat free mass.

PURPOSE: The purpose of this investigation was 1) to determine whether HMB supplementation results in an increase in strength and FFM during 8 wk of resistance training and 2) determine whether a higher dose of HMB provides additional benefits. METHODS: Thirty-seven, untrained, college-aged men were assigned to one of three groups: 0, 38, or 76 mg x kg(-1) x d(-1) of HMB (approximately equal to 3 and 6 g x d(-1), respectively). Resistance training consisted of 10 different exercises performed 3 d x wk(-1) for 8 wk at 80% of 1-repetition maximum (1RM). The 1RM was reevaluated every 2 wk with workloads adjusted accordingly. RESULTS: No differences were observed in 1RM strength among the groups at any time. However, the 38 mg x kg (-1) x d(-1) group showed a greater increase in peak isometric torque than the 0 or 76 mg.kg(-1) x d(-1) groups (P < 0.05). The 76 mg x kg(-1) x d(-1) group had a greater increase in peak isokinetic torque than the 0 or 38 mg x kg(-1) x d(-1) groups at 2.1, -3.15, and -4.2 rad x s(-1) (P < 0.05). Plasma creatine phosphokinase (CPK) activity was greater for the 0 mg x kg(-1) x d(-1) versus the 38 or 76 mg x kg(-1) x d(-1) groups at 48 h after the initial training bout (P < 0.05). In addition, no differences were observed in body fat between the three groups. However, the 38 mg x kg(-1) x d(-1) group exhibited a greater increase in FFM (P < 0.05). CONCLUSIONS: Although the IRM strength gains were not significantly different, HMB supplementation appears to increase peak isometric and various isokinetic torque values, and increase FFM and decrease plasma CPK activity. Lastly, it appears that higher doses of HMB (i.e., > 38 mg x kg(-1) x d(-1)) do not promote strength or FFM gains.

Adipose Tissue↗

PubMed2000

Beta-hydroxy-beta-methylbutyrate ingestion, part II: effects on hematology, hepatic and renal function.

PURPOSE: The purpose of this investigation was to examine the effects of differing amounts of beta-hydroxy-beta-methylbutyrate (HMB), 0, 36, and 76 mg x kg(-1) x d(-1), on hematology, hepatic and renal function during 8 wk of resistance training. METHODS: Thirty-seven, untrained collegiate males and were randomly assigned to one of the three groups, 0, 38, or 76 mg x kg(-1) x d(-1). Resistance training consisted of 10 exercises, performed 3 d x wk(-1) for 8 wk at 80% of their 1-repetition maximum. Blood and urine was obtained before training, 48 h after the initial session, 1 wk, 2 wk, 4 wk, and at 8 wk of resistance training. Blood was analyzed for glucose, blood urea nitrogen, hemoglobin, hepatic enzymes, lipid profile, total leukocytes, and individual leukocytes. Urine was analyzed for pH, glucose, and protein excretion. RESULTS: The 38 mg x kg(-1) x d(-1) group had a greater increase in basophils compared with 0 or 76 mg x kg(-1) x d(-1) groups (P < 0.05). No difference occurred in any other blood and urine measurements. CONCLUSION: These data indicate that 8 wk of HMB supplementation (< or = 76 mg x kg(-1) x d(-1)) during resistance training had no adverse affects on hepatic enzyme function, lipid profile, renal function, or the immune system.

Adolescent↗

PubMed2000

Progressive resistance training reduces myosin heavy chain coexpression in single muscle fibers from older men.

The purpose of this study was to examine myosin heavy chain (MHC) and myosin light chain (MLC) isoforms following 12 wk of progressive resistance training (PRT). A needle biopsy was taken from the vastus lateralis to determine fiber-type expression [ATPase (pH 4.54) and MHC/MLC] in seven healthy men (age = 74.0 +/- 1.8 yr). Subjects were also tested for 1-repetition maximum (1-RM), pre- and posttraining. The progressive knee extensor protocol consisted of three sets at 80% of 1-RM 3 days/wk for 12 wk. Freeze-dried, single muscle fibers were dissected for MHC and MLC analysis and then subjected to SDS-PAGE and silver staining, pre- and posttraining. MHC expression increased in the I (10.4%; P < 0.05) and decreased in I/IIa (9.0%; P < 0.05), I/IIa/x (0.9%; P < 0.05), and IIa/x (8.9%; P < 0.05) isoforms, with no change in the IIa and IIx isoforms, pre- vs. posttraining (total fibers = 3,059). The MLC(3f)-to-MLC(2) ratio did not change with the PRT in either the MHC I or MHC IIa isoforms (total fibers = 902), pre- to posttraining. ATPase fiber distribution did not significantly differ following training (I: 50. 4 +/- 6.7 vs. 51.9 +/- 7.9, IIa: 36.8 +/- 5.3 vs. 41.1 +/- 7.0, IIb: 12.8 +/- 5.6 vs. 7.0 +/- 4.0%; pre- vs. posttraining, respectively). 1-RM increased (51.9%; P < 0.05) from pre- to posttraining. The PRT provide a stimulus for alterations in MHC isoforms, which demonstrated a decrease in all hybrid isoforms and an increase in MHC I expression (not found in the ATPase results), unlike the MLC ratio (3:2), which was not altered with training.

Adenosine Triphosphatases↗

PubMed2000

Effects of postexercise carbohydrate-protein feedings on muscle glycogen restoration.

The purpose of this investigation was to determine the effects of postexercise eucaloric carbohydrate-protein feedings on muscle glycogen restoration after an exhaustive cycle ergometer exercise bout. Seven male collegiate cyclists [age = 25.6 +/- 1.3 yr, height = 180.9 +/- 3.2 cm, wt = 75.4 +/- 4.0 kg, peak oxygen uptake (VO(2 peak)) = 4.20 +/- 0.2 l/min] performed three trials, each separated by 1 wk: 1) 100% alpha-D-glucose [carbohydrate (CHO)], 2) 70% carbohydrate-20% protein (PRO)-10% fat, and 3) 86% carbohydrate-14% amino acid (AA). All feedings were eucaloric, based on 1.0 g. kg body wt(-1). h(-1) of CHO, and administered every 30 min during a 4-h muscle glycogen restoration period in an 18% wt/vol solution. Muscle biopsies were obtained immediately and 4 h after exercise. Blood samples were drawn immediately after the exercise bout and every 0.5 h for 4 h during the restoration period. Increases in muscle glycogen concentrations for the three feedings (CHO, CHO-PRO, CHO-AA) were 118 mmol/kg dry wt; however, no differences among the feedings were apparent. The serum glucose and insulin responses did not differ throughout the restoration period among the three feedings. These results suggest that muscle glycogen restoration does not appear to be enhanced with the addition of proteins or amino acids to an eucaloric CHO feeding after exhaustive cycle exercise.

Adult↗