Browsing by Subject "Exercise -- Physiological aspects."
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Item The effects of active and passive recovery on blood lactate in collegiate female tennis players.(2007-03-08T15:33:24Z) Coffer, Larry W.; Greenwood, Mike.; Health, Human Performance and Recreation.; Baylor University. Dept. of Health, Human Performance and Recreation.Purpose: To examine the effects of active and passive recovery on lactate in females and to determine if a relationship exists between power and blood lactate concentration. Methods: Nine (9) female athletes performed two Wingate Power Tests. One test ended with passive recovery, the other ended with active recovery. Lactate was drawn during the recovery periods. From the Wingate Test, power indices were obtained. A t-test and an ANOVA were performed to evaluate differences in active and passive recovery and Pearson’s correlations were used to examine relationships between power and lactate values. Results: Active recovery significantly (p< 0.03) increased lactate removal compared to passive recovery. There were no significant correlations between lactate and power measures. Conclusions: Active recovery increases the rate of lactate removal in females; however, lactate measures are not correlated to the power measures from the Wingate Test.Item Effects of low- and high-intensity resistance exercise on skeletal muscle specific transcription factor activity and myosin heavy chain gene expression in males.(2007-02-07T19:00:17Z) Wilborn, Colin D.; Willoughby, Darryn Scott, 1963-; Health, Human Performance and Recreation.; Baylor University. Dept. of Health, Human Performance and Recreation.A single bout of resistance training is capable of activating the expression of many diverse groups of genes including myosin heavy chain (MHC) isoforms and the myogenic regulatory factors (MRF). However, the role of exercise intensity in regards to the effects on transcription and protein synthesis are not well defined. Therefore, the purpose of this study was to investigate the effects of exercise intensity on MRF mRNA and protein and MHC mRNA isoforms. Thirteen male participants (21.5 ± 2.9 yrs, 86.1 ± 19.5 kg, 69.7 ± 2.7in) completed two bouts [low-intensity (LI = 65% 1-RM) and high-intensity (HI = 85% 1-RM)] of single-legged resistance exercise. The resistance exercise bout consisted of four sets of leg press and leg extension. Muscle biopsies were obtained from each leg immediately before exercise (PRE), and at 30 minutes (30MPST), 2 hours (2HRPST), and 6 hours (6HRPST) following each resistance exercise bout. Data were analyzed using RT-PCR for mRNA expression and ELISA for protein expression. Statistical analyses were performed by utilizing a 2 x 4 MANOVA (level of significance was set at p < 0.05). Results indicated that MHC I, IIb, and IIx all significantly increased in response to resistance exercise (p < 0.001). Furthermore, exercise intensity/volume played a role with LI high volume exercise stimulating a more positive response in MHC I (p < 0.001) and HI eliciting a greater response in MHC IIb and IIx (p < 0.001). In regards to the MRF, resistance exercise significantly increased the expression of Myogenin, Myf5, and MRF-4 mRNA (p < 0.05). Furthermore, LI high volume exercise stimulated a more positive response in MyoD, Myogenin, and Myf5 mRNA (p < 0.05), as well as MyoD, Myogenin, and MRF-4 protein (p < 0.05). MRF-4 protein significantly increased at 6HRPST over the baseline values (p < 0.05). Changes in MyoD and Myogenin mRNA were also found to be significantly correlated (p < 0.05) to changes in MHC I, IIa, IIb, and IIx mRNA. We can conclude from the findings of this study that both the MHC mRNA and MRF mRNA respond very quickly and positively in response to resistance exercise, in addition to LI high volume exercise eliciting a more positive response in most MRF mRNA and protein.Item Effects of low- and high-intensity single-leg resistance exercise on the mitogen-activated protein kinase ERK1/2 family signal transduction response in skeletal muscle of untrained males.(2007-02-14T21:45:18Z) Taylor, Lemuel W.; Willoughby, Darryn Scott, 1963-; Health, Human Performance and Recreation.; Baylor University. Dept. of Health, Human Performance and Recreation.Acute resistance exercise signals responses in the body to promote adaptations to the exercise stimulus. One key response during and following exercise is the role of signal transduction in the skeletal muscle (MAPK family) and its downstream effects on muscular adaptation. Therefore, the purpose of this study was to determine the differential response of a prominent signal transduction pathway following a high-(HI) and a low-intensity (LI) bout of acute resistance exercise. Participants completed a single-legged bout of HI (8-10 reps at 85% of 1-RM) and LI (18-20 reps at 65% of 1-RM) resistance exercise designed to reach muscular fatigue in a randomized, crossover design. Venous blood and muscle biopsies were taken at PRE, 30PST, 2HRPST, and 6HRPST for the two resistance exercise sessions (RES), with an additional blood draw occurring at POST time point. Serum analyses included cortisol, insulin, GH, IGF-1, and IGFBP-3. Muscle analyses included phosphorylated IGF-1R, MEK1, ERK1/2, and activated Elk-1. Statistical analyses utilized a 2X4 MANOVA for muscle and a 2X5 MANOVA for serum variables on delta responses (p>0.05). RES resulted significant increases in cortisol (p<0.001), GH (p<0.001), insulin (p<0.01), and IGFBP-3 (p<0.001) in serum, with the peak elevations occurring by 30MPST, with no significant differences observed between exercise intensities. RES resulted in significant increases in pIGF-1R (p<0.05), pMEK1 (p<0.001), pERK1/2 (p<0.001), and Elk-1(p<0.001) from baseline levels in muscle, with the peak activation by the 2HRPST time point. The LI RES resulted in a significant difference in pIGF-1R (p<0.05) and Elk-1 (p<0.05) activation. The results of this study indicate that acute RES of both HI and LI results in similar responses in the serum markers cortisol, insulin, GH, and IGFBP-3. The RES also up-regulated various levels of the ERK1/2 signal transduction pathway in skeletal muscle, with some beneficial responses observed in the LI group. Thus, these findings suggest that exercise intensity is not as important in up-regulating these anabolic and signaling mechanisms as once thought and that exercising to muscular fatigue may be a more important aspect of an acute exercise bout. Additionally, the effect of higher exercise volume may also have a positive effect on these responses.Item Effects of prophylactic supplementation of N-acetyl-cysteine and epigallocatechin gallate on markers of oxidative stress, inflammation and apoptosis after eccentric contraction-induced injury in untrained males.(2007-02-07T18:58:56Z) Kerksick, Chad M.; Willoughby, Darryn Scott, 1963-; Health, Human Performance and Recreation.; Baylor University. Dept. of Health, Human Performance and Recreation.The purpose of this study was the examine the effects of 14 days of prophylactic supplementation of N-acetyl-cysteine (NAC) and epigallocatechin gallate (EGCG) on changes in peak torque production, muscle soreness, muscle damage, oxidative stress, inflammation and apoptosis after a single damaging bout of eccentric muscle contractions. Thirty healthy, recreationally active males (20.0±1.8 years, 160±7.1cm, 167.4±37.3 kg) were randomized in a double-blind fashion to ingest daily either 1800 mg of NAC, 1,200 mg of EGCG, or 1,500 mg of glucomannan placebo (PLC) in a prophylactic fashion for 14 days. After supplementation, subjects completed one eccentric exercise bout (100 repetitions @ 30o•s-1) of the dominant knee extensors. Participants completed strength and soreness assessments while providing fasting blood samples and vastus lateralis muscle biopsies (no 72 h biopsy) before and after supplementation, as well as 6h, 24h, 48h and 72h post-exercise to assess changes in muscle damage, oxidative stress, inflammation, and apoptosis. Separate 3 x 6 repeated measures ANOVA with a probability level of 0.05 was used for the statistical analysis with LSD post-hoc comparisons for all significant interactions. Significant reductions in peak torque as well as increases in soreness and creatine kinase at 6 h post-ex were found in all groups. No changes (p > 0.05) were observed for the indicators of oxidative stress, serum superoxide dismutase, serum 8-isoprostane and muscle glutathione reductase, as well as the indicators of stress and inflammation, serum cortisol and tumor necrosis factor-alpha. For the apoptosis markers, significant increases (p < 0.05) in muscle levels of bax, bcl-2, caspase-3 enzyme activity and decreases in total DNA content were observed in all groups with no significant differences among groups, whereas no changes (p>0.05) were reported for cytochrome C. At all time points, PLC demonstrated greater caspase-3 enzyme activity and lower levels of total DNA content in comparison to either supplementation group. An eccentric bout of muscle contractions appears to significantly increases muscle damage and apoptosis with no changes in oxidative stress and inflammation. More research is needed to determine the impact supplementation with EGCG and NAC may have on changes related to apoptosis and eccentric exercise.