Biomedical subjects

Allen C Parcell

Publications and source records attributed to Allen C Parcell.

13 recordsLinked to original sources

PubMed2006

Temporal response of desmin and dystrophin proteins to progressive resistance exercise in human skeletal muscle.

We have investigated the adaptations of the cytoskeletal proteins desmin and dystrophin in relationship to known muscular adaptations of resistance exercise. We measured desmin, dystrophin, and actin protein contents, myosin heavy chain (MHC) isoform distribution, muscle strength, and muscle cross-sectional area (CSA) during 8 wk of progressive resistance training or after a single bout of unaccustomed resistance exercise. Muscle biopsies were taken from the vastus lateralis of 12 untrained men. For the single-bout group (n=6) biopsies were taken 1 wk before the single bout of exercise (week 0) and 1, 2, 4, and 8 wk after this single bout of exercise. For the training group (n=6), biopsies were taken 1 wk before the beginning of the program (week 0) and at weeks 1, 2, 4, and 8 of the progressive resistance training program. Desmin, dystrophin, and actin protein levels were determined with immunoblotting, and MHC isoform distribution was determined using SDS-PAGE at each time point for each group. In the training group, desmin was significantly increased compared with week 0 beginning at week 4 (182% of week 0; P<0.0001) and remained elevated through week 8 (172% of week 0; P<0.0001). Desmin did not change at any time point for the single-bout group. Actin and dystrophin protein contents were not changed in either group at any time point. The percentage of MHC type IIa increased and MHC type IIx decreased at week 8 in the training group with no changes occurring in the single-bout group. Strength was significantly increased by week 2 (knee extension) and week 4 (leg press), and it further increased at week 8 for both these exercises in the training group only. Muscle CSA was significantly increased at week 4 for type II fibers in the training group only (5,719+/-382 and 6,582+/-640 microm2, weeks 0 and 4, respectively; P<0.05). Finally, a significant negative correlation was observed between the desmin-to-actin ratio and the percentage of MHC IIx (R=-0.31; P<0.05, all time points from both groups). These data demonstrate a time course for muscular adaptation to resistance training in which desmin increases shortly after strength gains and in conjunction with hypertrophy, but before changes in MHC isoforms, whereas dystrophin remains unchanged.

Actins↗

PubMed2006

Ballistic stretching increases flexibility and acute vertical jump height when combined with basketball activity.

Stretching is often included as part of a warm-up procedure for basketball activity. However, the efficacy of stretching with respect to sport performance has come into question. We determined the effects of 4 different warm-up protocols followed by 20 minutes of basketball activity on flexibility and vertical jump height. Subjects participated in 6 weeks (2 times per week) of warm-up and basketball activity. The warm-up groups participated in ballistic stretching, static stretching, sprinting, or basketball shooting (control group). We asked 3 questions. First, what effect does 6 weeks of warm-up exercise and basketball play have on both flexibility and vertical jump height? We measured sit and reach and vertical jump height before (week -1) and after (week 7) the 6 weeks. Flexibility increased for the ballistic, static, and sprint groups compared to the control group (p < 0.0001), while vertical jump height did not change for any of the groups. Our second question was what is the acute effect of each warm-up on vertical jump height? We measured vertical jump immediately after the warm-up on 4 separate occasions during the 6 weeks (at weeks 0, 2, 4, and 6). Vertical jump height was not different for any group. Finally, our third question was what is the acute effect of each warm-up on vertical jump height following 20 minutes of basketball play? We measured vertical jump height immediately following 20 minutes of basketball play at weeks 0, 2, 4, and 6. Only the ballistic stretching group demonstrated an acute increase in vertical jump 20 minutes after basketball play (p < 0.05). Coaches should consider using ballistic stretching as a warm-up for basketball play, as it is beneficial to vertical jump performance.

Adult↗

PubMed2005

Desmin increases with high-intensity concentric contractions in humans.

To investigate the role desmin may play in muscular adaptation to exercise, we measured desmin protein content in the vastus lateralis muscle of seven untrained men in response to 8 weeks of high-intensity cycle training. Training involved 15-s sprints separated by rest for 5 min. Subjects began with four sprints twice per week, and progressed to six sprints three times per week. Peak power was measured before and after training with a 30-s maximal sprint test. Mean power during the first 15 s increased significantly after training (P < 0.05). Desmin and actin protein levels were determined by immunoblotting, from pretraining and posttraining muscle biopsies. Desmin protein levels were increased by 60% after training (P < 0.01), whereas actin protein levels did not change with training. We conclude that the cytoskeletal protein desmin increases in response to a high-tension, concentric-only load consequent to sprint training. Desmin appears to increase as the force generating capacity of the muscle increases. A reinforced desmin cytoskeleton may be necessary for increased force generation by the muscle.

Adult↗

PubMed2005

Single-fiber MHC polymorphic expression is unaffected by sprint cycle training.

PURPOSE: The present investigation examined single-fiber MHC alterations in response to high-intensity, short-duration, sprint cycle training. METHODS: Ten untrained college-age male subjects participated in 8 wk of a progressive sprint cycle training program. Training involved 15-s maximal sprints separated by 5 min of rest beginning with four sprints x 2 d in week 1 and increasing to six sprints x 3 d at week 8. Muscle samples from the vastus lateralis were obtained before and after training. A 30-s sprint cycle test was used to evaluate performance before and after training. RESULTS: For the 30-s sprint, mean power and total work increased from pre to post. Single-fiber analyses revealed a reduction in the MHC IIx isoform (2.0 +/- 1.0 to 0.2 +/- 0.1%, pre to post, P < 0.05) and an increase in MHC IIa (P = 0.08), whereas there was no change in hybrid fiber composition (total hybrids = 24%). Generally, MHC IIa content increased and MHC IIx decreased (P < 0.05) as demonstrated by homogenate analyses of tissue samples. CONCLUSIONS: We report that as little as 32 min of high-intensity sprint cycle training over 8 wk is sufficient to improve sprinting performance. This training response is accompanied by an increase in MHC IIa and reduction in MHC IIx content of the vastus lateralis. However, short-duration, high-intensity, sprint cycle training does not cause a reduction in hybrid muscle fiber content.

Adult↗

PubMed2005

Aerobic and resistance exercise sequence affects excess postexercise oxygen consumption.

Excess postexercise oxygen consumption (EPOC) may describe the impact of previous exercise on energy metabolism. Ten males completed Resistance Only, Run Only, Resistance-Run, and Run-Resistance experimental conditions. Resistance exercise consisted of 7 lifts. Running consisted of 25 minutes of treadmill exercise. Vo(2) was determined during treadmill exercise and after each exercise treatment. Our findings indicated that treadmill exercise Vo(2) was significantly higher for Resistance-Run compared with Run-Resistance and Resistance Only at all time intervals. At 10 minutes postexercise, Vo(2) was greater for Resistance Only and Run-Resistance than for Resistance-Run. At 20 and 30 minutes, Vo(2) following Resistance Only was significantly greater than following Run Only. In conclusion, EPOC is greatest following Run-Resistance; however, treadmill exercise is more physiologically difficult following resistance exercise. Furthermore, the sequence of resistance and treadmill exercise influences EPOC, primarily because of the effects of resistance exercise rather than the exercise combination. We recommend performing aerobic exercise before resistance exercise when combining them into 1 exercise session.

Adult↗

PubMed2004

Glycemic and insulinemic responses to protein supplements.

OBJECTIVE: The effects of common servings of commercially marketed nutritional protein supplements on blood glucose and insulin responses were studied in 12 healthy men after ingestion of feedings that had varying carbohydrate and protein compositions. DESIGN: Fasting subjects consumed a 50-gram glucose drink, a white bagel, peanuts, a protein bar, or a protein drink in a counterbalanced fashion. SETTING: Subjects rested in a supine position and were not disturbed while blood samples were drawn at rest and at 10-minute intervals during the ensuing 2 hours. RESULTS: The area under the curve for glucose was greater in the glucose drink group vs all treatment groups except the white bagel group ( P <.05). At 20 to 40 minutes, plasma glucose was elevated in the glucose drink group vs the peanuts group, the protein bar group, and the protein drink group ( P <.05). The glycemic response was greater in the glucose drink group vs the white bagel group at 30 minutes (8.1+/-0.5 vs 6.5+/-0.3 mmol/L, respectively) ( P <.05). The area under the curve for insulin was lower in the peanuts group vs all treatment groups ( P <.05). Insulin concentrations peaked at 40 minutes in the glucose drink group (285.5+/-18.3 pmol) and was similar in all but the peanuts group (130.5+/-14.3 pmol) ( P <.05). CONCLUSIONS: A common serving of a commercially available protein supplement resulted in a marked insulin response with no glycemic response because of the lack of carbohydrate content. Inasmuch as many such supplements similar in composition are marketed on the bases of their nutritional energy benefits, these data underscore the need to educate consumers regarding appropriate fuel for exercise and nutritional supplement composition.

Adult↗

PubMed2004

Inadequate carbohydrate intake following prolonged exercise does not increase muscle soreness after 15 minutes of downhill running.

In Delayed Onset Muscle Soreness (DOMS), muscles become sore 24 to 48 hours after eccentric and unaccustomed activity. Fiber stiffness, due to decreased muscle glycogen, may predispose muscle to greater damage during eccentric exercise. This study sought to determine if inadequate carbohydrate intake following a protocol to decrease muscle glycogen would increase DOMS after 15 min of downhill running. Thirty-three male subjects (age, 18-35 years) were randomized into 3 groups for testing over a 7-day period. The depletion (DEP) group (n= 12) underwent a glycogen depletion protocol prior to a 15-min downhill run designed to induce DOMS. The repletion (FED) group (n = 10) underwent a glycogen depletion protocol followed by a carbohydrate repletion protocol (>80% CHO) prior to downhill running. The third (ECC) group (n = 11) performed only the downhill running protocol. Subjective muscle soreness, isometric force production, relaxed knee angle, and thigh circumference were measured pretreatment and on days 1, 2, 3, 4, and 6 post treatment. Subjective muscle soreness for all groups increased from 0 cm pretreatment to 3.05 +/- 0.72 cm (on a 10-cm scale) on day 1 post treatment (p<.05). All groups were significantly different from baseline measurements until day 4 post treatment. Each group experienced a decline in isometric force from 281 +/- 45 N pre- to 253 +/- 13 N on day 1 post treatment (p <.05). The decrease in isometric force persisted in all groups for 4 days post treatment. Increases in thigh circumference and relaxed knee angle elevations in all 3 groups were statistically different (p <.05) from pretreatment until day 4. No differences were noted between groups for any of the parameters examined. In the current study, 15 min of downhill running is sufficient to cause DOMS with the associated functional and morphological changes; however, inadequate carbohydrate intake after a glycogen depleting exercise does not appear to exacerbate DOMS and the associated symptoms.

Adolescent↗

PubMed2004

Cordyceps Sinensis (CordyMax Cs-4) supplementation does not improve endurance exercise performance.

It is purported that supplementation with Cordyceps Sinensis (CordyMax Cs-4) will improve oxidative capacity and endurance performance. The intent of this investigation was to examine the effects of CordyMax Cs-4 supplementation on VO<(2peak,) ventilatory threshold, and endurance performance in endurance-trained cyclists. Twenty-two male cyclists participated in 5 weeks of supplementation with CordyMax Cs-4 tablets (3 g/d). Training intensity was maintained by weekly documentation and reporting throughout the 5-week period. Subjects completed a VO(2peak) test and work-based time trial prior to and following the supplementation period. VO(2peak) was similar within and between placebo (PLA) and treatment (CS) groups prior to (59.9 +/- 5.9 vs. 59.1 +/- 5.4 ml/kg/min, respectively) and following (60.1 +/- 5.5 vs. 57.1 +/- 5.8 ml/kg/min, respectively) the supplementation period. Ventilatory threshold (VT) was measured at 72 +/- 10% of VO(2peak) in P and T prior to supplementation and did not change in either group following the supplementation. PLA completed the time trial in 61.4+/- 2.4 min compared to 62.1+/- 4.0 min in T. Time trial measurements did not differ between groups, nor did they change in response to supplementation. It is concluded that 5 weeks of CordyMax Cs-4 supplementation has no effect on aerobic capacity or endurance exercise performance in endurance-trained male cyclists.

Adult↗

PubMed2003

Single muscle fiber myosin heavy chain distribution in elite female track athletes.

PURPOSE: Myosin heavy chain (MHC) characterization of tissue samples from the gastrocnemius muscle of six elite female athletes and 10 untrained females was performed using myosin ATPase histochemistry and gel electrophoresis. Athletes were of national and international caliber, whereas their untrained counterparts were healthy individuals not involved in a regular exercise program. METHODS: Muscle biopsies for the athletes were performed 14 wk into their training season and analyzed with sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and myosin ATPase techniques. RESULTS: Electrophoretic analysis of single muscle fibers from elite athletes revealed a MHC phenotype composition of 46 +/- 6% type I, 21 +/- 6% type IIa, and 0% type IIx, whereas 34% of the single fibers expressed multiple MHC isoforms. When compared with the elite women, untrained subjects demonstrated higher percentages of type I MHC and lower percentages of IIa MHC muscle fibers, 57 +/- 5 and 16 +/- 3%, respectively (P < 0.05). Similar to the female athletes, 27% of the fibers from untrained women possessed multiple myosin isoforms. Myosin ATPase staining demonstrated a greater percentage of type I fibers in untrained subjects versus the elite women (67 +/- 3 vs 41 +/- 2%, P< 0.05) (mean +/- SE), whereas the athletes had a higher percentage of type IIa fibers compared with the untrained women (49 +/- 5 vs 19 +/- 2%, P< 0.05). There were no differences in the percentage of IIb fibers between elite and untrained women (11 +/- 4 vs 14 +/- 2%, respectively). CONCLUSIONS: Whereas a preponderance of hybrid fibers is generally observed in untrained populations, the diverse MHC phenotype seen in these elite female athletes is uncommon. These unique findings are attributed to the chronic and varied nature of training in which these athletes were involved.

Adult↗

PubMed2002

Prediction of maximum oxygen consumption from walking, jogging, or running.

The purpose of this study was to develop a submaximal, 1.5-mile endurance test for college-aged students using walking, jogging, or running exercise. College students (N = 101: 52 men, 47 women), ages 18-26years, successfully completed the 1.5-mile test twice, and a maximal graded exercise test. Participants were instructed to achieve a "somewhat hard" exercise intensity (rating of perceived exertion = 13) and maintain a steady pace throughout each 1.5-mile test. Multiple linear regression generated the following prediction equation: VO2 max = 65.404 + 7.707 x gender (1 = male; 0 =female) - 0.159 x body mass (kg) - 0.843 x elapsed exercise time (min; walking, jogging orrunning). This equation shows acceptable validity (R = .86, SEE = 3.37 ml x kg(-1) min(-1)) similar to the accuracy of comparable field tests, and reliability (ICC = .93) is also comparable to similar models. The statistical shrinkage is minimal (R(press) = 0.85, SEE(press) = 3.51 ml x kg(-) x min(-1)); hence, it should provide comparable results when applied to other similar samples. A regression model (R =.90, and SEE = 2.87 ml x kg(-1) min(-1)) including exercise heart rate was also developed: VO2 max = 100.162 +/- 7.301 x gender(1 = male; 0 =female) - 0.164 x body mass (kg) - 1.273 x elapsed exercise time -0.156 x exercise heart rate, for those who have access to electronic heart rate monitors. This submaximal 1.5-mile test accurately predicts maximal oxygen uptake (VO2max) without measuring heart rate and is similar to the 1.5-mile run in that it allowsfor mass testing and requires only a flat, measured distance and a stopwatch. Further, it can accommodate a wide range of fitness levels (from walkers to runners).

Adolescent↗

PubMed2002

Minimum rest period for strength recovery during a common isokinetic testing protocol.

PURPOSE: The intent of this investigation was to determine the minimal time for a between sets rest period during a common isokinetic knee extension strength-testing protocol. Based on a review of the literature, a set was considered a group of four maximal coupled contractions at a specific velocity. METHODS: Eleven normal, healthy college-age men underwent unilateral knee extension testing to determine their individual isokinetic peak torque at 60, 120, 180, 240, and 300 degrees.s-1. Velocities were administered in ascending order. Between sets, rest periods of 15, 60, 180, and 300 s were assigned to subjects in a counterbalanced fashion. RESULTS: There were no differences in peak torque at the beginning velocity of 60 degrees.s-1 among any of the rest periods. At 120 degrees.s-1, peak torque production during the 15-s rest period trial was similar to 60 s but lower than 180 and 300 s. Peak torques at 180, 240, and 300 degrees.s-1 produced during the 15-s rest period test were significantly lower than measured torques at the same velocities during the 60, 180, and 300-s rest period tests (P < 0.05). There were no differences in peak torque production between the 60, 180, and 300-s rest period tests. CONCLUSION: These data demonstrate that during a common isokinetic strength testing protocol a between set rest period of at least 60 s is sufficient for recovery before the next test set.

Adult↗

PubMed2002

Effects of warm-up before eccentric exercise on indirect markers of muscle damage.

PURPOSE: To test whether active and passive warm-up conducted before eccentric exercise attenuates clinical markers of muscle damage. METHODS: Untrained subjects were exposed to one of five conditions: low-heat passive warm-up (N = 10), high-heat passive warm-up (N = 4), or active warm-up (N = 9), preceding eccentric exercise; eccentric exercise without warm-up (N = 10); or high-heat passive warm-up without eccentric exercise (N = 10). Passive warm-up of the elbow flexors was achieved using pulsed short-wave diathermy, and active warm-up was achieved by concentric contraction. Creatine kinase (CK) activity, strength, range of motion, swelling, and muscle soreness were observed before treatment (baseline) and 24, 48, 72, and 168 h after treatment. RESULTS: High-heat passive warm-up without eccentric exercise did not affect any marker of muscle damage and was used as our control group. Markers of muscle damage were not different between groups that did or did not conduct warm-up before eccentric exercise. The active warm-up and eccentric groups exhibited a greater circumferential increase than controls (P < 0.0002), however, that was not observed after passive warm-up. Additionally, the active warm-up group exhibited a greater CK response than controls at 72 h (P < 0.05). The high-heat passive warm-up before eccentric exercise group exhibited significant change from controls at the least number of time points, but due to a small sample size (N = 4), these data should be viewed as preliminary. CONCLUSION: Our observations suggest that passive warm-up performed before eccentric exercise may be more beneficial than active warm-up or no warm-up in attenuating swelling but does not prevent, attenuate, or resolve more quickly the other clinical symptoms of eccentric muscle damage as produced in this study.

Adolescent↗

PubMed2002

Effects of L-tyrosine and carbohydrate ingestion on endurance exercise performance.

To test the effects of tyrosine ingestion with or without carbohydrate supplementation on endurance performance, nine competitive cyclists cycled at 70% peak oxygen uptake for 90 min under four different feeding conditions followed immediately by a time trial. At 30-min intervals, beginning 60 min before exercise, each subject consumed either 5 ml/kg body wt of water sweetened with aspartame [placebo (Pla)], polydextrose (70 g/l) (CHO), L-tyrosine (25 mg/kg body wt) (Tyr), or polydextrose (70 g/l) and L-tyrosine (25 mg/kg body wt) (CHO+Tyr). The experimental trials were given in random order and were carried out by using a counterbalanced double-blind design. No differences were found between treatments for oxygen uptake, heart rate, or rating of perceived exertion at any time during the 90-min ride. Plasma tyrosine rose significantly from 60 min before exercise to test termination (TT) in Tyr (means +/- SE) (480 +/- 26 micromol) and CHO+Tyr (463 +/- 34 micromol) and was significantly higher in these groups from 30 min before exercise to TT vs. CHO (90 +/- 3 micromol) and Pla (111 +/- 7 micromol) (P < 0.05). Plasma free tryptophan was higher after 90 min of exercise, 15 min into the endurance time trial, and at TT in Tyr (10.1 +/- 0.9, 10.4 +/- 0.8, and 12.0 +/- 0.9 micromol, respectively) and Pla (9.7 +/- 0.5, 10.0 +/- 0.3, and 11.7 +/- 0.5 micromol, respectively) vs. CHO (7.8 +/- 0.5, 8.6 +/- 0.5, and 9.3 +/- 0.6 micromol, respectively) and CHO+Tyr (7.8 +/- 0.5, 8.5 +/- 0.5, 9.4 +/- 0.5 micromol, respectively) (P < 0.05). The plasma tyrosine-to-free tryptophan ratio was significantly higher in Tyr and CHO+Tyr vs. CHO and Pla from 30 min before exercise to TT (P < 0.05). CHO (27.1 +/- 0.9 min) and CHO+Tyr (26.1 +/- 1.1 min) treatments resulted in a reduced time to complete the endurance time trial compared with Pla (34.4 +/- 2.9 min) and Tyr (32.6 +/- 3.0 min) (P < 0.05). These findings demonstrate that tyrosine ingestion did not enhance performance during a cycling time trial after 90 min of steady-state exercise.

Adult↗