Biomedical subjects

Michael R McGuigan

Publications and source records attributed to Michael R McGuigan.

14 recordsLinked to original sources

PubMed2006

The effects of amino acid supplementation on hormonal responses to resistance training overreaching.

The purpose of this investigation was to examine the effects of amino acid supplementation on muscular performance and resting hormone concentrations during resistance training overreaching. Seventeen resistance-trained men were randomly assigned to either an amino acid (AA) or a placebo (P) group and underwent 4 weeks of total-body resistance training designed to induce a state of overreaching. The protocol consisted of two 2-week phases (phase 1, 3 sets of 8 exercises performed for 8-12 repetitions; phase 2, 5 sets of 5 exercises performed for 3-5 repetitions). Muscle strength and resting blood samples were determined before (T1) and at the end of each training week (T2-T5). One-repetition maximum squat and bench press decreased at T2 in the P group but not in the AA group; both groups showed similar increases in strength at T3 to T5. Significant elevations in serum creatine kinase and uric acid were observed at T2 in the P group; the elevation in creatine kinase correlated highly to reductions in 1-repetition maximum squat (r = -0.67, r(2) = 0.45). Significant elevations in serum sex hormone-binding globulin were observed during overreaching in the P group from T2 to T5; this response was abolished in the AA group. Significant reductions in total testosterone were observed in the P group at T4 compared with T1, and total testosterone values were higher for the AA group than for the P group from T2 to T4. Serum 22-kd growth hormone concentrations were elevated at T2 to T5 in P group only. No differences were observed in resting cortisol and insulinlike growth factor 1. Hemoglobin concentrations were significantly reduced at T2 to T5 in the P group. These results indicate that the initial impact of high-volume resistance training is muscle strength reduction and hormonal/biochemical alterations. It appears that amino acid supplementation is effective for attenuating muscle strength loss during initial high-volume stress, possibly by reducing muscle damage by maintaining an anabolic environment.

Adult↗

PubMed2006

Resistance training and reduction of treatment side effects in prostate cancer patients.

PURPOSE: To examine the effect of progressive resistance training on muscle function, functional performance, balance, body composition, and muscle thickness in men receiving androgen deprivation for prostate cancer. METHODS: Ten men aged 59-82 yr on androgen deprivation for localized prostate cancer undertook progressive resistance training for 20 wk at 6- to 12-repetition maximum (RM) for 12 upper- and lower-body exercises in a university exercise rehabilitation clinic. Outcome measures included muscle strength and muscle endurance for the upper and lower body, functional performance (repeated chair rise, usual and fast 6-m walk, 6-m backwards walk, stair climb, and 400-m walk time), and balance by sensory organization test. Body composition was measured by dual-energy x-ray absorptiometry and muscle thickness at four anatomical sites by B-mode ultrasound. Blood samples were assessed for prostate specific antigen (PSA), testosterone, growth hormone (GH), cortisol, and hemoglobin. RESULTS: Muscle strength (chest press, 40.5%; seated row, 41.9%; leg press, 96.3%; P < 0.001) and muscle endurance (chest press, 114.9%; leg press, 167.1%; P < 0.001) increased significantly after training. Significant improvement (P < 0.05) occurred in the 6-m usual walk (14.1%), 6-m backwards walk (22.3%), chair rise (26.8%), stair climbing (10.4%), 400-m walk (7.4%), and balance (7.8%). Muscle thickness increased (P < 0.05) by 15.7% at the quadriceps site. Whole-body lean mass was preserved with no change in fat mass. There were no significant changes in PSA, testosterone, GH, cortisol, or hemoglobin. CONCLUSIONS: Progressive resistance exercise has beneficial effects on muscle strength, functional performance and balance in older men receiving androgen deprivation for prostate cancer and should be considered to preserve body composition and reduce treatment side effects.

Aged↗

PubMed2006

Effects of elastic bands on force and power characteristics during the back squat exercise.

Athletes commonly use elastic bands as a training method to increase strength and performance. The purpose of this study was to investigate the effect of elastic bands on peak force (PF), peak power (PP), and peak rate of force development (RFD) during the back-squat exercise (BSE). Ten recreationally resistance-trained subjects (4 women, 6 men, mean age 21.3 +/- 1.5 years) were tested for their 1 repetition maximum (1RM) in the BSE (mean 117.6 +/- 48.2 kg) on a Smith machine. Testing was performed on 2 separate days, with 2 sets of 3 repetitions being performed for each condition. Testing was conducted at 60% and 85% of 1RM with and without using elastic bands. In addition, 2 elastic band loading conditions were tested (B1 and B2) at each of the 2 resistances. No bands (NB) represents where all of the resistance was acquired from free-weights. B1 represents where approximately 80% of the resistance was provided by free-weights, and approximately 20% was provided by bands. B2 represents where approximately 65% of the resistance was provided by free-weights, and approximately 35% was provided from bands. The subjects completed the BSE under each condition, whereas PF, PP, and RFD was recorded using a force platform. There was a significant (p < 0.05) increase in PF between NB-85 and B2-85 of 16%. Between B1-85 and B2-85, PF was increased significantly by 5% (p < 0.05). There was a significant (p < 0.05) increase in PP between NB-85 and B2-85 of 24%. No significant differences were observed in RFD during the 85% conditions or for any of the measured variables during the 60% conditions (p < 0.05). The results suggest that the use of elastic bands in conjunction with free weights can significantly increase PF and PP during the BSE over free-weight resistance alone under certain loading conditions. The greatest differences are observed during the higher loading conditions, with the B1-85 condition appearing to be optimal for athletic performance of the ones we tested. The strength training professional could use variable resistance training (VRT) to increase PF and PP more than the traditional BSE can. VRT could also be used to train these 2 performance characteristics together, which might be especially useful in season, when weight-room training volume can sometimes be limited.

Adult↗

PubMed2006

The effects of carbohydrate loading on repetitive jump squat power performance.

The beneficial role of carbohydrate (CHO) supplementation in endurance exercise is well documented. However, only few data are available on the effects of CHO loading on resistance exercise performance. Because of the repetitive use of high-threshold motor units, it was hypothesized that the power output (power-endurance) of multiple sets of jump squats would be enhanced following a high-CHO (6.5 g CHO kg body mass(-1)) diet compared to a moderate-CHO (4.4 g CHO kg body mass(-1)) diet. Eight healthy men (mean +/- SD: age 26.3 +/- 2.6 years; weight 73.0 +/- 6.3 kg; body fat 13.4 +/- 5.0%; height 178.2 +/- 6.1 cm) participated in 2 randomly assigned counterbalanced supplementation periods of 4 days after having their free-living habitual diet monitored. The resistance exercise test consisted of 4 sets of 12 repetitions of maximal-effort jump squats using a Plyometric Power System unit and a load of 30% of 1 repetition maximum (1RM). A 2-minute rest period was used between sets. Immediately before and after the exercise test, a blood sample was obtained to determine the serum glucose and blood lactate concentrations. No significant difference in power performance existed between the 2 diets. As expected, there was a significant (p </= 0.05) decrease in power performance between the repetitions in every set. Blood lactate concentrations were significantly higher postexercise with both the high-CHO and the moderate- or lower-CHO diet, but there were no differences between conditions. The results indicated that the power output during multiple sets of maximal jump squats was not enhanced following a higher-CHO diet compared to a moderate- or lower-CHO diet. These data show that elevated carbohydrate intake is not needed to optimize a repetitive power-endurance performance when it is done as the first exercise in a workout.

Adult↗

PubMed2006

Eccentric utilization ratio: effect of sport and phase of training.

The eccentric utilization ratio (EUR), which is the ratio of countermovement jump (CMJ) to static jump (SJ) performance, has been suggested as a useful indicator of power performance in athletes. The purpose of the study was to compare the EUR of athletes from a variety of different sports and during different phases of training. A total of 142 athletes from rugby union, Australian Rules Football, soccer, softball, and field hockey were tested. Subjects performed both CMJ and SJ on a force plate integrated with a position transducer. The EUR was measured as the ratio of CMJ to SJ for jump height and peak power. The rugby union, Australian Rules Football, and hockey athletes were tested during off-season and preseason to provide EUR data during different phases of training. For men, EUR for soccer, Australian Rules Football, and rugby was greater than softball (effect size range, 0.83-0.92). For women, EUR for soccer was greater than field hockey and softball (0.86- 1.0). There was a significant difference between the jump height and peak power method for the Australian Rules Football, rugby, and field hockey tests conducted preseason (p < 0.05). For field hockey, there was a significant increase in EUR from off-season to preseason. Athletes in sports such as soccer, rugby union, and Australian Rules Football appear to have higher EUR values, which reflects the greater reliance on stretch shortening activities in these sports. It does appear that EUR can be used to track changes in training with the values significantly increasing from off-season to preseason. The EUR provides the practitioner with information about the performance of athletes and appears to be sensitive to changes in the type of training being undertaken.

Adult↗

PubMed2005

Maximal strength and cortisol responses to psyching-up during the squat exercise.

We studied the effect of psyching-up on one-repetition maximum (1-RM) performance and salivary cortisol responses during the squat exercise. Ten men (age 21.6+/-1.4 years; mean+/-s) and ten women (age 22.4+/-2.8 years) with weight training experience of 4.5+/-2.0 years participated in this study. One-repetition maximum squats were performed on a Smith machine during each of two different intervention conditions that were counterbalanced and consisted of a free choice psych-up and a cognitive distraction. Saliva samples were obtained at the beginning of each test session and immediately after the final 1-RM attempt. No significant difference in 1-RM was identified between psyching-up (104+/-50 kg) and cognitive distraction (106+/-52 kg). Performing a 1-RM in the squat exercise significantly increased salivary cortisol concentrations during both conditions (P<0.05). There was no significant difference in salivary cortisol responses between conditions. These results suggest that psyching-up does not increase 1-RM performance during the squat exercise in strength-trained individuals.

Adult↗

PubMed2005

"Psyching-up" enhances force production during the bench press exercise.

We investigated the effect of "psyching-up" on force production during the bench press. Twelve men (mean age +/- SD: 27.4 +/- 11.2 years) and 8 women (20.9 +/- 2.5 years) with strength-training experience performed 5 bench press repetitions on a modified Biodex isokinetic dynamometer during 3 interventions. The interventions were counterbalanced and included a free-choice psych-up, a cognitive distraction, and an attention-placebo. Peak force recorded after psyching-up (mean +/- SD: 764 +/- 269 N.m) was significantly different from both distraction (703 +/- 282 N.m, p = 0.003) and attention-placebo (708 +/- 248 N.m, p = 0.01). The mean percentage increase in peak force from distraction to psyching-up was 11.8% (6 to 18%, 95% confidence interval [CI]) and 8.1% from placebo to psyching-up (3 to 13%, 95% CI). The results of the present study indicate that psyching-up may increase force production during the bench press exercise in participants with at least 1 year strength-training experience.

Adult↗

PubMed2005

Influence of contraction velocity in untrained individuals over the initial early phase of resistance training.

The purpose of this study was to determine the early phase adaptations in short-term traditional (TRT) versus superslow (SST) resistance training. Sixteen apparently healthy subjects participated in this study. Subjects were pretested and posttested for their 1 repetition maximums (1RM) in the squat and bench press, peak power in a countermovement jump (CMJ) and squat jump (SJ), and body composition using dual energy x-ray absorptiometry. Subjects participated in an 8-week resistance training program in either SST (n = 9, 3 men, 6 women), using 50% of 1RM, or TRT (n = 7, 3 men, 4 women), using 80% of 1RM. Both groups trained 3 days per week. The TRT and SST groups improved in strength by 6.8 and 3.6% in the squat exercise and by 8.6 and 9.1% in the bench press, respectively. Peak power for the CMJ increased significantly in the TRT group, from 23.0 +/- 5.5 W/kg to 25.0 +/- 6.3 W/kg; no such increase was seen with respect to the SST group. Both groups' 1RM increased significantly for both the bench press and the squat. No changes in body composition were seen for either group. The results of this study suggest that TRT is more effective for improving peak power than SST.

Adaptation, Physiological↗

PubMed2004

Reliability of performance of elite Olympic weightlifters.

There are no published data on the reliability of competitive strength performance, even though it has a pronounced effect on athletes' medal prospects and the ability of coaches and athletes to identify factors that affect competitive performance. The purpose of this investigation was to analyze the reliability of elite olympic weightlifters over a series of international weightlifting meets. We obtained official results of international competitions over an 18-month period from 1999 until the 2000 Olympic Games at the International Weightlifting Federation website. The measure of reliability was the typical within-athlete variation, derived as the coefficient of variation (CV) by 2-way analysis of variance of log-transformed weights lifted for the snatch, clean and jerk, and total. The results of this analysis were (a) within-athlete variations were as follows: snatch, 2.7% (95% likely range, 2.4-3.2%); clean and jerk, 2.3% (1.7-3.6%); total weight lifted, 2.5% (2.2-2.9%); (b) men and women: the variation was higher for the women compared with the men in both snatch (ratio of CV, 1.4) and clean and jerk (ratio of CV, 1.5), and for the total weight lifted (ratio of CV, 1.3); and (c) the top 5 athletes were almost always more reliable than the bottom-half athletes. Recent work has shown that the smallest worthwhile performance is about half the within-athlete variation, so coaches and sport scientists should focus on enhancements of as little as 1.2% in total weight lifted for elite olympic weightlifters.

Competitive Behavior↗

PubMed2004

Quantitation of resistance training using the session rating of perceived exertion method.

The purpose of this study was to apply the session rating of perceived exertion (RPE) method, which is known to work with aerobic training, to resistance training. Ten men (26.1 +/- 10.2 years) and 10 women (22.2 +/- 1.8 years), habituated to both aerobic and resistance training, performed 3 x 30 minutes aerobic training bouts on the cycle ergometer at intensities of 56%, 71%, and 83% Vo(2) peak and then rated the global intensity using the session RPE technique (e.g., 0-10) 30 minutes after the end of the session. They also performed 3 x 30 minutes resistance exercise bouts with 2 sets of 6 exercises at 50% (15 repetitions), 70% (10 repetitions), and 90% (4 repetitions) of 1 repetition maximum (1RM). After each set the exercisers rated the intensity of that exercise using the RPE scale. Thirty minutes after the end of the bout they rated the intensity of the whole session and of only the lifting components of the session, using the session RPE method. The rated intensity of exercise increased with the %Vo(2) peak and the %1RM. There was a general correspondence between the relative intensity (%Vo(2) peak and % 1RM) and the session RPE. Between different types of resistance exercise at the same relative intensity, the average RPE after each lift varied widely. The resistance training session RPE increased as the intensity increased despite a decrease in the total work performed (p < 0.05). Mean RPE and session RPE-lifting only also grew with increased intensity (p < 0.05). In many cases, the mean RPE, session RPE, and session RPE- lifting only measurements were different at given exercise intensities (p < 0.05). The session RPE appears to be a viable method for quantitating the intensity of resistance training, generally comparable to aerobic training. However, the session RPE may meaningfully underestimate the average intensity rated immediately after each set.

Adult↗

PubMed2004

Monitoring exercise intensity during resistance training using the session RPE scale.

This study investigated the reliability of the session rating of perceived exertion (RPE) scale to quantify exercise intensity during high-intensity (H), moderate-intensity (M), and low-intensity (L) resistance training. Nine men (24.7 +/- 3.8 years) and 10 women (22.1 +/- 2.6 years) performed each intensity twice. Each protocol consisted of 5 exercises: back squat, bench press, overhead press, biceps curl, and triceps pushdown. The H consisted of 1 set of 4-5 repetitions at 90% of the subject's 1 repetition maximum (1RM). The M consisted of 1 set of 10 repetitions at 70% 1RM, and the L consisted of 1 set of 15 repetitions at 50% 1RM. RPE was measured following the completion of each set and 30 minutes postexercise (session RPE). Session RPE was higher for the H than M and L exercise bouts (p < or = 0.05). Performing fewer repetitions at a higher intensity was perceived to be more difficult than performing more repetitions at a lower intensity. The intraclass correlation coefficient for the session RPE was 0.88. The session RPE is a reliable method to quantify various intensities of resistance training.

Adult↗

PubMed2004

Training vs. body image: does training improve subjective appearance ratings?

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.

Adolescent↗

PubMed2003

Effect of explosive resistance training on titin and myosin heavy chain isoforms in trained subjects.

The purpose of this investigation was to evaluate changes in myosin heavy chain (MyHC) and titin isoforms after using various loads during explosive jump squat training. Twenty-four male athletic subjects were recruited for this study. Two experimental groups performed 8-weeks of jump squats using either 30% (n = 9) or 80% (n = 9) of their previously determined 1 repetition maximum. A third group served as controls (n = 6). Muscle biopsies were obtained before and after 8 weeks from vastus lateralis. The analysis of titin within these subjects confirmed that human skeletal muscle contains 2 isoforms of titin. There was no significant group x time interaction for MyHC or titin isoform expression. The data from this investigation indicates that a relatively short period of explosive resistance training results in negligible changes in the expression of MyHC or titin isoforms.

Adult↗

PubMed2002

Effects of heavy resistance/power training on maximal strength, muscle morphology, and hormonal response patterns in 60-75-year-old men and women.

Eleven women (TRW; 64 +/- 4 yrs) and ten men (TRM; 65 +/- 5 yrs) participated in the strength/power training twice a week for 24 weeks. Basal concentrations of serum total and free testosterone, growth hormone (GH), dehydroepiandrosterone sulfate (DHEAS), cortisol and sex hormone binding globulin (SHBG) as well as acute responses of serum total and free testosterone, growth hormone (GH) were measured. Maximal 1RM strength in the squat, chair rise time and muscle fibre distribution and areas of type I and IIa and IIb of the vastus lateralis were also examined. 1RM squat increased in TRW by 26 (SD10)% (p < .001), and in TRM by 35 (7)% (p < .001) and chair rise time improved in both groups (p < .001). Fibre areas increased in type I, (p < .01), IIa (p < .01) and IIb (p < .01) in TRM and type I (p < .05) and IIa (p < .05) in TRW. The proportion of type IIa increased from 31% to 43% (p < .05) in TRW and that of type IIb decreased from 27% to 17% (p < .05) in TRW and from 25% to 17% (p < .05) in TRM. Individual concentrations of testosterone/cortisol ratios correlated (r = 0.63; p < .05) with the individual increases in 1RM strength in TRW. The exercise sessions resulted in acute increases in serum GH in both groups (p < .05) with a further increase (p < .01) up to 10 minutes post-loading in TRM at post-training.

Aged↗