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Biomedical subjects

J D Branch

Publications and source records attributed to J D Branch.

18 recordsLinked to original sources
PubMed2001

Effects of dehydration and rehydration on the one-repetition maximum bench press of weight-trained males.

Dehydration, a common practice among competitive athletes in sports including weight classes, has uncertain effects on strength. This study examined the effects of passive dehydration (D, approximately 2 hours in a sauna) followed by rehydration (R, approximately 2 hours of rest with water ad libitum) on bench press one-repetition maximum (1RM). Ten weight-trained males (x +/- SE; age = 25 +/- 1 years; mass = 85.5 +/- 5.2 kg; height = 173.5 +/- 1.7 cm; body fat = 17.8 +/- 2.2%; 1RM = 118 +/- 8 kg) completed 2 testing sessions (E1/E2 and D/R) consisting of, respectively, 2 euhydration 1RM measurements separated by 2 hours of rest; and D 1RM followed by R 1RM. Testing sessions were administered in counterbalanced order and separated by 1 week. D resulted in increases (p < 0.005) in body temperature, urine specific gravity, hematocrit, and hemoglobin (calculated 8% decrease in plasma volume) as well as decreased body mass (p < 0.005). 1RM was decreased following D (111.4 +/- 7.2 kg) compared to both E1 (118 +/- 7.6 kg, p = 0.0015) and R (117.3 +/- 7.8 kg, p = 0.0023), with no significant difference between E1 and R. A significant association (r = -0.67, p < 0.05) was observed between percent lean body mass (%LBM) and the change in 1RM following D. In conclusion, passive dehydration resulting in approximately 1.5% loss of body mass adversely affects bench press 1RM performance. The adverse affects of dehydration seem to be overcome by a 2-hour rest period and water consumption.

Adult↗
PubMed2000

Use of creatine and other supplements by members of civilian and military health clubs: a cross-sectional survey.

A survey was used to collect anonymous cross-sectional data on demographics, exercise habits, and use of creatine and other supplements by exercisers in civilian (C) and military (M) health clubs. M (n = 133) reported more aerobic training and less use of creatine and protein supplements than C (n = 96, p <.05). Supplement users (SU, n = 194) and nonusers (SNU, n = 35) engaged in similar frequency and duration of aerobic exercise, as well as number of resistance exercise repetitions, but SU completed more sets for each resistance exercise (x- +/- SE, 5 +/- 1) than SNU (3 +/- 1, p < or =.05). Significant (p < or =.05) associations were observed between SU and resistance training goal of strength (as opposed to endurance), as well as greater frequency of resistance training. Male gender, resistance training goal of strength, lower frequency and duration of aerobic training, and use of protein, b-hydroxy-b-methyl butyrate, and androstenedione/dehydroepiandrosterone supplements were all associated with creatine use (p <.05). For creatine users, the dose and length of creatine supplementation was 12.2 +/- 2.7 g.day-1 for 40 +/- 5 weeks. Popular magazines were the primary source of information on creatine (69%) compared to physicians (14%) or dietitians (10%, p < or =.0001). This study underscores two potential public health concerns: (a) reliance on popular media rather than allied-health professionals for information on creatine, and (b) use of creatine, a popular supplement with unknown long-term effects, in combination with other anabolic supplements of questionable efficacy and/or safety.

Adult↗
PubMed1999

Physiological effects of constant versus variable power during endurance cycling.

PURPOSE: Previous theoretical research found that varying power slightly to counter external conditions may result in improved performance during cycling time trialing, but it is not known whether such power variations result in added physiological stress. Thus, the purpose of this study was to determine whether variable power (VP) cycling produced greater physiological stress than constant power (CP) cycling of the same mean intensity. METHODS: Eight trained male cyclists (age 28 +/- 2 yr, mass 74.4 +/- 2.3 kg, VO2max 4.24 +/- 0.13 L x min(-1), weekly training 277 +/- 44 km) performed three 1-h ergometer trials. The first trial was performed at a self-paced maximal effort. The mean power from that trial was used to determine the power for the CP trial (constant effort at mean power) and the VP trial (alternating +/- 5% of mean power every 5 min). RESULTS: No differences were found between the CP and VP trials in mean VO2 (CP 3.33 +/- 0.11 L x min(-1), VP 3.26 +/- 0.12 L x min(-1)), mean heart rate (CP 158 +/- 3 min(-1), VP 159 +/- 3 min(-1)), mean blood lactate concentration (CP 4.2 +/- 0.7 mM, VP 4.3 +/- 0.7 mM), or mean RPE (CP 13.9 +/- 0.4, VP 14.1 +/- 0.4). CONCLUSION: Therefore, during a strenuous 1-h effort (78% of VO2max), subjects experienced no additional physiological stress by varying power +/- 5% compared with that during a constant power effort.

Adult↗
PubMed1999

Blood pressure responses to acute static and dynamic exercise in three racial groups.

PURPOSE: African Americans have a higher incidence of hypertension than other racial groups. Furthermore, some research suggests that normotensive individuals who exhibit exaggerated blood pressure (BP) responses to exercise may be at risk for future hypertension. This study sought to determine whether normotensive African Americans exhibited exaggerated BP responses to static exercise or dynamic exercise relative to Caucasian Americans and Asian Americans. METHODS: Thirty normotensive subjects participated from each of the three racial groups (15 men and 15 women). Subjects held 30% of maximal voluntary contraction (right knee extension) for 3 min, and BP was recorded during the 3rd min. On a separate occasion, subjects cycled for six min at a power equivalent to 70% of VO2 reserve, and BP was recorded during the 6th min. RESULTS: Static exercise produced large, significant increases in both systolic and diastolic BP (35 +/- 1.5 and 29 +/- 1.3 mm Hg, respectively). Dynamic exercise produced large, significant increases in systolic BP (51 +/- 1.6 mm Hg) and moderate, yet significant, increases in diastolic BP (8 +/- 1.0 mm Hg). There were no significant differences between racial groups in BP response to either static exercise or dynamic exercise. However, during dynamic exercise, men had a higher systolic BP response than did women. CONCLUSIONS: African Americans who are normotensive at rest do not exhibit a greater BP response to static exercise or dynamic exercise than do Caucasian Americans or Asian Americans.

Asian People↗
PubMed1999

Effect of 14 weeks of resistance training on lipid profile and body fat percentage in premenopausal women.

OBJECTIVES: To study the effects of a supervised, intensive (85% of one repetition maximum (1-RM)) 14 week resistance training programme on lipid profile and body fat percentage in healthy, sedentary, premenopausal women. SUBJECTS: Twenty four women (mean (SD) age 27 (7) years) took part in the study. Subjects were randomly assigned to either a non-exercising control group or a resistance exercise training group. The resistance exercise training group took part in supervised 45-50 minute resistance training sessions (85% of 1-RM), three days a week on non-consecutive days for 14 weeks. The control group did not take part in any structured physical activity. RESULTS: Two way analysis of variance with repeated measures showed significant (p < 0.05) increases in strength (1-RM) in the exercising group. There were significant (p < 0.05) decreases in total cholesterol (mean (SE) 4.68 (0.31) v 4.26 (0.23) mmol/1 (180 (12) v 164 (9) mg/dl)), low density lipoprotein (LDL) cholesterol (2.99 (0.29) v 2.57 (0.21) mmol/l (115 (11) v 99 (8) mg/dl), the total to high density lipoprotein (HDL) cholesterol ratio (4.2 (0.42) v 3.6 (0.42)), and body fat percentage (27.9 (2.09) v 26.5 (2.15)), as well as a strong trend towards a significant decrease in the LDL to HDL cholesterol ratio (p = 0.057) in the resistance exercise training group compared with their baseline values. No differences were seen in triglycerides and HDL cholesterol. No changes were found in any of the measured variables in the control group. CONCLUSIONS: These findings suggest that resistance training has a favourable effect on lipid profile and body fat percentage in healthy, sedentary, premenopausal women.

Adolescent↗
PubMed1999

Exercise training and intensity does not alter vascular volume responses in women.

PURPOSE: The effect of endurance training on vascular volumes in females has received little research attention. Further, the effect of exercise training intensity on vascular volumes is unknown. Therefore, we investigated the hypothesis that greater hematologic changes would be induced in women by higher exercise intensity during endurance training. METHODS: There were 26 healthy, sedentary adult females with the following characteristics (mean +/- SD): maximal oxygen consumption (VO2max) = 30.0+/-6.6 ml x kg(-1) x min(-1); age = 32+/-5 yr; body mass index (BMI) = 23.7+/-3.6 kg x m(-2)) who were randomly assigned to control (CON, n = 8); high intensity (HI, 80% of VO2max, n = 10), or low intensity (LO, 40% of VO2max, n = 8) cycle ergometer training groups. Training, conducted 3-5 (3.37+/-0.05) d x wk(-1) for 12 wk, was supervised. Estimated exercise energy expenditure was equated across training groups, progressing from 150-375 kcal per session (mean +/- SE across training weeks = 298+/-0.34 and 297+/-0.37 kcal per session for HI and LO, respectively). Plasma volume (PV, T-1824 dilution); calculated total blood (TBV) and red cell volumes (RCV); calculated total hemoglobin (THb); erythropoietin concentration ([Epo]) and selected hematologic variables were measured at baseline and weeks 2, 4, 8 and 12 of training. RESULTS: The observed relative (percent) changes in PV, TBV, RCV and THb from pre-training baseline values were not statistically significant. Decreases (p < 0.05) in hematocrit (Hct), hemoglobin ([Hb]) and RBC count were observed in both training groups. Mean corpuscular Hb (MCH) and Hb concentration (MCHC) increased (p < 0.05) during training. [Epo] was decreased at week 2 compared with baseline (p < 0.03), but was similar to baseline at weeks 4, 8 and 12. CONCLUSIONS: Within the limits of this study, endurance training did not increase PV, TBV, RCV and THb in previously sedentary females regardless of the intensity of training.

Adaptation, Physiological↗
PubMed1998

Creatine supplementation and exercise performance: an update.

Creatine, a natural nutrient found in animal foods, is alleged to be an effective nutritional ergogenic aid to enhance sport or exercise performance. Research suggests that oral creatine monohydrate supplementation may increase total muscle creatine [TCr], including both free creatine [FCr] and phosphocreatine [PCr]. Some, but not all, studies suggest that creatine supplementation may enhance performance in high-intensity, short-term exercise tasks that are dependent primarily on PCr (i.e., < 30 seconds), particularly laboratory tests involving repeated exercise bouts with limited recovery time between repetitions; additional corroborative research is needed regarding its ergogenic potential in actual field exercise performance tasks dependent on PCr. Creatine supplementation has not consistently been shown to enhance performance in exercise tasks dependent on anaerobic glycolysis, but additional laboratory and field research is merited. Additionally, creatine supplementation has not been shown to enhance performance in exercise tasks dependent on aerobic glycolysis, but additional research is warranted, particularly on the effect of chronic supplementation as an aid to training for improvement in competitive performance. Short-term creatine supplementation appears to increase body mass in males, although the initial increase is most likely water. Chronic creatine supplementation, in conjunction with physical training involving resistance exercise, may increase lean body mass. However, confirmatory research data are needed. Creatine supplementation up to 8 weeks has not been associated with major health risks, but the safety of more prolonged creatine supplementation has not been established. Creatine is currently legal and its use by athletes is not construed as doping.

Adenosine Triphosphate↗
PubMed1998

Relationship between % heart rate reserve and % VO2 reserve in treadmill exercise.

For exercise prescription purposes, it is often assumed that % heart rate reserve (%HRR) provides equivalent intensities to %VO2max. However, a recent study from this laboratory demonstrated that during cycling exercise %HRR is not equivalent to %VO2max, but is instead equivalent to a percentage of the difference between resting and maximal VO2, i.e., % VO2reserve (%VO2R). The current study examined these relationships during treadmill exercise. Fifty adults performed Bruce protocol treadmill tests to exhaustion. For each subject, data obtained at rest, at the end of each stage, and at maximum were used to determine linear regressions of %HRR versus %VO2max, and of %HRR versus %VO2R. For %HRR versus %VO2max the mean intercept and slope were -6.1+/-0.7 and 1.10+/-0.01, respectively, with a mean r of 0.990+/-0.002. For %HRR versus %VO2R, the mean intercept and slope were 1.5+/-0.6 and 1.03+/-0.01, respectively, with a mean r of 0.990+/-0.002. Both regressions differed statistically from the line of identity (i.e., intercept of 0 and slope of 1). However, the regression of %HRR versus %VO2R was significantly closer (P < 0.001 ) to the line of identity than was the regression of %HRR versus %VO2max. We conclude that %HRR should be considered as an indicator of %VO2R, not %VO2max, when prescribing treadmill exercise, as was previously concluded for cycling exercise.

Adolescent↗
PubMed1998

Red cell volume and [erythropoietin] responses during exposure to simulated microgravity.

In order to test the hypothesis that normal gravity is an important influence on human serum [Erythropoietin] ([Epo]), the hematologic response to 16 d of 6 degrees head-down tilt (HDT, n = 6 men) was compared with 16 d of normal gravity exposure (CON, n = 7 men). Prior to bed rest, CON and HDT subjects, respectively, were similar in the following characteristics (mean +/- SD): age = 40 +/- 3, 39 +/- 6 yr; height = 181 +/- 5, 182 +/- 6 cm; weight = 88.5 +/- 11.3, 81.7 +/- 12.0 kg; maximal oxygen consumption in supine 6 degrees head-down tilt position (VO2max) = 2.63 +/- 0.38, 2.67 +/- 0.52 L.min-1; hematocrit = (Hct) 41.6 +/- 2.4, 43.0 +/- 3.4%; hemoglobin ([Hb]) = 15.1 +/- 1.0, 14.5 +/- 1.0 g.100 ml-1; plasma volume (PV) = 3829 +/- 857, 3768 +/- 512 ml; and [Epo] = 11.6 +/- 2.9, 10.0 +/- 6.2 mU.ml-1. Calculated red cell volume (RCV) was greater in HDT than CON (2845 +/- 410 vs. 2139 +/- 253 ml, p < 0.05) at baseline. Decreases in PV (-15%, 580 ml, p < 0.05) and an insignificant decrease in RCV (-12%, 354 ml, p = 0.07) were observed in the HDT group, with a concurrent 6% increase in [Hb] (p < 0.05). PV, RCV and [Hb] remained unchanged in the CON group. [Epo] remained unchanged during HDT (12.2 +/- 3.2; 10.8 +/- 3.8; 11.2 +/- 3.1; 11.2 +/- 2.6 mU.ml-1 for HDT days 1, 2, 8 and 16, respectively). There was no difference between CON and HDT groups in [Epo] before or during HDT. It was concluded that the insignificant change (-12%) in RCV observed during HDT was insufficient to stimulate an increase in [Epo], probably because the content of oxygen in arterial blood remained unaffected. The observation that [Epo] remained unchanged despite this loss of RCV during HDT also suggests a possible decrease in the responsiveness of the erythropoietic system to [Epo].

Adult↗
PubMed1997

Twelve weeks of endurance exercise training does not affect iron status measures in women.

OBJECTIVE: This study examined the effects of 12 weeks of endurance exercise training on iron status measures in previously inactive women and compared the effects of weight-bearing endurance exercise training and non-weight-bearing endurance exercise on iron status measures. DESIGN: Randomized, experimental study. SUBJECTS: Thirty-one healthy, inactive women (aged 23 to 43 years) with apparently normal iron stores (serum ferritin concentration > or = 20 micrograms/L) were recruited from the local area by newspaper advertisements and campus mailings. Twenty-one subjects completed the study (mean +/- standard deviation for age = 32 +/- 5 years, for body mass index = 23.1 +/- 4.9, and for maximum oxygen consumption [VO2max] = 33.8 +/- 6.3 mL/kg per minute). INTERVENTION: Subjects were randomly assigned to one of three groups: an inactive control group, a walking/running group, or a cycling group. Subjects in the two exercise groups trained three to four times per week at 80% VO2max for 12 weeks. Exercise training sessions were monitored and energy expenditure increased from 150 kcal per session (week 1) to 375 kcal per session (weeks 9 to 12). Subjects in the inactive control group were instructed to maintain their normal activity patterns for the duration of the study. All subjects were instructed to maintain their normal dietary habits. MAIN OUTCOME MEASURES: Serum ferritin concentration, serum iron concentration, percentage saturation of transferrin, total iron-binding capacity, serum haptoglobin concentration, and other selected hematologic variables were measured at baseline and at weeks 2, 4, 8, and 12. STATISTICAL ANALYSES: Repeated measures analysis of variance was used to examine group x time interactions in changes in iron status measures. Statistical significance was reached at P < .05. RESULTS: Analysis of variance indicated that serum ferritin concentration did not change significantly (P = .59) during the 12 weeks in the walking/running group (mean +/- standard deviation from 41.28 +/- 14.22 to 27.41 +/- 9.74 micrograms/L) or the cycling group (from 65.81 +/- 37.62 to 41.06 +/- 26.38 micrograms/L) compared with the control group (from 47.55 +/- 15.87 to 31.56 +/- 10.57 micrograms/L). Values for serum iron, total iron-binding capacity, percentage saturation of transferrin, and haptoglobin also did not change significantly (P > .30) in the walking/running or cycling groups compared with the control group. APPLICATIONS/CONCLUSIONS: Results of this study suggest that participation in 12 weeks of moderate-intensity endurance exercise training (walking/running or cycling) is not associated with negative effects on selected measures of iron status in healthy, previously untrained women with normal iron stores (serum ferritin > or = 20 micrograms/L).

Adult↗
PubMed1997

Effects of exercise mode on hematologic adaptations to endurance training in adult females.

BACKGROUND: The subjects were 26 healthy, sedentary adult females with the following characteristics: maximal oxygen consumption (VO2max) = 32.0 +/- 7.2 ml.kg-1.min-1; age = 32 +/- 5 yr; body mass index (BMI) = 23.2 +/- 3.4 kg.m-2 who were randomly assigned to control (CON; N = 8); treadmill training (TM; N = 8); or cycle ergometer training (CY; N = 10) to test the hypothesis that hematologic adaptations to endurance exercise training are specific to mode of exercise. METHODS: Training, conducted 3-5 (3.4 +/- 0.06) d.week-1 at 80% of mode specific VO2max for 12 weeks, was supervised and progressive, with estimated exercise energy expenditure equated across training groups. Plasma volume (PV, T-1824 dilution); calculated total blood (THb) and red cell volumes (RCV); calculated total hemoglobin (THb) and other hematologic variables were measured at baseline and weeks 2, 4, 8 and 12 of training. RESULTS: Across 12 weeks of training, PV was decreased (95% of baseline) in the TM group but increased (106% of baseline) in the CY group (p = 0.06). Similar trends were observed for RCV (p = 0.15) and TBV (p = 0.08). These results are in contrast to reported changes in PV, TBV and RCV in males following training. Hemodilution was observed in both training groups, reflected by decreases (p < 0.05) in hematocrit (Hct), hemoglobin (Hb) and RC count. Mean corpuscular Hb (MCH) and Hb content (MCHC) increased (p < 0.05) with training. These changes, as well as trend toward increased (p = 0.08) mean corpuscular volume (MCV), suggested the probable presence of a RC population with a lower mean age and decreased oxyhemoglobin affinity. The possibility of Type II error cannot be discounted in these trends, which suggest that PV, TBV and RCV may be affected by mode of endurance exercise in females.

Adaptation, Physiological↗
PubMed1996

Effect of Eleutherococcus senticosus on submaximal and maximal exercise performance.

We investigated the effect of Eleutherococcus senticosus Maxim L (ESML) on performance during submaximal and maximal aerobic exercise. Twenty highly trained distance runners randomly assigned in matched pairs to either an experimental (ESML) or placebo (PL) group, participated in an 8-wk double-blind study during which they completed five trails of a 10-min treadmill run at their 10 km (10K) race pace and a maximal treadmill test (T(max)). Following a baseline trail, ESML and PL consumed, respectively, 3.4 ml of ESML extract or placebo daily for 6 wk. Subjects were tested every 2 wk during supplementation and 2 wk following withdrawal. Heart rate (HR), oxygen consumption (VO2), expired minute volume (VE), ventilatory equivalent for oxygen (VE/VO2), respiratory exchange ratio (RER), and rating of perceived exertion (RPE) were measured during the 10K and T(max) tests. Resting, post-10K and post-T(max) blood samples were analyzed for serum lactate. No significant differences were observed between ESML and PL for: HR, VO2, VE, VE/VO2, RER, or RPE; T(max) time to exhaustion; or serum lactate. The data do not support an ergogenic effect of ESML supplementation on selected metabolic, performance, or psychologic parameters associated with submaximal and maximal aerobic exercise tasks.

Adult↗
PubMed1992

Training for endurance sport.

1) An endurance athlete's performance level is determined largely by three physiological variables: maximal aerobic power, lactate threshold, and economy. Training strategies should be directed toward improvement of these factors. 2) Successful endurance training programs typically include an individually constructed combination of three major training strategies. These are long duration, moderate intensity training; moderate duration, high intensity training; and short duration, very high intensity training. 3) Endurance training involves a large daily expenditure of energy, and much of this energy is derived from catabolism of carbohydrates. Accordingly, it is essential that the endurance athlete's diet be rich in complex carbohydrates and provide the total amount of energy needed to maintain energy balance.

Diet↗
PubMedDate not supplied

Moderate intensity exercise training improves cardiorespiratory fitness in women.

Among women, there is an increased prevalence of sedentary lifestyle and less participation in physical activity at levels recommended by the Surgeon General. As a result, women have been identified as a target group in public health initiatives to increase physical activity. The health-related benefits of habitual, moderate intensity physical activity are well documented in the epidemiological literature, but less is known about the effect of such physical activity on cardiorespiratory fitness. Our hypothesis was that moderate and vigorous exercise training regimens of similar estimated energy expenditure would result in similar changes in cardiorespiratory fitness. Eighteen sedentary premenopausal women with the following baseline characteristics [x +/- SE]: maximal oxygen consumption (Vo2max) = 29.5+/-1.5 ml x kg(-1) x min(-1); age = 33+/-1 years; height = 162.6+/-0.9 cm; mass = 62.7+/-2.3 kg, were randomly assigned to either vigorous (HI, 80% Vo2max, n = 10) or moderate intensity (MOD, 40% Vo2max, n = 8) cycle ergometer training groups. Exercise training was conducted 3-4 (3.37+/-0.05) days/week for 12 weeks in a supervised and progressive manner, with estimated exercise energy expenditure equated across both training groups. Vo2max and time to exhaustion increased significantly in both groups (p<0.05), with no difference between groups. Both groups had lower (p<0.05) posttraining submaximal heart rates (HR), respiratory exchange ratios (RER), and ratings of perceived exertion (RPE) during graded exercise testing, with no significant differences between the groups in posttraining values. Women participating in moderate intensity exercise training as recommended in basic public health guidelines demonstrate an increase in cardiorespiratory fitness similar to that elicited by vigorous training.

Adult↗