Search Results

You are looking at 31 - 40 of 140 items for :

  • "lean body mass" x
Clear All
Restricted access

J. David Branch

Background: Creatine supplementation (CS) has been reported to increase body mass and improve performance in high-intensity, short-duration exercise tasks. Research on CS, most of which has come into existence since 1994, has been the focus of several qualitative reviews, but only one meta-analysis, which was conducted with a limited number of studies. Purpose: This study compared the effects of CS on effect size (ES) for body composition (BC) variables (mass and lean body mass), duration and intensity (≤30 s, [ATP-PCr = A]; 30–150 s [glycolysis = G]; >150 s, [oxidative phosphorylation = O]) of the exercise task, type of exercise task (single, repetitive, laboratory, field, upper-body, lower-body), CS duration (loading, maintenance), and subject characteristics (gender, training status). Methods: A search of MEDLINE and SPORTDiscus using the phrase “creatine supplementation” revealed 96 English-language, peer-reviewed papers (100 studies), which included randomized group formation, a placebo control, and human subjects who were blinded to treatments. ES was calculated for each body composition and performance variable. Results: Small, but significant (ES > 0, p ≤ .05) ES were reported for BC (n = 163, mean ± SE = 0.17 ± 0.03), ATP-PCr (n = 17, 0.24 ± 0.02), G (n = 135, 0.19 ± 0.05), and O (n = 69, 0.20 ± 0.07). ES was greater for change in BC following a loading-only CS regimen (0.26 ± 0.03, p = .0003) compared to a maintenance regimen (0.04 ± 0.05), for repetitive-bout (0.25 ± 0.03, p = .028) compared to single-bout (0.18 ± 0.02) exercise, and for upper-body exercise (0.42 ± 0.07, p < .0001) compared to lower (0.21 ± 0.02) and total body (0.13 ± 0.04) exercise. ES for laboratory-based tasks (e.g., isometric/isotonic/isokinetic exercise, 0.25 ± 0.02) were greater (p = .014) than those observed for field-based tasks (e.g., running, swimming, 0.14 ± 0.04). There were no differences in BC or performance ES between males and females or between trained and untrained subjects. Conclusion: ES was greater for changes in lean body mass following short-term CS, repetitive-bout laboratory-based exercise tasks ≤ 30 s (e.g., isometric, isokinetic, and isotonic resistance exercise), and upper-body exercise. CS does not appear to be effective in improving running and swimming performance. There is no evidence in the literature of an effect of gender or training status on ES following CS.

Restricted access

Norikazu Hirose and Chikako Nakahori

Purpose:

To describe cross-sectional age differences in change-of-direction performance (CODp) in female football players and investigate the relationship between CODp and linear-sprint speed, muscle power, and body size.

Methods:

A sample of 135 well-trained female football players was divided into 8 age groups. Anthropometry (height, body mass, and lean body mass) and athletic performance (10-m sprint speed, 10-m × 5-CODp, and 5-step bounding distance) were compared to determine interage differences using ANOVA. Then, the participants were divided into 3 age groups: 12- to 14-y-olds, 15- to 17-y-olds, and ≥ 18 y-olds. Simple- and multiple-regression analyses were conducted to determine the correlation between CODp and the other measurement variables in each age group.

Results:

Age-related differences were found for CODp (F = 10.41, P < .01), sprint speed (F = 3.27, P < .01), and bounding distance (F = 4.20, P < .01). Post hoc analysis revealed that the CODp of 17-y-old players was faster than that of 16-y-old players (P < .01), with no interage differences in sprint speed and bounding distance. Sprint speed and bounding distance were weakly correlated with CODp in 15- to ≥18-y-old players, but only sprint speed was correlated with CODp in 12- to 14-y-old players.

Conclusions:

CODp improves from 16 to 17 y of age in female players. Linear-sprint speed, muscle power, and body size were weakly correlated with the age differences in CODp.

Restricted access

Stephan P. Clancy, Priscilla M. Clarkson, Michael E. DeCheke, Kazunori Nosaka, Patty S. Freedson, John J. Cunningham and Bruce Valentine

The effects of 9 weeks of daily chromium supplementation (200μg Cr as picolinate) were investigated in a double-blind design in football players during spring training. Testing was done pre-, mid-, and postsupplementation on the following criterion measures: urinary chromium excretion, girth and skinfold measures, percent body fat and lean body mass, and isometric and dynamic strength. With the exception of 2 variables (of 65 variables analyzed), no significant group by trials interactions were found (based on a repeated measures ANOVA). The two exceptions were unrelated and inconsequential. For 27 of the 38 subjects, average urinary chromium loss at pre was 0.36 μg/24 hr, whereas it was undetectable (< 0.1 μg/24 hr) for 10 subjects and excessive in 1 subject (2.4 μg/24 hr). Subjects receiving chromium supplements demonstrated urinary chromium losses five times greater than those in the placebo group at mid and post. Chromium picolinate supplementation was ineffective in bringing about changes in body composition or strength during a program of intensive weight-lifting training.

Restricted access

Scott C. Forbes, Nathan Sletten, Cody Durrer, Étienne Myette-Côté, D. Candow and Jonathan P. Little

High-intensity interval training (HIIT) has been shown to improve cardiorespiratory fitness, performance, body composition, and insulin sensitivity. Creatine (Cr) supplementation may augment responses to HIIT, leading to even greater physiological adaptations. The purpose of this study was to determine the effects of 4 weeks of HIIT (three sessions/week) combined with Cr supplementation in recreationally active females. Seventeen females (age = 23 ± 4 yrs; BMI = 23.4 ± 2.4) were randomly assigned to either Cr (Cr; 0.3 g・kg-1・d-1 for 5 d followed by 0.1 g・kg-1・d-1 for 23 days; n = 9) or placebo (PLA; n = 8). Before and after the intervention, VO2peak, ventilatory threshold (VT), time-trial performance, lean body mass and fat mass, and insulin sensitivity were assessed. HIIT improved VO2peak (Cr = +10.2%; PLA = +8.8%), VT (Cr = +12.7%; PLA = +9.9%), and time-trial performance (Cr = -11.5%; PLA = -11.6%) with no differences between groups (time main effects, all p < .001). There were no changes over time for fat mass (Cr = -0.3%; PLA = +4.3%), whole-body lean mass (Cr = +0.5%; PLA = -0.9%), or insulin resistance (Cr = +3.9%; PLA = +18.7%). In conclusion, HIIT is an effective way to improve cardiorespiratory fitness, VT, and time-trial performance. The addition of Cr to HIIT did not augment improvements in cardiorespiratory fitness, performance or body composition in recreationally active females.

Restricted access

Krystyna Burkhard-Jagodzinska, Krystyna Nazar, Maria Ladyga, Janina Starczewska-Czapowska and Lech Borkowski

Twelve girls who trained in rowing were examined twice a year for 4 years. Their initial age was 11.7 ± (SD) 0.2 yrs. Control groups consisted of 13 girls age 11.5±0.3 yrs and 18 girls age 14.4±0.3 yrs examined simultaneously with trained girls in the first and last year of the study, respectively. The examination involved basic anthropometry, estimation of sexual maturation (Tanner scale), 2-day food records, measurements of resting metabolic rate, energy expenditure following glucose ingestion (50 g), and determinations of blood glucose and plasma insulin concentrations prior to and 2 hrs after glucose load. Body mass, height, and fat content were slightly greater in trained girls. None of the subjects reported disturbances in menstrual function, and the age of menarche was similar for all. Both trained and untrained girls reported similar daily energy intake closer to the lower limit or slightly below the estimates of energy requirements for adolescents. Resting metabolic rate calculated per kg of total body mass or lean body mass was lower in trained girls, while the thermogenic effect of glucose was greater. Plasma insulin concentrations measured 2 hrs after glucose ingestion were lower in trained girls. The results suggest that in circumpubertal girls, increased physical activity leads to energy conservation at rest in postabsorptive state and a tendency toward enhancement of food-induced thermogenesis.

Restricted access

Michael H. Stone, Kimberly Sanborn, Lucille L. Smith, Harold S. O'Bryant, Tommy Hoke, Alan C. Utter, Robert L. Johnson, Rhonda Boros, Joseph Hruby, Kyle C. Pierce, Margaret E. Stone and Brindley Garner

The purpose of this investigation was to study the efficacy of two dietary supplements on measures of body mass, body composition, and performance in 42 American football players. Group CM (n = 9) received creatine monohy-drate, Group P (n = 11) received calcium pyruvate. Group COM (n = 11) received a combination of calcium pyruvate (60%) and creatine (40%), and Group PL received a placebo. Tests were performed before (Tl) and after (T2) the 5-week supplementation period, during which the subjects continued their normal training schedules. Compared to P and PL. CM and COM showed significantly greater increases for body mass, lean body mass, 1 repetition maximum (RM) bench press, combined 1 RM squat and bench press, and static vertical jump (SVJ) power output. Peak rate of force development for SVJ was significantly greater for CM compared to P and PL. Creatine and the combination supplement enhanced training adaptations associated with body mass/composition, maximum strength, and SVJ; however, pyruvate supplementation alone was ineffective.

Restricted access

Hugo Ribeiro Zanetti, Lucas Gonçalves da Cruz, Camilo Luís Monteiro Lourenço, Giovana Castilho Ribeiro, Marco Aurélio Ferreira de Jesus Leite, Fernando Freitas Neves, Mário Leon Silva-Vergara and Edmar Lacerda Mendes

Background:

Highly active antiretroviral therapy (HAART) is associated with high total cholesterol (TC), low-density lipoprotein cholesterol (LDL-c), triglyceride (TG), and C-reactive protein (CRP) levels. The natural course of the HIV infection reduces the high-density lipoprotein level (HDL-c). Thus, physical exercise plays a key role in reducing the effects of HAART and HIV.

Methods:

Thirty people living with HIV (PLHIV) were randomized to the nonlinear resistance training (NLRT) and control (CON) groups. The NLRT group underwent 12 weeks of resistance training, whereas the CON group maintained usual daily activities. All volunteers underwent anthropometric, body composition, and biochemical assessments at the beginning and end of 12 weeks.

Results:

After 12 weeks, the NLRT group had increased lean body mass (P < .0001), and a reduction in body fat mass (P < .0001) and body fat percentage (P < .0001). The levels of TC (P < .0001), LDL-c (P = .049), TG (P < .0001), and CRP (P = .004) were reduced, and the HDL-c level increased (P < .0001).

Conclusion

Twelve weeks of NLRT causes beneficial changes in the body composition, lipid profile, and inflammation markers in PLHIV, and it can be used in this patient population.

Restricted access

Kyle M. Tarpenning, Steven A. Hawkins, Taylor J. Marcell and Robert A. Wiswell

Quadriceps strength and mass peak in the third decade of life, plateau, and then decline from the fifth decade on. To examine the influence of chronic endurance training and age on lean mass and leg strength, women runners (n = 62, age 43–69 years) and sedentary participants (n = 33, age 43–66 years) were divided into 40-, 50-, and 60-year age groups. Absolute isokinetic concentric torque did not differ between runners and sedentary women (97.9 ± 19.5 and 104.6 ± 22.7 N · m, respectively, p = .18) but was different between age groups independent of exercise status (107.6 ± 18.4, 97.1 ± 19.9, and 90.1 ± 21.4 N · m, for 40s, 50s, and 60s, respectively, p < .05). Lean body mass also differed by age group (p < .05) but did not change differently among runners and sedentary women. These findings suggest that chronic endurance training might not influence the loss of muscle mass and muscle strength that occur with aging.

Restricted access

Niina Lintu, Kai Savonen, Anna Viitasalo, Tuomo Tompuri, Jussi Paananen, Mika P. Tarvainen and Timo Lakka

Background:

There are few studies on determinants of cardiorespiratory fitness (CRF) among girls and boys separately in population samples of children.

Methods:

We therefore investigated the determinants of CRF, assessed by maximal workload per height using allometric scaling, in a population sample of 162 girls and 177 boys aged 6 to 8 years. We used automated bootstrap feature selection and linear regression models.

Results:

The strongest determinants of CRF among girls were maximal heart rate (HR; standardized regression coefficient [β] = 0.31, P < .001), unsupervised physical activity (β = 0.29, P < .001), lean body mass (β = 0.23, P = .001), and errors in static balance test (β = –0.16, P = .02), accounting altogether for 25.7% of variation in CRF. In boys, unsupervised physical activity (β = 0.24, P < .001), resting HR (β = –0.25, P < .001), hand grip strength (β = 0.21, P = .001), errors in static balance test (β = –0.16, P = .01), organized football (β = 0.16, P = .01), and unsupervised trampoline jumping (β = 0.14, P = .04) were the strongest determinants of CRF, accounting altogether for 29.7% of variation in CRF.

Conclusions:

These findings suggest that unsupervised physical activity is sufficient in improving CRF in both sexes. Furthermore, larger muscle mass and better balance are associated with higher CRF that has to be taken into account when assessing CRF using maximal cycle ergometer exercise test among children.

Restricted access

Christine L. Wells and Steven P. Hooker

Physiological variables identified as important factors in athletic performance are discussed in relation to the spinal cord injured (SCI) athlete. These include body composition, pulmonary function, cardiorespiratory efficiency, muscular strength and endurance, and anaerobic power. SCI athletes are less fat and have a larger lean body mass than nonathletes, and male SCI are less fat than female SCI. Static lung volumes are usually below normal values in SCI subjects, but athletic SCI subjects tend to have higher values than sedentary SCI. Sedentary SCI subjects have lower aerobic power (O2max) than the general able-bodied (AB) sedentary population on tests of arm cranking or wheelchair ergometry. Low-lesion paraplegics generally achieve O2max values comparable to AB subjects. O2max is inversely related to level of injury, that is, the higher the SCI, the lower the O2max. However, elite SCI athletes are capable of achieving very high levels of O2max during arm exercise. SCI subjects respond well to strength and muscular endurance training. Paraplegic subjects achieve higher anaerobic power scores than quadriplegic subjects. Increases in O2max occur at about the same magnitude as in AB subjects. The required intensity level appears to be about 70–80% of maximal heart rate reserve.