This paper reviews the growth and development of skeletal mass in youth and the effects of physical activity upon the bone mass in young people. The different methods to measure the bone mass are described such as anthropometrics, radiographics, dual energy X-ray absorptiometry, quantitative computed tomography, and ultrasound. Two different mechanisms are important for the formation and plasticity of bone: a central hormonal mechanism (with estrogen production) and a local mechanism (based on mechanical forces of gravity and muscle contractions). This local mechanism is closely connected to physical activity patterns and therefore discussed in more detail. Thereafter the natural course of the development of the bone mass during youth is described, taking into account the pubertal stages of boys and girls and also the age at which the maximal bone mass (peak bone mineral density) will be reached. The last part is devoted to the effects of physical activity on bone mass based on results of randomized controlled trials. Although the number of experimental studies are scarce, significant effects of weight bearing activity and high impact strength training programs are shown on the side specific bone mineral density in both boys and girls.
Linda B. Houtkooper, Veronica A. Mullins, Scott B. Going, C. Harmon Brown and Timothy G. Lohman
This study characterized body composition profiles of elite American heptathletes and cross-validated skinfold (SKF) and bioelectrical impedance analysis (BIA) field method equations for estimation of percent body fat (%Fat) using dual energy x-ray absorptiometry (DXA) as the criterion. Weight, height, fat mass (FM), fat-free mass (FFM), bone mineral density (BMD), and %Fat were measured in 19 heptathletes using standard measurement protocols for DXA, SKFs and BIA. The ages, heights, and weights were respectively 25.5 ± 3.5 years, 175.0 ± 6.6 cm, 67.3 ± 7.1 kg. DXA estimates of mean ± SD values for body composition variables were 57.2 ± 6.1 kg FFM, 10.1 ± 2.6 kg FM, 114 ± 7% BMD for age/racial reference group, and 15 ± 3.0 %Fat. Ranges of bias values for %Fat (DXA minus SKF or BIA) were, respectively, −0.5 to 1.6% and −5.5 to −1.2%. Ranges for standard errors of estimate and total errors were, respectively, SKF 2.4–2.5%, 2.4–2.8% and BIA 3.0%, 5.0–6.5%. Regression analyses of the field methods on DXA were significant (p < .05) for all SKF equations but not BIA equations. This study demonstrates that elite American heptathletes are lean, have high levels of BMD, and that SKF equations provide more accurate estimates of %Fat relative to DXA than estimates from BIA equations.
Alex S. Ribeiro, Fábio Luiz C. Pina, Soraya R. Dodero, Danilo R. P. Silva, Brad J. Schoenfeld, Paulo Sugihara Júnior, Rodrigo R. Fernandes, Décio S. Barbosa, Edilson S. Cyrino and Julio Tirapegui
The aim of this study was to analyze the effects of 8 weeks of conjugated linoleic acid (CLA) supplementation associated with aerobic exercise on body fat and lipid profile on obese women. We performed a randomized, double-blinded and placebo-controlled trial with 28 obese women who received 3.2 g/day of CLA or 4 g/day of olive oil (placebo group) while performing an 8-week protocol of aerobic exercise. Dietary intake (food record), body fat (dual-energy X-ray absorptiometry), and biochemical analysis (blood sample) were assessed before and after the intervention period. Independent of CLA supplementation, both groups improved (p < .05) oxygen uptake (CLA group, 13.2%; PLC group, 14.8%), trunk fat (CLA group, −1.0%; PLC group, −0.5%), leg fat (CLA group, −1.0%; PLC group, −1.6%), and total body fat (CLA group, −1.7%; PLC group, −1.3%) after the 8-week intervention. No main effect or Group × Time interaction was found for total cholesterol, triglycerides, and plasma lipoproteins (p > .05). We conclude that CLA supplementation associated with aerobic exercise has no effect on body fat reduction and lipid profile improvements over placebo in young adult obese women.
Gary Slater, David Jenkins, Peter Logan, Hamilton Lee, Matthew Vukovich, John A. Rathmacher and Allan G. Hahn
This investigation evaluated the effects of oral β-Hydroxy-β-Methylbutyrate (HMB) supplementation on training responses in resistance-trained male athletes who were randomly administered HMB in standard encapsulation (SH), HMB in time release capsule (TRH), or placebo (P) in a double-blind fashion. Subjects ingested 3 g · day−1 of HMB or placebo for 6 weeks. Tests were conducted pre-supplementation and following 3 and 6 weeks of supplementation. The testing battery assessed body mass, body composition (using dual energy x-ray absorptiometry), and 3-repetition maximum isoinertial strength, plus biochemical parameters, including markers of muscle damage and muscle protein turnover. While the training and dietary intervention of the investigation resulted in significant strength gains (p < .001) and an increase in total lean mass (p = .01), HMB administration had no influence on these variables. Likewise, biochemical markers of muscle protein turnover and muscle damage were also unaffected by HMB supplementation. The data indicate that 6 weeks of HMB supplementation in either SH or TRH form does not influence changes in strength and body composition in response to resistance training in strength-trained athletes.
Alex S. Ribeiro, Brad J. Schoenfeld, Danilo R.P. Silva, Fábio L.C. Pina, Débora A. Guariglia, Marcelo Porto, Nailza Maestá, Roberto C. Burini and Edilson S. Cyrino
The purpose of this study was to compare different split resistance training routines on body composition and muscular strength in elite bodybuilders. Ten male bodybuilders (26.7 ± 2.7 years, 85.3 ± 10.4 kg) were randomly assigned into one of two resistance training groups: 4 and 6 times per week (G4× and G6×, respectively), in which the individuals trained for 4 weeks, 4 sets for each exercise performing 6–12 repetitions maximum (RM) in a pyramid fashion. Body composition was assessed by dual energy X-ray absorptiometry, muscle strength was evaluated by 1RM bench-press testing. The food intake was planned by nutritionists and offered individually throughout the duration of the experiment. Significant increases (p < .05) in fat-free mass (G4× = +4.2%, G6× = +3.5%) and muscular strength (G4× = +8.4%, G6× = +11.4%) with no group by time interaction were observed. We conclude that 4 and 6 weekly sessions frequencies of resistance training promote similar increases in fat-free mass and muscular strength in elite bodybuilders.
Nai-Hsin Meng, Chia-Ing Li, Chiu-Shong Liu, Wen-Yuan Lin, Chih-Hsueh Lin, Chin-Kai Chang, Tsai-Chung Li and Cheng-Chieh Lin
To compare muscle strength and physical performance among subjects with and without sarcopenia of different definitions.
A population-based cross-sectional study.
857 community residents aged 65 years or older.
Sarcopenia was defined according to the European Working Group of Sarcopenia in Older People consensus criteria. Dual-energy X-ray absorptiometry measured lean soft tissue mass. Sarcopenic participants with low height-adjusted or weight-adjusted skeletal muscle index (SMI) were classified as having h-sarcopenia or w-sarcopenia, respectively. Combined sarcopenia (c-sarcopenia) was defined as having either h- or w-sarcopenia. The participants underwent six physical performance tests: walking speed, timed up-and-go, six-minute walk, single-leg stance, timed chair stands, and flexibility test. The strength of five muscle groups was measured.
Participants with h-sarcopenia had lower weight, body mass index (BMI), fat mass, and absolute muscle strength (p ≤ .001); those with w-sarcopenia had higher weight, BMI, fat mass (p < .001), and low relative muscle strength (p ≤ .003). Participants with c-sarcopenia had poorer performance in all physical performance tests, whereas h-sarcopenia and w-sarcopenia were associated with poor performance in four tests.
Subjects with h- and w-sarcopenia differ significantly in terms of obesity indicators. Combining height- and weight-adjusted SMIs can be a feasible method to define sarcopenia.
Thomas B. Walker, Jessica Smith, Monica Herrera, Breck Lebegue, Andrea Pinchak and Joseph Fischer
The purpose of this study was to investigate the ability of whey-protein and leucine supplementation to enhance physical and cognitive performance and body composition. Thirty moderately fit participants completed a modified Air Force fitness test, a computer-based cognition test, and a dual-energy X-ray-absorptiometry scan for body composition before and after supplementing their daily diet for 8 wk with either 19.7 g of whey protein and 6.2 g leucine (WPL) or a calorie-equivalent placebo (P). Bench-press performance increased significantly from Week 1 to Week 8 in the WPL group, whereas the increase in the P group was not significant. Push-up performance increased significantly for WPL, and P showed a nonsignificant increase. Total mass, fat-free mass, and lean body mass all increased significantly in the WPL group but showed no change in the P group. No differences were observed within or between groups for crunches, chin-ups, 3-mile-run time, or cognition. The authors conclude that supplementing with whey protein and leucine may provide an advantage to people whose performance benefits from increased upper body strength and/or lean body mass.
Alessandra Madia Mantovani, Scott Duncan, Jamile Sanches Codogno, Manoel Carlos Spiguel Lima and Rômulo Araújo Fernandes
Physical activity level is an important tool to identify individuals predisposed to developing chronic diseases, which represent a major concern worldwide.
To identify correlates of daily step counts measured using pedometers, as well as analyze the associations between health outcomes and 3 different amounts of daily physical activity.
The sample comprised 278 participants (126 men and 153 women) with a mean age of 46.51 ± 9.02 years. Physical activity was assessed using pedometers for 7 consecutive days, and 3 amounts of daily physical activity were considered: ≥10,000 steps/day, ≥7500 steps/day, and <5000 steps/day. Sleep quality was assessed through a questionnaire, and dual-energy x-ray absorptiometry was used to measure body fat. Sociodemographic and anthropometric data were also collected.
The percentages of adults achieving at least 10,000 and 7500 steps/day on a minimum of 5 days of the evaluated week were 12.9% and 30.9%, respectively. Adults who reached ≥7500 steps/day had a lower likelihood of being obese (odds ratio [OR] = 0.38, 95% confidence interval [CI], 0.17–0.85) and reporting worse sleep quality (OR = 0.58, 95% CI, 0.34–0.99). Adults who reached <5000 steps/day had a higher likelihood of reporting worse sleep quality (OR = 2.11, 95% CI, 1.17–3.82).
Physical activity in adulthood, as measured by pedometer, constituted a behavior related to lower adiposity and better sleep quality.
Heidi L. Petersen, C. Ted Peterson, Manju B. Reddy, Kathy B. Hanson, James H. Swain, Rick L. Sharp and D. Lee Alekel
This study determined the effect of training on body composition, dietary intake, and iron status of eumenorrheic female collegiate swimmers (n = 18) and divers (n = 6) preseason and after 16 wk of training. Athletes trained on dryland (resistance, strength, fexibility) 3 d/wk, 1.5 h/d and in-water 6 d/wk, nine, 2-h sessions per week (6400 to 10,000 kJ/d). Body-mass index (kg/m2; P = 0.05), waist and hip circumferences (P ≤ 0.0001), whole body fat mass (P = 0.0002), and percentage body fat (P ≤ 0.0001) decreased, whereas lean mass increased (P = 0.028). Using dual-energy X-ray absorptiometry, we found no change in regional lean mass, but fat decreased at the waist (P = 0.0002), hip (P = 0.0002), and thigh (P = 0.002). Energy intake (10,061 ± 3617 kJ/d) did not change, but dietary quality improved with training, as refected by increased intakes of fber (P = 0.036), iron (P = 0.015), vitamin C (P = 0.029), vitamin B-6 (P = 0.032), and fruit (P = 0.003). Iron status improved as refected by slight increases in hemoglobin (P = 0.046) and hematocrit (P = 0.014) and decreases in serum transferrin receptor (P ≤ 0.0001). Studies are needed to further evaluate body composition and iron status in relation to dietary intake in female swimmers.
Herculina S. Kruger, Lize Havemann-Nel, Chrisna Ravyse, Sarah J. Moss and Michael Tieland
Black women are believed to be genetically less predisposed to age-related sarcopenia. The objective of this study was to investigate lifestyle factors associated with sarcopenia in black South African (SA) urban women.
In a cross-sectional study, 247 women (mean age 57 y) were randomly selected. Anthropometric and sociodemographic variables, dietary intakes, and physical activity were measured. Activity was also measured by combined accelerometery/heart rate monitoring (ActiHeart), and HIV status was tested. Dual energy x-ray absorptiometry was used to measure appendicular skeletal mass (ASM). Sarcopenia was defined according to a recently derived SA cutpoint of ASM index (ASM/height squared) < 4.94 kg/m2.
In total, 8.9% of the women were sarcopenic, decreasing to 8.1% after exclusion of participants who were HIV positive. In multiple regressions with ASM index, grip strength, and gait speed, respectively, as dependent variables, only activity energy expenditure (β = .27) was significantly associated with ASM index. Age (β = –.50) and activity energy expenditure (β = .17) were significantly associated with gait speed. Age (β = –.11) and lean mass (β = .21) were significantly associated with handgrip strength.
Sarcopenia was prevalent among these SA women and was associated with low physical activity energy expenditure.