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.
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.
Jerry L. Mayhew, Michael G. Bemben and Donna M. Rohrs
The purpose of this study was to determine the relationships among the seated shot put (SSP), bench press power (BPP), and body composition in adolescent wrestlers. Seventy-five wrestlers from three high schools were tested during their preseason training. Upper body power was tested with a plate-loaded bench press machine equipped with infrared sensors attached to a digital timer. Each subject was given three trials with a constant 24.5-kg load (CLP) and with a variable load equal to 60% of body mass (VLP). Skinfolds were used to estimate body composition. The SSP was significantly related to both CLP and VLP as well as to body mass, lean body mass (LBM), and % fat. Removing the effect of body mass reduced the relationship between SSP and both CLP and VLP. Removing the effect of LBM had a slightly greater effect on the relationships between SSP and both CLP and VLP, although the correlations remained significant. Therefore it appears that the SSP is only moderately related to upper body power in adolescent wrestlers and may be greatly influenced by size and muscularity.
Three papers which between them raise controversial issues, apply laboratory measures to sport performance, and expose gaps in knowledge were selected for commentary. The first paper (Sports Med. 2016;46:1451–1460) reviews the literature on peak V̇O2 in relation to body size and recommends that peak V̇O2 in youth is best expressed via allometric scaling of lean body mass. The second paper (Pediatr Exerc Sci. 2016;28:456–465) reports that maturity status has no effect on peak V̇O2, respiratory compensation point, or ventilatory threshold in youth soccer players once data have been allometrically normalized by lower limb muscle volume. It concludes that in future this technique should be used to compare the aerobic fitness of youth soccer players. The third paper (Eur J Appl Physiol. 2016;116:1781–1794) demonstrates that V̇O2 kinetics determined in a laboratory is related to measures associated with soccer match play and might distinguish superior performance within a group of highly trained youth players. The commentary stresses the importance of experimental rigor, emphasizes the need for appropriate scaling of physiological variables, challenges spurious correlations with health-related variables, endorses the use of a range of aerobic fitness measures, welcomes the application of laboratory data to sport performance, and identifies areas for future research.
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.
Eduardo Federighi Baisi Chagas, Mariana Rotta Bonfim, Bruna Camilo Turi, Nair Cristina Margarida Brondino and Henrique Luiz Monteiro
Declines in ovarian function in postmenopausal women may contribute to increase inflammatory cytokines, which can lead to chronic diseases. However, studies have shown that exercise interventions are important to manage inflammatory conditions. Thus, the objective of this study was to analyze the effect of exercise intervention on inflammatory markers among obese and postmenopausal women.
70 women composed the sample (Exercise group [EG; n = 35] and nonexercise group [nEG; n = 35]). IL-6, TNF-α, and IL-10 were the inflammatory markers analyzed. Exercise program was 20 weeks long and consisted of aerobic and neuromuscular training. Data about chronic diseases, medication use, dietary intake, body composition and biochemical variables were collected.
EG showed significant reductions in body mass index, waist circumference and body fat percentage, as well as increased lean body mass. EG showed significant reductions in TNF-α and significant interaction between group and intervention time. Reductions in IL-10 were identified only in nEG. Substantial effect of exercise intervention was observed with increased ratio of IL-10/IL-6 and IL-10/TNF-α.
Combination of aerobic exercise and resistance training was effective in reducing inflammation. Thus, implementation and maintenance of similar exercise programs can contribute to reduce chronic inflammation among obese postmenopausal women.
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.
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
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.
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.
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).
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.
Niina Lintu, Kai Savonen, Anna Viitasalo, Tuomo Tompuri, Jussi Paananen, Mika P. Tarvainen and Timo Lakka
There are few studies on determinants of cardiorespiratory fitness (CRF) among girls and boys separately in population samples of children.
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.
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.
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.
Norikazu Hirose and Chikako Nakahori
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.
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.
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.
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.