Jorge Perez-Gomez

Influence of extracurricular sport activities on body composition and physical fitness in boys: a 3-year longitudinal study.

Objective:To analyse the effect of extracurricular physical activities on fat mass accumulation and physical fitness during growth in early pubertal males.Design:Longitudinal study.Subjects:A total of 42 male children (9.4±1.4 years, Tanner I–II and 12.7±1.5 years, Tanner III–IV, before and after the 3.3 years follow-up, respectively), randomly sampled from the population of Gran Canaria (Spain), 26 of them physically active (PA, at least 3 h per week during 3 years) and 16 non-physically active (non-PA).Measurements:Body composition (dual-energy X-ray absorptiometry), anthropometrics (body circumferences and skinfolds) and physical fitness variables (dynamic and isometric force, anaerobic capacity and maximal aerobic power) were determined in all subjects.Results:Both groups had comparable body sizes at the start and the end of the study. Body mass index increased with growth more in the PA than in the non-PA group (P<0.05). However, fat mass accumulation with growth was lower in the PA than in the non-PA (P<0.05). There was a positive relationship between the increment of total and trunkal fat mass, especially in non-active children (r 2=0.93). In contrast, there was an inverse relationship between the total lean mass growth and the accumulation of total and regional fat mass (r=−0.37 to −0.41, all P<0.05). Physical fitness was maintained in the PA, while it worsened in the non-PA children.Conclusions:Without any dietary intervention, children who regularly participate in at least 3 h per week of sports activities are more protected against total and regional fat mass accumulation. They also increase their total lean and bone mass to a greater extent than children who do not participate in extracurricular sport activities. In addition, PA children maintain their physical fitness during growth, while it deteriorates in the non-PA children.

Muscular development and physical activity as major determinants of femoral bone mass acquisition during growth

Objectives: To investigate to what extent bone mass accrual is determined by physical activity and changes in lean, fat, and total body mass during growth. Methods: Twenty six physically active and 16 age matched control boys were followed up for three years. All subjects were prepubertal at the start of the survey (mean (SEM) age 9.4 (0.3) years). The weekly physical activity of the active boys included compulsory physical education sessions (80–90 minutes a week), three hours a week of extracurricular sports participation, and occasional sports competitions at weekends. The physical activity of the control group was limited to the compulsory physical education curriculum. Bone mineral content (BMC) and areal density (BMD), lean mass, and fat mass were measured by dual energy x ray absorptiometry. Results: The effect of sports participation on femoral bone mass accrual was remarkable. Femoral BMC and BMD increased twice as much in the active group as in the controls over the three year period (p<0.05). The greatest correlation was found between the increment in femoral bone mass and the increment in lean mass (BMC r  =  0.67 and BMD r  =  0.69, both p<0.001). Multiple regression analysis revealed enhancement in lean mass as the best predictor of the increment in femoral bone BMC (R  =  0.65) and BMD (R  =  0.69). Conclusions: Long term sports participation during early adolescence results in greater accrual of bone mass. Enhancement of lean mass seems to be the best predictor of this bone mass accumulation. However, for a given muscle mass, a greater level of physical activity is associated with greater bone mass and density in peripubertal boys.

Effects of weight lifting training combined with plyometric exercises on physical fitness, body composition, and knee extension velocity during kicking in football

The effects of a training program consisting of weight lifting combined with plyometric exercises on kicking performance, myosin heavy-chain composition (vastus lateralis), physical fitness, and body composition (using dual-energy X-ray absorptiometry (DXA)) was examined in 37 male physical education students divided randomly into a training group (TG: 16 subjects) and a control group (CG: 21 subjects). The TG followed 6 weeks of combined weight lifting and plyometric exercises. In all subjects, tests were performed to measure their maximal angular speed of the knee during in-step kicks on a stationary ball. Additional tests for muscle power (vertical jump), running speed (30 m running test), anaerobic capacity (Wingate and 300 m running tests), and aerobic power (20 m shuttle run tests) were also performed. Training resulted in muscle hypertrophy (+4.3%), increased peak angular velocity of the knee during kicking (+13.6%), increased percentage of myosin heavy-chain (MHC) type IIa (+8.4%), increased 1 repetition maximum (1 RM) of inclined leg press (ILP) (+61.4%), leg extension (LE) (+20.2%), leg curl (+15.9%), and half squat (HQ) (+45.1%), and enhanced performance in vertical jump (all p < or = 0.05). In contrast, MHC type I was reduced (-5.2%, p < or = 0.05) after training. In the control group, these variables remained unchanged. In conclusion, 6 weeks of strength training combining weight lifting and plyometric exercises results in significant improvement of kicking performance, as well as other physical capacities related to success in football (soccer).

Strength training combined with plyometric jumps in adults: sex differences in fat-bone axis adaptations

Leptin and osteocalcin play a role in the regulation of the fat-bone axis and may be altered by exercise. To determine whether osteocalcin reduces fat mass in humans fed ad libitum and if there is a sex dimorphism in the serum osteocalcin and leptin responses to strength training, we studied 43 male (age 23.9 2.4 yr, mean +/- SD) and 23 female physical education students (age 23.2 +/- 2.7 yr). Subjects were randomly assigned to two groups: training (TG) and control (CG). TG followed a strength combined with plyometric jumps training program during 9 wk, whereas the CG did not train. Physical fitness, body composition (dual-energy X-ray absorptiometry), and serum concentrations of hormones were determined pre- and posttraining. In the whole group of subjects (pretraining), the serum concentration of osteocalcin was positively correlated (r = 0.29-0.42, P < 0.05) with whole body and regional bone mineral content, lean mass, dynamic strength, and serum-free testosterone concentration (r = 0.32). However, osteocalcin was negatively correlated with leptin concentration (r = -0.37), fat mass (r = -0.31), and the percent body fat (r = -0.44). Both sexes experienced similar relative improvements in performance, lean mass (+4-5%), and whole body (+0.78%) and lumbar spine bone mineral content (+1.2-2%) with training. Serum osteocalcin concentration was increased after training by 45 and 27% in men and women, respectively (P < 0.05). Fat mass was not altered by training. Vastus lateralis type II MHC composition at the start of the training program predicted 25% of the osteocalcin increase after training. Serum leptin concentration was reduced with training in women. In summary, while the relative effects of strength training plus plyometric jumps in performance, muscle hypertrophy, and osteogenesis are similar in men and women, serum leptin concentration is reduced only in women. The osteocalcin response to strength training is, in part, modulated by the muscle phenotype (MHC isoform composition). Despite the increase in osteocalcin, fat mass was not reduced.

Bone Mass and the CAG and GGN Androgen Receptor Polymorphisms in Young Men

Background To determine whether androgen receptor (AR) CAG (polyglutamine) and GGN (polyglycine) polymorphisms influence bone mineral density (BMD), osteocalcin and free serum testosterone concentration in young men. Methodology/Principal Findings Whole body, lumbar spine and femoral bone mineral content (BMC) and BMD, Dual X-ray Absorptiometry (DXA), AR repeat polymorphisms (PCR), osteocalcin and free testosterone (ELISA) were determined in 282 healthy men (28.6±7.6 years). Individuals were grouped as CAG short (CAGS) if harboring repeat lengths of ≤21 or CAG long (CAGL) if CAG >21, and GGN was considered short (GGNS) or long (GGNL) if GGN ≤23 or >23. There was an inverse association between logarithm of CAG and GGN length and Wards Triangle BMC (r = −0.15 and −0.15, P<0.05, age and height adjusted). No associations between CAG or GGN repeat length and regional BMC or BMD were observed after adjusting for age. Whole body and regional BMC and BMD values were similar in men harboring CAGS, CAGL, GGNS or GGNL AR repeat polymorphisms. Men harboring the combination CAGL+GGNL had 6.3 and 4.4% higher lumbar spine BMC and BMD than men with the haplotype CAGS+GGNS (both P<0.05). Femoral neck BMD was 4.8% higher in the CAGS+GGNS compared with the CAGL+GGNS men (P<0.05). CAGS, CAGL, GGNS, GGNL men had similar osteocalcin concentration as well as the four CAG-GGN haplotypes studied. Conclusion AR polymorphisms have an influence on BMC and BMD in healthy adult humans, which cannot be explained through effects in osteoblastic activity.

Androgen receptor gene polymorphisms lean mass and performance in young men

The exon-1 of the androgen receptor (AR) gene contains two repeat length polymorphisms which modify either the amount of AR protein inside the cell (GGNn, polyglycine) or its transcriptional activity (CAGn, polyglutamine). Shorter CAG and/or GGN repeats provide stronger androgen signalling and vice versa. To test the hypothesis that CAG and GGN repeat AR polymorphisms affect muscle mass and various variables of muscular strength phenotype traits, the length of CAG and GGN repeats was determined by PCR and fragment analysis and confirmed by DNA sequencing of selected samples in 282 men (28.6±7.6 years). Individuals were grouped as CAG short (CAGS) if harbouring repeat lengths of ≤21 and CAG long (CAGL) if CAG >21. GGN was considered short (GGNS) or long (GGNL) if GGN ≤23 or >23, respectively. No significant differences in lean body mass or fitness were observed between the CAGS and CAGL groups, or between GGNS and GGNL groups, but a trend for a correlation was found for the GGN repeat and lean mass of the extremities (r=−0.11, p=0.06). In summary, the lengths of CAG and GGN repeat of the AR gene do not appear to influence lean mass or fitness in young men.

Look before you leap: on the issue of muscle mass assessment by dual-energy X-ray absorptiometry (reply to Jordan Robert Moon comments)

Our colleague Jordan Robert Moon starts his letter by saying that: “The authors state in the title, as well as in the methods, that the investigation measured muscle mass” (Perez-Gomez et al. 2008b). However, we never said this in the title or anywhere in the manuscript. This imprecision would seem to be used by our colleague to build a case. Despite his comments, the lean body mass of the extremities, as determined by dual-energy X-ray absorptiometry (DXA), can be used as a surrogate of the muscle mass assessed by magnetic resonance (MRI) (Kim et al. 2002). This is the reason why we (Ara et al. 2004, 2006; Calbet et al. 2001; Perez-Gomez et al. 2008a; Vicente-Rodriguez et al. 2003) and others (in some 200 papers) have published results assuming equivalence between the appendicular DXA-measured lean mass (ALM-DXA) and the muscle mass of the extremities, starting with the seminal paper by HeymsWeld et al. (1990). Despite the assertion of Mr. Moon, it is not possible to measure muscle mass directly in vivo; that is, all methods rely on estimations and calculations based on tissue density (DXA, MRI, TAC) and also geometric assumptions (MRI, TAC). All these methods have errors. There is little doubt that MRI is the best option to assess the muscle mass; however ALM-DXA is comparable to MRI for the assessment of the skeletal muscle mass of the extremities. MRI muscle mass values may deviate from the actual muscle mass (in some instances almost as much as DXA, particularly if intramuscular fat mass is not excluded from the MRI analysis). This is due to the fact that MRI requires manual digitalization of the images (slices) to deWne the boundaries of the muscles, combined with some geometrical assumptions to “Wll the gaps” between consecutive MRI images. In addition, to avoid too long interrogation periods, whole-body MRI interrogation normally uses 10 mm slice thickness with a gap between slices (sometimes of 40 mm or more). Thus, this means that the results obtained are aVected by geometrical assumptions, since each slice is treated as a fraction of a cylinder and the space between consecutive slices is simply interpolated. Because of the propagation of error, the greater the number of MRI slices to digitize, the higher will be the error. Even supposing that the MRI geometrical assumptions have no error, this kind of examination has a technical error between 1 and 2% (Kim et al. 2006). This error is close to the error of the regional lean mass assessment with DXA in our laboratory. A weakness of DXA is that it includes the inXuence of skin lean tissue into the ALMDXA value, but this aVects males and females equally in our study. Despite the latter, ALM-DXA explains 98.2% of the variability in MRI-measured appendicular muscle mass, when the intramuscular adipose tissue is separated from skeletal muscle in each image slice (Kim et al. 2006). This remarkably close agreement between ALM-DXA and MRI skeletal muscle mass assessment justiWes the use DXA to determine the muscle mass of the extremities in humans. Trying to correct for a 1.8% potential deviation with a predicting equation, which was developed with another population, using a diVerent DXA scanner, and that has an EES between 0.5 and 1.5 kg (depending on the body size of the subject) may lead to greater error than just taking the lean J. A. L. Calbet (&) · J. Perez-Gomez · G. Vicente-Rodriguez · I. Ara · H. Olmedillas · J. Chavarren · C. Dorado Department of Physical Education, University of Las Palmas de Gran Canaria, Campus Universitario de TaWra, 35017 Las Palmas de Gran Canaria, Canary Islands, Spain e-mail: lopezcalbet@terra.es; lopezcalbet@gmail.com

Influence of contextual variables and the pressure to keep category on physical match performance in soccer players

Previous studies have analysed the influence of contextual variables on performance and physical demands in soccer. However, the points needed to remain in the category have been an element that has not been analysed previously. The aim of the present study was to investigate the influence of match location, match period, strength of the opponent and the points required to keep category on physical performance in professional soccer players. Fourteen Spanish second B Division League matches played by a professional football team were analysed during the 2016/17 season using GPS devices. The 10 main players of each match used the GPS throughout the match. The variables of Total Distance (m), High Intensity Distance (m), High intensity Accelerations (n), Sprint Time (s) and Sprint Distance (m) were analysed. The most notable differences are found in Total Distance covered. Away games accumulated significantly more distance than those played at home, but only in the second half (+230.65 m, IC95%: 21.94 to 438.19, ES: 0.46, p = 0.031). There are no differences depending on the strength of the opponent. However, players covered greater distances during the first half in those matches that were played furthest from salvation (+235.86 m, 95% CI: 49.03 to 422.70, ES: 0.51, p = 0.014). Total Distance is the main parameter affected by situational variables. In addition, the pressure of being further away from saving the category increases the distance covered by players in a game.