Jan Boone

Physical fitness of elite Belgian soccer players by player position.

Abstract Boone, J, Vaeyens, R, Steyaert, A, Vanden Bossche, L, and Bourgois, J. Physical fitness of elite Belgian soccer players by player position. J Strength Cond Res 26(8): 2051–2057, 2012—The purpose of this study was to gain an insight into the physical and physiological profile of elite Belgian soccer players with specific regard to the players position on the field. The sample consisted of 289 adult players from 6 different first division teams. The players were divided into 5 subgroups (goalkeepers, center backs, full backs, midfielders, and strikers) according to their self-reported best position on the field. The subjects performed anaerobic (10-m sprint, 5 × 10-m shuttle run [SR], squat jump [SJ], and countermovement jump [CMJ]) and aerobic (incremental running protocol) laboratory tests. The strikers had significantly shorter sprinting times (5-, 5- to 10-m time, and SR) compared with the midfielders, center backs, and goalkeepers, whereas the full backs were also significantly faster compared with the goalkeepers and the center backs. The goalkeepers and the center backs displayed higher jumping heights (total mean SJ = 40.7 ± 4.6 cm and CMJ = 43.1 ± 4.9 cm) compared with the other 3 positions, whereas the strikers also jumped higher than the full backs and the midfielders did. Regarding the aerobic performance, both full backs and the midfielders (61.2 ± 2.7 and 60.4 ± 2.8 ml·min−1·kg−1, respectively) had a higher V[Combining Dot Above]O2max compared with the strikers, center backs, and goalkeepers (56.8 ± 3.1, 55.6 ± 3.5, and 52.1 ± 5.0 ml·min−1·kg−1, respectively). From this study, it could be concluded that players in different positions have different physiological characteristics. The results of this study might provide useful insights for individualized conditional training programs for soccer players. Aside from the predominant technical and tactical skills, a physical profile that is well adjusted to the position on the field might enhance game performance.

Effect of Exercise Protocol on Deoxy[Hb + Mb]: Incremental Step versus Ramp Exercise

PURPOSE The aim of the present study was to investigate whether the sigmoid pattern of deoxy[Hb + Mb] during incremental exercise is specific to non-steady-state conditions. METHODS Ten highly trained cyclists performed an incremental step (40 W x 3 min(-1)) and ramp (35 W x min(-1)) exercise. Deoxy[Hb + Mb] was measured at the distal and proximal sites of the musculus vastus lateralis throughout the exercises using near-infrared spectroscopy. Deoxy[Hb + Mb] was set out as a function of work rate (% peak power), and using curve-fitting techniques, the best-fitting model was determined. RESULTS These procedures showed that the sigmoid pattern also provided the best fit for the pattern of deoxy[Hb + Mb] in the step exercise. Furthermore, it was observed that the sigmoid model was similar for the ramp (d = 6.9% +/- 1.1% and 6.9% +/- 1.4% x %(-1) peak power; c/d = 52.1% +/- 3.8% and 52.1% +/- 4.5% peak power, for the proximal and distal measurement sites, respectively) and the step exercise (d = 7.4% +/- 1.5% and 6.4% +/- 1.5% x %(-1) peak power; c/d = 52.3% +/- 6.0% and 52.5% +/- 4.2% peak power, for the proximal and distal measurement sites, respectively). The pattern of deoxy[Hb + Mb] was not influenced by measurement site. CONCLUSIONS From the present study, it can be concluded that the sigmoid pattern of deoxy[Hb + Mb] during incremental exercise is not specific to non-steady-state conditions. It was hypothesized that this pattern is an expression of a nonlinear Q x m/V x O2m relationship, related to changes in muscle fiber-type recruitment.

The VO2 response to submaximal ramp cycle exercise: Influence of ramp slope and training status.

The aim of the study was to test whether ramp slope and training status interact in the oxygen uptake (VO2) response during submaximal ramp exercise. Eight cyclists (VO2 peak=67.8+/-3.7 ml min(-1)kg(-1)) and eight physically active students (PA students) (VO2 peak=49.1+/-4.3 ml min(-1)kg(-1)) performed several ramp protocols, respectively, 25 and 40 W min(-1) for the cyclists and 10, 25 and 40 W min(-1) for the PA students. Vo(2) was plotted as a function of time and work rate up to the gas exchange threshold (GET). Faster ramp elicited a significantly shorter mean response time (MRT) in both groups, and MRT was significantly longer for each ramp protocol in the PA students (126+/-32s, 76+/-15s and 50+/-6s for ramp 10, ramp 25 and ramp 40, respectively) compared to the cyclists (61+/-9s and 40+/-11s for ramp 25 and ramp 40, respectively). Ramp 40 showed less steep Delta VO2/Delta W than ramp 25 in both groups (p<0.01) and Delta VO2/Delta W was less steep for each ramp protocol in PA students (p<0.01) (9.82+/-0.30 ml min(-1)W(-1) and 9.33+/-0.45 ml min(-1)W(-1) for ramp 25 and ramp 40, respectively) compared to cyclists (10.31+/-0.40 ml min(-1)W(-1) and 10.05+/-0.48 ml min(-1)W(-1) for ramp 25 and ramp 40, respectively). In the PA students, Delta VO2/Delta W did not differ between ramp 10 and ramp 25. Statistical analysis showed no interaction effects between ramp slope and training status for MRT (p=0.62) and Delta VO2/Delta W (p=0.35).

Dietary arginine supplementation speeds pulmonary VO2 kinetics during cycle exercise.

PURPOSE To test the hypothesis that L-arginine (the substrate for nitric oxide synthase [NOS]) administration slows the VO2 kinetics at the onset of moderate-intensity exercise in humans. METHODS Seven physically active males were randomly assigned to receive either placebo (lactose) or L-arginine hydrochloride capsules (7.2 g x d(-1)) for 14 d in a double-blind crossover design, with a 7-d washout period between the two conditions. On day 11 and day 14 of each condition, the subjects completed two consecutive 6-min bouts of cycle exercise at 80% of the ventilatory threshold with a 12-min rest interval. VO2 was measured on a breath-by-breath basis, and VO2 kinetics were determined with a single exponential model from the averaged data derived from four repetitions. Capillary and venous blood samples were taken to determine plasma [La] and serum [arginine], respectively. RESULTS There were no differences in circulating lactate either before or during exercise. However, serum [arginine] was higher (P < 0.05) in the arginine condition at rest (119.0 +/- 12.6 vs 103.6 +/- 15.7 micromol x L(-1) in the control condition) and after exercise (113.3 +/- 26.0 vs 103.8 +/- 12.6 micromol x L(-1) in the control condition). With regard to the pulmonary VO2 kinetics, no significant difference was observed in the time at which the phase II response emerged or in the phase II amplitude between the two conditions. However, contrary to our hypothesis, the time constant was significantly reduced after arginine administration (i.e., 13.9 +/- 3.1 vs 15.8 +/- 2.6 s in the control condition, P < or = 0.014). CONCLUSION Exogenous L-arginine administration speeds the phase II pulmonary VO2 response by 12% at the onset of moderate-intensity exercise in humans.

Encouraging Spontaneous Synchronisation with D-Jogger, an Adaptive Music Player That Aligns Movement and Music

In this study we explore how music can entrain human walkers to synchronise to the musical beat without being instructed to do so. For this, we use an interactive music player, called D-Jogger, that senses the users walking tempo and phase. D-Jogger aligns the music by manipulating the timing difference between beats and footfalls. Experiments are reported that led to the development and optimisation of four alignment strategies. The first strategy matched the musics tempo continuously to the runners pace. The second strategy matched the musics tempo at the beginning of a song to the runners pace, keeping the tempo constant for the remainder of the song. The third alignment starts a song in perfect phase synchrony and continues to adjust the tempo to match the runners pace. The fourth and last strategy additionally adjusts the phase of the music so each beat matches a footfall. The first two strategies resulted in a minor increase of steps in phase synchrony with the main beat when compared to a random playlist, the last two strategies resulted in a strong increase in synchronised steps. These results may be explained in terms of phase-error correction mechanisms and motor prediction schemes. Finding the phase-lock is difficult due to fluctuations in the interaction, whereas strategies that automatically align the phase between movement and music solve the problem of finding the phase-locking. Moreover, the data show that once the phase-lock is found, alignment can be easily maintained, suggesting that less entrainment effort is needed to keep the phase-lock, than to find the phase-lock. The different alignment strategies of D-Jogger can be applied in different domains such as sports, physical rehabilitation and assistive technologies for movement performance.

Characteristics of high-level youth soccer players: variation by playing position

Abstract The present study aimed to investigate positional differences in 744 high-level soccer players, aged 8 to 18 years. Players were assigned to six age groups (U9–U19) and divided into four playing positions (goalkeeper (GK), defender (DEF), midfielder (MF) and attacker (ATT)). MANOVA and effect sizes were used to examine anthropometrical and functional characteristics between all positions in all age groups. The main findings of the study were that GKs and DEFs were the tallest and heaviest compared with MFs and ATTs in all age groups. Further, between U9–U15, no significant differences in functional characteristics were found, except for dribbling skill, which MFs performed the best. In the U17–U19 age groups, ATTs seemed to be the most explosive (with GKs), the fastest and the more agile field players. These results suggest that inherent physical capacities (i.e., speed, power, agility) might select players in or reject players from an attacking position, which is still possible from U15–U17. Apparently, players with excellent dribbling skills at younger age are more likely to be selected to play as a MF, although, one might conclude that the typical physical characteristics for different positions at senior level are not yet fully developed among young soccer players between 8 and 14 years.

The Oxygen Uptake Response to Incremental Ramp Exercise

An incremental ramp exercise is a protocol that is frequently used in the domain of exercise testing to get an insight into the exercise tolerance of both healthy active populations (including athletes) and patients, due to the specific characteristics of the protocol. The continuous and linear increase in work rate is not only less strenuous for populations with a very low exercise capacity but it requires the aerobic metabolism to adapt to the continuously changing conditions. Therefore, this protocol can provide important information on the adaptive capacity of individuals to exercise in non-steady-state conditions. The ramp exercise has also been used in the past two decades to get an insight into the underlying mechanisms of the oxygen uptake (

The interrelationship between muscle oxygenation, muscle activation, and pulmonary oxygen uptake to incremental ramp exercise: influence of aerobic fitness

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The oxygen uptake response to incremental ramp exercise: methodogical and physiological issues.

O2) response (and kinetics) to exercise. Against the expectations, it has been shown that the parameters that quantify the

Quadriceps Muscle Fatigue in Trained and Untrained Boys

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