Movement patterns in elite Brazilian youth soccer.

AIM: The aim of this study was to determine standards for the total distance covered (DC) and motion pattern characteristics of young Brazilian soccer players during competitive matches. METHODS: Seventy-five young soccer players from 5 of the most successful soccer clubs of Sao Paulo's Soccer Federation were divided in 3 categories: under-15 years (U15), under-17 years (U17) and under-20 years (U20) with 25 soccer players in each age group. In the U15 each half lasts for 30 min, in the U17 40 min and in the U20 45 min. The individual measurements were made during games following accepted video-recording methodology. The players were grouped by position: fullbacks, wingers (WG), defensive midfielders, offensive midfielders (OMF) and strikers (STK). The following indices were determined: total distance, and distance jogging, walking, and sprinting. Age and position differences were determined by ANOVA. RESULTS: The intensity of the U15 (118 m/min) was significantly greater (P<0.05) than U17 (108 m/min) and U20 (109 m/min). WG and midfielders show greater DC than the other players in all other positions. STK and OMF show increased sprinting in U15 and U17 groups, respectively, and WG in U20s. The U15 group showed the greatest mean intensity when the time of each group was corrected to meters per minute. CONCLUSION: The results show differences in running volume and intensity between the age groups during match play. The data suggest that earlier development, physical training and tactical organization in the young soccer player leads to a high level of energy during competition.

Maximal oxygen uptake during exercise using trained or untrained muscles.

Maximal oxygen uptake, VO2 max, was determined for cyclists, long-distance runners and non-athletes during uphill running (treadmill) and cycling (cycloergometer) to compare trained and untrained muscles. Blood lactate, maximal heart rate and maximal ventilation during work were also measured. VO2 max was higher for runners and non-athletes during exercise on the treadmill and higher for cyclists during exercise on the cycloergometer. For runners and non-athletes, maximal heart rate accompanied the increase in VO2 max, whereas similar values were obtained for cyclists on both ergometers. Maximal ventilation during work accompanied the difference in VO2 max in both groups of athletes but among non-athletes it was similar during exercise on both the cycloergometer and the treadmill. Blood lactate was similar during exercise on both ergometers for all groups. These results suggest that the quantitative effects of training on cardiovascular and respiratory functions may only be properly evaluated by using an ergometer which requires an activity similar to that usually performed by the subjects. Cycle riding may possibly induce significant and specific alterations in the muscles involved in the exercise, thus increasing peripheral O2 uptake even after stabilization of maximal cardiac output, whereas running may well induce an improvement of all factors which are responsible for aerobic work power.

Ventilatory responses during electrically induced muscular work in anesthetized dogs, after both deafferentation and cross circulation of hindlimbs.

1. The role of the neural afferent component from moving limbs during exercise hyperpnea has been studied in dogs. The influence of neural and humoral effects was evaluated by dorsal root section and limb cross-circulation. 2. Respiratory minute volume (Ve), frequency (f), tidal volume (VT) and oxygen consumption (VO2) were measured in anesthetized dogs submitted to light electrically-induced exercise (ventral root stimulation of L6 or L7), both before and after deafferentation. 3. In control experiments the increase of respiratory minute volume (Ve) was directly proportional to VO2, and primarily due to changes in frequency. After dorsal root section (L1 to S1), VO2 increased, but no significant changes were observed in the other respiratory parameters. 4. In contrast to the deafferentation experiments, no changes were detected either in Ve or in f during exercise in the cross-circulation experiments. 5. It is concluded that during light exercise reflexes generated by moving limbs are important for triggering the exercise tachypneic response.

Potassium-induced ventilatory reflexes originating from the dog hindlimb during rest and passive exercise.

1. It has been previously shown that Ketalar-anesthetized dogs do not exhibit alterations either in ventilation or in oxygen uptake during passive motion. In the present study, the same model was used to study the effects induced by increasing extracellular K+ to the concentration achieved during active exercise. 2. The isolated hindlimbs of twelve dogs anesthetized with ketamine hydrochloride i.v., after induction with sodium pentobarbital, were perfused with control (2.8 mM KCl) and experimental (8 mM KCl) physiological solutions under resting conditions, and in passive motion. 3. Respiratory minute volume (VE), respiratory rate (f) and tidal volume (VT) were determined by collecting the expired air in a Tissot gasometer. 4. During the control perfusion, the values of VE, f and VT for passive exercise did not differ significantly from those obtained under resting conditions. However, during perfusion with 8 mM KCl, a significant increase in VE was observed, possibly due to an increase of VT under resting conditions and to an increase of f during passive exercise. 5. The results suggest that passive exercise can induce a significant increase in ventilation only when accompanied by local chemical changes such as an increase in extracellular K+.