A MODEL BASED COMPUTATIONAL APPROACH TO HUMAN VERTICAL JUMPING

A subject specific forward dynamic 3-actuator torque-driven model of the human musculoskeletal system was created, based on measure- ments of individual subject characteristics. The goal was to simu- late a common strength exercise: squat jump with and without extra load. Hip, knee and ankle resultant net torques were modeled from experimental data. Elastic components were not considered. Two models were created for each joint, and then implemented into sim- ulations. Subsequently they were compared to each other to estab- lished which one best matched actual performances. By analyzing kinematic and kinetic experimental data at the instant of the toe-off, it was shown that accurate joint torque models implemented in a sim- ple computer simulation could reproduce squat jumps. The model that best matched actual jumps was used to optimize jump height performance with and without extra load. A linear decreasing of the jump height was found as the load increased. The load at which the model would not be able to take-off was predicted. In addition, joint and global power outputs for different extra load conditions were es- timated. It seemed that global power output probably suffered from a slight inaccuracy of simulated vertical ground reaction forces. It was concluded that a computational approach combined with exper- imental data, is an original way to conduct research in strength and conditioning training. It would help coaches, athletes and scientists to better understand human performances. This investigation is the first step in a wider project aiming to evaluate the advantages of the individual subject approach for understanding strength exercise tasks

Effect of K1 Fight on vertical jump, reaction time, and lactate production

Introduction: K1 is a combat sport with punches, kicks and knee blows. Two parameters may influence athletes\u2019 performance: injuries (e.g., Zazryn et al., 2003) and fatigue. Some studies were conducted to determine fighters physiological profile such as VO2max (Gosh et al., 1995; Guidetti et al., 2002). However, the effects of fatigue during official K1 fights remain unknown. Therefore, the aim of this study was to determine the effects of fatigue induced by an official K1 fight on vertical jump, simple visual reaction time, lactate accumulation and tactical behaviors. Methods: Eight male volunteers were recruited during regional Italian K1-style amateur competition. Mean (\ub1 SD) age, height, weight and training experience were 24.3 \ub1 1.8 yrs, 173.8 \ub1 5.6 cm, 73.3 \ub1 9.4 kg, 5.6 \ub1 2.2 yrs, respectively. Subjects performed three rounds of 90 s with 60 s rest among rounds. Tests included counter movement jumps, simple visual reaction time (both were measured with an optojump system, Microgate, Italy) and blood lactate (Lactate PRO). They were performed before warm-up and after fights. Vertical jumps and simple visual reaction times were determined 8 minutes after the end of the third round due to judge\u2019s decision and prize giving. Blood lactate was collected 2 minutes after the end of the fight. A complete match-analysis was also made using a camcorder (blow numbers). Results: Match-analysis showed 86 \ub1 23 total blows. No difference was found among rounds. However, punches (39 \ub1 16) and kicks (37 \ub1 16) number during fights was bigger (p<0.001) than knees (10 \ub1 10). While no difference among rounds was found for punches and kicks, knee blows were greater during the third round regarding with the first and second round (+4.8 \ub1 4.1, 2.8 \ub1 3.2, 2.4 \ub1 3.6, respectively, p<0.05). After the end of the fights, blood lactate was found to be on average 15.3 \ub1 1.6 mmol/L. Simple reaction times significant increased (+7.8 \ub1 5.6%; p<0.01) and no difference was found in vertical jump heights. Discussion: Our data showed an altered number of blows among rounds. The increased knee blow number may be due to either or both tactical behaviors and technical economy. High values of blood lactate suggested a key role of anaerobic metabolism in K1 fights. Although high lactate values, vertical jump heights were surprisingly unchanged, this may be due to long rest duration between the end of the fights and post-tests. After the fight, simple visual reaction tim

Effect of Kickboxing Fight on vertical jump, muscle power, and metabolic indexes

Introduction: Combat sports alternate both anaerobic and aerobic efforts (Smith, 2006). Powerful and fast anaerobic actions are of paramount importance for explosive punch or kick attacks, feigns and defensive actions. Some authors examined the effects of fight on blood lactate production among different combat sports (Khanna et al., 2006). However, especially during kickboxing fights, the effects of fatigue on muscle power and metabolic indexes remain unknown. Therefore, the aim of this research was to determine the effects of fatigue induced by a kickboxing fight on vertical jump, bench press peak power, heart rate, and blood lactate accumulation. Methods: Eleven athletes (5 females and 6 males) volunteered for the experiment. Females mean (\ub1 SD) age, height, weight and training experience were 29.6 \ub1 3.8 yrs, 164.8 \ub1 3.9 cm, 59.0 \ub1 2.4 kg, 6.4 \ub1 1.3 yrs, respectively. Males group was 26.5 \ub1 6.2 yrs, 178.3 \ub1 3.4 cm, 78.3 \ub1 10.5 kg, 8.0 \ub1 1.0 yrs, respectively. Subjects performed unofficial fights with three 120 s rounds with 60 s rest among rounds. Fights were conducted in accordance with kickboxing rules (low kick style). Athletes, referee, and coaches used their usual competition behavior. One day before fights, pre-tests were performed to determine bench press peak power using an accelerometer (Myotest, Switzerland), and vertical jump height during counter movement jumps (Optojump, Microgate, Italy). Just before fights and after warm-up, basal lactate (Lactate PRO, Japan) was collected. Heart rate (TMpro, Hosand Technologies, Italy) has been continuously recorded during fights. Finally, immediately after the end of the third round, bench press peak power, vertical jump height, and blood lactate values were evaluated for post-tests. Results: At pre-test, a sex effect was found for both bench press peak power and vertical jump height, with males demonstrating greater values than females (p<0.05). During rounds, heart rate was on average 93 \ub1 1 % of the maximal heart rate. After fights, blood lactate concentration significantly increased until 13.6 \ub1 2.3 mmol/L (p<0.001). After fights no time effect was found for both bench press peak power and counter movement jump height. Discussion: This study highlighted high heart rate and blood lactate values suggesting anaerobic metabolism plays a key role in kickboxing fights. However, aerobic power also plays an important role during recovery (e.g., lactate clearance). Neuromuscular indexes (vertical jump height and bench press peak power) were surprisingly unchanged although a fight-induced fatigue. These data could be explained by the non specific nature of these tests regarding with kickboxing skills

The aerobic mechanism in the 400 metres

Revue des variations des conclusions des études sur les caractéristiques énergétiques de la discipline : différences entre athlètes masculins et féminins, différences entre athlètes de type sprinters et athlètes de type endurance, différences entre méthodologies et différences engendrées par le niveau de performance des athlètes étudié

Relationship between balance capacity and jump ability in amateur soccer players of different age

It\u2019s well known that in many sport activities, a technical gesture performed in situation of balance is more effective and easier to perform. Short-term balance training (BT), seems to be effective for rapidly improving the muscular strength and for reducing imbalances between corresponding limbs (1, 2). The latter may be of particular interest for the prevention of injuries in the youthful soccer teams. The aim of the present study was to investigate the link between balance and strength in young soccer players. The experiment was carried out on 133 young male soccer players (age: 18.2\ub11.9). The Libra Fixed Point (LPF)- Libra Closed Eye (LB) balance tests as well as the Counter Movement Jump (CMJ-CMJMono) tests resulted significantly (P<0.05) correlated (r=0.43 and r=0.63, respectively; P<0.01). Significant correlations (P<0.05) were found between the balance LPF and CMJ (r=-0.36, P<0.01), between LB and CMJ (R=-0.22, P<0.05), between LPF and CMJMono (r=-0.48, P<0.01) and between LB and CMJMono tests (r=-0.42, P<0.01). These results suggest interest on the effects of Balance Training