Igor Jukić

Effects of sprint and plyometric training on muscle function and athletic performance.

The purpose of this study was to evaluate the effects of sprint training on muscle function and dynamic athletic performance and to compare them with the training effects induced by standard plyometric training. Male physical education students were assigned randomly to 1 of 3 groups: sprint group (SG; n = 30), plyometric group (PG; n = 30), or control group (CG; n = 33). Maximal isometric squat strength, squat-and counter-movement jump (SJ and CMJ) height and power, drop jump performance from 30-cm height, and 3 athletic performance tests (standing long jump, 20-m sprint, and 20-yard shuttle run) were measured prior to and after 10 weeks of training. Both experimental groups trained 3 days a week; SG performed maximal sprints over distances of 10–50 m, whereas PG performed bounce-type hurdle jumps and drop jumps. Participants in the CG group maintained their daily physical activities for the duration of the study. Both SG and PG significantly improved drop jump performance (15.6 and 14.2%), SJ and CMJ height (∼10 and 6%), and standing long jump distance (3.2 and 2.8%), whereas the respective effect sizes (ES) were moderate to high and ranged between 0.4 and 1.1. In addition, SG also improved isometric squat strength (10%; ES = 0.4) and SJ and CMJ power (4%; ES = 0.4, and 7%; ES = 0.4), as well as sprint (3.1%; ES = 0.9) and agility (4.3%; ES = 1.1) performance. We conclude that short-term sprint training produces similar or even greater training effects in muscle function and athletic performance than does conventional plyometric training. This study provides support for the use of sprint training as an applicable training method of improving explosive performance of athletes in general.

RELIABILITY AND FACTORIAL VALIDITY OF AGILITY TESTS FOR SOCCER PLAYERS

Sporis, G, Jukic, I, Milanovic, L, and Vucetic, V. Reliability and factorial validity of agility tests for soccer players. J Strength Cond Res 24(3): 679-686, 2010-The purpose of this study was to evaluate the reliability and factorial validity of agility tests used in soccer. One hundred fifty (n = 150), elite, male, junior soccer players, members of the First Junior League Team, volunteered to participate in the study. The slalom test (ST) sprint 4 × 5 m (S4 × 5) and sprint 9-3-6-3-6-9 m with 180° turns (S180°) tests had a greater reliability coefficient (α = 0.992, 0.979, and 0.976), whereas the within-subject variation ranged between 2.9 and 5.6%. The mentioned 6 agility tests resulted in the extraction of 2 significant components. The S4×5 test had the lowest correlation coefficient with the first component (r = 0.38), whereas the correlation coefficients of the other 5 agility tests were higher than 0.63. The T-test (TT) showed statistically significant differences between the defenders and midfielders (p < 0.05) and between the defenders and attackers (p < 0.05). Statistical significant differences were determined between the attackers and defenders in the sprint 9-3-6-3-9 m with backward and forward running (SBF) and p < 0.05. It can be concluded that of the 6 agility tests used in this study, the SBF, TT, and S180° are the most reliable and valid tests for estimating the agility of soccer players. According to the results of the study, the TT proved to be the most appropriate for estimating the agility of defenders, the SBF, and S180° for estimating the agility of midfielders, whereas the S4 × 5 test can be used for estimating the agility of attackers.

Fitness Profiling in Soccer: Physical and Physiologic Characteristics of Elite Players

Sporis, G, Jukic, I, Ostojic, SM, and Milanovic, D. Fitness profiling in soccer: physical and physiologic characteristics of elite players. J Strength Cond Res 23(7): 1947-1953, 2009-The purpose of this study was to evaluate whether players in different positional roles have a different physical and physiologic profile. For the purpose of this study, physiologic measurements were taken of 270 soccer players during the precompetitive period of 2005/06 and the precompetitive period of 2006/07. According to the positional roles, players were categorized as defenders (n = 80), midfielders (n = 80), attackers (n = 80), and goalkeepers (n = 30). Analysis of variance (ANOVA) was use to determinate differences between team positions. Goalkeepers are the tallest and the heaviest players in the team. They are also the slowest players in the team when sprinting ability over 10 and 20 meters is required. Attackers were the quickest players in the team when looking at sprint values over 5, 10, and 20 meters. There were statistically significant differences between attacker and defenders when measuring vertical jump height by squat jump. Goalkeepers were able to perform better on explosive power tests (squat jump and countermovement jump) than players in the field. Midfielders had statistically significant superior values of relative oxygen consumption, maximal heart rate, maximal running speed, and blood lactate than defenders and attackers. Defenders had more body fat than attackers and midfielders (p < 0.05). Coaches are able to use this information to determine which type of profile is needed for a specific position. It is obvious that players in different positions have different physical and physiologic profiles. Experienced coaches can use this information in the process of designing a training program to maximize the fitness development of soccer players with one purpose only, to achieve success in soccer.

The Biological Age of 14-year-old Boys and Success in Adult Soccer: Do Early Maturers Predominate in the Top-level Game?

Talent identification and development in soccer is often biased by maturation-related differences of young athletes. However, there is no information available about success rates for youth maturing at different tempos to achieve success in elite adult soccer. The purposes of this study were to determine the prevalence of different maturational groups among boys playing soccer, and to track them for competence in adult performance. A prospective cohort study design was used to follow 55, 14-year-old boys playing in Serbian youth soccer Division I over eight years. At the age of 14, biological age using skeletal age rates was determined, and participants were categorized as early maturers (EaM), normal maturers (NoM), and late maturers (LaM). Game competence for adult soccer at age 22 was described as elite if an individual played for clubs competing in top-five international soccer leagues (La Liga, Premier League, Bundesliga, Serie A, and Ligue 1), and/or has become a member of an adult National team. Among boys in our study group, 43.8% were categorized as EaM, 35.4% as NoM, and 20.8% as LaM (P = 0.11). A significant difference in biological age was found among maturational groups at age 14, with EaM > NoM > LaM (P > 0.0001). When assessed for adult soccer competence, 33.3% of participants (16 out of 48 players) succeed in achieving elite level. Elite soccer competence acquired 60.1% players from the group of LaM, 38.1% from NoM, and 11.8% from EaM (P > 0.0001). Our comparative analysis suggests that soccer excludes early maturing boys and favors late maturing boys as level of performance increases.

Reliability and factorial validity of flexibility tests for team sports.

Sporis, G, Vucetic, V, Jovanovic, M, Jukic, I, and Omrcen, D. Reliability and factorial validity of flexibility tests for Team Sports. J Strength Cond Res 25(4): 1168-1176, 2011-The main goal of this method paper was to evaluate the reliability and factorial validity of flexibility tests used in soccer, and to do crossvalidation study on 2 other team sports using handball and basketball players. The second aim was to compare the validity of the different tests and evaluate the flexibility of soccer players; the third was to determine the positional differences between attackers, defenders, and midfielders in all flexibility tests. One hundred and fifty (n = 150) elite male junior soccer players, members of the First Croatian Junior League Teams, and 60 (n = 60) handball and 60 (n = 60) basketball players also members of the First Croatian Junior League Teams volunteered to participate in the study, tested for the purpose of crossvalidation. The SAR and V-SAR had the greatest AVR and ICC. The within-subjects variation ranged from between 0.3 and 3.8%. The lowest value of CV was found between the LSPL and LSPR. Low to moderate statistically significant correlation coefficients were found among all the measured flexibility tests. It was observed that the greatest correlations existed between the SAR and V-SAR (r = 0.65) and between the LLSR and LLSL (r = 0.56). Statistically significant correlations were also observed between the BLPL and BLPR (r = 0.62). The principal components factor analysis of 9 flexibility tests resulted in the extraction of 3 significant components. The results of this study have the following implications for the assessment of flexibility in soccer: (a) all flexibility tests used in this study have the acceptable between and within-subjects reliability and they can be used to estimate the flexibility of soccer players; (b) the LSPL and LSPR tests are the most reliable and valid flexibility tests for the estimation of flexibility of professional soccer players.

The effects of six weeks of training on physical fitness and performance in teenage and mature top-level soccer players

The main aim of the present study was to investigate the effects of soccer-specific training on physical fitness components in adolescent elite soccer players and make comparisons with older counterparts. Twenty two male soccer players from the Serbian First Division team were allocated to two assigned trials according to age – young group (YG) and mature group (MG). Players in their teenage years (19 years and younger) were assigned to YG (10 subjects) and others to MG (12 subjects). Between the first and second test session, all subjects followed six weeks of soccer-specific periodized training programme. There were no differences between groups at preand post-training trial for body mass, vertical jump height, average anaerobic power and VO2max (P>0.05). Body fat was significantly lower in YG before and after training program as compared to MG (P<0.05). Body mass and fat dropped significantly in both groups after training program (P<0.05). Furthermore, average anaerobic power and VO2max along with vertical jump height, were significantly improved in both groups (P<0.05) at posttraining performance. Finally, the magnitude of change in VO2max was significanty superior in MG as compared to YG after training program (18.3 vs. 7.8%; P<0.05). The findings of the present study indicate that the trainability indices are not highly influenced by age in top-level soccer players. (Biol.Sport 26:379-387, 2009)

The Effect of Cigarette Smoking History on Muscular and Cardiorespiratory Endurance

The purpose of this study was to investigate the effect of cigarette smoking history on physical fitness in younger adults. Small, insignificant differences in BMI between non-smokers and smokers were shown regardless of cigarette smoking history duration. Although the differences in muscular endurance increased in the samples with progressing cigarette smoking history duration, a highly significant difference in aerobic endurance was observed between the group of non-smokers and smokers with a history of smoking up to 5 years and persisted at the same level in smokers with a history of smoking for longer than 10 years.

Evidence-based post-exercise recovery strategies in basketball

Abstract Basketball can be described as a moderate-to-long duration exercise including repeated bouts of high-intensity activity interspersed with periods of low to moderate active recovery or passive rest. A match is characterized by repeated explosive activities, such as sprints, jumps, shuffles and rapid changes in direction. In top-level modern basketball, players are frequently required to play consecutive matches with limited time to recover. To ensure adequate recovery after any basketball activity (i.e., match or training), it is necessary to know the type of fatigue induced and, if possible, its underlying mechanisms. Despite limited scientific evidence to support their effectiveness in facilitating optimal recovery, certain recovery strategies are commonly utilized in basketball. It is particularly important to optimize recovery because players spend a much greater proportion of their time recovering than they do in training. Therefore, the main aim of this report is to facilitate useful information that may lead to practical application, based on the scientific evidence and applied knowledge specifically in basketball.

Which is more important for reducing the odds of metabolic syndrome in men: Cardiorespiratory or muscular fitness?

To examine combined associations of cardiorespiratory fitness (CRF) and muscular fitness (MF) with metabolic syndrome (MetSy) in a sample of young men.

How reliable are the equations for predicting maximal heart rate values in military personnel

OBJECTIVES The purpose of this study was to evaluate the validity and reliability of equations for predicting maximal values of heart rate (HR) in military personnel. METHODS Five hundred and nine members of the Croatian Armed Forces (age 29.1 +/- 5.5 years; height 180.1 +/- 6.6 cm; body mass 83.4 +/- 11.3 kg; maximal oxygen uptake [VO2(max)] 49.7 +/- 6.9 mL O2/kg/min) were tested. The graded exercise test with gas exchange measurements was used to determine VO2(max) and maximum HR (HR(max)). The analysis of variance was used to determine the differences between the equations to calculate HR(max). RESULTS The analysis of variance yielded statistically significant differences between seven HR equations (p < 0.05). The values from Stevens Creeks (HR(max) = 205 - [age/2]) and Fox and Haskells (HR(max) = 220 - age) equations had the highest correlation with the HRmax obtained by the graded exercise test. CONCLUSION The authors recommend using the HR(max) values from the Stevens Creek and the Fox and Haskell equations for the purpose of training, testing, and daily exercise routine in military personnel.