Franco M. Impellizzeri

Factors influencing physiological responses to small-sided soccer games

Abstract The aim of this study was to examine the effects of exercise type, field dimensions, and coach encouragement on the intensity and reproducibility of small-sided games. Data were collected on 20 amateur soccer players (body mass 73.1 ± 8.6 kg, stature 1.79 ± 0.05 m, age 24.5 ± 4.1 years, [Vdot]O2max 56.3 ± 4.8 ml · kg−1 · min−1). Aerobic interval training was performed during three-, four-, five- and six-a-side games on three differently sized pitches, with and without coach encouragement. Heart rate, rating of perceived exertion (RPE) on the CR10-scale, and blood lactate concentration were measured. Main effects were found for exercise type, field dimensions, and coach encouragement (P < 0.05), but there were no interactions between any of the variables (P > 0.15). During a six-a-side game on a small pitch without coach encouragement, exercise intensity was 84 ± 5% of maximal heart rate, blood lactate concentration was 3.4 ± 1.0 mmol · l−1, and the RPE was 4.8. During a three-a-side game on a larger pitch with coach encouragement, exercise intensity was 91 ± 2% of maximal heart rate, blood lactate concentration was 6.5 ± 1.5 mmol · l−1, and the RPE was 7.2. Typical error expressed as a coefficient of variation ranged from 2.0 to 5.4% for percent maximal heart rate, from 10.4 to 43.7% for blood lactate concentration, and from 5.5 to 31.9% for RPE. The results demonstrate that exercise intensity during small-sided soccer games can be manipulated by varying the exercise type, the field dimensions, and whether there is any coach encouragement. By using different combinations of these factors, coaches can modulate exercise intensity within the high-intensity zone and control the aerobic training stimulus.

Physiology of small-sided games training in football: a systematic review.

Small-sided games (SSGs) are played on reduced pitch areas, often using modified rules and involving a smaller number of players than traditional football. These games are less structured than traditional fitness training methods but are very popular training drills for players of all ages and levels. At present, there is relatively little information regarding how SSGs can best be used to improve physical capacities and technical or tactical skills in footballers. However, many prescriptive variables controlled by the coach can influence the exercise intensity during SSGs. Coaches usually attempt to change the training stimulus in SSGs through altering the pitch area, player number, coach encouragement, training regimen (continuous vs interval training), rules and the use of goalkeepers. In general, it appears that SSG exercise intensity is increased with the concurrent reduction in player number and increase in relative pitch area per player. However, the inverse relationship between the number of players in each SSG and exercise intensity does not apply to the time-motion characteristics. Consistent coach encouragement can also increase training intensity, but most rule changes do not appear to strongly affect exercise intensity. The variation of exercise intensity measures are lower in smaller game formats (e.g. three vs three) and have acceptable reproducibility when the same game is repeated between different training sessions or within the same session. The variation in exercise intensity during SSGs can also be improved with consistent coach encouragement but it is still more variable than traditional generic training methods. Other studies have also shown that SSGs containing fewer players can exceed match intensity and elicit similar intensities to both long- and short-duration highintensity interval running. It also appears that fitness and football-specific performance can be improved equally with SSG and generic training drills. Future research is required to examine the optimal periodization strategies of SSGs training for the long-term development of physiological capacity, technical skill and tactical proficiency.

Physiological assessment of aerobic training in soccer

Physiological assessment of soccer training usually refers to the measurement of anatomical, physiological, biochemical and functional changes specific to the sport discipline (training outcome). The quality, quantity and organization of physical exercises (training process) are, on the other hand, usually described by the external work imposed by the coach on his or her athletes. In this review, we demonstrate that this approach is not appropriate in soccer, as training is often based on group exercises. The physiological stress (internal load) induced by such training often differs between individuals. Here, we present some physiological laboratory-based tests and field tests used to evaluate training outcomes in soccer, together with methods based on heart rate and perceived exertion to quantify internal load imposed during training. The integrated physiological assessment of both training outcome and process allows researchers: (1) to improve interpretation of physical tests used to verify the effectiveness of training programmes; (2) to evaluate the organization of the training load in order to design periodization strategies; (3) to identify athletes who are poor responders; (4) to control the compliance of the training completed to that planned by the coach; and (5) to modify the training process before the assessment of its outcome, thus optimizing soccer performance.

Validity of a repeated-sprint test for football.

Three studies involving 108 football players were conducted to examine the reliability of a repeated-shuttle-sprint ability (RSSA) test and its ability to differentiate between players of various competitive levels and playing positions. Study 1: Short-term reliability was determined in 22 professional players completing the RSSA test (6 x 40-m sprints with 20 s of recovery between sprints) on two separate occasions. Study 2: Long-term reliability (seasonal changes) was examined in 31 professional players completing the RSSA test four times (during the preseason period, at the start, middle and end of the competitive season). Study 3: 108 players were divided and compared according to competitive level or playing position. Standard error of measurement values expressed as coefficient of variation for RSSA mean time and best time were 0.8 and 1.3 % (short-term reliability) and 0.9 and 1.2 % (long-term reliability), respectively. The smallest worthwhile changes were 0.5 % for both mean and best time. Professional players showed better RSSA performance than amateur players, and defenders displayed the lowest RSSA performance. In conclusion, the RSSA test showed adequate construct validity but only RSSA mean time showed sufficient reliability to detect large training-induced changes but not small important differences.

Validity and reliability of Optojump photoelectric cells for estimating vertical jump height.

Glatthorn, JF, Gouge, S, Nussbaumer, S, Stauffacher, S, Impellizzeri, FM, and Maffiuletti, NA. Validity and reliability of Optojump photoelectric cells for estimating vertical jump height. J Strength Cond Res 25(2): 556-560, 2011-Vertical jump is one of the most prevalent acts performed in several sport activities. It is therefore important to ensure that the measurements of vertical jump height made as a part of research or athlete support work have adequate validity and reliability. The aim of this study was to evaluate concurrent validity and reliability of the Optojump photocell system (Microgate, Bolzano, Italy) with force plate measurements for estimating vertical jump height. Twenty subjects were asked to perform maximal squat jumps and countermovement jumps, and flight time-derived jump heights obtained by the force plate were compared with those provided by Optojump, to examine its concurrent (criterion-related) validity (study 1). Twenty other subjects completed the same jump series on 2 different occasions (separated by 1 week), and jump heights of session 1 were compared with session 2, to investigate test-retest reliability of the Optojump system (study 2). Intraclass correlation coefficients (ICCs) for validity were very high (0.997-0.998), even if a systematic difference was consistently observed between force plate and Optojump (−1.06 cm; p < 0.001). Test-retest reliability of the Optojump system was excellent, with ICCs ranging from 0.982 to 0.989, low coefficients of variation (2.7%), and low random errors (±2.81 cm). The Optojump photocell system demonstrated strong concurrent validity and excellent test-retest reliability for the estimation of vertical jump height. We propose the following equation that allows force plate and Optojump results to be used interchangeably: force plate jump height (cm) = 1.02 × Optojump jump height + 0.29. In conclusion, the use of Optojump photoelectric cells is legitimate for field-based assessments of vertical jump height.

Fitness determinants of success in men's and women's football

Abstract In this study, we examined gender and age differences in physical performance in football. Thirty-four elite female and 34 elite male players (age 17 ± 1.6 to 24 ± 3.4 years) from a professional football club were divided into four groups (n = 17 each) according to gender and competitive level (senior males, senior females, junior males, and junior females). Players were tested for specific endurance (Yo-YoIR1), sprint over 15 m (Sprint-15m), vertical jump without (CMJ) or with (ACMJ) arm swing, agility (Agility-15m), and ball dribbling over 15 m (Ball-15m). The Yo-YoIR1 and Agility-15m performances showed both a gender and competitive level difference (P < 0.001). Senior and junior males covered 97 and 153% more distance during the Yo-YoIR1 than senior and junior females, respectively (P < 0.001). Gender but not age differences were found for Sprint-15m performance (P < 0.001). No difference in vertical jump and Ball-15m performances were found between senior and junior males (P > 0.05). More marked gender differences were evident in endurance than in anaerobic performance in female players. These results show major fitness differences by gender for a given competitive level in football players. It is suggested that training and talent identification should focus on football-specific endurance and agility as fitness traits in post-adolescent players of both sexes.

Reliability of isokinetic strength imbalance ratios measured using the Cybex NORM dynamometer

The main aim of this study was to examine the absolute and relative reliability of some commonly used strength imbalance indices such as concentric hamstring‐to‐concentric quadriceps ratio, eccentric hamstring‐to‐concentric quadriceps ratio and bilateral concentric and eccentric strength ratios. An additional aim was to examine the reliability of the peak torque and work of the knee extensor and flexor muscles measured using the Cybex NORM dynamometer. Eighteen physically active healthy subjects (mean ± standard deviation, age 23 ± 3 years, height 176 ± 5 cm, body mass 74 ± 8 kg) were tested three times with 96 h between sessions. Peak torque, average work, unilateral and bilateral ratios were determined at 60, 120, 180 and −60° s−1. Low (0·34) to moderate (0·87) relative reliability (intraclass correlation coefficient, ICC) was found for strength imbalance ratios with eccentric hamstring‐to‐concentric quadriceps ratio showing the greater ICC (>0·80). High ICC values (0·90–0·98) were found for peak torque and average work. Absolute reliability (standard error of measurement) ranged from 3·2% to 8·7% for strength imbalance ratios and from 4·3% to 7·7% for peak torque and average work measurements. This study established the reliability of the most common strength imbalance ratios and of absolute isokinetic muscle strength assessed using the Cybex NORM.

Effects of intermittent-endurance fitness on match performance in young male soccer players.

Castagna, C, Impellizzeri, F, Cecchini, E, Rampinini, E, and Barbero Alvarez, JC. Effects of intermittent-endurance fitness on match performance in young male soccer players. J Strength Cond Res 23(7): 1954-1959, 2009-The purpose of this study was to examine the effect of specific endurance (Yo-Yo Intermittent recovery test level 1, Yo-Yo IR1) on match performance in male youth soccer. Twenty-one young, male soccer players (age 14.1 ± 0.2 years) were involved in the study. Players were observed during international championship games of corresponding age categories and completed the Yo-Yo IR1 on a separate occasion. Physical (distance coverage) and physiological match demands were assessed using Global Positioning System technology and heart rate (HR) short-range telemetry, respectively. During the match (two 30-minutes halves), players covered 6,204 ± 731 m, of which 985 ± 362 m (16%) were performed at high intensities (speed >13 km·h−1, HIA). A significant decrement (3.8%, p = 0.003) in match coverage was evident during the second half. No significant (p = 0.07) difference between halves was observed for HIA (p = 0.56) and sprint (speed >18 km·h−1, SPR) distances. During the first and second halves, players attained the 86 ± 5.5 and 85 ± 6.0% of HRmax (p = 0.17), respectively. Peak HR during the first and second halves were 100 ± 4 and 99.4 ± 4.7% of HRmax, respectively. Yo-Yo IR1 performance (842 ± 352 m) was significantly related to match HIA (r = 0.77, p < 0.001) and total distance (r = 0.65, p = 0.002). This studys results showed that specific endurance, as determined by Yo-Yo IR1 performance, positively affects physical match performance in male young soccer players. Consequently, the Yo-Yo IR1 test may be regarded as a valid test to assess game readiness and guide training prescription in male youth soccer players.

Effect of match-related fatigue on short-passing ability in young soccer players.

PURPOSE To examine whether the fatigue accumulated during match play or determined by short bouts of high-intensity intermittent activities affect short-passing ability in junior soccer players. A further aim was to examine the influence of physical fitness as measured using the Yo-Yo Intermittent Recovery Test (YYIRT) on the changes in short-passing ability after a 5-min simulation of high-intensity activities (HIS). METHODS Sixteen players (mean +/- SD: age 17.6 +/- 0.5 yr, height 174 +/- 7 cm, body mass 68 +/- 6 kg) participated in the study. A quasi-experimental control-period design was used for the study. Short-passing ability was measured using the Loughborough Soccer Passing Test (LSPT). Players completed the LSPT in two sessions during the 1-wk control period, followed by two unofficial matches during which the LSPT was performed during and after the first and the second halves of the game. Furthermore, the change in LSPT performance was determined after 5 min of HIS. RESULTS A decline in LSPT performance was found during and after the game (P < 0.01). The accuracy of the LSPT decreased after the HIS. A significant correlation was found between the YYIRT scores and the decline in LSPT performance (accuracy, total time, total time with penalties) after HIS (r = -0.51 to -0.65; P < 0.05). CONCLUSIONS This study showed that the fatigue developed during a match and after relatively short bouts of high-intensity intermittent activities has a detrimental effect on short-passing ability, and that the fatigue-related decline in technical proficiency for a given intensity is associated with the fitness level of the players.

Hip muscle weakness in patients with symptomatic femoroacetabular impingement

OBJECTIVE Femoroacetabular impingement (FAI) is a pathomechanical process, which may cause hip pain, disability and early development of hip osteoarthritis (OA) in young and active adults. Patients with FAI experience functional disability during dynamic weight-bearing activities, which could originate from weakness of the hip muscles. The objective of this study was to compare hip muscle strength between patients with symptomatic FAI and healthy controls. It was hypothesized that patients would present overall hip muscle weakness compared to controls. METHODS A total of 22 FAI patients and 22 controls matched for gender, age, and body mass participated in the study. We evaluated isometric maximal voluntary contraction (MVC) strength of all hip muscle groups using hand-held and isokinetic dynamometry, and electromyographic (EMG) activity of the rectus femoris (RF) and tensor fasciae latae (TFL) muscles during active flexion of the hip. RESULTS FAI patients had significantly lower MVC strength than controls for hip adduction (28%), flexion (26%), external rotation (18%) and abduction (11%). TFL EMG activity was significantly lower in FAI patients compared with controls (P=0.048), while RF EMG activity did not differ significantly between the two groups (P=0.056). CONCLUSIONS Patients with symptomatic FAI presented muscle weakness for all hip muscle groups, except for internal rotators and extensors. Based on EMG recordings, it was demonstrated that patients with symptomatic FAI have a reduced ability to activate TFL muscle during hip flexion. These findings provide orthopedic surgeons with objective information about the amount and specificity of hip muscle weakness in patients with FAI. Future research should investigate the relationship between hip muscle weakness, functional disability and overuse injury risks, as well as the effects of hip muscle strengthening on clinical outcomes in individuals with symptomatic FAI.