Physical development and match analysis of elite youth soccer players

This thesis examined the physical development and match performance of elite youth academy soccer players some of whom were likely to progress to become professional soccer players. Physical characteristics such as standing height, body mass and estimated body fat composition, physical performance and match performance were explored. Furthermore, the relationships between physical performance and match running performance were examined in players from the U9 to U18 age group squads. Finally, the influence of biological maturity on physical characteristics, physical performance and match running performance in these elite youth soccer players was investigated and recommendations are made concerning talent identification and player development. One hundred and eighty-three elite soccer players (chronological age: 8.9 to 18.7 years; age grouping U9-U18) from an English Premier League Academy in the East Midlands were assessed for standing height, body mass, skinfolds, 30 m sprint, slalom and 505 agility, squat jump, counter movement jump with and without arms, Yo-Yo intermittent recovery test (level 1) and Multi-stage fitness test. All physical and performance variables measured in the study developed over time with chronological age except for the sum of 4 skinfold sites and estimated body fat composition (squad mean ± SD, U9 vs. U17: standing height, 139.4 ± 4.8 cm vs. 181.3 ± 5.6 cm; body mass, 33.6 ± 3.9 kg vs. 72.6 ± 5.7 kg; 30 m sprint, 5.26 ± 0.25 vs. 4.15 ± 0.11 s; slalom agility test, 4.83 ± 0.25 vs. 3.96 ± 0.09 s; counter movement jump with arms, 30 ± 3 cm vs. 48 ± 6 cm; the Yo-Yo intermittent recovery test (level 1), 787 ± 333 vs. 2617 ± 573 m). Standing height, body mass, 10, 15, and 30 m sprint times, performance on both agility tests, performance of squat jump and counter movement jump with arms; performance on the Yo-Yo intermittent recovery test (level 1) and on Multi-stage fitness test continued developing until the players reached the U17 squad. Moreover, the highest rate of development in standing height, body mass and all physical fitness tests occurred between the U9-U13 squads. Distance run during match play by 9 to 16 year old boys varied from 4056 (U9) to 7697 (U16) m per match (p < 0.05), and varied from 4675 to 6727 m∙hour-1 of a match (p < 0.05). The U11-U16 squads covered a greater distance by high speed running (range: 487-553 m∙hour-1) compared to the U9 (178 m∙hour-1) and U10 (219 m∙hour-1) squads (p < 0.05 for all). Similarly, the percentage of time spent in high speed running by the U9 (1.1 %) and U10 (1.3 %) squads was less than that seen in the U11-U16 (2.6-3.0 %) squads (p < 0.05 for all). Chronological age accounted for 43% (p < 0.01), and the Multi-stage fitness test performance explained 7% (p < 0.05) of the variance in total distance covered per hour of a match in the U11-U16 group. Chronological age (p < 0.01) and the Multi-stage fitness test performance (p < 0.05) accounted for 10% and 11% respectively of the variance in percentage of time spent in moderate speed running. Chronological age accounted for 11 % of the variance in the percentage of time spent in high speed running (p < 0.01), whereas 30 m sprint and the Multi-stage fitness test performances explained 15% and 8% respectively of the variance in percentage of time spent in high speed running (p < 0.05 for both). The U9 and U10 squads showed a positive relationship between 20 m sprint time and distance covered in moderate speed running per hour of a match (r = 0.54, p < 0.05). In the U11-U13 squads relationships were evident between performance in 5, 10, 15, 20 and 30 m sprint (r = -0.67 to -0.46), the 3 standing vertical jumps (r = 0.46 to 0.73) and the 2 endurance tests (r = 0.45 to 0.60), and distance covered by moderate and high speed running per hour of a match (p < 0.05 for all). However, in the U14-U16 squads no significant relationships were evident. When stage of genital development was used to categorise players, standing height and body mass in the U12, U13 and U14 squads were positively influenced by biological maturity (p < 0.05 for all). The more mature players in the U13 squad also performed better in counter movement jump without arms and the Multi-stage fitness test (p < 0.05 for both). When stage of pubic hair development was used to categorise players, maturity status showed a positive influence on standing height and slalom agility test performance in the U12 squad (p < 0.05 for both) and on standing height and body mass in the U14 squad (p < 0.05 for both). When estimated chronological age at peak height velocity was used to categorise players, earlier maturing players were heavier (p < 0.01) and performed worse in counter movement jump without arms (p < 0.05) than later maturers in the U9 and U10 squads. Earlier maturers were taller (p < 0.01), heavier (p < 0.01) and possessed a thicker sum of 4 skinfold sites (p < 0.05) and higher estimated body fat (p < 0.01) compared to the later maturers in the U11 and U12 squads. Moreover, early maturers covered a greater distance than late maturers in the multi-stage fitness test (p < 0.05) in the U13 and U14 squads. In the U15 and U16 squads, early maturers were heavier and possessed thicker sum of 4 skinfold sites and higher estimated body fat compared to the late maturers (p < 0.01 for all). Furthermore, early maturers possessed a thicker sum of 4 skinfold sites (p < 0.05), higher estimated body fat (p < 0.01) and covered a shorter distance during the Yo-Yo intermittent recovery test (p < 0.01) compared to later maturers in the U17 and U18 squads. When stage of genital development was used to categorise players, the U12 and U13 players in stage 4 covered a greater distance in high speed running during a match than players in stage 3 (p < 0.05). There was a tendency for this still to be the case when distance was standardised into per hour of a match (p = 0.065). In the U9 and U10 squads, compared to later maturers, earlier maturers were given greater playing time during a match (p < 0.05), and consequently covered a greater distance during match play (p < 0.05). In the U13 and U14 squads, earlier maturers covered more distance per hour of a match and spent a higher percentage of time in high speed running when compared to their later maturing counterparts (p < 0.05 for both). In summary this research has provided the most extensive description yet of the physical characteristics, field test performance and match performance of elite youth soccer players. In addition, for the first time the effect of biological maturity (using 3 different methods of assessment) on a wide range of field tests and on match performance has been reported. The major changes in physical characteristics, field test performance and match performance between 10 and 14 years of age suggest that coaches should avoid as many selection decisions as possible during this age period, that they should take into account the fact that match distances covered at high speeds will be affected by maturity at these ages and that they should be aware that at present, coaches choose to give more mature players additional pitch time which obviously gives them an advantage in terms of playing development. An enhanced awareness of these findings in the coaching community could lead to an improved development and more appropriate selection decisions for elite youth soccer players in England

High-intensity demands of 6-a-side small-sided games and 11-a-side matches in youth soccer players

Purpose. The purposes of the present study were to examine: high-intensity running distance during 6-a-side small-sided games (SSGs) and 11-a-side matches (11M) in youth soccer players using speed and metabolic power approaches and; the magnitude of difference between high-intensity running distance calculated with the two approaches. Method. Eleven outfield players (age = 16.3 ± 0.6 years) performed SSGs with three pitch sizes (small SSG (SSGS), medium SSG (SSGM) and large SSG (SSGL)) and 11M. A Global Positioning System (15 Hz) was employed to calculate total distance covered, distance covered at a speed ≥ 4.3 m∙s-1 (TS) and metabolic power of ≥ 20 W·kg-1 (TP). Results. The total distance covered increased from SSGS through to SSGL (P < 0.001) and was greater during 11M and SSGL compared to other SSGs (P < 0.01). TS and TP increased from SSGS (TS vs. TP = 98 ± 55 vs. 547 ± 181 m) through to SSGL (538 ± 167 vs. 1050 ± 234 m, P < 0.001). TS and TP during 11M (370 ± 122 vs. 869 ± 233 m) was greater than SSGS (P < 0.001 for both) and less than SSGL (P < 0.05 for both). The magnitude of difference between TS and TP (%) reduced with an increase in pitch size during SSGs and was greater in SSGS (615 ± 404%, P < 0.001) and SSGM (195 ± 76%, P < 0.05) and smaller in SSGL (102 ± 33%, P < 0.01) compared to 11M (145 ± 53%). Conclusion. SSGs can replicate the high-intensity demands of 11M and the speed approach underestimates high-intensity demands of SSGs and 11M compared to the metabolic power approach

Exposure to high solar radiation reduces self-regulated exercise intensity in the heat outdoors

High radiant heat load reduces endurance exercise performance in the heat indoors, but this remains unconfirmed in outdoor exercise. The current study investigated the effects of variations in solar radiation on self-regulated exercise intensity and thermoregulatory responses in the heat outdoors at a fixed rating of perceived exertion (RPE). Ten male participants completed 45-min cycling exercise in hot outdoor environments (about 31 °C) at a freely chosen resistance and cadence at an RPE of 13 (somewhat hard). Participants were blinded to resistance, pedal cadence, distance and elapsed time and exercised at three sunlight exposure conditions: clear sky (mean ± SD: 1072 ± 91 W·m−2; HIGH); thin cloud (592 ± 32 W·m−2; MID); and thick cloud (306 ± 52 W·m−2; LOW). Power output (HIGH 96 ± 22 W; MID 103 ± 20 W; LOW 108 ± 20 W) and resistance were lower in HIGH than MID and LOW (P < .001). Pedal cadence was lower, the core-to-skin temperature gradient was narrower, body heat gain from the sun (SHG) was greater and thermal sensation was higher with increasing solar radiation and all variables were different between trials (P < .01). Mean skin temperature was higher in HIGH than MID and LOW (P < .01), but core temperature was similar between trials (P = .485). We conclude that self-regulated exercise intensity in the heat outdoors at a fixed RPE of somewhat hard is reduced with increasing solar radiation because of greater thermoregulatory strain, perceived thermal stress and SHG. This suggests that reduced self-selected exercise intensity during high solar radiation exposure in the heat may prevent excessive core temperature rise.PostprintPeer reviewe

Greater thermoregulatory strain in the morning than late afternoon during judo training in the heat of summer.

PurposeThe time-of-day variations in environmental heat stress have been known to affect thermoregulatory responses and the risk of exertional heat-related illness during outdoor exercise in the heat. However, such effect and risk are still needed to be examined during indoor sports/exercises. The current study investigated the diurnal relationships between thermoregulatory strain and environmental heat stress during regular judo training in a judo training facility without air conditioning on a clear day in the heat of summer.MethodsEight male high school judokas completed two 2.5-h indoor judo training sessions. The sessions were commenced at 09:00 h (AM) and 16:00 h (PM) on separate days.ResultsDuring the sessions, indoor and outdoor heat stress progressively increased in AM but decreased in PM, and indoor heat stress was less in AM than PM (mean ambient temperature: AM 32.7±0.4°C; PM 34.4±1.0°C, PConclusionsThis study indicates a greater thermoregulatory strain in the morning from 09:00 h than the late afternoon from 16:00 h during 2.5-h regular judo training in no air conditioning facility on a clear day in the heat of summer. This observation is associated with a progressive increase in indoor and outdoor heat stress in the morning, despite a less indoor heat stress in the morning than the afternoon

Combined effects of solar radiation and airflow on endurance exercise capacity in the heat

This study investigated the combined effects of different levels of solar radiation and airflow on endurance exercise capacity and thermoregulatory responses during exercise-heat stress. Ten males cycled at 70% peak oxygen uptake until exhaustion in an environmental chamber (30°C, 50% relative humidity). Four combinations of solar radiation and airflow were tested (800 W⋅m-2 and 10 km⋅h-1 [High-Low], 800 W⋅m-2 and 25 km⋅h-1 [High-High], 0 W⋅m-2 and 10 km⋅h-1 [No-Low], and 0 W⋅m-2 and 25 km⋅h-1 [No-High]). Participants were exposed to solar radiation by a ceiling-mounted solar simulator (Metal halide lamps) and the headwind by two industrial fans. Time to exhaustion was shorter (p &lt; 0.05) in High-Low (mean ± SD; 35 ± 7 min) than the other trials and in High-High (43 ± 6 min) and No-Low (46 ± 9 min) than No-High (61 ± 9 min). There was an interaction effect in total (dry + evaporative) heat exchange which was less in High-Low and High-High than No-Low and No-High, and in No-Low than No-High (all p &lt; 0.001). Core temperature, heart rate and thermal sensation were higher in high (High-Low and High-High) than no (No-Low and No-High) solar radiation trials and in lower (High-Low and No-Low) than higher (High-High and No-High) airflow trials (p &lt; 0.05). Mean skin temperature and rating of perceived exertion were higher in high than no solar radiation trials (p &lt; 0.05). This study indicates that combining high solar radiation and lower airflow have negative effects on thermoregulatory and perceptual strain and endurance exercise capacity than when combining high solar radiation and higher airflow and combining no solar radiation and lower/higher airflow during exercise-heat stress.</p