Injury incidence in male elite youth football players is associated with preceding levels and changes in training load

Objectives

Elite youth football players miss out on a large part of seasonal training due to injury. Limited research suggests an association between external and internal training load (TL) and injury incidence in elite youth football. This study analysed external and internal TL variables and their association with injury incidence in a group of male elite youth football players over four seasons.

Methods

Measures of external and internal TL and injury incidence of 56 male elite youth football players (age 17-19 years) were collected throughout four seasons. Heart rate, session rating of perceived exertion andGlobal Positioning System (GPS) variables were analysed. Individual players' TL during the 30 days leading up to injury was compared with 30-day injury-free control periods. Change in TL through the periods was also analysed.

Results

Eighty-five injuries were included for analysis, showing that for most TL variables, the average levels were significantly lower during the period leading up to injury. Significant increases for the majority of TL variables were also found during the periods leading up to injury, while the control periods did not show any significant change.

Conclusion

A lower and/or increasing average TL volume over 30 days might increase the risk of injury in male elite youth football players. Avoiding long-term drops in TL and balance increases in TL might be beneficial to reduce injury risk.

Walking football for Health - physiological response to playing and characteristics of the players

Walking Football (WF) is one type of recreational football increasing in popularity, targeting older adults. Further knowledge on the intensity and physical workload of WF, characteristics of the players, the social context, and reasons for playing WF is needed. Thus, the aim of the study was to characterize the individuals that regularly play WF and their experience of WF, and the physiological characteristics of the sport. Sixty-three players from three clubs taking part in organised WF in Sweden were included. The players participated in up to four WF-games and underwent performance tests and answered a questionnaire. The participants mean age was 70.9 years, ranging from 63 to 85 years with 71% (n = 27) of the men and 68% (n = 13) of the women having a BMI > 25. Fifty-one percent (n = 27) of the players had hypertension, and 73% (n = 39) regularly used prescription drugs due to illness. During WF, the players covered on average 2,409 m (2,509 m for men and 2,205 m for women, p = .001). Expressed in percentage of their age-estimated maximal heart rate, mean heart rate represented 80 ± 9 and 80 ± 8% of max for men, and 78 ± 9 and 79 ± 9% of max for women in the first and second halves, respectively, hence WF can be considered a moderate intensity activity for older adults. The main reason for WF participation was to socialize. WF includes a considerable number of accelerations and decelerations, making it more energetically and mechanically demanding than walking.

Physical workload and fatigue pattern characterization in a top-class women's football national team: a case study of the 2019 FIFA Women's World Cup

BACKGROUND

With the growing scientific interest in women's football it is critical to understand the match demands and fatigue patterns during a top-class women's competition.

METHODS

Physical characteristics and performance of top-class women football matches during the 2019 FIFA Women's World Cup was investigated from data collected using global positioning system for 21 outfield players during the tournament.

RESULTS

Relative total distance (TD; m·min^-1) was moderately lower (P≤0.05, ES:0.6) in the final match (96.1±5.0 m·min^-1) compared to the first (104.1±5.9 m·min^-1) match. Performance in relative total high-speed running (THSR; m·min^-1) declined -27.5% (P≥0.05) throughout the tournament following peak performance in the third match (M3) (5.3±1.7 m·min^-1). Match performance between halves was reduced -25.4±0.13% (P≤0.05, ES:1.2-2.3) across all measures in M3. Relative high-intensity running (HIR; 25.9±3.5 m·min^-1) and THSR (9.8±1.5 m·min^-1) were greater (P≤0.05, ES:0.2-0.7) for forwards, while midfielders performed greater (P≤0.05, ES:0.6) relative total distance (102.0±5.5 m·min^-1), compared to central defenders (HIR: 16.1±3.7 m·min^-1; THSR: 3.1±1.6 m·min^-1; TD: 92.5±5.7 m·min^-1). Reductions in relative HIR between halves (-10.9%), within the first half (-31.0%), and the start and end of the match (-36.9%) were most pronounced for midfielders (P≤0.05, ES:0.6-2.3). Across all matches, relative THSR performance was reduced, with moderate to large differences (P≤0.001, ES: 0.7-0.8) observed between halves, within the first half, and throughout the match.

CONCLUSIONS

In conclusion, specific fatigue patterns observed within and between matches throughout the women's World Cup, may be influenced by playing positions, the rank of the opposition, as well as the stage of the tournament.

Muscle Metabolism and Fatigue during Simulated Ice Hockey Match-Play in Elite Players

PURPOSE

The present study investigated muscle metabolism and fatigue during simulated elite male ice hockey match-play.

METHODS

Thirty U20 male national team players completed an experimental game comprising three periods of 8 × 1-min shifts separated by 2-min recovery intervals. Two vastus lateralis biopsies were obtained either during the game (n = 7) or pregame and postgame (n = 6). Venous blood samples were drawn pregame and at the end of the first and last periods (n = 14). Activity pattern and physiological responses were continuously monitored using local positioning system and heart rate recordings. Further, repeated-sprint ability was tested pregame and after each period.

RESULTS

Total distance covered was 5980 ± 199 m with almost half the distance covered at high skating speeds (>17 km·h). Average and peak on-ice heart rate was 84% ± 2% and 97% ± 2% of maximum heart rate, respectively. Muscle lactate increased (P ≤ 0.05) more than fivefold and threefold, whereas muscle pH decreased (P ≤ 0.05) from 7.31 ± 0.04 pregame to 6.99 ± 0.07 and 7.13 ± 0.11 during the first and last periods, respectively. Muscle glycogen decreased by 53% postgame (P ≤ 0.05) with ~65% of fast- and slow-twitch fibers depleted of glycogen. Blood lactate increased sixfold (P ≤ 0.05), whereas plasma free fatty acid levels increased 1.5-fold and threefold (P ≤ 0.05) after the first and last periods. Repeated-sprint ability was impaired (~3%; P ≤ 0.05) postgame concomitant with a ~10% decrease in the number of accelerations and decelerations during the second and last periods (P ≤ 0.05).

CONCLUSIONS

Our findings demonstrate that a simulated ice hockey match-play scenario encompasses a high on-ice heart rate response and glycolytic loading resulting in a marked degradation of muscle glycogen, particularly in specific sub-groups of fibers. This may be of importance both for fatigue in the final stages of a game and for subsequent recovery.

Match Running Performance on Three Different Competitive Standards in Norwegian Soccer

The aim of the study was to compare running performance of three competitive standards and to examine the effects of being promoted to a higher league in Norwegian football. One clubʼs first and second team were included. The first team consisted of professional soccer players playing at Level 2 (2015 season) and Level 1 (2016 season). The second team consisted of amateurs playing at Level 4. A fully automatic tracking system was used to examine running performance, divided into different running-speed categories and playing position. Forty-one matches were included containing 278 observations. Level 1 performed 61 and 51% sprinting compared to Level 2 and Level 4 but similar high-speed running. Similar high-speed running distances were observed only for the different playing positions at Level 1 compared to Level 2 and 4. The sprinting distance was greater for the central defender and attacker, and the number of accelerations was greater for central midfielders and wide midfielders’ playing at Level 1 compared to lower competitive standards. In conclusion, better competitive standards resulted in greater high-intensity actions than lower leagues in Norwegian soccer. Furthermore, only central defenders and attackers increased their high-intensity locomotions when the team was promoted.

Fatigue Responses in Various Muscle Groups in Well-Trained Competitive Male Players after a Simulated Soccer Game

We examined the degree of post-game fatigue and the recovery pattern in various leg and upper-body muscle groups after a simulated soccer game. Well-trained competitive male soccer players (n = 12) participated in the study. The players completed the Copenhagen Soccer Test, a 2 x 45 min simulated soccer protocol, following baseline measures of maximal voluntary contractions of multiple muscle groups and systemic markers of muscle damage and inflammation at 0, 24 and 48 h into recovery. All muscle groups had a strength decrement (p ≤ 0.05) at 0 h post-match with knee flexors (14 ± 3%) and hip abductors (6 ± 1%) demonstrating the largest and smallest impairment. However, 24 h into recovery all individual muscles had recovered. When pooled in specific muscle groups, the trunk muscles and knee joint muscles presented the largest decline 0 h post-match, 11 ± 2% for both, with the performance decrement still persistent (4 ± 1%, p ≤ 0.05) for trunk muscles 24 h into recovery. Large inter-player variations were observed in game-induced fatigue and recovery patterns in the various muscle groups. Markers of muscle damage and inflammation peaked 0 h post-match (myoglobin) and 24 h into recovery (creatine kinase), respectively, but thereafter returned to baseline. Intermittent test performance correlated with creatine kinase activity 24 h after the Copenhagen Soccer Test (r = -0.70; p = 0.02). In conclusion, post-game fatigue is evident in multiple muscle groups with knee flexors showing the greatest performance decrement. Fatigue and recovery patterns vary markedly between muscle groups and players, yet trunk muscles display the slowest recovery.

Skeletal muscle and performance adaptations to high-intensity training in elite male soccer players: speed endurance runs versus small-sided game training

Purpose

To examine the skeletal muscle and performance responses across two different exercise training modalities which are highly applied in soccer training.

Methods

Using an RCT design, 39 well-trained male soccer players were randomized into either a speed endurance training (SET; n = 21) or a small-sided game group (SSG; n = 18). Over 4 weeks, thrice weekly, SET performed 6–10 × 30-s all-out runs with 3-min recovery, while SSG completed 2 × 7–9-min small-sided games with 2-min recovery. Muscle biopsies were obtained from m. vastus lateralis pre and post intervention and were subsequently analysed for metabolic enzyme activity and muscle protein expression. Moreover, the Yo–Yo Intermittent Recovery level 2 test (Yo–Yo IR2) was performed.

Results

Muscle CS maximal activity increased (P < 0.05) by 18% in SET only, demonstrating larger (P < 0.05) improvement than SSG, while HAD activity increased (P < 0.05) by 24% in both groups. Na⁺–K⁺ ATPase α₁ subunit protein expression increased (P < 0.05) in SET and SSG (19 and 37%, respectively), while MCT4 protein expression rose (P < 0.05) by 30 and 61% in SET and SSG, respectively. SOD2 protein expression increased (P < 0.05) by 28 and 37% in SET and SSG, respectively, while GLUT-4 protein expression increased (P < 0.05) by 40% in SSG only. Finally, SET displayed 39% greater improvement (P < 0.05) in Yo–Yo IR2 performance than SSG.

Conclusion

Speed endurance training improved muscle oxidative capacity and exercise performance more pronouncedly than small-sided game training, but comparable responses were in muscle ion transporters and antioxidative capacity in well-trained male soccer players.

Development of an alternative method for determination of terpene lactones in ginkgo dry extract

A new liquid chromatographic mass spectrometric (LC-MS) method for determination of terpene lactones in ginkgo dry extract has been developed. The new method has several advantages over the existing European Pharmacopoeia (Ph. Eur.) method for analysis of terpene lactones in ginkgo dry extract, the major ones being a very simple sample pre-treatment and an excellent selectivity. 5 terpene lactones were analysed with a precision expressed as relative standard deviation (RSD) of 0.4-3.1% and a mean relative error (RE) within +/-4.6%. The method was used to analyse 9 samples of ginkgo dry extracts from 3 different extract producers. The content of bilobalide was found to be in the range of 2.6-3.4% in all samples, whereas the sum of ginkgolides A, B and C was found to be in the range of 3.0-3.6%. Ginkgolide J was found in the range of 0.3-0.6%.