Abdolhamid Daneshjoo

Bilateral and unilateral asymmetries of isokinetic strength and flexibility in male young professional soccer players.

This study investigated bilateral and unilateral asymmetries of strength and flexibility in male young professional soccer players. Thirty-six soccer players (age: 18.9 ± 1.4 years) participated in this study. A Biodex Isokinetic Dynamometer was used to assess the hamstring and quadriceps strength at selected speeds of 60°/s, 180°/s and 300°/s. Hip joint flexibility was measured using a goniometer. No difference was observed in conventional strength ratio, dynamic control ratio and fast/slow speed ratio between the dominant and non-dominant legs (p>0.05). All but one of the players (97.2%) had musculoskeletal abnormality (bilateral imbalance > 10%) in one or more specific muscle groups. The dominant leg had greater hip joint flexibility compared with the non-dominant leg (108.8 ± 10.7° versus 104.6 ± 9.8°, respectively). The findings support the hypothesis that physical performance and movement pattern experienced during soccer playing may negatively change the balance of strength in both legs (bilateral strength balance), but not on the same leg of the young male professional soccer players. The results can be helpful for trainers and coaches to decide whether the players need to improve their balance and strength which in turn may prevent injury. It is suggested that in professional soccer training, quadriceps and hamstrings muscle strength, as well as hip joint flexibility should not be overlooked.

THE EFFECTS OF INJURY PREVENTION WARM-UP PROGRAMMES ON KNEE STRENGTH IN MALE SOCCER PLAYERS

The study investigates the effects of the 11+ and HarmoKnee injury prevention programmes on knee strength in male soccer players. Under-21-year-old players (n=36) were divided equally into: the 11+, HarmoKnee and control groups. The programmes were performed for 24 sessions (20-25 min each). The hamstrings and quadriceps strength were measured bilaterally at 60°·s-1, 180°·s-1 and 300°·s-1. The concentric quadriceps peak torque (PT) of the 11+ increased by 27.7% at 300°·s-1 in the dominant leg (p<0.05). The concentric quadriceps PT of HarmoKnee increased by 36.6%, 36.2% and 28% in the dominant leg, and by 31.3%, 31.7% and 20.05% at 60°·s-1, 180°·s-1 and 300°·s-1 in the non-dominant leg respectively. In the 11+ group the concentric hamstring PT increased by 22%, 21.4% and 22.1% at 60°·s-1, 180°·s-1 and 300°·s-1, respectively in the dominant leg, and by 22.3%, and 15.7% at 60°·s-1 and 180°·s-1, in the non-dominant leg. In the HarmoKnee group the hamstrings in the dominant leg showed an increase in PT by 32.5%, 31.3% and 14.3% at 60°·s-1, 180°·s-1 and 300°·s-1, and in the non-dominant leg hamstrings PT increased by 21.1% and 19.3% at 60°·s-1 and 180°·s-1 respectively. The concentric hamstrings strength was significantly different between the 11+ and control groups in the dominant (p=0.01) and non-dominant legs (p=0.02). The HarmoKnee programme enhanced the concentric strength of quadriceps. The 11+ and HarmoKnee programmes are useful warm-up protocols for improving concentric hamstring strength in young professional male soccer players. The 11+ programme is more advantageous for its greater concentric hamstring strength improvement compared to the HarmoKnee programme.

Effectiveness of Injury Prevention Programs on Developing Quadriceps and Hamstrings Strength of Young Male Professional Soccer Players

Abstract Muscular strength is an important factor which is crucial for performance and injury prevention in most sports. The purpose of this study was to evaluate the effects of the FIFA’s Medical Assessment and Research Centre 11+ and HarmoKnee injury prevention programs on knee strength of young professional male soccer players. Thirty-six soccer players (age: 18.9 ± 1.4 years) were divided equally into three groups; the 11+, HarmoKnee and control groups. The programs were performed for 24 sessions. Hamstring and quadriceps strength was measured using the Biodex System 3 at 30°, 60° and 90° of knee flexion. The 11+ increased quadriceps strength in the dominant leg by 19.7% and 47.8% at 60°and 90° knee flexion, respectively, and in the non-dominant leg by 16%, 35.3% and 78.1 % at 30°, 60° and 90° knee flexion, respectively. The HarmoKnee group, however, showed increased quadriceps strength only at 90° i.e., by 85.7% in the dominant leg and 73.8% in the non-dominant leg. As for hamstring strength, only the 11+ group demonstrated an increment by 24.8% and 19.8% at 30° and 60° knee flexion in the dominant leg, and in the nondominant leg, by 28.7% and 13.7% at 30° and 60° knee flexion, respectively. In conclusion, both warm-up programs improve quadriceps strength. The 11+ demonstrated improvement in hamstring strength while the HarmoKnee program did not indicate any improvement. We suggest adding eccentric hamstring components such as Nordic hamstring exercise to the HarmoKnee program in order to enhance hamstring strength.

Long-term effects of the 11+ warm-up injury prevention programme on physical performance in adolescent male football players: a cluster-randomised controlled trial

ABSTRACT This study examined the long-term effects of the 11+ on physical performance in adolescent male football (soccer) players. Eighty-two 14- to 16-year-old male football players (11+ = 42 players, control = 40 players) participated. Teams were randomised to control (CON) and intervention (INT) groups. INT applied the 11+ injury prevention programme for 30 weeks at least twice a week as a warm-up. CON performed their standard warm-up. Motor performance tests were conducted 1 week prior and 1 week after the competition season. We used magnitude-based inferences and linear mixed-effects models to analyse performance test results. INT showed superior results compared to CON in the vertical jump height 7.5% (95%-CI 4.4%, 10.7%), the Bosco 15-s-jump test 7.2% (95%-CI 2.2%, 12.4%), and the Illinois agility test −2.6% (95%-CI −4.1%, −1.1%). Possibly beneficial effects in favour of INT were found in the 9.1 m sprint test −3.1% (95%-CI −6.1%, 0.1%). Possibly harmful effects (i.e. in favour of CON) were observed in the dribbling test 2.8% (95%-CI −0.8%, 6.4%). The 11+ warm-up programme can improve different performance measures in football players. Coaches might implement additional dribbling drills next to the 11+ to achieve improvements observed in dribbling ability when using a regular warm-up programme.

Correction: Analysis of Jumping-Landing Manoeuvers after Different Speed Performances in Soccer Players.

There is an error in the Acknowledgements of the published article. The Acknowledgements should read: This study was supported by UM/MOHE/ HIR Project No. D000014-16001. The authors are grateful to Dr. Mohammadtaghi Amiri-Khorasani for expert guidance during the early stage of this project and Dr. Jos Vanrenterghem for his valuable comments. The authors also acknowledge the expert guidance of Nafiseh Khalaj, who contributed to biomechanics data collection and manuscript preparation (related to data collection).