There are two major categories of risk factors: intrinsic athlete related and extrinsic environment related (Daneshjoo 2013). A key point is that the risk factors can also be divided into adjustable and non-adjustable factors. Although non-adjustable risk factors such as gender and age may be of interest, it is necessary to understand the factors which are modifiable through intervention programs, such as strength, balance, and flexibility. One of the factors that are very important in knee injuries, and lower body injuries, is strength of the muscles surrounding the knee. The essential functions of these muscles are to protect, support and stabilize joints of the skeletal system. Inadequate strength of these muscles is associated with injuries (Daneshjoo 2013). Strength increases can be considered as one of the most important intrinsic factors in preventing injuries as well as re-injuries especially in the lower body. Isokinetic testing enables precise muscle strength assessment in athletes, which could in turn be used in injury prevention programs (Daneshjoo 2013).
Daneshjoo (2013) investigated the effects of the 11+ and HarmoKnee injury prevention programs 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 programs were performed for 24 sessions (20-25 min each). The 11+ consists of three parts, beginning with running exercises (part I), followed by six exercises to develop strength, balance, muscle control and core stability (part II), and ending with advanced running exercises (part III). The different levels of difficulty would improve the programs efficiency and enable coaches and players to individually adapt to the program. The 11+ takes approximately 20-25 minutes to complete and replaced the usual warm-up before general training. All exercises (27 exercises) focus on core stability, neuromuscular control, eccentric hamstrings strength and agility. These exercises were performed three times per week as a warm-up program. The aim of the HarmoKnee prevention program is to increase overall awareness of injury risk, to provide a structured warm-up protocol, and to increase strength, which may improve movement patterns and reduce knee injuries. The training protocol consists of five parts: warm-up, muscle activation, balance, strength, and core stability. Total program duration was 20 to 25 minutes. Similar to the 11+, the HarmoKnee was also performed three times per week as warm-up before the general training. For comparison, the control group was asked to continue with their regular team training and warm-up such as running across the pitch and static stretching. In addition, before the commencement of the study, the control group was promised that they would receive the intervention program 8 weeks later.
The results showed that the HarmoKnee program increased concentric quadriceps strength only within groups (comparing pre- and post-tests). There were no significant differences that were observed between groups. Overload is required for measurable concentric and eccentric quadriceps muscular adaptation in young male professional soccer players (Daneshjoo 2013). This revealed that the 11+ and HarmoKnee program increased concentric and eccentric hamstring strength in young male professional soccer players, within groups. The 11+ program significantly increased concentric hamstring strength, within and between groups. The 11+ program has more impact than the HarmoKnee program on increasing concentric hamstring strength in young male professional soccer players.
1. Daneshjoo A, Mokhtar A, Rahnama N, Yusof A. The effects of injury prevention warm-up programmes on knee strength in male soccer players. Biol Sport. 2013 Dec;30(4):281-
Written by Chris Barber, CPT