Core stability training is gaining popularity in the running community as more runners are made aware of how weakness in the “core” of the body can negatively influence lower extremity biomechanics and running performance. The lumbar, pelvis and hip region together are considered to be the core of the body and optimal core function involves both mobility and stability. When the core is functioning efficiently, advantageous length-tension relationships are maintained which allow the runner to produce strong movements in the extremities. More importantly, proper core stability can help maximize running performance, maintain the center of gravity over the base of support, control lower extremity limb motion while running, and help prevent running-related injuries.
From a biomechanical perspective, proper core strength and flexibility is essential to control and allow proper biomechanics while running to prevent injuries from occurring. In addition, it has been hypothesized that hip muscle weakness or inflexibility can play a significant role in the development of running-related injuries. A recent study by Niemuth (2005) investigated a group of 30 runners with a variety of musculoskeletal injuries compared to runners with no injuries. Factors such as training, leg dominance, previous injuries, and hip muscle strength were analyzed to determine what factors play the greatest role in the development of running injuries. The results indicated that the injured runners demonstrated significantly weaker hip abductor (located on the outside of the hip) and hip flexor (located on the front of the hip) muscles compared to their non-injured limb and compared to the control group. A study by Ferber (2006) was recently completed to determine if rehabilitation involving hip strengthening and flexibility could effectively resolve pain associated with various running-related injuries. Patients reported the amount of pain they were experiencing using a 10cm visual analog scale. Patellofemoral pain syndrome, iliotibial band syndrome, medial tibial stress syndrome, Achilles tendinopathy, and plantar fasciitis accounted for the majority of injuries. Measurements of hip muscle flexibility and strength were recorded and analyzed each patient’s running biomechanics. Based on the biomechanical and clinical evaluation, a rehabilitation program was prescribed to improve hip strength and/or flexibility where necessary. Upon follow-up, patients reported a 75% improvement in pain on average and 89% reported at least a 50% improvement in pain. Subsequently, these patients also exhibited significant improvements in hip muscle strength and flexibility. These results suggest that a hip strength and flexibility rehabilitation program, based on the biomechanics of running, can effectively resolve pain associated with running injuries. Surprisingly, these studies are the first to show an association between hip muscle strength and flexibility and the development and rehabilitation of lower extremity overuse injuries in runners.
Both of these studies suggest that core strengthening and flexibility exercises should be one part of your overall running, strength, and flexibility program to help prevent and properly treat common running related injuries. While these studies involve a variety of running related injuries, other studies have also suggested that core stability is a primary contributing factor to the development of iliotibial band syndrome.
CORE STABILITY AND DEVELOPMENT OF IT BAND SYNDROME
Iliotibial band syndrome (ITBS) is the second leading cause of knee pain in runners and is the number one cause of lateral knee pain (Taunton, 2002). ITBS is an overuse running injury that results from repetitive friction of the IT band over the outside of the knee joint, with biomechanical studies demonstrating a maximal zone of impingement at approximately 30 degrees of knee flexion which occurs soon after heel strike when running. One of the primary hip abductor muscles is located within the IT band and functions to reduce lateral forces during running. Some authors have suggested that weakness or inhibition of the hip abductor muscles leads to a decreased ability to stabilize the pelvis and adequately control lower limb alignment while runningthus resulting in excessive forces sustained by the IT band.
Fredericson (2000) randomly selected 24 runners with ITBS and compared hip abductor strength to a control group of 30 non-injured runners. In agreement with the findings of Niemuth (2005), these authors also reported that runners with ITBS exhibited significantly weaker hip abductor muscle strength in the affected limb compared to the non-injured limb and compared to the healthy runners. These authors also reported that following a 6-week hip abductor strengthening program, 22 of 24 ITBS patients demonstrated a 35% to 50% increase in abductor muscle strength and were free of ITBS pain while running. Therefore, this study is strong evidence that a relationship exists between hip abductor muscle weakness, side-to-side imbalances in strength, and the development and effective treatment of ITBS. While this study demonstrates a link between hip muscle strength and ITBS, there is only one study that has examined running biomechanics in runners with ITBS. Ferber (2006) examined differences in hip biomechanics between 35 runners who had previously sustained ITBS and 35 runners with no knee-related running injuries. These authors used a 3-dimensional camera system to measure joint angles along with force plates to measure ground reaction forces and then calculated the knee and hip joint forces associated with running. The results indicated that the ITBS group exhibited a significantly greater peak hip and knee angles similar to a more “knock-kneed” running posture and significantly greater knee joint forces compared to the control group. Similar to the other investigations, these authors also suggested that weakness of the hip abductor muscles may result in changes in running biomechanics which may necessitate greater passive restraint from the IT band while running and, over time, lead to the development of ITBS. Therefore, adeqaute hip muscle strength, in paticular the hip abductors, and proper core stability is important to help prevent running injuries such as ITBS.
Various rehabilitation interventions are specifically designed for improving core stability. Most notably are Pilates, Swiss ball, and medicine ball exercises. Regardless of the specific exercise initiated for core stabilization training, several principles should be followed in developing a core stability training program to produce the best outcome (Clark, 2000). First, the training program should be systematic and in each phase of training, specific goals should be met. Second, the program should be progressive which includes a succession from straight plane to multi-plane movements, from isometric to concentric contractions, from slow to fast movements, from nonresisted to resisted movements, from no limb movement to the addition of limb movement and from lying down positions to standing. Finally, the program should be functional. For example, isolated movements may be proficient for targeting specific muscles, but the gains in strength and stability may not carry over into functional movement of running. After all, researchers have shown that good core stability seems to be a key factor to preventing and effectively rehabilitating from overuse injuries for runners of all ages.
References available on request.