Monday, January 20, 2014
Is Core Really Important For Performance? - Part I
The term core conjures up a lot of different images for people. Many think of six pack abs and training sessions that include hours of sit ups. The term core training has been over utilized in the training literature and yet it is probably the most misunderstood area and region. It is this misunderstanding which tends to lead to core training that is performed incorrectly a majority of the time. With the increased focus on functional training, many envision incorporating throwing a medicine ball at the floor as an appropriate form of core training. But what is the core and is it really that important?
The definition of the core varies from author to author. This is often due to the complexity of this region. This complexity comes from all the variables which influence loading and stability of the region. J. Porterfield & C. DeRosa, in their textbook, Mechanical Low Back Pain: Perspectives in Functional Anatomy provide a comprehensive review of the core as well as all the structures which contribute to loading and stability of this region. Considering from a musculoskeletal perspective, this review indicates that there are ~30 muscles which directly or indirectly provide some stability to the lumbar spine. Knowing this, when considering the core, we should consider superiorly anything from the pecs/upper thoracic spine to inferiorly the quadriceps/hamstrings. Although the hamstrings and quadriceps’ contribution is somewhat controversial, when you consider the facial envelop for the quadriceps and hamstrings and its continuation into the abdominal fascia and thoracolumbar fascia we can see its influence here. When you also consider the origin for both of these muscles, you can easily see the how both the fascia and origin would influence position of the pelvis and hence impact the core.
It has been well understood and vetted in the research the importance of core stability to prevent low back pain. However, what has not been as well understood is the impact that core stability has on performance. Biomechanically and logically, it makes sense but there has not been an abundance of research showing it. Butcher et al, where one of the first to correlate core stability with performance measures. In 2007, they looked at the impact of core training on vertical takeoff velocity.
Methods: Fifty five athletes were selected from various sports including basketball, dance, running, football, hockey, martial arts, rowing, rugby, slow pitch, soccer, swimming and volleyball. None of them had previous history of low back pain (in last 12 months) or lower extremity injury. Subjects were assigned to one of four groups: trunk stability training (TS), leg strength training (LS), combination trunk and leg strengthening (TL) and non-training group (CO). Training groups were given a periodized program for 9 weeks and instructed to train 3xs/week. Vertical takeoff velocity was determined from performing countermovement jump onto a force plate.
Results: All three training groups experienced improvements in vertical takeoff velocity when compared to the control group. The truck stability group had the most significant increase in vertical takeoff in comparison to the control group at 3 weeks; however, at 9 weeks, the combined trunk and leg strengthening group had the most significant gain. Based on the results, it indicates that trunk stability training does have an impact on vertical takeoff velocity. Since vertical takeoff velocity has a direct correlation to vertical jump height, this would indicate that core stability would increase vertical jump.
Discussion: This is a great article and begins to make the case for core stabilization training to improve athletic performance. This said, when looking at the training or specifically the exercise selection, the core stabilization exercises could be considered very low grade/intensity for the level of athletes. All of the exercises selected (with the exception of one) were in supine, prone or sidelying. Therefore, would the training effect be even greater if these were done in combination with exercises in more upright, sport like, or full weight bearing positions? When looking at the leg strengthening exercise selection, these would also be considered low grade/intensity. None of the exercises selected where full weight bearing and were sitting, supine or prone. With the change in length tension relationships in standing versus prone/supine/sitting, is the full training effect carried over to the activity? So although this study gave us some good indication that stability training can in fact improve performance, are we only seeing half the picture? Had the exercises selected been more representative of the positions needed for upright sport participation, would we have seen even greater impact on vertical jump?
In part II, we will look at recent study which also evaluates the impact of core stabilization on vertical jump in soccer players.