Last week we discussed how core stability can impact injury
rates as well as impact team performance.
But we concluded with the question, is there an impact on individual
performance. If we look at the research,
it would clearly indicate an impact on individual performance. For example, in 2007 Butcher et al showed
that improvements in trunk stability resulted in increased in vertical takeoff
velocity. Although the authors were not
able to assess vertical jump directly, improvements in vertical takeoff
velocity is correlated to improvements in vertical jump. This is as far back as 2007 yet skeptics
continue to question the validity of whether or not there is a direct correlation
to improvements in core strength and vertical jump performance. However, this debate was put to rest when Hoshikawa et al in 2013
showed that improvements in core stability resulted in improvements in vertical
jump in soccer players. The authors of
this study showed that improvements in core stability resulted in improvements
in hip extensor strength and vertical jump performance. In other words, stabilize the pelvis and the
hip extensors can generate more force resulting in higher vertical jump.
But how do we identify this in our athletes? If you do not have access to a comprehensive
movement assessment or biomechanical analysis (like the 3D-DMA™) then there are
some simple things you can look for in your athletes. In our recent blog series on gluteus medius
weakness, we talked about various positions of the pelvis during movement that
can indicate weakness. You can also see
these same movements during athletic participation.
One study published in October 2013 by Oyama et al showed the
effect of excessive contralateral trunk lean on pitching biomechanics and performance
in baseball pitchers. Before we get into
the specifics of the paper, we should first define contralateral trunk
lean. Some authors will define it as
contralateral trunk lean and some as retro-trendelenburg. For the purposes of this paper, those two
terms are synonymous with one another.
Diagram A demonstrates how the authors define it in this study as it
appears during the throwing cycle. The
ideal position is to “keep the head balanced over the stride foot” at maximal
shoulder external rotation. When the
head is not balanced over the stride foot (as in this picture here), valgus
stress at the elbow is increased. This
lateral trunk lean “not keeping head balanced over stride foot” was shown by Fleisig et al in 2006 to
increase valgus load to the medial elbow.
It is this increase in valgus stress that leads to medial elbow pain and
puts the athlete at risk for ulnar collateral ligament (UCL) injury. The purpose of the Oyama study was to see if
this could be observed on 2D video and
whether or not this movement resulted in greater loading to the joint
and slower ball speed.
Methods: In this study, 72 high school baseball
pitchers 3-dimensional pitching biomechanics, ball speed and frontal view
pitching technique was captured with both 2D cameras as well as a 3D vicon
system. Each pitcher was fitted with
reflective markers and performed 5 to 10 submaximal pitches. After warm up, each was asked to pitch as
fast and as accurate as possible at an X in the strike zone. It was considered
a strike if they hit the strike zone. Each
pitcher pitched until 5 qualifying pitches and minimum of 3 strike pitches were
captured. For each pitch, kinematic and
kinetic data, videos and ball speed were all captured. The point of maximal shoulder external
rotation was identified and at that point, the amount of contralateral trunk
lean was also identified.
Results: Pitchers who demonstrated excessive
contralateral trunk lean pitched with a higher ball speed than those who did
not (32.6 m/sec or 72.9 mph vs. 31.1 m/sec or 69.6 mph). Those with excessive trunk lean also
experienced greater proximal elbow force (103.9 N or 23.4 lbs vs. 93.2 N or
20.9 lbs) and proximal shoulder force (104.8 N or 23.6 lbs vs. 94.3 N or 21.2
lbs). There were also greater loads noted at ball release with an increase in
valgus loading at the elbow and an increased shoulder internal rotation
moment.
Discussion:
Although this excessive lateral trunk lean was associated
with increases in velocity, there was also an increase in loading at the
shoulder and elbow. Although, upon
initial review, these load variances might not seem that significant, a 2-4 lb
load increase to the shoulder and elbow joint, when done repetitively over time
can lead to shoulder injuries (labral tears, rotator cuff tears, etc.) or elbow
injuries (UCL tears, elbow pain, etc.).
Although this study showed some positive performance gains
(3 mph) with this altered position, there could be other factors fitting into
that. Some factors to consider are the
average time of play for those who had increased speed, height and age of the
players. When looking at these factors,
there is not much variance between those with trunk lean and those
without. Two other factors not mentioned
in this study was if there was a previous report of injury or pain in those
with trunk lean and those without and training (specifically coaching on
pitching technique) amongst the two groups.
The other question that arises is if core/hip strength were
improved, would this trunk lean improve and would performance also
improve? Although we don’t have a
particular study telling us this, we do know from basic biomechanics that
improvements in hip/core strength results in improved kinetic energy transfer
from the lower kinetic chain to the hips to the core/shoulder/elbow and
eventually ball. Increases in kinetic
energy transfer equates to increased throwing velocity.
So the question becomes, do you correct the technique at the
expense of velocity? Or could targeted
strengthening to the area result in self-correction and performance
enhancement? This could and would be a
hotly contested debate between clinical call (yes to decrease risk of injury)
and coaching call (no as performance might suffer). Whether right or wrong, when making that
decision one must consider:
- Increased stress to the
elbow and shoulder increases risk for shoulder and elbow pathology. Injury will shorten career and have a
much larger impact on long term performance.
- Lateral trunk lean or
retro-trendelenburg (demonstrated above) has also been shown to increase
stress to the lumbopelvic region (highlighted) and increase risk for knee
pathology.
- Lateral trunk lean or
retro-trendelenburg at the hip in single leg stance is commonly associated
with gluteus medius and core weakness.
Improvement in strength and endurance in these areas has been shown
to have a direct impact on transfer of kinetic energy.
Considering the above, if addressed both from a coaching
perspective (improving the throwing biomechanics) and addressing the
strength/proprioceptive deficits of the core, then one should see improvements
in both performance as well as decreased loading to the shoulder and elbow
(hence reduce risk for injury). That
considered, then core and hip strengthening could be and should be a critical
component of pre-season and in season training for pitchers.
We hope that you found this blog insightful and useful. Stay tuned next week as we continue to
provide insightful literature reviews with practical applications. As we stated previously, stay tuned and if
you like what you see, SHARE THE PASSION!
It is the biggest compliment you can give. Follow us on Twitter @ACL_prevention and
tweet about it. #DMAOnTheMove and help
us spread the passion and #movementonmovement.
Build Athletes to Perform…Build
Athletes to Last!™
Trent
Nessler, PT, MPT, DPT:
CEO/Founder ACL, LLC | Author | Innovator in Movement Science and Technology.
Dr. Nessler is a physical therapist and CEO/Founder of ACL,
LLC. He is the researcher and developer the Dynamic Movement Assessment™, Fatigue Dynamic
Movement Assessment™, 3D-DMA™, author of the textbook Dynamic
Movement Assessment: Enhance Performance and Prevent Injury, and
associate editor for International Journal of Athletic Therapy &
Training. For more information, please see our website at www.aclprogram.com
No comments:
Post a Comment