In the past Blog post
I tried to bring attention to the vital aspects of targeting strengthening of
the gluteal, low back and core musculature in hopes of actualizing a dual
outcome: 1) stronger prime movers for sprinter/jumpers/throwers and 2)
elimination of muscular imbalances that can lead to injury.
Teaching athletes how
to properly activate the gluteus and low back muscle groups, while also
strengthening them, will alleviate the common problem of over-stressing the
hamstrings AS most athletes have overloaded their hamstrings to do the work of
the gluteus and low back muscles. The root cause of many chronic hamstring
problems usually involves 1) postural alignment problems of the pelvis, 2) activation
of the hamstrings to do the work of the gluteus group and 3) weaknesses of the
hamstrings relative to the stresses of specific movement patterns of sprinting
and jumping.
Reviewing common
sports injuries will reveal that hamstring strains or pulls are high on the
list of reoccurring sports injuries. The hamstring musculature is made up of
four muscles in the back of the thigh and can be stretched as you bend forward
to touch your toes. Three of the four hamstring muscles, the semitendonosis,
semimembranosis and long head of biceps femoris all cross BOTH the hip and knee
joints. These three are the true hamstring muscles and have a common origin at
the ischial tuberosity (bony protuberance at the bottom of the pelvis). The
insertion of these muscles is to the tibia and fibula below the knee (the two
leg bones that make up the lower leg). The fourth hamstring muscle (short head
of the biceps femoris) only crosses the knee joint.
There are two primary
types of hamstring injuries and each affects a different area of the hamstring
musculature. The first hamstring injury is most common in younger athletes and
is caused by a sudden motion, such as an explosive jump, sprint or kick. In
this type of injury, the strain occurs in the thick belly of the muscle,
resulting in pain the middle of the back of the thigh. Swelling, and later
bruising, may be present in this area, and the athlete may limp or utilize
crutches to take weight off of the injured leg.
Training errors in
activities such as cycling and running is the usual cause of the second type of
hamstring injury. In this case the hamstring strain occurs at the tendinous
insertion on the ischial tuberosity of the pelvis. Tri-athletes, duathletes and
long distance runners are common sufferers of this injury, and will complain of
pain in the lower buttock region that increases in severity as the foot of the
injured leg strikes the ground.
Regardless of the
type of hamstring injury, by understanding the biomechanics of running, it
becomes easier to understand why hamstring injuries occur and how to prevent
them. With BOTH types of injury, preventative strengthening exercises and the
teaching of proper activation techniques are effective strategies for
prevention.
In simplifying the
Biomechanics of Running we can break running down to two phases: 1) the stance
phase and 2) the swing phase. The stance phase consists of the
foot-strike, mid-stance and toe-off while the swing phase consists of follow through, hip flexion and hip
extension backwards towards the ground. During an eccentric contraction, muscle
fibers will slowly elongate to slow down a particular motion, while a
concentric contraction involves a muscle shortening to lift and object or move
a limb in a particular direction. During leg decent and foot-strike, the pelvis
flexes forward and the leg extends and the hamstring muscles are eccentrically
contracting to slow down both of these particular movements. When the eccentric
load exceeds the strength of the muscles fibers, tearing of the hamstring
fibers occurs, resulting in a strain or tear of the fibers.
Flexibility and
strength training of the hamstring muscles, and the nearby muscles surrounding
the pelvis and thigh, will reduce the risk of injury.
Strengthening the
abdominal and gluteus musculature is important in the prevention of the
hamstring strain because these muscles aid the hamstrings in decelerating
flexion of the pelvis during the heel strike.
Flexibility of the
hip flexors and low back musculature is also important in the prevention of
hamstring injuries. Tight
hip flexors and low back muscles cause excessive flexion of the pelvis during
foot-strike and increased tension and stress on the hamstrings. Tightness in
these muscles also inhibits strengthening of the gluteus and abdominal muscles.
Proper
pelvic alignment is critical to performance of proper sprint and jump mechanics
AND in the prevention of hamstring injuries. In the last Blog I emphasized
teaching the activation and strengthening of the gluteus and lower back muscles
because: “These
two muscle groups are mainly responsible for the sprinter or jumper to be fully
engaged and connected from the ground up. “
Postural alignment of
the pelvis through a balanced approach to the strengthening of gluteus, low
back and hamstring muscle groups is critical in achieving mechanical efficiency
for sprinting and jumping movements.
Think of the pelvis
as a bucket that is full of water. If we keep it level, no water will spill
out. If the pelvis tilts forward (as a result of tight hip flexors and weak low
back) then the hamstrings are put on stretch (causing tightness and tension)
while the low back curvature is increased (which can cause low back pain,
strain and tightness). Both of these
conditions risk immediate injury to the hamstring group while sprinting or
jumping.
Researchers looking at
full body kinematics and ground reaction force data from athletes while
sprinting found that all three major hamstring muscles reached peak strain,
produced peak force and formed much negative (eccentric contractions for energy
absorption) during terminal swing of the leg.
The biomechanical
load differed for each hamstring muscle; Long Head of Biceps Femoris exhibited
the largest peak strain, the Semitendinosis displayed the greatest lengthening
velocity, and the Semimembranosus produced the highest peak force, absorbed and
generated the most power, and performed the largest amount of positive and
negative work.
ALL THIS OCCURRED AT
THE SAME TIME during terminal leg swing. This indicates that hamstring
injury prevention or rehab programs should target strengthening exercises that
involve eccentric contractions performed with high loads at longer
musculotendon lengths. If you have my
book “Strength and Power for Maximum Speed”, then you already know the key
strength exercises that specifically target this.
The next Blog post
will address exercise selection criteria for strengthening all the critical
muscle groups responsible for improvements in sprinting and jumping
performances.
No comments:
Post a Comment