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Muscle Imbalance in Mountain Biking
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09 June 2011
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Quadriceps Muscle Imbalance
and Risk of Injury to Knee in Mountain Bikers
With South Africa's abundance of
mountains, wild life, open space and picturesque beauty, it's no
wonder mountain biking is becoming a popular sport among South
Africans and international tourists. With mountainous regions
found in all nine of South Africa's provinces, it's hard not to
find a mountain bike nearby.
Whether you are a seasoned professional or just starting out,
correct training is imperative - that doesn't just mean "time in
the saddle". Many mountain bikers have made this grave error and
have paid the price. Due to the nature of the uneven mountain bike
trails and the surrounding terrain one muscle group in
particular needs to be well conditioned. The muscle group in
question are the quadriceps muscles - the reason for giving them
extra attention is twofold: firstly stronger quads will aid in
increased force generation which is needed to move over uneven
terrain, the second job is to act as a shock absorber and help the
knees in dissipating upward force coming from the ground.
Imbalance in strength and firing (contracting) of these muscles
during knee extensions can affect proper movement mechanics of the
knee. Many people may not realise that the quadriceps muscle is
made up of four individual muscles - vastus medialis oblique (VMO),
rectus femoris, vastus lateralus (VL) and vastus intermedialus. The
most important of these muscles is the VMO. The general movement of
the quads is knee extension; however the quads also directly affect
the way in which the knee cap (patella) glides up and down in its
groove on the femur.
In an optimally functioning quad (no imbalance), the patella runs
evenly up and down in its groove - however if there's an imbalance
in the quads during knee extensions there is uneven force
distribution acting on the patella. This results in an altered
glide of the patella in its groove, causing the patella to grind on
usually the lateral side of the groove which results in pain being
experienced in the knee.
Muscle imbalance in the quadriceps is common and is usually only
noticed when muscles start fatiguing or during maximal effort.
Common reasons attributed to quad muscle imbalances are poor muscle
development due to inadequate training, poor biomechanics, and/or
other imbalances of other muscle groups, such as the gluteal muscle
group.
The most common quad muscle affected that results in the imbalance
is the VMO, this is generally due to the VMO being the most
sensitive of the quadriceps, and therefore the quickest to be
inhabited by pain and inflammation. This forms part of an
unforgiving cycle - muscle weakness leads to incorrect gliding of
the patella causing pain, pain inhabits VMO, further increasing the
muscle imbalance (weakness) which results in more pain and swelling
and further VMO inhibition and so the cycle continues.
Correct training for mountain biking should also include a strong
resistance training regiment focusing on all four quads, gluts,
hamstrings and core exercises as well as time in the saddle...
Stuart Main.
Jackson and Wright Biokineticists
Centre for Sports Medicine Umhlanga
www.centreforsportsmedicine.co.za
Gareth Harrington
Physiotherapist
Holroyd & Goodenough Physio- Hillcrest
Tel: 031 7642918
Email: hillcrest@thephysio.co.za
www.physiolink.co.za
