Muscles

Muscles are bands of soft tissue fibres that contract and relax to stabilise or move joints. The function of muscles is to produce force and cause bones to move, or joints to flex, extend, rotate or move laterally. Muscles function in pairs to produce movement and when the first muscle contracts, the second muscle relaxes to allow movement. When the second muscle contracts the first muscle relaxes to allow movement in the opposite direction. The relationship between these muscle pairs is referred to as “antagonists”. Muscular contraction is felt as muscular tension. Within this section the words contraction and tension are used interchangeably.

Flexion and extension, abduction and adduction, rotation, supination and pronation and eversion and inversion are opposite movements that are controlled by muscle pairs.

Muscle Contraction

For example, a skier resisting the force from the snow during the control phase of a turn is concentrically contracting the lateral quadriceps while eccentrically contracting the hamstrings.

Two processes by which muscles create contraction are voluntary or reflexive. When a skier completes a turn on gentle groomed terrain, leg flexion may be voluntary. However, when skiing the zipper line of a mogul run, the legs most often flex reflexively in an automatic response to absorb the terrain.

Any muscular contraction requires a stimulus. Flexing the ankles to move forward and pressure the front of the skis requires flexion of the tibialis anterior muscle on the front of the lower leg, near the shin. This happens in response to a brain signal and electrical impulse through the nervous system that causes the muscle to contract. This signal stimulates the nerves in the muscle by a process called innervation. Any type of muscular contraction or change in tension, whether voluntary or reflexive, requires innervation. Competent skiers maintain a functional degree of tension to some degree at all times in order to stimulate (or innervate) the muscle groups required for management of, and reaction to, forces. This functional tension allows a skier to react more quickly, adapting to ever changing speeds, terrain, and snow conditions.

In general, skiing with functional tension describes having a degree of tension in the following muscles and muscle groups used in skiing.

Muscles of the Lower Leg

The muscles of the lower legs control foot and ankle movements. As the ankle is in direct contact with the ski boot and the ski boot is the lever that transmits forces to the skis, ankle movements are important for fore/aft, lateral (edging and weight shifting) movements. Many of the following muscles of the lower legs also work to maintain an athletic stance and aid in knee flexion.

The Tibialis Anterior – is on the outside of the tibia and is primarily responsible for ankle flexion or dorsiflexion. The function of dorsiflexion (lifting the top of the foot toward the shin) is essential for managing fore/aft movement and to stabilise the leg and foot on uneven ground. These muscles are most active during short turns and bump skiing.

As mentioned above, ankle dorsiflexion combined with subtalar eversion and forefoot abduction of the foot) causes pronation of the foot (big toe side rotates down). The tibialis anterior plays an essential role in the lateral movements to engage the inside edge of the outside ski.

The Gastrocnemius and Soleus – these two muscles on the back of the lower leg constitute the calf muscle. They are powerful muscles and play an important role in skiing. The gastrocnemius flexes the knee joint, and develops muscular tension. The soleus plays an important role in maintaining standing posture because if not for its constant pull, the body would fall forward. When these both extend they plantar flex the ankle. Plantar flexion presses the ball of the foot into the boot.

The Peroneus Longus and Brevis – are on the outer side of the calf/lower leg and evert the ankle at the subtalar joint. These are the primary muscles in the lower leg used to engage and hold the inside edge of the outside ski.

Muscles of the Upper Legs, Pelvis & Hip Joint

The muscles in the upper leg and hip joint play important roles in rotation and edging of the skis as well as fore/aft and lateral balance and vertical movement. The pelvis is part of the upper body and many of the muscles in the pelvic area can also be described as part of the core.

The Gluteus Maximus – among other muscles, help stabilise both the pelvis and upper body. Muscles around the pelvis control the hip joint, which moves in all directions in a complex relationship of muscular actions and ranges of motion.

Below, these muscles are grouped into categories of movement.

Extension

These muscles play an important role in all extension movements, and in managing pressure coming from the snow. They also help to control the rate and range of flexion.

Knee extensors – Quadriceps Femoris is a large muscle group consisting of four muscles on the front of the thigh which act together to extend or straighten the leg.

Hip extensors – these enable movement of the thigh behind the torso.

In skiing these muscles, while in active contraction, will lessen flexion in the legs.

Gluteus maximus – (sometimes referred to informally as the “glutes”) is the main extensor muscle of the hip joint. These large muscles are posterior (back of) pelvis and are responsible for maintaining the torso in an upright posture. Strong glutes are important to resist the powerful forces of skiing.

Hamstrings – are three posterior (back of) thigh muscles. The function of these muscles is to flex the knee joint, adduct the leg, and extend the hip joint to move the femur behind the torso.

Flexion

These muscles play an important role in all flexion movements, and in managing pressure. These muscles also help to control the rate and range of extension.

Knee flexors (hamstrings) – these muscles act together to bend the knee. The hamstrings also provide stability at the knee joint helping the anterior cruciate ligament to prevent forward movement of the tibia on the femur. The hamstrings oppose the quadriceps to flex the leg.

Hip flexors – this group of muscles act to flex the femur towards the pelvis, i.e. pull the knee upward. They are located at the front of the abdomen and leg and in skiing they are used in flexion movements.

Rectus femoris – one of the four quadriceps muscles and the only one that crosses the hip joint. This enables it to operate as a hip flexor as well as a knee extensor.

Iliopsoas – found on the front of the femur through to top of the pelvis. The function of this is hip flexion, which means bringing the femur up towards the torso or moving the torso towards the femur.

Sartorius – found on the inside of the femur, the longest muscle in the body functions as an important flexor and rotator of the femur at the hip joint. The sartorius muscle is so long that it crosses and acts upon both the hip and knee joints. Acting on the hip joint, the sartorius works as a flexor, abductor, and lateral rotator of the femur with the assistance of the other major muscles of the hip. At the knee joint the sartorius helps to flex the leg. Combining all of these functions into one movement, the sartorius pulls the foot and ankle towards the knee of the opposite leg.

Hip rotators – this group of muscles is found at the posterior (back) of the pelvis and into the upper femur. The hip medial (inside) and lateral (outside) rotators are very important in balancing and supporting the other movements of the hip joint. They help stabilise the femur in the hip socket and these muscles rotate the femur at the hip joint. If the knees are pointed towards each other while standing, the femurs are rotated medially (internally). If the knees are pointed away from each other the femurs are rotated laterally (externally).

Rotation of the femur – whether internally or externally – is one of the main ways to control the direction that the skis point. A number of muscles play a supportive role in rotation of the femurs.

This is a list of the main muscles…

Internal rotation:

• Gluteus minimus
• Tensor fasciae latae
• Adductor minimus, adductor longus, pectineus

External rotation:

• Gluteus maximus
• Gluteus medius
• Sartorius
• Adductor brevis and magnus

Hip Abductors – these muscles enable the leg to move away from the midline of the body. In combination with the hip adductors (inner thigh) these muscles aid in lateral balance and in aligning the skeletal structure with the forces acting on it. They also play an important role in rotation of the legs to turn the skis.

• Gluteus
• Medius
• Sartorius

Hip Adductors – these are the inner thigh muscles and enable the legs to move toward the midline of the body. These muscles aid in lateral balance in that they keep the skier’s COG in alignment with the inside edge of the outside ski. They also play an important role in rotation of the legs to turn to skis.

• Adductor longus
• Adductor brevis
• Adductor magnus

In most examples of effective skiing the legs turn and move laterally under a stable upper body.

Muscles of the Torso & Core

Torso muscles are commonly referred to as “the core” muscles. Recall that the spine, and therefore the torso, is inherently unstable. The primary purpose of the core muscles is to add stability to this structure, allowing a skier to accurately make adjustments for balance. Core muscles also create the torque required to rotate and make lateral movements of the legs as needed.

These muscles stabilise the spine and therefore the whole torso. In skiing they are responsible for enabling skiers to maintain fore/aft and lateral balance and providing a stable upper body to facilitate rotation of the legs.

Abdominal Muscles – The Core

The abdominal muscles are a group of six muscles that extend from various places on the ribs to various places on the pelvis. Together these muscles make up the “natural belt” which provides stabilisation for the lower back, as well as enabling movement in the torso. These muscles must be engaged for a stable upper body and they also assist in the breathing process.

The more structurally deeper and closer to the spine the particular abdominal muscle is, the more effect it has over stabilisation of the torso.

From deep to superficial the abdominal muscles are:

Transverse abdominal – the deepest abdominal muscle and has the most effect on stabilising the lumbar spine. The transverse abdominal runs from the sides of the torso (lateral) to the front of the torso (anterior).

Internal obliques (x2) and external obliques (x2) – these two pairs of abdominal muscles are on each side of the torso. The external obliques are more superficial. Both sets of obliques affect stabilisation of the core, but slightly less because of their more superficial position. They are involved in rotation and lateral flexion movements of the spine.

Rectus abdominis – (often called the “six pack”) is the most superficial of the abdominal muscles. It is a long flat muscle, which extends along the length of the front of the abdomen and together with the external obliques affects stabilisation of the core, but not as much as the deeper abdominal muscles. This muscle is responsible for flexing the lumbar spine and as such maintaining accurate alignment of the pelvis.

Upper Torso Muscles

Latissimus dorsi – this powerful muscle group on the lower back is responsible for lateral flexion and rotation of the spine. These are also responsible for adduction, extension and internal rotation of the arm.

Trapezius – this muscle primarily affects movements of the arms and shoulders. It is a triangular shaped muscle that runs from the centre of the back up to the neck and across the shoulder blades. This helps to maintain good posture for the upper spine, neck and head.

Rhomboids – these muscles run from the base of the neck to the shoulder blade and help to hold the shoulders back and maintain good posture.

Shoulder muscles – in skiing the shoulder muscles are important for good posture and stability of the torso and arms and consist of:

Deltoid muscles – which wrap right around the top of the shoulders giving the shoulders versatility and a greater range of movement.

Rotator cuff muscles – these are located beneath the shoulder and help hold the arms in place.

Chest & Arm Muscles

Pectorals – these run across the surface of the chest and in skiing help to stabilise the upper body including the arms.

Biceps – located at the front of the upper arm and used to flex the arm at the elbow. In skiing they are used together with the forearm muscles and wrist in the pole swing.

Triceps – located at the back of the upper arms, these muscles oppose the biceps and come into play to extend the arm.

Back Muscles

These muscles and muscle groups also form part of the core. They play an important role in stabilising and controlling movements of the upper body and therefore play an essential role in balancing movements. These muscles extend and rotate the spinal vertebrae.

The spinal extensors – are attached to the back of the spine. They are a set of muscles that straighten and rotate the back and enable standing up and lifting of objects. The extensors counterbalance the action of the abdominals.

Erector spinae – is not just one muscle, but a group of muscles and tendons which run more or less the length of the spine on both sides from the sacrum or sacral region to the base of the skull. These muscles lie on either side of the vertebrae column and extend throughout the lumbar, thoracic, and cervical regions (lower, middle, and upper back and the neck).

The spinal flexors – are in the front of the spine and include the abdominal muscles. These muscles when contracting concentrically enable flexion or forward bend. They are important in lifting and controlling the arch in the lower back.

All torso flexors and extensors can produce lateral flexion of the spine when acting unilaterally.

Multifidus – these are thin muscles on either side of the vertebrae, from the sacrum to the cervical region. These muscles are responsible for stablisation of the joints within the spine in particular for initial stabilisation of the lumbar spine during physical activity, i.e. stabilisation before any movement of the arms or legs occurs. Engagement of these muscles allows force to be directed over a larger area. In doing so, they help protect the discs that cushion spinal vertebrae.