Running Economy and Biomechanics Flashcards
Running economy
Running economy is the oxygen cost of running at a specific velocity. Athletes who are able to consume less oxygen while running at a given velocity are said to have better running economy.
Other physiological factors that lead to successful endurance running include improved VO2 max, vVO2max, lactate-threshold speed, max velocity, fatigue-resistance and running-specific strength
Ground Contact Time
When a runner’s left foot makes contact with the ground, the left hip, left knee, and left ankle flex, and the left foot pronates to absorb impact forces.
Excessive and overly prolonged braking forces can have a negative impact on running economy.
Reducing Ground Contact Time
Decreasing ground-contact time is one of the key ways to reduce the time spent in the deceleration stage
Improving neuromuscular responsiveness and running-specific strength and stability, in addition to paying attention to the position of the foot in relation to the body’s center of mass at foot strike, can help reduce ground contact time
Improving Form
Short, high intensity hill repetitions are good workouts for improving strength and stability in the hips.
Form drills can be used to improve a runner’s stride and cadence.
Body Position
- Lean
Keeping the hips, trunk and head in alignment, athletes can further improve their running posture by leaning forward slightly, typically around 3–5 degrees, from the ankles.
It’s important to note that mild variations in lean are normal throughout the running gait. However, athletes should avoid bending from the waist as they run. This lean should help to improve horizontal propulsion. - Head, Neck and Eyes
The athlete’s head position should be balanced and neutral, with eyes focused on the road about 25 to 35 feet in front of them. There should be very little energy expenditure by the neck and shoulder muscles, which remain relaxed. - Arms and Arm Swing
When done properly, the arm swing helps to balance the trunk as the opposite knee drives forward. Proper form consists of a near-90 degree angle bend at the elbow with a direct, forward-and-back movement of the arm. Hands should be unclenched and relaxed to prevent added tension.
The rate at which the hand swings back to the side of the hip, and then the elbow swings forward to the side of the hip, should match the cadence of the legs.
Poor arm swing can be disruptive to cadence and running form. It is an indicator of lack of core strength and can have a small, negative impact on running economy.
4. Hips and Glutes
Hip strength plays a huge role in supporting the running motion. During the stance phase of the running gait, the athlete’s muscles absorb the impact forces, store elastic energy and propel the body.
Increasing hip and glute strength allows a runner to absorb more of the impact forces with his pelvis than with his ankles and the knees. Runners with weaker gluteus medius may cause excessive internal rotation that needs to be corrected, Strong and stable hips and glutes help runners maintain and improve form, economy and running performance.
The most economical and performance-enhancing position for the pelvis is to keep it level from front to back and side to side. An anterior tilt of the pelvis (tipping pelvis forward) decreases the maximum forward angle of the leg and changes the movement. During the swing phase, the leg will not swing as far.
5. Rotation
During running, the trunk rotates most when the legs come forward during swing. For example, when the left leg comes forward prior to impact with the ground by the left foot, the torso rotates counter-clockwise to balance this “de-stabilizing” forward movement of the left leg.
The active muscle contractions that produce a rotation use oxygen and energy, and then, after the excessive rotating, even more oxygen and energy are expended to move the torso back into neutral position. Therefore, the trunk should rotate only slightly in order to reduce energy and oxygen consumption.
6. Posture
Proper running form begins with good posture. The center of the hips, trunk and head should all be in alignment—although not necessarily completely vertical.
The core maintains posture by stabilizing and coordinating the upper body. The abdominal muscles, lower back and hips provide a connection point between the legs and upper body through which force and energy are transferred. The core also serves as a base or anchor point against which the legs do their work.
Posture issues to watch for include runners tucking their chin into their chest or letting their head fall back behind their shoulders. Some runners may hunch forward, especially when fatigued. These issues can impact lean and horizontal propulsion.
Over-pronation
Pronation is a normal occurrence that involves the inward, rolling movement of the ankle as it distributes impact forces during the stance phase of the gait.
Over-pronation involves an excessively inward movement of the ankle during stance. It increases the stresses on the muscles, tendons and ligaments of the foot, lower part of the leg, and knee. Over-pronation may be a risk factor for Plantar Fasciitis and tendinitis of the posterior tibialis. It may occur in runners with functionally weak feet, ankles and legs.
Over-supination
Supination involves an outward rolling of the foot during the stance phase of running. It is actually a normal part of the running gait. Over-supination may occur, however, and cause athletes to expend extra energy to correct their stance.
Over-supination increases forces in the foot, ankle, and leg causing stress reactions and may be a risk factor for stress fractures.
Hip Hiking
When the gluteus medius/minimus are weak or inhibited, the tensor fasciae latae or quadratus lumborum (QL) will compensate by becoming the prime mover. The most impaired movement pattern of hip abduction is when the QL initiates the movement, which results in hip hiking during the swing phase of gait.
If an athlete is favoring one leg, or getting a better stride off of one leg, this could be a sign of tightness, soreness, or an abnormality. Soreness can be addressed with rest and strengthening,
Valgus Knee
Also referred to as medial knee displacement, valgus knee causes increased stress across the medial (inner) compartment of the knee. It is characterized by hip adduction and hip internal rotation. The opposite side of the pelvis will usually drop during valgus collapse as well.
Inadequate gluteal/hip strength, inadequate ankle dorsiflexion mobility along with tight lower leg musculature, impaired quad function and inadequate medial hamstring strength can all contribute to this biomechanical abnormality.
Both mobility drills and static stretches have been shown to be effective for improving ankle dorsiflexion mobility. The glutes/hips, quads and hamstrings can all be strengthening in a running-specific way.
