NESTA Biomechanics Specialist flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Third-class lever

A lever in which the applied force acts between the axis and the resistance. Most human joints are third-class levers, favoring speed and range of motion over force output.

Moment arm

The perpendicular distance from a joint axis to the line of action of a force. It determines the torque that force produces at that joint.

Mechanical advantage

The ratio of the moment arm of the applied force to the moment arm of the resistance. Values below 1.0 mean the muscle must produce more force than the load.

Force-velocity relationship

Concentric muscle force decreases as shortening velocity increases, while eccentric force increases with lengthening velocity up to a plateau. This shapes power-load relationships in training.

Muscle force-length relationship

Muscle force output is highest near resting length due to optimal actin-myosin overlap and declines when the muscle is very shortened or very lengthened.

Eccentric contraction

A muscle action in which the muscle lengthens while producing tension. Eccentric actions can generate roughly 1.2 to 1.6 times more force than concentric actions.

Biarticular muscle insufficiency

A muscle crossing two joints cannot produce full range at both simultaneously. Active insufficiency occurs when shortened; passive insufficiency occurs when stretched at both joints.

Scapular upward rotation force couple

Upper trapezius, lower trapezius, and serratus anterior work together to rotate the scapula upward during arm elevation, preserving subacromial space.

Sagittal plane movements

Movements occurring in the sagittal plane include flexion and extension, such as a biceps curl or a squat. The axis of rotation is frontal.

Prime mover of elbow flexion

Brachialis is the strongest elbow flexor regardless of forearm position. Biceps brachii and brachioradialis assist, with the biceps also supinating the forearm.

Hip extension musculature

Gluteus maximus and the hamstrings are the primary hip extensors. Gluteus maximus dominates during forceful extension, while hamstrings contribute across hip and knee.

Overhead squat screening

A screen assessing bilateral symmetry, ankle and hip mobility, and trunk control. Heels lifting, knee valgus, or excessive forward lean indicate specific mobility or stability deficits.

Knee valgus

Inward collapse of the knee during squatting or landing. It reflects insufficient hip abductor and external rotator control relative to adductor and internal rotator forces.

Upper crossed pattern

A postural pattern of tight upper trapezius, levator scapulae, pectorals, and suboccipitals with weak deep cervical flexors and lower and mid trapezius.

Lower crossed pattern

A postural pattern of tight hip flexors and lumbar erectors with weak abdominals and gluteus maximus. It is associated with anterior pelvic tilt and lumbar hyperextension.

Plumb line posture landmarks

In ideal standing alignment the line passes through the earlobe, acromion, greater trochanter, slightly anterior to the knee axis, and slightly anterior to the lateral malleolus.

Sticking point

The point in a lift where resistance torque is greatest relative to muscle torque, often near the bottom-to-mid ascent of a squat or just off the chest in a bench press.

Volume load

A measure of training work calculated as sets multiplied by repetitions multiplied by load. It quantifies mechanical stress and is used to track and progress training.

Accentuated eccentric loading

A method using a heavier eccentric phase than concentric phase, often with supramaximal loads around 105 to 125 percent of concentric maximum, requiring spotters or specialized equipment.

Post-activation potentiation

A temporary increase in force or power output after a heavy or high-velocity conditioning activity. It is largest with short rest intervals in trained individuals.

Bench press shoulder positioning

Retract and depress the scapulae, plant the feet, and keep elbows roughly 45 to 75 degrees from the torso to reduce anterior shoulder stress.

Deadlift bar path

Keep the bar over the midfoot and close to the body throughout the lift. A closer bar reduces the moment arm at the lumbar spine and lowers shear stress.

Squat knee tracking

The knees should track in line with the toes during squatting. Inward collapse increases valgus loading, while excessive forward translation raises patellofemoral stress.

Plyometric landing mechanics

Land softly with hip and knee flexion and the knee aligned over the second toe. This distributes force over a longer time and reduces valgus loading.

Stretch-shortening cycle

A sequence of eccentric, amortization, and concentric phases that stores and releases elastic energy. A short amortization phase increases power output.

Sprint stride determinants

Sprint velocity equals stride length multiplied by stride frequency. Stride length is more sensitive to force production, while stride frequency reflects neural factors.

Fast versus slow stretch-shortening cycle

Fast stretch-shortening cycle activities have an eccentric phase under about 250 milliseconds, such as jumps and bounds. Slow stretch-shortening cycle activities last longer.

Plyometric volume

Plyometric volume is counted in foot contacts per session. Beginners typically start around 40 to 60, while advanced athletes may reach 100 to 150.

Corrective exercise sequence

A four-step sequence: inhibit overactive tissue, lengthen shortened tissue, activate underactive muscle, then integrate the pattern into a functional movement.

Nordic hamstring exercise

An eccentric hamstring exercise that shifts peak torque to longer muscle lengths and reduces hamstring strain injury incidence when performed regularly.

Acute to chronic workload ratio

The ratio of recent training load to longer-term average load. Ratios above roughly 1.5 have been associated with elevated injury risk in athletes.

Specificity principle

Adaptations match the specific movement pattern, joint angle, velocity, and contraction type trained. Training should mimic the target task's biomechanics.