NESTA Biomechanics Specialist cheat sheet

Lever classification: first class = axis between force and resistance (neck extension); second class = resistance between axis and force (calf raise); third class = force between axis and resistance (biceps curl, most human limbs).

Torque = force × moment arm; the moment arm is the perpendicular distance from the line of force to the joint axis, not the distance along the bone.

Mechanical advantage = moment arm of applied force ÷ moment arm of resistance; most human joints operate below 1.0, favoring speed and range over force.

Newton's three laws applied to training: inertia (mass resists acceleration), acceleration proportional to net force, and equal-opposite ground reaction forces.

Work = force × displacement; power = work ÷ time = force × velocity. Peak power occurs at intermediate loads, not maximal loads.

Concentric action shortens the muscle and produces force while shortening; eccentric action lengthens under tension and can produce roughly 1.2–1.6× concentric force.

Muscle force-length relationship: force is highest near resting length due to optimal actin-myosin overlap and declines at shortened and lengthened extremes.

Force-velocity relationship: concentric force falls as shortening velocity rises; eccentric force rises with lengthening velocity up to a plateau.

Sagittal plane movements: flexion/extension; frontal plane: abduction/adduction, lateral flexion; transverse plane: rotation, horizontal abduction/adduction.

Prime movers by joint action: shoulder flexion = anterior deltoid, clavicular pectoralis major; shoulder extension = latissimus dorsi, posterior deltoid, teres major.

Elbow flexion = biceps brachii, brachialis, brachioradialis; brachialis is the strongest flexor regardless of forearm position.

Hip extension = gluteus maximus, hamstrings; hip flexion = iliopsoas, rectus femoris, sartorius, tensor fasciae latae.

Knee extension = quadriceps (rectus femoris is the only biarticular head, also flexing the hip); knee flexion = hamstrings and gastrocnemius.

Scapular upward rotation is produced by the combined force couple of upper and lower trapezius plus serratus anterior.

Biarticular muscles (hamstrings, rectus femoris, gastrocnemius) can be actively or passively insufficient, limiting simultaneous full range at both joints.

Muscle roles: agonist produces the movement, antagonist opposes it, synergist assists or stabilizes, and fixator stabilizes the origin.

Overhead deep squat screening criteria: heels down, knees tracking over toes, thighs at or below parallel, torso upright, arms overhead without lumbar extension.

Knee valgus during squat or landing indicates insufficient hip abductor/external rotator control relative to adductor and hip internal rotator forces.

Anterior pelvic tilt with lumbar hyperextension in overhead squat suggests hip flexor or lumbar extensor tightness and weak abdominals or glutes.

Excessive forward trunk lean in squat points to limited ankle dorsiflexion or hip flexion mobility, or weak quadriceps relative to load.

Plumb line landmarks in standing posture: earlobe, acromion, greater trochanter, slightly anterior to knee axis, and slightly anterior to lateral malleolus.

Upper crossed pattern: tight upper trapezius, levator scapulae, pectorals, and suboccipitals paired with weak deep cervical flexors and lower/mid trapezius.

Lower crossed pattern: tight hip flexors and lumbar erectors paired with weak abdominals and gluteus maximus.

Single-leg squat asymmetry (pelvic drop, knee valgus, trunk lean) indicates frontal-plane control deficits and is associated with higher lower-extremity injury risk.

Resistance torque at a joint = external load × horizontal distance from the joint axis; leverage changes through range, so the sticking point is where resistance torque is greatest relative to muscle torque.

Sticking point in a squat occurs near the bottom-to-mid ascent; in a bench press it occurs shortly after the bar leaves the chest.

Free weights impose a vertical gravity vector, so the moment arm varies through range; machines with cams can alter resistance to match the strength curve.

Eccentric overload can be achieved with supramaximal loads (about 105–125% of concentric 1RM) or by accentuated eccentric loading with spotters or specialized equipment.

Volume load = sets × repetitions × load; it quantifies mechanical work performed and is used to track training stress.

Force output in a lift is limited by the weakest link in the kinetic chain, so technique changes that reduce a joint's moment arm shift load to stronger structures.

Training at long muscle lengths (full range) produces greater hypertrophy and fascicle length adaptations than partial-range work at short lengths.

Post-activation potentiation is enhanced by high-load or high-velocity conditioning activity and is largest with short rest intervals (roughly 3–10 minutes) in trained individuals.

Deadlift: bar over midfoot, hips between knee and shoulder height, neutral spine, bar path close to the body to minimize the back's moment arm.

Bench press: scapulae retracted and depressed, feet planted, bar touches lower sternum, and elbows at roughly 45–75 degrees from the torso to reduce anterior shoulder stress.

Overhead press: bar over midfoot, ribs down, glutes engaged; excessive lumbar extension indicates insufficient thoracic or shoulder mobility.

Back squat: bar over midfoot, knees track in line with toes, hip and knee extend simultaneously, and the bar stays over the base of support.

Lunge: front knee tracks over the midfoot with the tibia near vertical; excessive anterior knee translation increases patellofemoral and knee extensor stress.

Plyometric landing: knees and hips flex to absorb force, land softly, and keep the knee aligned over the second toe to reduce valgus loading.

Olympic lift derivatives: the second pull occurs with the bar near the hips, hips and knees extending explosively while the bar stays close to the body.

Sprinting mechanics: dorsiflexed ankle at ground contact, foot lands close to the center of mass, and a brief ground contact time supports faster sprinting.

Sprint velocity = stride length × stride frequency; both increase with training, but stride length is more sensitive to force production and stride frequency to neural factors.

Ground reaction forces in sprinting reach roughly 3–5× body weight per step; shorter ground contact time and higher vertical stiffness are associated with faster sprinting.

Horizontal force application is the strongest predictor of acceleration performance; vertical force matters more at maximum velocity.

Plyometric stretch-shortening cycle: eccentric phase stores elastic energy, amortization phase transmits it, and concentric phase releases it; a short amortization phase increases power output.

Eccentric phase duration under about 250 ms distinguishes fast SSC (jumps, bounds) from slow SSC (countermovement jump) activities.

Agility is a change of direction or velocity in response to a stimulus; change of direction speed is a preplanned movement and is a separate quality.

Penny hurdle and depth jump heights should allow ground contact time under about 250 ms and knee flexion of roughly 90–110 degrees on landing.

Plyometric volume is counted in foot contacts; beginners start around 40–60 contacts per session and advanced athletes may reach 100–150.

Corrective exercise sequencing: inhibit overactive tissue, lengthen shortened tissue, activate underactive muscle, then integrate into a functional movement pattern.

Eccentric hamstring training (Nordic curl) reduces hamstring strain injury incidence and shifts optimum angle of peak torque to longer muscle lengths.

Anterior cruciate ligament loading is highest with knee valgus, internal rotation, and stiff landings; cueing 'knees over toes' and softer landings reduces load.

Patellofemoral joint stress rises with increased knee flexion angle and quadriceps force; reducing deep flexion under high load lowers stress.

Shoulder impingement risk increases with decreased subacromial space during elevation; scapular upward rotation and posterior cuff strength preserve the space.

Acute:chronic workload ratio above about 1.5 has been associated with elevated injury risk; progressive load increases are preferred.

Bone stress injuries are associated with rapid increases in impact loading (running volume, plyometrics) and low energy availability.

Lumbar flexion under load increases shear and compressive stress on the intervertebral discs; maintaining a neutral spine during heavy loading reduces this stress.

Specificity (SAID principle): adaptations match the specific movement pattern, joint angle, velocity, and contraction type trained.

To develop maximal strength, use loads of roughly 85% 1RM or more for 1–6 reps; for power, use roughly 30–60% 1RM moved at maximal velocity.

Hypertrophy is typically trained with roughly 60–80% 1RM for 6–12 reps, with total volume being a primary driver.

Muscular endurance uses loads below about 60% 1RM for 15 or more reps; local muscular endurance improves with higher repetition sets.

Periodization models: linear periodization progresses from high volume/low intensity to low volume/high intensity; undulating periodization varies volume and intensity within the week.

Deload weeks reduce volume or intensity by roughly 40–60% to allow fatigue dissipation while retaining fitness.

Exercise order: place the most biomechanically demanding, highest-power movements first in a session when fatigue is lowest.

Rate of perceived exertion and velocity-based training (monitoring bar velocity loss) can autoregulate load to match daily readiness.

Youth resistance training: focus on technique and moderate loads; growth plate stress is low when loads are supervised and technique is sound.

Older adults lose type II fiber mass and power faster than strength; power training at moderate loads (about 40–60% 1RM) moved quickly benefits function.

Osteoporosis: avoid high-impact loading and loaded spinal flexion/rotation; favor weight-bearing, axial loading, and progressive resistance training.

Pregnancy: relaxin increases ligament laxity; avoid supine exercise after the first trimester and reduce high-impact or high-fall-risk activity.

Heat: core temperature rises with exercise; acclimatization over roughly 1–2 weeks increases plasma volume and sweat rate and lowers sodium loss.

Altitude: reduced partial pressure of oxygen lowers VO2max; performance declines roughly proportional to elevation above about 1,500 m.

Cold: muscle temperature and power output drop; a thorough warm-up restores force production and reduces injury risk in cold environments.

Hypoxia and heat both increase cardiovascular strain; combining heat and altitude multiplies physiological demand and requires a longer acclimatization period.