Biomech - Exam 3 Review

How do long bones develop?

Through endochondral ossification: cartilage is replaced by bone.

What is ossified at birth?

The diaphysis; the epiphyses are still cartilage.

What is the epiphyseal plate responsible for?

Longitudinal bone growth.

When do most epiphyseal plates close?

During puberty; some remain open until age 25.

How does circumferential bone growth occur?

Bone is deposited under the periosteum and absorbed at the medullary cavity.

What is a joint?

A location where two bones meet or articulate.

What are the two mechanical functions of joints?

Join bones while controlling motion; transfer force between bones.

What is joint stability?

Resistance to unwanted movement, shear, and traction dislocation.

What increases shear stability in a synovial joint?

A tighter bone-to-bone fit, determined by bone shape and cartilage support.

What increases traction stability?

Tensile forces from muscles and ligaments that pull bones together.

What is the function of a bursa?

A synovial-fluid-filled sac that pads over bone or ligament to reduce friction.

What is a tendon sheath?

A synovial-fluid-filled tube wrapped around a tendon to reduce friction.

What are muscle origin and insertion?

Origin: proximal attachment. Insertion: distal attachment.

What is a muscle's line of pull?

The direction of the resultant force at its attachment.

What characterizes longitudinal muscle arrangement?

Fibers align with the line of pull; examples include fusiform and strap.

What characterizes pennate muscle arrangement?

Fibers insert at an angle to the tendon.

What are the three types of pennate muscle arrangement?

Unipennate, bipennate, and multipennate.

What is concentric muscle action?

The active muscle shortens; torque is in the same direction as limb rotation.

What is eccentric muscle action?

The active muscle lengthens; torque is opposite the direction of limb rotation.

What is isometric muscle action?

The active muscle maintains the same length; torque occurs without limb rotation.

What is an agonist?

A muscle creating torque in the direction of the referred joint action; prime mover.

What is an antagonist?

A muscle creating torque opposite the referred joint action.

During elbow flexion, what are the agonist and antagonist?

Biceps brachii: agonist. Triceps brachii: antagonist.

What is a stabilizer muscle?

A muscle creating torque to prevent joint action or oppose an external force; also called a fixator.

What type of contraction does a stabilizer use?

Isometric contraction.

What is a neutralizer muscle?

A muscle that creates torque to prevent an undesired action of another muscle.

What is the unit of muscle tension development?

The sarcomere.

What stimulates muscle activation?

A motor neuron innervating the muscle.

How do myosin cross-bridges develop muscle tension?

Myosin attaches to actin, pulls, releases, then reattaches and pulls again.

What does greater physiological cross-sectional area mean?

Greater muscle force production.

How much force can muscle produce per cm² of cross-sectional area?

Approximately 30 N/cm².

What three major factors affect maximal muscle force?

Physiological cross-sectional area, muscle length, and contraction velocity.

What is the muscle force relationship for contraction velocity?

Eccentric > isometric > concentric.

How is physiological cross-sectional area measured in longitudinal muscles?

One cross section perpendicular to the fibers and line of pull includes all fibers.

How is physiological cross-sectional area measured in pennate muscles?

Multiple cross sections are needed because fibers and line of pull are angled.

What is passive muscle tension?

Tension from stretching connective tissue, including sarcolemma, endomysium, perimysium, and tendon.

What makes up whole-muscle tension?

The sum of active tension and passive tension.

At what muscle length can maximum tension develop?

Approximately 120% of resting length.

What characterizes Type I muscle fibers?

Slow-twitch oxidative (SO): slow tension development and highly fatigue resistant.

What characterizes Type IIA muscle fibers?

Fast-twitch oxidative-glycolytic (FOG): fast tension development and fatigue resistant.

What characterizes Type IIB muscle fibers?

Fast-twitch glycolytic (FG): fast tension development and fatigue quickly.

What is qualitative biomechanical analysis?

Evaluating performance through observation and descriptive comparisons.

What are the four steps of qualitative analysis?

Description, observation, evaluation, and instruction.

What is the purpose of the description step?

Identify effective technique, desired outcomes, performance measures, and success criteria.

What are two approaches to identifying effective technique?

Study elite performers/traditional technique or use a deterministic approach that breaks skills into subgoals.

What happens to observable errors as skill increases?

The size of observable errors and trial-to-trial variability decrease.

What should be considered when observing performance?

Who, where, and what to observe; environmental conditions; initial and subsequent trials.

What is the first step of performance evaluation?

Identify errors or deficiencies in performance.

What is the second step of performance evaluation?

Diagnose the magnitude of each error's effect.

Which performance errors should be corrected first?

Errors that increase injury risk; these are the highest priority.

What are three ways to rank performance errors?

Major to minor; earliest to latest; easiest to most difficult to correct.

What are the three parts of communicating corrections?

Explain the error, describe ideal technique, and develop a correction plan.

What are the steps in a teaching progression?

Break skill into parts, create drills, develop each part, combine parts, then perform the whole skill.

What is the principle of specificity in training?

Exercises and drills must be specific to the sport or activity.

What physical limitations can training address?

Strength, power, endurance, flexibility, cardiovascular fitness, and body composition.

What are the five steps of anatomical analysis?

Identify temporal phases, joint motions, muscle contractions, rapid accelerations/impacts, and extreme joint ROM.

Why divide an activity into temporal phases?

To break performance into specific phases or motions for analysis.

What is the difference between joint motion and joint position?

Motion describes movement occurring at a joint; position describes its orientation or location.

In anatomical analysis, what indicates concentric contraction?

A body segment speeds up or gets raised.

In anatomical analysis, what indicates eccentric contraction?

A body segment slows down or gets lowered.

In anatomical analysis, what indicates isometric contraction?

The body segment does not move.

Why identify rapid joint angular accelerations and impacts?

They show when active muscles must produce large forces and the joint positions involved.

Why identify extreme joint ranges of motion?

They identify when muscles and soft tissues may be stretched and injured.

What are the four types of mechanical stress?

Compression, tension, shear, and complex loading.

How does biological tissue respond to stress?

It adapts to the level of stress imposed on it.

What is hypertrophy?

An increase in tissue size in response to higher stress.

What is atrophy?

A decrease in tissue size in response to lower stress.

What is the physiologic loading zone?

Stress at the level tissue is currently adapted to; maintains tissue.

What is the physiologic training zone?

Stress greater than current adaptation, causing microdamage and beneficial remodeling.

What is the overload principle?

Systematically apply loads above the tissue's yield threshold and allow adequate recovery.

What is the pathologic underload zone?

Prolonged stress below adaptation levels, causing detraining and tissue weakening.

What are examples of pathologic underload?

Sedentary lifestyle, immobilization, and space flight.

What is the pathologic overload zone?

High stress causing substantial tissue damage.

What is a traumatic injury?

Injury from one application of high stress; examples include ligament tear, fracture, and muscle avulsion.

What is an overuse injury?

Injury caused by repeated applications of relatively low stress.

What determines overuse injury risk?

Number of repetitions and magnitude of stress; higher stress requires fewer repetitions.

Why is recovery important in preventing overuse injuries?

Without rest, stress is reapplied to tissue that is still damaged.

What is the tissue stress-threshold ranking?

Bone > tendon > ligament > cartilage.

What is bone's stress tolerance ranking?

Compression > tension > shear.

What stress directions do ligaments and tendons tolerate best?

Tension > shear.

Why do injury thresholds differ between people?

Genetics, training, nutrition, and previous tissue adaptations.

What are intrinsic injury factors?

Individual-related factors determining the ability to withstand loading.

What are extrinsic injury factors?

Task and environment factors, including imposed loading and performance conditions.

How do intrinsic and extrinsic factors affect injury?

Intrinsic factors set the threshold; extrinsic factors determine the potential to exceed it.

What is cross-training?

Rotating among different activities from day to day.

How does cross-training reduce injury risk?

Different loading patterns allow tissue remodeling and reduce cumulative repetitive loading.

What are key interventions to reduce injury risk?

Consider anthropometrics and posture, use appropriate equipment/locations, cross-train, and set reasonable goals.

What training increases should be gradual?

Frequency, intensity, and duration; avoid too much too soon.

What are temporal biomechanical variables?

Timing.

What are kinematic biomechanical variables?

Position, displacement, velocity, and acceleration.

What are kinetic biomechanical variables?

Force, energy, work, and power.

What is an advantage of laboratory data collection?

Controlled environments minimize measurement error and allow consistent repeated conditions.

What is a disadvantage of field data collection?

Equipment portability, mounting difficulties, and limited environmental control.

What is an analog signal in biomechanics?

A continuously varying measurement, often recorded as electronic voltage.

What is the typical consumer video sampling frequency?

30–60 frames per second (fps).

What sampling frequency do smartphones and digital cameras use?

120–240 fps.

What is a typical high-speed camera sampling frequency?

Approximately 1,000 fps, but at lower resolution.

What video sampling rate is adequate for most analyses?

Less than 100 fps; faster actions and impacts require higher fps.

What are the three tools/categories listed for measuring biomechanical variables?

Kinematic equipment, kinetic equipment, and electromyography (EMG).