Comp Exam

RESEARCH METHODS — Qualitative Research

Qualitative research is a non-numerical, interpretive approach to inquiry that seeks to understand the meaning, experiences, and perceptions underlying human behavior. Methods include in-depth interviews, focus groups, and participant observation. It is inductive — used to explore, generate hypotheses, and capture phenomena that cannot be measured numerically.

Advantage of Qualitative Research: Depth of Understanding

Qualitative research captures the "why" behind behaviors. For example, quantitative data may show a 35% dropout rate in youth sport, but only qualitative interviews can reveal the emotional, social, and contextual reasons behind that decision.

Advantage of Qualitative Research: Ecological Validity

Data is collected in natural, real-world settings rather than controlled labs, meaning findings reflect how people actually think, feel, and behave in context — critical in kinesiology where behavior is shaped by social and environmental factors.

Advantage of Qualitative Research: Flexibility

Research questions can evolve as new themes emerge from the data. This iterative process is a methodological strength when the goal is exploration rather than confirmation.

Advantage of Qualitative Research: Access to Subjective Experience

Qualitative research is the only appropriate method for phenomena that are inherently subjective and not quantifiable — such as an athlete's emotional experience during injury recovery or a community's cultural attitudes toward physical activity.

Mixed Methods Research

A research design that combines both qualitative and quantitative approaches. Quantitative methods establish WHAT is happening; qualitative methods explain WHY and HOW. Together they provide breadth and depth simultaneously.

How Mixed Methods Strengthens Research: Triangulation

Triangulation involves corroborating findings across multiple data sources. When quantitative results (e.g., decreased sport enjoyment scores) are reinforced by qualitative themes (athletes describing burnout and pressure), the validity and credibility of both findings is substantially increased.

How Mixed Methods Strengthens Research: Compensates for Limitations

Quantitative research cannot explain the mechanisms behind its findings; qualitative cannot generalize to large populations. Mixed methods compensates: e.g., if a fitness intervention shows null results quantitatively, qualitative interviews can reveal the logistical or psychosocial barriers that undermined adherence.

How Mixed Methods Strengthens Research: Instrument Development

Qualitative data can precede a quantitative study to identify constructs and themes that should be captured in a survey, ensuring the measurement tool has strong content validity and cultural relevance for the target population.

One-Way ANOVA

The appropriate statistical technique when comparing a continuous dependent variable (e.g., achievement scores) across three or more independent groups. It tests the null hypothesis that all group means are equal (H₀: μ₁ = μ₂ = μ₃) by comparing variance between groups to variance within groups, producing an F-ratio.

Why Use ANOVA Instead of Multiple t-Tests?

Conducting repeated t-tests across three or more groups inflates the familywise Type I error rate — the probability of falsely concluding a difference exists. ANOVA controls this error by testing all comparisons simultaneously within a single omnibus test.

Three Assumptions of One-Way ANOVA

1. Independence of observations (each participant in only one group). 2. Normality — DV is approximately normally distributed within each group (tested with Shapiro-Wilk). 3. Homogeneity of variance — variances across groups are approximately equal (tested with Levene's Test).

What to Do When ANOVA Assumptions Are Violated

If homogeneity of variance is violated → use Welch's ANOVA. If normality is severely violated with small samples → use the non-parametric Kruskal-Wallis H test.

Post-Hoc Tests After a Significant ANOVA

A significant ANOVA F-ratio only tells you that at least one group differs — not which ones. Post-hoc tests identify specific pairwise differences. Common options: Tukey's HSD (equal group sizes), Bonferroni correction (conservative), Games-Howell (when homogeneity of variance is violated).

Effect Size: Eta-Squared (η²)

A measure of practical significance for ANOVA. Quantifies the proportion of total variance explained by the group factor. Cohen's conventions: small = .01, medium = .06, large = .14. A statistically significant result with a small effect size may be practically meaningless.

Statistical Significance vs. Practical Significance

Statistical significance (p < .05) means there is less than a 5% probability the result is due to chance. Practical significance refers to whether the magnitude of the effect is meaningful in the real world — measured by effect size. A result can be statistically significant but practically trivial.

Electronic Questionnaire vs. Personal Interview: Validity of Responses

Electronic: Lower social desirability bias due to anonymity, but respondents cannot ask for clarification — risking misinterpretation. Personal interview: Higher social desirability bias (respondents may answer favorably), but the interviewer can probe, clarify, and follow up — improving construct and content validity.

Electronic Questionnaire vs. Personal Interview: Administrative Considerations

Electronic: Low cost, no travel, fast, can reach large samples simultaneously, minimal helpers needed. Personal interview: High cost, time-intensive (scheduling, conducting, transcribing), requires trained interviewers, but yields richer and deeper data.

Electronic Questionnaire: Key Weakness

Lower response rates — surveys are easy to ignore, creating non-response bias. Those who do not respond may differ systematically from those who do, threatening external validity.

Personal Interview: Key Strength

Produces rich, in-depth data capturing nuance, complexity, and unexpected themes in the participant's own language. Best for exploratory and phenomenological research where the goal is understanding, not hypothesis testing.

BIOMECHANICS — Three Cardinal Planes

1. Sagittal plane: divides the body into left and right; governs flexion/extension. 2. Frontal plane: divides the body into front and back; governs abduction/adduction. 3. Transverse plane: divides the body into upper and lower; governs rotation.

Sagittal Plane Movements in the Vertical Jump

Primary plane of motion. Key movements: hip flexion (countermovement) and hip extension (propulsion); knee flexion (loading) and knee extension (takeoff); ankle dorsiflexion (landing) and plantarflexion (takeoff); trunk flexion during countermovement. Dominant contributors to vertical force production.

Frontal Plane Movements in the Vertical Jump

Hip abductors (gluteus medius, minimus) control frontal plane pelvic stability and femoral alignment. Excessive dynamic knee valgus (medial knee collapse) is a major frontal plane deviation and one of the primary biomechanical risk factors for ACL injury.

Transverse Plane Movements in the Vertical Jump

Hip rotators control femoral rotation. Hip internal rotation combined with knee valgus during landing creates a dangerous combined loading pattern on the ACL — a key injury mechanism. Transverse plane control is critical for safe landing mechanics.

Why Focus on Sagittal Plane for Vertical Jump Analysis?

The depth and timing of the countermovement (peak knee and hip flexion) directly influences elastic energy storage and force production range. Optimal countermovement depth (~90–100° knee flexion) maximizes stretch-shortening cycle utilization. Sagittal plane kinematics are also most accurately captured with standard 2D video.

Stretch-Shortening Cycle (SSC)

A sequence in which a muscle is rapidly lengthened (eccentric phase, i.e., countermovement descent) immediately followed by a rapid shortening (concentric phase, i.e., propulsion). Elastic potential energy stored in the musculotendinous unit during the eccentric phase augments the force produced in the concentric phase, increasing power output beyond what concentric-only action could produce.

Camera Setup for Sagittal Plane Video Analysis

Camera must be placed perpendicular (orthogonal) to the plane of motion — directly to the side of the athlete at approximately hip height. Mounted on a stable tripod. The athlete should be centered in frame. Any angular deviation from orthogonal introduces perspective error that systematically distorts calculated joint angles.

Recommended Sampling Frequency for Jump Analysis

Minimum 120 Hz (frames per second). Higher frequencies (240 Hz) are preferable. The vertical jump is a rapid ballistic movement — too low a sampling frequency causes aliasing: the misrepresentation of peak joint angles and velocities because the peak occurs between frames.

Why Is Calibration Required in Video Analysis?

A calibration object of known dimensions (e.g., a meter stick) placed in the plane of motion allows Kinovea to convert pixel coordinates into real-world distances (meters). Without calibration, all measurements remain in pixel units and cannot be expressed as actual angles, velocities, or displacements.

Marker Placement for Lower Extremity Sagittal Analysis

Markers placed at: (1) Greater trochanter of the femur — hip joint center. (2) Lateral epicondyle of the femur — knee joint center. (3) Lateral malleolus of the fibula — ankle joint center. (4) 5th metatarsal head — foot. These four markers define three segments (thigh, shank, foot) and allow calculation of hip, knee, and ankle joint angles.

Digitization in Kinovea

The process of manually identifying the position of each anatomical marker in every video frame and recording its pixel coordinate pair (x, y). After calibration, Kinovea converts these pixel coordinates into real-world coordinates (meters), producing a time-series of position data for each landmark across the full movement.

Low-Pass Butterworth Filter in Biomechanics

Used to smooth raw coordinate data by removing high-frequency noise caused by marker placement error, skin movement artifact, and digitizing inaccuracy. A cutoff frequency of approximately 6–10 Hz is typical for jump and locomotion analysis. Preserves the actual movement signal while eliminating noise.

Joint Angle Calculation from Coordinate Data

The joint angle is calculated as the included angle between two segment vectors meeting at the joint center. For the knee: the angle between the thigh vector (hip-to-knee) and the shank vector (knee-to-ankle) at each time point, using trigonometric vector analysis. Kinovea has built-in angle tracking tools once markers are defined.

Angular Velocity in Biomechanics

The first derivative of the joint angle with respect to time (degrees/second or radians/second). Peak knee extension angular velocity during the propulsion phase of a vertical jump is a key indicator of explosive force production and is strongly correlated with jump height.

Countermovement Depth: Definition and Optimal Value

The minimum knee flexion angle (maximum knee flexion) reached during the downward phase before propulsion. Optimal countermovement depth is approximately 90–100° of knee flexion for most athletes — this maximizes utilization of the stretch-shortening cycle. Insufficient depth leaves elastic energy on the table; excessive depth increases time-to-takeoff and reduces power.

How to Infer Performance Improvement from Kinematic Data Over Time

Collect data at baseline, week 4, week 8, etc. Indicators of improvement: increased peak jump height (vertical hip displacement), increased peak knee extension angular velocity, movement toward optimal countermovement depth (~90–100°), and reduced intra-trial variability (greater consistency = improved motor control).

MOTOR LEARNING — Attention as a Human Performance Limitation

The human attentional system has a finite, limited capacity — it can only process a certain amount of information at any given moment. When task demands exceed available attentional resources, performance deteriorates, errors increase, and skill execution breaks down. Unlike a computer, it cannot be upgraded — it operates within fixed biological constraints.

Kahneman's Capacity Model (1973)

Proposes that attention is a single, general pool of mental resources with a limited total capacity. Tasks draw from this pool proportional to their difficulty and novelty. When combined task demands exceed capacity, performance on one or more tasks must be sacrificed. Explains why novices cannot simultaneously focus on technique AND read the environment.

Wickens' Multiple Resource Theory

Proposes that attention consists of multiple partially independent resource pools organized by: (1) processing stage (perceptual-cognitive vs. motor), (2) processing code (spatial vs. verbal), and (3) input modality (visual vs. auditory). Tasks interfere most when they compete for the same specific resource pool. Tasks using different channels can co-exist with less mutual interference.

Fitts' Stages of Motor Learning

Three stages: (1) Cognitive — skill execution is highly attention-demanding; learner consciously attends to every movement component. (2) Associative — attentional demands decrease as the movement is refined. (3) Autonomous — skill is highly automated; executed with minimal conscious attention, freeing resources for higher-order processing (tactics, environment scanning).

Attentional Demands: Beginner vs. Expert Athlete

Beginner: allocates nearly all attentional capacity to movement mechanics — no resources remain for environmental monitoring or tactical processing. Expert: motor program for the skill is highly automated, requiring minimal conscious attention, freeing cognitive resources for reading the game, anticipating, and making decisions simultaneously with skill execution.

Attentional Demands: Driving + Texting

Texting is visually, cognitively, and manually demanding — competing directly with driving across multiple resource channels. Combined demands far exceed available attentional capacity, causing degraded performance on both tasks: increased reaction time to hazards, decreased lane-keeping accuracy, reduced hazard detection rates.

Attentional Demands: Driving + GPS vs. Driving + Radio

GPS requires periodic visual and cognitive attention (reading screen, processing directions) — moderate competition for driving resources. Radio uses primarily the auditory channel with minimal cognitive processing — far less interference with driving. Illustrates Wickens' Multiple Resource Theory: different resource channels = less mutual interference.

Attentional Demands: Easy vs. Difficult Skills

An automated, well-practiced skill (e.g., a marathoner's gait) requires minimal attentional resources — allowing conversation or strategic thinking simultaneously. A novel or recently changed skill (e.g., a golfer implementing a new swing) becomes cognitively demanding again — full conscious attention is required, and distractions significantly impair performance.

Choking Under Pressure: Reinvestment Hypothesis

Under high pressure, athletes direct conscious attention to movement mechanics that were previously automated. This disruption of automatic motor control is the mechanism underlying choking. Coined by Masters (1992). Implication: train athletes in pressure conditions so automated motor programs remain robust when arousal increases.

Stimulus-Response (S-R) Compatibility

The degree of naturalness or intuitiveness in the relationship between a stimulus and the required response. Compatible pairings (stimulus and response are spatially, semantically, or conceptually congruent) produce faster responses, fewer errors, and lower attentional demands. Incompatible pairings produce slower, more error-prone responses requiring greater cognitive effort.

The Simon Effect

Experimental evidence for S-R compatibility: people respond faster and more accurately when the stimulus and response are on the same side of space — even when the spatial dimension is task-irrelevant. Demonstrates that spatial compatibility effects are powerful enough to interfere with performance automatically.

Example of S-R Compatibility Enhancing Performance: Catching

When a ball is thrown directly toward an athlete, the natural response is to bring hands toward the ball's trajectory — a spatially and perceptually compatible pairing. The stimulus (ball approaching) directly maps onto the response (move hands toward stimulus). Processing is rapid and automatic, minimizing reaction time.

Example of S-R Compatibility Enhancing Performance: Defensive Footwork

When defending against a player who drives right, the defender's compatible response is to step right — matching the stimulus direction to the response direction. This spatial S-R compatibility reduces reaction time and allows tight defensive coverage with less cognitive effort after extensive practice.

Example of S-R Incompatibility Causing Injury: Stiff-Legged Landing

The reflexive response to rapid downward movement is to stiffen the limbs — a naturally compatible protective response. However, stiff-legged landing dramatically increases peak ground reaction forces and ACL loading. The correct safe response (flex hips, knees, ankles to absorb force) is biomechanically incompatible with the reflex. Untrained athletes execute the compatible-but-dangerous response.

Example of S-R Incompatibility Causing Errors: Defensive Feints

Offensive players use feints to exploit S-R incompatibility: an initial body movement cues the defender to step one way, but the actual movement goes the other direction. The compatible response (react to the feint) is wrong. Elite offensive players are masters at engineering incompatible S-R situations to create separation.

Example of S-R Incompatibility: Novice Skier

A novice skier's instinct on a slope is to lean back (compatible with stumbling on flat ground) — but leaning back on skis reduces snow contact and eliminates steering control, greatly increasing fall risk. The correct response (lean forward into the hill) is incompatible with the instinctive reflex, requiring deliberate skill acquisition to override.

Practitioner Strategy: Build S-R Compatible Associations

Design practice with stimuli that match competition conditions as closely as possible (transfer-appropriate processing). Use anticipation training to help athletes read advance cues and initiate compatible responses before the stimulus is fully processed — the primary distinguishing factor between expert and novice perceptual skill.

Practitioner Strategy: Override Incompatible Reflexes — Perturbation Training

When the required safe response is incompatible with the reflexive response (e.g., soft landing vs. stiff-legged landing), use perturbation training — unexpected landing scenarios that force the neuromuscular system to develop flexible protective responses. ACL prevention programs (e.g., FIFA 11+) include this type of jump-landing training explicitly.

Practitioner Strategy: Train in Fatigue and Pressure Conditions

Under fatigue, high arousal, or time pressure, athletes revert to their most strongly conditioned S-R associations. Incompatible trained responses are most vulnerable to breakdown precisely when stakes are highest. Practice must include fatigue and pressure simulations to ensure correct responses remain accessible when cognitive and physical resources are depleted.

Practitioner Strategy: Anticipation Training for Incompatible Sport Situations

Teach athletes to ignore misleading cues (e.g., head and shoulder fakes) and focus on the most diagnostically valid information sources (e.g., hip and center-of-mass direction). This trains inhibition of the incompatible reflexive response and selective attention to reliable cues — a hallmark of expert perceptual decision-making.

Type I Error (False Positive)

Rejecting the null hypothesis when it is actually true — concluding there is a significant difference or effect when none actually exists. Controlled by the alpha level (typically set at p < .05, meaning a 5% acceptable probability of a Type I error). Conducting multiple t-tests inflates Type I error rate — ANOVA controls this.

Null Hypothesis (H₀)

A statement of no difference, no relationship, or no effect. Example: "There is no significant difference in achievement scores across the three class scheduling conditions" (H₀: μ₁ = μ₂ = μ₃). The goal of inferential statistics is to determine whether the evidence is sufficient to reject the null hypothesis.

Inductive vs. Deductive Research

Inductive: Starts with observations and builds toward theory — characteristic of qualitative research. Deductive: Starts with a theory or hypothesis and tests it against data — characteristic of quantitative research. Mixed methods research often involves both processes.

Ecological Validity

The degree to which research findings reflect real-world conditions and can be generalized to natural settings. Qualitative research and field-based studies tend to have high ecological validity. Tightly controlled laboratory experiments may sacrifice ecological validity for internal validity.

Internal Validity

The degree to which a study accurately establishes a causal relationship between the independent variable and the dependent variable, ruling out alternative explanations. Maximized through random assignment, control groups, blinding, and standardized procedures.

External Validity

The degree to which study findings can be generalized beyond the specific sample, setting, and conditions of the study. Random sampling, diverse samples, and ecologically valid settings improve external validity.

Kinetics vs. Kinematics (One-Sentence Distinction)

Kinematics describes WHAT the body is doing (position, velocity, angle) without reference to forces. Kinetics explains WHY the body moves the way it does — the forces, torques, and impulses that cause or resist motion.

Ground Reaction Force (GRF)

The force exerted by the ground on the body in reaction to the force the body exerts on the ground (Newton's Third Law). Measured with force plates. In vertical jumping, peak GRF during landing can exceed 3–5 times body weight — critical for understanding injury risk and lower extremity loading.

Dynamic Knee Valgus

Medial collapse of the knee during loading, jumping, or landing — a frontal and transverse plane deviation involving hip adduction, hip internal rotation, and knee medial displacement. A primary biomechanical risk factor for ACL injury. Caused by weak hip abductors and poor neuromuscular control of the lower extremity chain.