1. Ground Reaction Force (GRF) is defined as:
(A) Force applied by muscles on bones
(B) Force exerted by the ground on the body in response to contact
(C) Force due to gravity pulling downward
(D) Frictional resistance of the surface
2. The study of GRF is most relevant in:
(A) Astronomy
(B) Biomechanics
(C) Chemistry
(D) Genetics
3. Which law of motion explains ground reaction forces?
(A) Newton’s First Law
(B) Newton’s Second Law
(C) Newton’s Third Law
(D) Law of Gravitation
4. The main component of GRF during walking is:
(A) Vertical
(B) Horizontal
(C) Lateral
(D) Rotational
5. Vertical GRF is usually expressed in terms of:
(A) Body weight multiples
(B) Newton per meter
(C) Joules
(D) Watts
6. During running, peak vertical GRF can reach up to:
(A) 0.5 × body weight
(B) 1 × body weight
(C) 2–3 × body weight
(D) 5 × body weight
7. GRF is measured using:
(A) Stethoscope
(B) Force plate
(C) Microscope
(D) Spirometer
8. Which component of GRF is responsible for forward propulsion?
(A) Vertical
(B) Anterior–posterior
(C) Medial–lateral
(D) Torque
9. Which component of GRF helps control side-to-side balance?
(A) Vertical
(B) Anterior–posterior
(C) Medial–lateral
(D) Gravitational
10. In standing still, the vertical GRF is equal to:
(A) Zero
(B) Body mass
(C) Body weight
(D) Muscle force only
11. GRF during heel strike in walking shows:
(A) Double peak curve
(B) Flat constant line
(C) Random spikes
(D) No measurable force
12. The two peaks of vertical GRF during walking correspond to:
(A) Heel strike and toe-off
(B) Midstance and swing phase
(C) Flight phase and landing
(D) None of the above
13. GRF is important in analysis of:
(A) Gait
(B) Sports performance
(C) Rehabilitation
(D) All of the above
14. Higher GRFs are usually associated with:
(A) Slower movements
(B) Softer landings
(C) Faster running and jumping
(D) Standing posture
15. GRF during running without shoes compared to shoes is usually:
(A) Lower
(B) Higher
(C) Unchanged
(D) Zero
16. Which condition can be diagnosed using GRF abnormalities?
(A) Diabetes
(B) Gait disorders
(C) Hypertension
(D) Asthma
17. Medial–lateral GRF is highest in:
(A) Standing still
(B) Sprinting
(C) Jumping vertically
(D) Swimming
18. GRF data is often normalized to:
(A) Velocity
(B) Body weight
(C) Acceleration
(D) Age
19. Which factor can reduce peak GRF in landing?
(A) Stiff legs
(B) Increased knee flexion
(C) Rigid posture
(D) Locked joints
20. Excessive GRF can contribute to:
(A) Bone fractures
(B) Joint injuries
(C) Muscle strains
(D) All of the above
21. GRF is applied in which rehabilitation method?
(A) Balance training
(B) Gait retraining
(C) Orthotics assessment
(D) All of the above
22. The vertical GRF during walking typically shows how many peaks?
(A) One
(B) Two
(C) Three
(D) Four
23. GRF during running usually shows:
(A) One peak
(B) Two equal peaks
(C) Three peaks
(D) Flat profile
24. Which of the following surfaces generates higher GRF?
(A) Grass
(B) Sand
(C) Concrete
(D) Foam mat
25. Peak GRF in sprinting can reach up to:
(A) 1 × body weight
(B) 2 × body weight
(C) 4–5 × body weight
(D) 6–7 × body weight
26. GRF during vertical jumping primarily acts in which direction?
(A) Vertical
(B) Horizontal
(C) Medial
(D) Rotational
27. The anterior–posterior GRF has two phases:
(A) Braking and propulsion
(B) Swing and stance
(C) Flight and landing
(D) Heel strike and toe-off
28. Which type of shoe reduces vertical GRF peaks?
(A) High heels
(B) Running shoes with cushioning
(C) Barefoot
(D) Sandals
29. GRF is essential in determining:
(A) Muscle size
(B) Joint loading
(C) Heart rate
(D) Lung volume
30. The magnitude of GRF is influenced by:
(A) Speed of movement
(B) Body mass
(C) Surface stiffness
(D) All of the above
31. A high braking force in anterior–posterior GRF may indicate:
(A) Efficient gait
(B) Over-striding
(C) Energy saving
(D) Balance stability
32. Vertical GRF at midstance is usually:
(A) Less than body weight
(B) Equal to body weight
(C) Greater than body weight
(D) Zero
33. The “impact peak” in GRF occurs at:
(A) Midstance
(B) Initial heel contact
(C) Toe-off
(D) Swing phase
34. Which sport shows very high GRF values during landing?
(A) Basketball
(B) Swimming
(C) Cycling
(D) Rowing
35. GRF is lowest in:
(A) Standing still
(B) Running
(C) Jumping
(D) Sprinting
36. Which GRF component is most associated with slips and falls?
(A) Vertical
(B) Anterior–posterior
(C) Medial–lateral
(D) Torque
37. GRF patterns are different in:
(A) Children vs. adults
(B) Men vs. women
(C) Athletes vs. non-athletes
(D) All of the above
38. The maximum vertical GRF during walking is usually:
(A) Equal to body weight
(B) 1.2 × body weight
(C) 2 × body weight
(D) 3 × body weight
39. GRF is essential for calculating:
(A) Center of pressure
(B) Blood flow
(C) Body temperature
(D) Lung capacity
40. Increased cadence in running generally:
(A) Increases GRF impact peak
(B) Reduces GRF impact peak
(C) Has no effect on GRF
(D) Eliminates GRF
41. GRF is used in sports science for:
(A) Performance enhancement
(B) Injury prevention
(C) Equipment design
(D) All of the above
42. In rehabilitation, GRF feedback helps patients improve:
(A) Vision
(B) Balance and gait
(C) Lung capacity
(D) Heart rate
43. Force plates provide GRF data in:
(A) One dimension
(B) Two dimensions
(C) Three dimensions
(D) Four dimensions
44. The “propulsive peak” of anterior–posterior GRF occurs during:
(A) Heel strike
(B) Midstance
(C) Toe-off
(D) Swing phase
45. Which of these reduces GRF effectively?
(A) Hard ground
(B) Soft surfaces
(C) Heavy footwear
(D) Increased mass
46. GRF magnitude is directly proportional to:
(A) Time of contact
(B) Surface area of foot
(C) Acceleration of body
(D) Muscle strength
47. In running, shorter ground contact time usually results in:
(A) Lower GRF
(B) Higher GRF
(C) Constant GRF
(D) No GRF
48. The variability in GRF signals may indicate:
(A) Consistent gait
(B) Neuromuscular impairment
(C) Normal posture
(D) Stable movement
49. Peak braking force in anterior–posterior GRF usually occurs at:
(A) Heel strike
(B) Midstance
(C) Toe-off
(D) Flight phase
50. Understanding GRF is crucial for:
(A) Physics only
(B) Medicine only
(C) Biomechanics, physiotherapy, and sports science
(D) Chemistry