IB Sports, Exercise and Health Science practice questions.

A weightlifter increases the force produced by the quadriceps as the load on the bar is raised. Which change in the nervous input to the muscle produces most of this extra force?

• Only the largest motor units are recruited, and the smaller ones stay silent
• The firing frequency of the motor units already active falls
• More motor units are recruited and each fires more often
• Recruitment of motor units stops once half of them are active

Answer: More motor units are recruited and each fires more often

Force is graded by recruiting additional motor units and by raising the firing frequency of those already active. Recruitment follows the size principle, so the small fatigue-resistant units are brought in first and the largest are added only for the heaviest lifts.

A footballer swings the kicking leg forward from the hip with the knee extending, driving the ball straight ahead. In which plane and about which axis does this leg action occur?

• Frontal plane about the frontal (mediolateral) axis
• Sagittal plane about the frontal (mediolateral) axis
• Sagittal plane about the sagittal (anteroposterior) axis
• Transverse plane about the longitudinal (vertical) axis

Answer: Sagittal plane about the frontal (mediolateral) axis

Forward and backward movements such as hip flexion divide the body into left and right, so they occur in the sagittal plane, and the axis is always perpendicular to the plane, which makes it the frontal or mediolateral axis. Pairing the sagittal plane with a sagittal axis is the single most common error in this topic.

A selector watches one match and concludes that a player is a natural leader. According to Hollander's model of personality, why is this inference unsafe?

• What is visible in one match is the layer most easily changed by the situation
• The model treats all of its layers as equally stable, so one observation cannot mislead anyone
• The model applies only to individual sports and not to selection for a team
• The layers can be measured by questionnaire only and never by observation

Answer: What is visible in one match is the layer most easily changed by the situation

In Hollander's model stability falls and observability rises as one moves outwards, so what a spectator sees in a single match is the outer layer and it changes with the role and the occasion. The stable centre is inferred over repeated observation rather than read off one performance.

A track sprinter completes a 30 s all-out effort on a cycle ergometer against a fixed braking force. Which quality is this test designed to measure?

• Maximal oxygen uptake of the working legs
• Anaerobic power output and its decline
• Flexibility of the hip joint
• Efficiency of the aerobic system at steady state

Answer: Anaerobic power output and its decline

The 30 s maximal effort is predominantly anaerobic, drawing on the phosphagen system and anaerobic glycolysis, with the aerobic system already contributing a measurable share. Peak power and the fall in power across the effort are therefore its outcome measures, whereas maximal oxygen uptake requires expired air to be analysed during an incremental protocol.