Experimental techniques practice questions.

In the 20 m multi-stage fitness test the required running speed rises at each level. What is the purpose of that design?

• To keep the total duration of the test exactly the same for every participant
• To raise the intensity progressively until the participant cannot continue
• To allow the heart rate to return to resting between levels
• To hold the oxygen uptake constant while the speed changes

Answer: To raise the intensity progressively until the participant cannot continue

An incremental protocol drives every participant towards the limit of what they can sustain, so the level reached is a function of the participant rather than of a fixed workload. Fitter participants therefore last longer, which is precisely why the duration is not the same for everyone.

The spring in a skinfold caliper has weakened over several seasons, so the jaws close on the raised fold with less than the standard pressure. What effect does this have on the recorded skinfold thickness?

• It is underestimated, because a weaker spring allows the jaws to travel further and to compress the underlying muscle as well as the fold.
• It is overestimated, because the fold is compressed less than the protocol requires.
• It is unaffected, provided the same site is marked each time.
• It becomes less repeatable, but the mean of several readings stays correct.

Answer: It is overestimated, because the fold is compressed less than the protocol requires.

A calibrated caliper applies a constant jaw pressure so that every fold is compressed to the same degree. Less pressure leaves a thicker fold between the jaws, so the bias runs in one direction only and repeating the reading does not remove it.

A researcher must obtain a maximal oxygen uptake value for a wheelchair basketball player. Which protocol is appropriate, with the correct justification?

• A motorised treadmill test with the chair held on the belt, because running always recruits more muscle than any upper-body protocol can.
• A 20 m multi-stage fitness test, because field protocols carry the same validity in every population that has been studied.
• An incremental arm-crank ergometer test, because a treadmill cannot load the muscle mass with which this athlete actually exercises during her sport.
• A submaximal step test, because step protocols require no calibration of the work rate and can be run in any laboratory.

Answer: An incremental arm-crank ergometer test, because a treadmill cannot load the muscle mass with which this athlete actually exercises during her sport.

A maximal test has to stress the muscle mass the athlete uses, otherwise the plateau reflects the limits of an untrained or unused segment rather than central transport capacity. Arm-crank values are lower than leg-based values in the same person, so the two are never pooled.

A motorised treadmill displays a gradient of 2.0 % while the belt is in fact horizontal. Oxygen uptake at each stage is estimated from the displayed speed and gradient using an estimation equation. What is the effect on the estimated values?

• They scatter randomly about the true value from one stage to the next.
• They are unaffected, since the prediction equation depends on belt speed alone.
• They fall below the true oxygen uptake, because running on the level is mechanically less efficient than running uphill at the same speed.
• They lie above the athlete's true oxygen uptake at every stage.

Answer: They lie above the athlete's true oxygen uptake at every stage.

The equation credits the runner with vertical work that is not being performed, so the estimated cost exceeds the real one. The error is systematic, which is why an estimated value is never reported as a measured one.

Thirty players must be assessed for aerobic fitness in a single 60 min slot on a sports hall floor during a pre-season tour. Which property of the 20 m multi-stage fitness test makes it the appropriate choice in these circumstances?

• A whole group runs at the same time, needing only a marked area and an audio signal.
• Oxygen uptake is sampled directly from expired air, so no estimation equation is needed at any stage of the test.
• The score obtained is independent of the running economy of the individual player.
• A plateau in oxygen uptake is produced, which confirms that a maximal effort was reached.

Answer: A whole group runs at the same time, needing only a marked area and an audio signal.

The field test wins on throughput and equipment, not on accuracy: it estimates the value from a shuttle level rather than measuring expired gas. Where one athlete is tracked over a season with laboratory access, the treadmill protocol remains the better instrument.

During the first 5 s of a 30 s cycle ergometer sprint a track athlete performs 6000 J of work. Calculate the mean power output over this period. (in W, to the nearest whole number)

Answer: 1200

Power is work divided by time, so 6000 J / 5 s = 1200 W. Peak power in a maximal 30 s effort occurs in these opening seconds, while phosphocreatine stores are still high.