Chapter 20

Laboratory Assessment of Human Performance

EXERCISE PHYSIOLOGY Theory and Application to Fitness and Performance, 6th edition Scott K. Powers & Edward T. Howley Presentation revised and updated by Brian B. Parr, Ph.D.

University of South Carolina Aiken

Factors That Contribute to Physical Performance

Figure 20.1

What the Athlete Gains From Physiological Testing

• Benefits – Information regarding strengths and weaknesses • Can serve as baseline data to plan training programs – Feedback regarding effectiveness of training program – Understanding about the physiology of exercise • What physiological testing will not do: – Accurately predict performance from single battery of tests

Effective Physiological Testing

• Physiological variables tested should be relevant to the sport • • • • Tests should be valid and reliable Tests should be sport-specific Tests should be repeated at regular intervals Testing procedures should be carefully controlled • Test results should be interpreted to the coach and athlete

Direct Testing of Maximal Aerobic Power

• • • VO 2max is considered the best test for predicting success in endurance events – Other factors are also important Specificity of testing – Should be specific to athlete’s sport Exercise test protocol – Should use large muscle groups – Optimal test length 10-12 minutes • • • Start with 3 –5 minute warm-up Increase work rate to near maximal load Increase load stepwise every 1 –4 minutes until subject cannot maintain desired work rate

Direct Testing of Maximal Aerobic Power

• Criteria for VO 2max – Plateau in VO 2 • with increasing work rate Rarely observed in incremental tests – Blood lactate concentration of >8 mmoles•L -1 – Respiratory exchange ratio  1.15

– HR in last stage  10 beats•min -1 of HR max

Determining VO

2

Max

Figure 20.2

Determination of Peak VO 2 Paraplegic Athletes in

• • • Paraplegic athletes can be tested using arm exercise – Arm ergometers – Wheelchair ergometers Highest VO 2 measured during arm exercise is not considered VO 2max – Called “peak VO 2 ” Higher peak VO 2 using accelerated protocol – Test starts at 50–60% of peak VO 2 – Limits muscular fatigue early in test

Laboratory Tests to Predict Endurance Performance

• • • Lactate threshold – Exercise intensity at which blood lactic acid begins to systematically increase Critical power – Speed at which running speed/time curve reaches plateau Peak running velocity – Highest speed that can be maintained for >5 sec

• • •

Use of the Lactate Threshold to Evaluate Performance

Lactate threshold estimates maximal steady-state running speed – Predictor of success in distance running events Direct determination of lactate threshold (LT) – 2–5 minute warm-up – Stepwise increases in work rate every 1–3 min – Measure blood lactate at each work rate – LT is the breakpoint in the lactate/VO 2 graph Prediction of the LT by ventilatory alterations – Ventilatory threshold (T vent ) • Point at which there is a sudden increase in ventilation • Used as an estimate of LT

Lactate Threshold

Figure 20.3

Ventilatory Threshold

Figure 20.4

Measurement of Critical Power

• • • Critical power – Running speed at which running speed/time curve reaches a plateau – Power output that can be maintained indefinitely • However, most athletes fatigue in 30 when exercising at critical power –60 min Measurement of critical power – Subjects perform series of timed exercise trials to exhaustion Prediction of performance in events lasting 3 –100 min – Highly correlated with high VO 2max and LT

Concept of Critical Power

Figure 20.6

Measurement of Peak Running Velocity

• Predictor of performance in endurance events lasting <20 minutes – High correlation between peak running velocity and 5 km race time • Measurement of peak running velocity – Progressively increasing speed on treadmill – Highest speed that can be maintained for more than five seconds

Relationship Between Running Velocity and 5 km Race Performance

Figure 20.5

Tests to Determine Running Economy

• • Higher economy means that less energy is expended to maintain a given speed – Runner with higher running economy should defeat uneconomical runner in a race Measurement of the oxygen cost of running at various speeds – Plot oxygen requirement as a function of running speed – Greater running economy reflected in lower oxygen cost

The Oxygen Cost of Running

Figure 20.7

Estimating Distance Running Success Using LT and Running Economy

• • Close relationship between LT and maximal pace in 10,000 m race – Race pace at 5 m•min -1 above LT Predicting performance in a 10,000 m race – Measure VO 2max • Plot VO 2 vs. running speed – Determine lactate threshold • Plot blood lactate vs. VO 2 – VO 2 at LT = 40 ml•kg -1 •min -1 • VO 2 of 40 ml•kg m•min -1 -1 •min -1 = running speed of 200

10,000m



205 m•min -1 = 48.78 min

– Estimated 10,000 m running time

Running Economy and LT Results From Incremental Exercise Test

Figure 20.8

Determination of Maximal Anaerobic Power

• Tests of ultra short-term anaerobic power – Tests ATP-PC system – Jumping power tests – Running power tests • American football – Series of 40-yard dashes with brief recovery between • Soccer – Intermittent shuttle tests – Cycling power tests • Quebec 10 second test

Determination of Maximal Anaerobic Power

• Tests of short-term anaerobic power – Tests anaerobic glycolysis – Cycling tests • Wingate test – Subject pedals as rapidly as possible for 30 seconds against predetermined load (based on body weight) – Peak power indicative of ATP-PC system – Percentage of peak power decline is an index of ATP-PC system and glycolysis – Running tests • Maximal runs of 200 –800 m – Sport-specific tests

Energy System Contribution During Maximal Exercise

Figure 20.9

Series of 40-yard Dashes to Test Anaerobic Power

Figure 20.10

Evaluation of Muscular Strength

• • • • • Muscular strength – Maximal force that can be generated by a muscle or muscle group Isometric measurement – Static force of muscle using tensiometer Free weight testing – Weight (dumbbell or barbell) remains constant – 1 RM lift, handgrip dynamometer Isokinetic measurement – Variable resistance at constant speed Variable resistance devices – Variable resistance over range of motion

Printout From Isokinetic Dynamometer During a Maximal-Effort Knee Extension

Figure 20.14