Sonja SilvaHES 403 LabVO2 max4/23/15

Introduction:

VO2 max is the maximum amount of oxygen that your body can use while training at a maximum workload. It is used as a measure of metabolism and aerobic capacity in athletic performance. A higher VO2 max is better for optimal performance. The purpose of this lab was to determine VO2 max in individuals using a treadmill test.

Methods:

1) The subject was required to wear a heart rate monitor during the test. 2) The subject was connected to a breathing tube and headgear on the treadmill. Gas was

calibrated for the treadmill test.3) The subject warmed up by walking at a comfortable pace for three minutes. Resting heart

rate was recorded.4) The subject began running at a chosen speed for about eleven minutes or until volitional

fatigue, using a scale to indicate levels of fatigue.5) Grade was increased by 2% after the first minute, and 1% for every remaining minute

while a machine recorded VO2.

Results:

Our subject’s VO2 max was 61.8 ml/kg/min.

Conclusions:

VO2 max is a good measure of aerobic capacity in trained and untrained individuals. In this test, we were able to determine VO2 max based on several indicators: an RPE scale, age predicted heart rate, VO2 levels, and RER. VO2 is influenced by mitochondrial density, muscle fiber recruitment, and capillary density in the muscle, and therefore we should see a higher VO2 max in trained individuals (Richards 2012). Increased demand for oxygen and energy to the muscle that is elicited by training increases the mitochondrial density, the amount and types of muscle fibers recruited, and the capillary density to increase blood flow to the area. We generally want the test to last between 8 to 11 minutes. If it is too short, we risk not reaching the true VO2 max. If it is too long, the subject may be past the point of fatigue and VO2 will start to decrease.

The treadmill test is a good method of measuring VO2 compared to other methods. In the study “Validating the Arm-Leg Eliptical Ergometer”, it was shown that an elliptical ergometer can be used to determine VO2 max. However, there was a slight statistical variation in the correlation of heart rate and VO2 max between males and females. This could be due to higher muscle fiber recruitment in males due to the inherent difference in upper body strength between genders, leading to increased VO2 max on the ALE with increased heart rate. A treadmill test may be

better to account for this variation, when testing for aerobic capacity between males and females. ALE ergometer tests could be used for lower impact for special populations due to the fact that there is no statistical difference in VO2 max for both these tests.

In the treadmill VO2 max test, we used an RPE scale to determine fatigue. Once the subject reached a fatigue level of 16, we determined that the subject was one minute away from VO2 max. We can see from the graph of VO2 versus time that at the end of our test, VO2 began to level off. This is a good indicator that the subject reached VO2 max. The heart rate was also very close to the age predicted maximum of 197. Also, in the last minute of the test, RER should be close to 1.04. The subject’s RER approached 1.02 at the end of the test. It is likely that we achieved close to a true VO2 max due to these criteria for a good VO2 max test.

The graphs show that VO2 increased rapidly at the beginning of the test, likely due to the recruitment of muscle fibers and increased blood flow to tissues. It then began to level off as the subject reached VO2 max. Heart rate increased linearly as VO2 increased. Ventilation increased linearly over time, as we would expect from the subject requiring more oxygen with increasing exercise intensity. Between 8 and 10 minutes on the graph, ventilation increased rapidly. This is an indicator that the subject has reached a maximal workload, and the body is pausing to take in more oxygen. (Elsangedy 2013). This is true because the subject reported an RPE value of about 18 at this time. RER increased over time, likely due to increased carbohydrate oxidation with increased aerobic metabolism. We see an increase of VE/CO2 and VE/O2 over time, with VE/O2 overlapping at the end. We know that there is increased breathing off of CO2 compared to inhalation of O2 according to the RER value, so the overlap is due to the ratio of ventilation over CO2 exhaled, making the constant smaller. (See Appendix for graphs). This test showed appropriate physiological responses over time, and we were able to obtain a value close to the VO2 max for our subject.

Appendix:

4 5 6 7 8 9 10 11 12 13 14155160165170175180185190195200

20253035404550556065

Heart Rate and VO2 vs Time

Heart RateVO2

Time

Hear

Rat

e (b

pm)

VO2

(ml/

kg/m

in)

This graph describes the relationship between VO2 and Heart Rate over time.

4 5 6 7 8 9 10 11 12 13 142022242628303234363840

VE/CO2 and VE/O2 vs. Time

VE/CO2VE/O2

Time (min)

VE/C

O2

and

VE/O

2

This graph depicts aerobic threshold in terms of VE/CO2 and VE/O2 over time.

4 5 6 7 8 9 10 11 12 13 140

20

40

60

80

100

120

Ventilatory Breakpoint (VE vs. Time)

Time (min)

VE (L

/min

)

This graph demonstrates ventilatory breakpoint as Ventilation during exercise over time.

4 5 6 7 8 9 10 11 12 13 140.7

0.75

0.8

0.85

0.9

0.95

1

1.05

RER vs. Time

RER

Time (min)

RER

This graph is of RER or the ratio of substrate utilization over time.

References:

Brown, Andrew. Kueffner, Tannin. O’Mahony, Erin. Lockard, Michael. Validity of Arm-Leg Elliptical Ergometer for VO2max Analysis. “Journal of Strength and Conditioning Research.” Lippincott Williams and Wilkins.

Colorado State University. “Maximal Oxygen Consumption.” HES 403 Lab Manual. 2014.

Elsangedy, Hassan Mohamed. The rating of perceived exertion is not different at the ventilatory threshold in sedentary women with different body mass índices. “Journal of Exercise Science and Fitness.” Volume 11, Issue 2, Pages 102–106. December 2013. http://www.sciencedirect.com/science/article/pii/S1728869X13000397#

Klentrou, Panagiota. Ventilatory breakpoints in boys and men. “Human Kinetics Journals.” Volume 18, Issue 2, p. 216-225. May 2006. http://journals.humankinetics.com/pes-back-issues/pesvolume18issue2may/ventilatorybreakpointsinboysandmen

Richards, Jennifer. Muscle contraction duration and fibre recruitment influence blood flow and VO2independent of contractile work during steady-state exercise in humans. PubMed. NCBI. Exp Physiol. 2012 Jun; 97(6): 750–761. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3366163/