Relationship between ambient temperature and ventilatory
threshold in recreationally trained collegiate males
Anne C. Mackin
Faculty Collaborator: Paul F. Mellick, Ph.D.
University of St. Thomas, St. Paul, Minnesota
Abstract
Methods
Conclusions
Anne C. Mackin
Relationship between ambient temperature and ventilatory threshold in
recreationally trained collegiate males.
Since exercise activities are often performed under hot conditions, it is
important to investigate the effects of heat on different metabolic variables
during exercise.
Purpose: To determine the relationship between ambient temperature
and ventilatory threshold in recreationally trained collegiate males.
Methods: A VO2max test was performed using a treadmill with a generic
ramp protocol. A TrueOne 2400 Metabolic Measurement System from Par
VO Medics (Model: MMS-2400) was used to measure VO2max and Peak
Ventilation. Results: Through Minitab 16, the mean VO2max and Peak
Ventilation during both control and heated trials was calculated and a
significant difference was found between trials for each variable.
Conclusion: Based on results, the hypothesis that there is an inverse
relationship between temperature and ventilatory threshold was
confirmed. Further research could be done to strengthen the results by
recruiting a larger number of subjects or increasing the temperature of the
heated trial.
Participants
The purpose of this study was to determine the relationship between ambient
temperature and ventilatory threshold in recreationally trained collegiate males. Based
on the results, the hypothesis that there is an inverse relationship between
temperature and ventilatory threshold can be confirmed. A statistically significant
difference between the mean VO2max and mean Peak VE values for both control and
heated trials was found (p < 0.05). It was found that as temperature was increased,
heat-sensitive variables that affect an individual’s ventilatory threshold (VO2max and
Peak VE) were decreased. In heated trials it was found that both variables began to
increase non-linearly at a faster rate in comparison to control trials. This could be due
to a lower VO2max, which would cause lactic acidosis to occur earlier during exercise.
This will consequently cause higher levels of CO2 in the blood, increasing minute
ventilation.
Eight recreationally trained collegiate males volunteered to participate in the current study. Demographic
information was collected from all subjects and reported in Figure 1. All of the subjects signed IRB consent (IRB
#51709-1) and were instructed on the metabolic test procedure.
Procedures
A VO2max test was performed using a treadmill with a generic ramp protocol (Figure 2). A TrueOne 2400 Metabolic
Measurement System (Figure 4) from Par VO Medics (Model: MMS-2400, Murray, UT) was used to measure the
VO2max of each subject. Heart rate was measured using a Polar heart rate monitor from Polar Electro Inc. (Woodbury,
NY). After a two-minute warm up, the participant began running at their average mile pace with a 2% increase in
grade every two minutes. The participant ran until they reached their VO2max, as signaled by a RER > 1.15, plateau of
VO2, participant reaching their maximum heart rate or as signaled from the participant to the researcher. The
participant completed a cool down no less than two minutes. This procedure was tested on two separate occasions,
one at standard room temperature (22.60.5 oC) and the second at an increased room temperature (27.50.5 oC).
Temperature was recorded using a Davis Vantage VUE (Model: 6351, Hayward, CA).
Statistical Analysis
Variables were tested with a paired t-test at the 0.05 confidence level and analyzed using Minitab 16 software.
Introduction
During exercise in hot environments, the human body has the ability to
maintain sufficient cardiac output and blood pressure in order to dissipate
body heat while sustaining muscle force generation (Cheuvront, 2010). As
the body begins to rely not solely on aerobic metabolism, anaerobic
metabolism increases and accordingly, lactic acid production increases.
Lactic acidosis, in addition to an increase in carbon dioxide (CO2)
concentration in the blood (transported as bicarbonate ion), contributes to
an increase in pulmonary ventilation (Poole, 1985). An individual’s
ventilatory threshold (VT) depends upon their maximal volume of oxygen
consumed (VO2MAX). A higher VO2MAX signifies aerobic training adaptations
have occurred and a direct increase in aerobic performance can be seen.
Therefore, anything that reduces VO2MAX impairs aerobic performance
(Chen, 2013). It has been established that environmental heat stress
decreases an individual’s VO2MAX (Cheuvront) and increases minute
ventilation (Chiba, 2011). As ventilation and VO2 increase at a faster rate,
anaerobic metabolism begins to produce lactic acid earlier during exercise-inducing hyperventilation and an excessive output of CO2 (Chiba).
Consequently, the increased rate of these heat-sensitive metabolic
variables decreases VT.
Since exercise activities are often performed under hot conditions, it is
important to investigate the effects of the heat on different metabolic
variables during exercise. I aimed to test the hypothesis that there is an
inverse relationship between temperature and ventilatory threshold.
Therefore, the purpose of this study was to determine the relationship
between ambient temperature and ventilatory threshold in recreationally
trained collegiate males.
Though a sample of eight participants was sufficient enough to detect a difference
between the means of both tested variables, further studies should be done with a
larger number of subjects in order to increase the validity. As the ambient temperature
was only slightly increased, further studies should be performed with a larger increase
in temperature.
Number of Participants
Age
Height (cm)
Weight (kg)
8
20.6±0.92
177.9±6.15
83.3±12.9
Figure 1. Demographics Information.
Results
Descriptive statistics presented in Figure 3 showed a significant difference (p-value < 0.05) between the mean
VO2max of the Control Trial and the mean VO2max of the Heated Trial. Figure 3 also showed a significant difference
between the mean Peak Ventilation of the Control Trial and the mean Peak Ventilation of the Heated Trial.
VO2max (ml/kg/m) Peak VE (L/min)
Control Trial (22.6±0.5oC) 51.4±4.9
146.7±16.5
Heated Trial (27.5±0.5oC) 49.4±4.3*
129.1±13.6*
* p < 0.05
Figure 3. Mean values and standard deviations of VO2max values and Peak VE values in Control and Heated Trials.
References
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Acknowledgements
I would like to thank Dr. Paul Mellick for his support and guidance throughout this
study as well as all of the subjects who participated. I would also like to extend a
gracious thank you to Mr. Randy Mueller, Chief Engineer of the Physical Plant at the
University of Saint Thomas, for his help in coordinating the temperature differences of
the lab.
Figure 2. Participant performing Heated VO2max test.
Figure 4. TrueOne 2400 Metabolic Measurement System.