Lab answers

7

Lab 8: Thermoregulation During Exercise

Name: Date:

Human thermoregulatory responses rely heavily on the cardiovascular system to maintain a normal core body temperature. It is important to maintain a balance between heat production, heat gain, and heat loss. During exercise, particularly in a hot and humid climate, the cardiovascular system is taxed due to the need for delivery of oxygen rich blood to the working muscles and increased blood flow to the skin for heat dissipation. This competition for blood flow can have a negative impact on performance. Sweating provides a means for dissipating heat from the body to the environment. But too much sweat loss can result in a significant loss of plasma volume, which can also have a negative impact on performance.

Procedures

1. Each subject will complete two exercise sessions of 60 minutes each on two different occasions under similar environmental conditions.

2. One exercise session will include drinking 200mL (~7 ounces) of water every 15 minutes (0, 15, 30, 45, 60), and the other exercise session will not include drinking water.

3. Measure and record weight (kg).

4. Record room temperature (ºC) and relative humidity (%).

5. Put on heart rate monitor and pair with cycle ergometer. Record resting heart rate (HR).

6. Using the temporal thermometer, measure and record temperature (ºC).

7. Warm up by riding the cycle ergometer for 5 minutes at a rating of perceived exertion (RPE) between 1 (Very Light) and 2 (Light).

8. Self-select a workload at a comfortable pedaling frequency (60-80 rpm) at an RPE of 3 (Moderate) to 4 (Somewhat Hard). Record and sustain this workload for 60 minutes.

9. Record HR, RPE, and temperature every 5 minutes during exercise.

10. Monitor subjects for signs of heat stress. If a subject shows signs of heat stress, exercise will be terminated, and the subject will be cooled down.

11. After exercise, measure and record weight (kg).

Data Table 8.0: Fluid Replacement

Name:	Sex:	Age (yr):	Height (cm):
Weight (kg) Pre:	Weight (kg) Post:	Workload (watts):	Fluid Intake (L):
Room Temp (°C) Pre:	Relative Humidity (%) Pre:	Room Temp (°C) Post:	Relative Humidity (%) Post
Time (min)	HR (bpm)	RPE	Skin Temperature (ºC)
Rest
5
10
15
20
25
30
35
40
45
50
55
60

Data Table 8.1: No Fluid Replacement

Name:	Sex:	Age (yr):	Height (cm):
Weight (kg) Pre:	Weight (kg) Post:	Workload (watts):	Fluid Intake (L):
Room Temp (°C) Pre:	Relative Humidity (%) Pre:	Room Temp (°C) Post:	Relative Humidity (%) Post
Time (min)	HR (bpm)	RPE	Skin Temperature (ºC)
Rest
5
10
15
20
25
30
35
40
45
50
55
60

Questions

1. Use the provided Excel spreadsheet to calculate the following variables:

a. Sweat rate in liters per hour for each condition (fluid replacement, no fluid replacement) for each subject.

i. Sweat rate (L/hour) = [Weightpre (kg) + Water Intake (L) – Weightpost (kg)] ÷ Exercise Duration (hours)

ii. Note: 1 liter = approximately 1 kg.

b. Means and standard deviations for Age, Weight (Pre & Post), HR for each stage, RPE for each stage, Skin temperature for each stage, Sweat rate for each exercise condition

c. Percent difference between exercise with fluid replacement and exercise without fluid replacement using the means for the following variables (Percent difference = ((Value 1 – Value 2)/((Value 1 + Value 2)/2)) *100):

i. Heart rate

ii. RPE

iii. Skin temperature

iv. Sweat Rate

d. Create a separate line graph for each of the following variables with time as the x-axis and the variable as the y-axis (use the mean for each variable) with both conditions on the same graph (fluid replacement, no fluid replacement):

i. Heart rate

ii. RPE

iii. Temperature

e. Create a bar graph showing the difference in sweat rate between the two exercise conditions (fluid replacement, no fluid replacement)

2. Describe the differences between the two exercise sessions in terms of heart rate (HR), rating of perceived exertion (RPE), skin temperature, and sweat rate.

3. Why is the demand on the cardiovascular system greater when exercising in a hot/humid environment?

HR(bpm)

RPE

Temp