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Effects of bodyweight aerobic exercise compared to resistance training on cardiovascular

and respiratory system homeostasis

Vanesa Robledo

Trent University

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Introduction

All living organisms must exchange materials with their environment, often through

diffusion and osmosis (Reece 2014). In complex organisms with multiple cell layers that have no

direct access to the environment, circulatory systems and respiratory systems have evolved over

time to facilitate this exchange. Circulatory systems contain a fluid, vessels to transfer the fluid,

and a heart to pump the fluid through the vessels (Reece et. al. 2014). Mammalian cardiovascular

systems are closed double circulatory systems: the pulmonary circuit and the systemic circuit.

Arteries carry blood out of the heart, loading oxygen and unloading carbon dioxide in red blood

cells to be carried to the mammal’s tissues into capillaries, and veins carry oxygen-poor blood

toward the heart (Reece et. al. 2014). Blood also carries white blood cells, platelets, stem cells,

water, ions, proteins, nutrients, wastes, and hormones (Reece et. al. 2014). In the mammalian

respiratory system, air is inhaled through the nostrils and travels to the larynx into the trachea

which branches off into the branchlike bronchi and bronchioles in the lungs (Reece et. al. 2014).

At the end of the bronchioles are alveoli that dissolve oxygen and diffuse it into capillaries for

blood uptake (Reece et. al. 2014). Mammals pull air into their lungs using muscle contraction to

lower pressure and carry out gas exchange and exhales the air by increasing inner pressure

(Reece et. al. 2014). This is because gas travels from areas of high pressure to low pressure.

These systems help with the uptake, management, and emittance of important materials in

mammals, namely oxygen (O2) and carbon dioxide (CO2).

To maintain these processes, mammals employ negative feedback homeostasis.

Homeostasis is the maintenance of conditions at a certain set point through detection of changes,

or stresses, in the environment and responding to reduce the change in the internal environment

(Reece et. al. 2014). The process of homeostasis in organisms is important to maintain an

internal balance (Reece et. al. 2014), allowing organisms to live in a changing environment.

Mechanisms such as gas exchange, nutrient absorption, and maintenance of internal body

temperature can only work in specific conditions, and homeostasis returns them to stable

conditions regardless of the external environment.

One major form of stress on whole-body homeostasis is physical exercise, and numerous

adaptations have been developed in organisms to respond to these changes (Hawley et. al. 2014).

This is due to the increased metabolism through use of skeletal muscle, leading to a response

from numerous homeostatic mechanisms such as nutrient and oxygen supply (Hawley et. al.

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2014). Humans have evolved these adaptions for physical prowess to escape predators and

acquire food (Hawley et. al. 2014). Today, there has been a decline of physical activity (Lavie et.

al. 2015; Vuori et. al. 2013; Martínez-González et. al. 1999). Sedentary lifestyles, or a lack of

vigorous physical activity are associated with an increased risk in obesity, cardiovascular disease

and adverse health effects on numerous human processes (Tremblay et. al. 2010; Booth et. al.

2012). Obesity is currently on the rise and is associated with numerous medical conditions,

including diabetes, cardiovascular disease, pulmonary complications, decreased mobility, and

depression (Pi-Sunyer 2009). Thus, for the sake of public health and healthcare systems, it is

important that the mechanisms of exercise are well-studied and conveyed to the public.

Exercise can involve aerobic exercise, commonly known as cardio; resistance training;

and a combination of both. Aerobic exercises often involve cardiorespiratory endurance

exercises, and resistance training develops strength using external resistance or bodyweight

exercise (Council on Physical Fitness and Sports 1996). A study by Mann et. al. found that

increased calorie expenditure with aerobic exercise reduces cholesterol levels, decreasing risk of

cardiovascular disease from chronically high cholesterol levels. They also found that high-

volume resistance training, which involves the use of lighter weights at higher repetitions, can be

a viable alternative to or complement aerobic training. A combination of aerobic and resistance

training has also been associated with an increase hemoglobin (HbA1c) levels (Church et. al.

2010). However, studies rarely examine the differences between aerobic and resistance training

and its effects on homeostasis.

This experiment will examine the mechanisms of cardiovascular and respiratory

homeostasis after exercise in humans. The homeostatic processes will be measured by breathing

rate and pulse at rest and after strenuous exercise. In this experiment, homeostatic responses of

three types of strenuous exercise will be measured: aerobic exercise, resistance exercise and a

combination of both. This study aims to quantify differences – if such exist – between aerobic

and resistance training on cardiovascular and respiratory homeostasis. Since aerobic exercise

requires an increased uptake of oxygen, this study hypothesizes that both the breathing rate and

pulse will increase more than with resistance training. Resistance exercise involves the use of

skeletal muscle contraction, uses ATP hydrolysis (Reece et. al. 2014) and is more involved with

nutrient and ion uptake, as opposed to gas exchange and heart rate.

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Methods

Homeostatic mechanisms of the cardiovascular and respiratory system were measured

through measuring pulse rate and breath rate of the subject. The pulse rate of the individual was

measured by using the index and middle finger for the carotid pulse (in the neck) and counting

the number of beats over one minute, timed using a stopwatch. Breath rate was measured by

counting the number of breaths taken by one minute using a stopwatch. The rates at rest were

taken after sitting at rest for 5 minutes. After 5 minutes of intense exercise, the pulse and breath

rate were taken immediately after exercise, 2 minutes after exercise, and every 2 minutes after

that for twenty minutes. Between exercise sets, at least 40 minutes passed to allow for pulse rate

and breathing rate to return to rest.

The subject is 20 years old, female, 163 cm tall, weighing 57 kg, and a non-smoker who

is of average fitness and is active 3 times a week. The subject had eaten at least one hour prior to

exercise. The subject underwent three different exercise sets: one consisting of entirely resistance

training, one with aerobic training, and a combination of both at the Trent University Athletics

Complex. The resistance exercise consisted of using weights in which each repetition held every

three seconds for 15 repetitions, so the set is 45 seconds long. Between each set is 30 seconds of

rest. The exercise consisted of doing one set of bicep curls, weighted squats, leg curls, and

dumbbell bench presses each, at a weight that is 5 to 10 lbs. less than what is possible for the

subject to allow for more repetitions, shorter rest time and avoid muscle strain. The aerobic

exercise consisted of jump rope for 5 minutes. The combination exercise was a combination of

half of the resistance training regime (bicep curls and barbell squats) and jump rope for 2.5

minutes. Refer to Appendix Table 1 for the full regimen.

Results

Immediately after exercise, the subject experienced elevated heart rate and breathing rate

compared to resting rate (Figure 1 and Figure 2). Some sweating, flushing of the skin was

observed on the subject after the aerobic exercise and combination exercise, but none after the

resistance exercise. In both aerobic and combination exercises, the pulse rate and breathing rate

are at its highest points immediately after exercise (Figure 1a, 1c and Figure 2a, 2c). The

aerobic exercise yielded the highest pulse rate after exercise at 116 beats per minute, whereas the

combination exercise resulted in the highest breath rate at 22 breaths per minute. There is a

general trend of the rates lowering and fluctuating around the resting rate in the case of pulse

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rate, and at a rate higher than the resting rate for breathing rate. However, in resistance exercises,

the breath rate and pulse rate varied more widely and did not have the same pattern of being the

highest immediately after exercise (Figure 1b, 2b).

(A)

(B)

(C)

Figure 1. The measured pulse rate, in beats per minute, after aerobic (A), resistance (B), and combination (C)

exercise. The resting rate was 75 beats/minute for (A) and 74 for (B) and (C). Note that the resistance exercise

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pulse immediately after exercise is not higher than the following breathing rates and is lower than that of

aerobic (A) and combination (C).

(A)

(B)

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Figure 2. The measured respiratory rate, in breaths per minute, after aerobic (A), resistance (B), and

combination (C) exercise. The resting breath rate for all exercises were 14 breaths per minute. Note that the

rate increases in resistance exercise (B). Also, note that (C) has the lowest breathing rate at 6 minutes after

exercise (8 breaths/minute), and may be an outlier.

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Discussion

i. Homeostatic responses of exercise

Exercise is a stress that involves the increased use of skeletal muscle, which results in a

variety of physiological responses to maintain homeostasis (Hawley et. al. 2014). A dramatic

response is observed due to the increased need for oxygen and ATP to be supplied to muscle

(Hawley et. al. 2014). This procedure measured two of these physiological responses: pulse rate

and breathing rate, to measure the response of the cardiovascular and respiratory system

respectively after 5 minutes of intense exercise. Three different sets of exercise were compared:

aerobic training, resistance training, and a combination of both. As hypothesized, the aerobic

exercises and to a lesser extent, the combination exercise, resulted in a higher rate of pulse rate

and breathing rate than the resistance exercise. Both aerobic and combination exercises resulted

in high pulse and breathing rates immediately after exercise, and then lowered and fluctuated

around a certain point. The pulse rate returned to around resting rate faster than the breathing

rate, which stayed elevated after 20 minutes in aerobic and combination exercises.

Compared to data from similar subjects from previous years (refer to Appendix Table 4),

the numbers for both pulse rate and are generally much higher. There may be unknown factor(s)

contributing to the discrepancy, such as differences in blood pressure, errors in measuring

breathing and pulse rate, or differences in intensity of exercise. However, the pulse rate generally

meets the same pattern of being high immediately after exercise and returning to resting rate, and

the breathing rate remains higher than the resting rate longer than the pulse to return to its resting

rate, which is similar to findings collected in this study.

The respiratory rate was higher than the resting rate even after the recovery period of

exercise in aerobic and combination training due to homeostatic responses in the body. As

breathing, or ventilation increases, there is an increase in oxygen (O2) uptake and carbon dioxide

(CO2) removal (Reece et. al. 2014). The increased presence of CO2 increases the blood pH. In

response, excess carbon dioxide must be released through breathing it out at a faster rate to

maintain homeostasis of blood pH at around 7.4 (Reece et. al. 2014).

Some sweat and flushed skin was observed after aerobic and combination exercise.

Sweating is a cooling mechanism employed by the body to maintain internal body temperature in

response to heat (Reece et. al. 2014). During exercise, the metabolism increases, producing heat

(Reece et. al. 2014). Metabolic heat production can increase up to ten to twentyfold, 30% of

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which is actually used and 70% that must be released (Lim et. al. 2008), which can be done

through sweating. Due to the increased use of skeletal muscle during exercise, it requires

increased blood flow. This results in reduced skin blood flow, or vasoconstriction, to prioritize

skeletal muscle movement (Hawley et. al. 2014), which can result in blanched skin and flushed

skin around muscles.

Once exercise stops, or the stress is removed, the body continues to maintain

homeostasis. The breathing rate slows when the excess CO2 is removed from the body and the

pH returns to normal and the pulse rate slows when there is no longer a need for increased

oxygen to the skeletal muscle.

ii. Aerobic compared to resistance training and both

Knowing how different types of exercise affect homeostasis differently is important when

considering types of exercise to implement for health reasons. Mann et. al. describes that low-

intensity resistance training can be an alternative to aerobic exercise for less mobile individuals.

Aerobic exercise resulted in more dramatic responses to the measured parameters of

cardiovascular and respiratory homeostasis than resistance exercise, which may affect metabolic

homeostasis more. Resistance exercise has also been shown to reduce insulin sensitivity in

adolescents, but seem to have no effects on blood glucose concentration (Sigal et. al. 2014)

However, more studies need to be done.

iii. Limitations

Only one subject was studied and compared to a limited data pool. Further studies could

use multiple subjects to examine individual variation in recovery. Other parameters that could be

included are age, height, weight, fitness level, and other habits such as smoking that may affect

cardiovascular and respiratory homeostasis. For instance, males have a more pronounced sweat

response (Ichinose-Kuwahara et. al. 2010) and a greater ratio of lean body mass than women,

resulting in a higher resting metabolism (Buchholz et. al. 2001), which may suggest sexual

differences in response to homeostasis not covered by this study. This study is only limited to

young, healthy, active females. Another aspect not covered by this study is measurement of the

metabolic homeostatic response, which was hypothesized to be more pronounced in resistance

training.

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Furthermore, as stated above, the exercise may not have been intense enough. Resistance

training may not have a significant effect on pulse and breathing rate, or the weights should have

been heavier to induce more stress.

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References

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diseases. Comprehensive Physiology, 2(2), 1143-1211.

Buchholz, A. C., Rafii, M., & Pencharz, P. B. (2001). Is resting metabolic rate different between

men and women?. British Journal of Nutrition, 86(06), 641-646.

Charkoudian, N. (2003). Skin blood flow in adult human thermoregulation: how it works, when

it does not, and why. Mayo Clinic Proceedings, 78(5), 603-612.

Church, T. S., Blair, S. N., Cocreham, S., Johannsen, N., Johnson, W., Kramer, K., Sparks, L.

(2010). Effects of aerobic and resistance training on hemoglobin A1c levels in patients with type

2 diabetes: a randomized controlled trial. Jama, 304(20), 2253-2262.

Council on Physical Fitness and Sports. Physical activity and health: a report of the Surgeon

General. Sudbury: Jones & Bartlett Learning; 1996.

Hawley, J. A., Hargreaves, M., Joyner, M. J., & Zierath, J. R. (2014). Integrative biology of

exercise. Cell, 159(4), 738-749.

Ichinose-Kuwahara, T., Inoue, Y., Iseki, Y., Hara, S., Ogura, Y., & Kondo, N. (2010). Sex

differences in the effects of physical training on sweat gland responses during a graded exercise.

Experimental Physiology, 95(10), 1026-1032.

Lavie, C. J., Arena, R., Swift, D. L., Johannsen, N. M., Sui, X., Lee, D. C., Blair, S. N. (2015).

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Lim, C. L., Byrne, C., & Lee, J. K. (2008). Human thermoregulation and measurement of body

temperature in exercise and clinical settings. Annals Academy of Medicine Singapore, 37(4), 347.

Mann, S., Beedie, C., & Jimenez, A. (2014). Differential effects of aerobic exercise, resistance

training and combined exercise modalities on cholesterol and the lipid profile: review, synthesis

and recommendations. Sports Medicine, 44(2), 211-221.

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Pi-Sunyer X. The Medical Risks of Obesity (2009). Postgraduate Medicine, 121(6), 21-33.

Reece, J. B., Urry, L. A., Cain, M. L. 1., Wasserman, S. A., Minorsky, P. V., Jackson, R., &

Campbell, N. A. (2014). Campbell Biology (Canadian ed.).

Sigal, R. J., Alberga, A. S., Goldfield, G. S., Prud’homme, D., Hadjiyannakis, S., Gougeon, R.,

Wells, G. A. (2014). Effects of aerobic training, resistance training, or both on percentage body

fat and cardiometabolic risk markers in obese adolescents: the healthy eating aerobic and

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Appendix

Appendix Table 1. Exercise regimen as followed by the subject.

Aerobic 5 minutes skipping with jump rope

Resistance 15 repetitions of 20 lbs. of bicep curls (45 s)

30 s rest

15 repetitions of 10 lbs. of weighted squats (45 s)

30 s rest

15 repetitions of 20 lbs. of weighted lunges (45 s)

30 s rest

15 repetitions of 20 lbs. of dumbbell bench press (45 s)

Combination 15 repetitions of 10 lbs. of bicep curls (45 s)

30 s rest

15 repetitions of 30 lbs. of weighted squats (45 s)

30 s rest

2.5 minutes skipping jump rope

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Appendix Table 2. Rate data of pulse rate for subject at rest and after exercise.

Time After Exercise (min) Aerobic (beats/minute) Resistance (beats/minute) Combination (beats/min)

0 116 79 110

2 88 74 71

4 71 60 78

6 81 76 84

8 71 78 72

10 74 84 80

12 78 78 74

14 78 78 70

16 84 77 78

18 84 72 73

20 84 84 78

At rest 75 74 74

Appendix Table 3. Raw data of breathing rate for subject at rest and after exercise.

Time After Exercise (min) Aerobic (beats/minute) Resistance (beats/minute) Combination (beats/min)

0 19 14 22

2 15 13 17

4 10 11 19

6 14 15 8

8 11 12 12

10 9 13 16

12 12 18 17

14 12 15 18

16 15 18 17

18 9 15 15

20 9 18 18

At rest 14 14 14

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Appendix Table 4. Data collected from previous years containing subjects that meet the same

characteristics as the subject in this study.