IB Biology HL Internal Assessment
The effect of load on heart rate
Research question: To what extent does the heart rate change in teenagers
aged 17-19 when working at 65 per cent (15 repetitions) compared with 90 per
cent (4 repetitions) of their one-repetition maximum when using the leg press
machine in the gym?
Anne Breitenstein
Table of Contents
1. Personal Engagement.....................................................................................................2
2. Aim.................................................................................................................................3
2.1 Research question.........................................................................................................3
2.2 Hypothesis....................................................................................................................3
3. Variables........................................................................................................................3
4. Background information.................................................................................................5
,5. Procedure for determining each participant´s one-repetition maximum (1RM)...............6
5.1 Procedure for determining 65 and 90 per cent of each participant´s 1RM.....................7
5.2 Method:........................................................................................................................8
6. Safety, ethical or environmental issues...........................................................................8
8. Data presentation.........................................................................................................11
9. Paired t-test..................................................................................................................13
10. Conclusion..................................................................................................................14
11. Evaluation..................................................................................................................14
12. Appendix....................................................................................................................15
13. Bibliography...............................................................................................................17
1. Personal Engagement
Whilst thinking about which topic or theme to choose for my Internal Assessment, I
knew from the beginning I wanted to do an experiment with humans, rather than a
scientific one in the lab with different concentrations and solutions. One of the
reasons why is because I have always been very outgoing, especially as a kid, and
interacting with people is something I love doing. I fancied doing my Internal
Assessment on a topic I genuinely cared about so after establishing I wanted to do a
human investigation, I began to think about my interests and hobbies and decided to
write them all down on a piece of paper. This really helped me to visualize my
thoughts more effectively. I then numbered each of them from 1 to 10, 1 being the
most interesting and important to me, 10 being the least.
The topic of health and fitness was numbered 1. I am very fascinated about the
importance of keeping fit and taking care of yourself, whether that be mentally or
physically, and one aspect of that for me is fitness. I discovered my passion for the
gym a year and a half ago.
At the beginning of my fitness journey, I paid more attention to the physical benefits
that the gym could bring to me, as well as to the number in the scale or the number
of calories burned in the treadmill. Over time, the gym has become much more than
that. It has become a place where I can simply work and focus on myself, and
distract myself from all the worries or stress that arise from school or my personal
life. The gym has made me realize that real strength arises from the ability to make
yourself do things even when you do not want to, and it has taught me to rely on self-
discipline because motivation comes and goes.
, My obsession with the number on the scale or calories burned reduced once I
became aware of the principle of progressive overload, which consists of increasing
the weight of the exercise (load), the repetitions or sets performed over time. Once I
began to apply progressive overload to my workouts, I noticed I felt better mentally,
more powerful, stronger, as well as more confident in myself. However, I was
somewhat confused as I could not really figure out when it was that my body was
actually working the hardest: when I was lifting light weights or when I was lifting
heavier weights. In both occasions, I would sweat, and both my heart rate and
breathing rate would increase. However, I could not determine which one actually led
my body to work the hardest, as I did not own an Apple Watch nor a heart rate
monitor to compare and measure the intensity of my workouts.
Therefore, I became curious to know, and after being unable to find much relevant,
specific information on this topic, I decided to explore it myself by gathering my own
data and bringing forward my own procedure. Though there are many ways to
measure exercise intensity, I decided that measuring the heart rate was going to be
the most helpful measure as it is a very common one, and offers a more objective
look at exercise intensity. The reasons why will be explained further down.
2. Aim
To investigate how the heart rate of teenagers aged 17-19 changes when working at
65 per cent (15 repetitions) compared to when working at 90 per cent (4 repetitions)
of their one-repetition maximum when using the leg press machine in the gym.
2.1 Research question
To what extent does the heart rate of teenagers aged 17-19 change when working at
65 per cent (15 repetitions) compared with 90 per cent (4 repetitions) of their one-
repetition maximum when using the leg press machine in the gym?
2.2 Hypothesis
My alternative hypothesis, (H1), is that working at 65 per cent (15 repetitions) of the
one-repetition maximum leads to a higher heart rate than working at 90 per cent (4
repetitions). This is because
My null hypothesis, (H0), is that working at 65 per cent (15 repetitions) and 90 per
cent (4 repetitions) of the one-repetition maximum will have the same effect on heart
rate.
3. Variables
3.1 Independent Variable: The independent variable in this experiment is the 65 per
cent (15 repetitions) and 90 per cent (4 repetitions) of the participant´s one-repetition
maximum. Details of how these will be determined will be stated later in this
investigation.
3.2 Dependent Variable: The dependent variable in this investigation is the change
in heart rate. It will be measured at rest and after both 4 and 15 repetitions are
performed, using a heart rate monitor, with a degree of uncertainty of +/- 1 beats per
minute. It will be used to later calculate the mean percentage heart rate change.
3.3 Controlled Variables:
Type of exercise: The type of exercise performed must be the same for each
participant, and in this investigation, it is the leg press machine. This is
