Sample IB Biology Lab

Sample IB Biology Lab

Factors Affecting Muscle Fatigue:

The Effect of External Temperature on the Rate of Index Finger Lifts

Background Information:

Muscle fatigue has many factors that come into play. ATP, adenosine tri-phosphate,

the energy source for all muscles, is required for a muscle contraction to take place. Usually,

ATP is created aerobically, with the presence of O 2 . If O 2 is depleted, the body switches to

anaerobic ATP production. Anaerobic metabolism produces lactic acid as a byproduct. Some

scientists have reason to believe that lactic acid is not the culprit in muscle fatigue though. 3

Calcium, Ca 2+ , however, does affect muscle fatigue. Studies have shown that tiny

leaks of calcium in the muscles stimulates an enzyme which attacks muscle fibers. These

calcium leaks accelerate the onset of muscle fatigue, although it is more prevalent in athletes

who push their muscles regularly, thus not really pertaining to this investigation. 4

ATP is required in the sarcomere of a muscle cell to release the myosin cross head

bridge from the actin molecules. If there is not a sufficient amount of ATP, the myosin

remains attached to the actin, and can no longer swivel. Regardless of whether or not there is

still a presence of calcium, without the ATP, the muscle fatigues. 2

Homeostatic mechanisms in the body take into account the external temperature of the

body, and with a negative feedback response, adjust the body accordingly to prolong life.

Thermoregulation acts when the body is in undesirably low temperatures, senses by receptors

on the skin. Blood vessels constrict so as to keep in as much heat as possible. Sometimes, in

extreme cases, blood flow is reduced to a very minimal level to the body’s extremities, such

as the hands, to save the body’s core systems. Because of this, less oxygen is delivered to

muscles in lower temperatures, thus inducing a switch to anaerobic metabolism quicker than

in higher temperatures. 1

Dr. Funk 4/1/09 1:58 PM

Comment: Background information is

focused on the specific lab topic. It gives

information that is key to understanding what

is going on in the lab better. This information

may also be used in the conclusion to support

or refute the hypothesis.

Research Question: What is the effect of varying external temperatures on the rate of index

finger lifts for a 17-year-old female? How does this speak to muscle fatigue onset?

Hypothesis: If the muscles which raise the index finger are exposed to varying external

temperatures, then the rate of index finger lifts will increase as the temperature of the external

environment rises, because when muscles fall below desired temperatures blood vessels

constrict decreasing the amount of oxygen to the muscles which aids in the production of ATP

and the onset of muscle fatigue, while higher temperatures dilate the blood vessels and allow

more oxygen to reach the muscle enabling higher endurance.

Dr. Funk 4/1/09 1:59 PM

Comment: A focused research question that

includes both the IV and the DV.

Dr. Funk 4/1/09 2:00 PM

Comment: Hypothesis includes a prediction

for specific responses to the IV. In addition, it

has reasoning for why this might be true.



Independent variable: Temperature of external environment

0°C, 10°C, 20°C(control), 30°C, and 40°

Dependant variable: Rate of index finger lifts

Calculated by # of finger lifts (50) / time taken to perform finger lifts(seconds)

Control: Rate of index finger lifts at 20°C, or room temperature.

Constant Variables:

• Type of finger - index: different fingers have different strengths and thus different

finger endurances. Changing fingers skews the results.

• Hand – non-dominant: The dominant hand on a person has greater endurance than the

non-dominant hand, thus changing hands would skew results.

• Person – 17-year-old female: Different people have different finger endurances, thus

not keeping the person performing the finger lifts constant would skew results.

• Surface of action – flat counter: different surfaces could make the finger lifts

easier/harder. Lifts need to remain the same difficulty throughout the lab.

• Height of lift – 5cm: Not lifting high enough would give an underestimate of the time,

while lifting too high would give an overestimate of time.

• Arm position: differing arm positions could alter the amount of blood flow to the

finger, which must remain constant.

• Altitude of action: Oxygen amounts inhaled must remain constant, and changing

altitudes during the lab would skew the data.

Dr. Funk 4/1/09 2:02 PM

Comment: Both the IV and DV are clearly

identified. The range of the IV is also clearly


Dr. Funk 4/1/09 2:02 PM

Comment: Control is clearly identified.

Dr. Funk 4/1/09 2:01 PM

Comment: This section explains the impact

that each of the controlled variables might

have on the results if they are not kept constant

in each trial. Several different factors that

could affect the outcome are considered and

discussed here.


Ruler, index finger of the left hand of a 17-year-old female, water, heat source for water, ice,

thermometer (°C), stopwatch, towel, calculator

Procedure * :

Data Collection:

1. Start by performing this procedure in room temperature external conditions, close to


2. Have a test subject perform 50 finger lifts with the index finger of their left hand while

another person times them. Record times on data table.

a. Timer must record time every 10 finger lifts until the test subject has reached

50, at which time would be considered the “total time”.

3. Repeat exercise an additional two times.

4. Change the external temperature of the subjects finger by creating a water bath with

the set temperature of either 0°C, 10°C, 30°C or 40°C.

5. Place hand in water bath for 5 minutes, to allow the hand’s muscles, blood vessels,

and skin to adjust.

6. Remove hand from water bath, dry with a towel, and repeat steps 2-3. Remember to

record data every set of 10 finger lifts.

7. Adjust water bath for another temperature and repeat exercise until data has been

collected for all five temperature settings.

Dr. Funk 4/1/09 2:04 PM

Comment: The procedure is specific, written

in third person, and has included the controlled

variables. In addition, there is a good range of

data for the IV being collected (0˚C-40˚C) as

well as multiple trials for each level of the IV.

* This may require a second person to record time values.


Data Processing:

1. Calculate the average of each trial by adding up the times and dividing by three to find

the average.

Dr. Funk 4/1/09 2:04 PM

Comment: The formulas for processing data

are clearly given. In addition, the data is

manipulated and processed in a variety of ways

to better understand the results.

2. Calculate † the uncertainty, or standard error, by dividing the sample standard

deviation, S x , of the data by the square root of the number of observations/trials, n.

a. Standard deviation can be calculated as

b. Plug in the standard deviation into the following equation for standard error,

where n is the number of observations/trials:

3. From the average values calculated for each trial, translate data into a line graph,

where the Number of Finger Lifts is on the x-axis and the time taken to perform that

Number of Finger Lifts on the y-axis.

a. There should be 5 lines – one for each external environment temperature.

b. Uncertainty values are included as error bars.

4. Calculate the rate of finger lifts by dividing 50 lifts by the average total time for each

temperature setting after adding and subtracting the uncertainty. There should be a

range two values, thus offering a range of rates.

Diagram of height

regulation and finger lift


Dr. Funk 4/1/09 2:05 PM

Comment: Diagrams for the experimental

design are provided and clearly labeled.

Diagrams can help to explain any experimental


† A calculator will make calculations easier. Enter data for trials in a list, and STAT>CALC>1-Var Stats will

give you the mean and standard deviation of the data in the list.


Average Time Elapsed after a Number of Lifts / seconds

# of Lifts 0°C 10°C 20°C 30°C 40°C

10 4.06± .1 3.76± .1 3.66± .3 2.95± .1 2.85± .1

20 7.97 ±.2 7.55± .1 7.13 ±.2 5.99 ±.1 5.64 ±.2

30 11.8 ±.2 11.7 ±.1 10.6 ±.3 9.12 ±.2 8.45 ±.3

40 15.9 ±.4 15.6 ±.3 13.9 ±.3 12.15± .1 11.48± .3

50 19.8 ±.1 19.4 ±.3 17.4 ±.5 15.33 ±.1 14.34 ±.3

Rate (# of

lifts/total time) (2.45, 2.52) (2.54, 2.62) (2.78, 2.95) (3.2 , 3.3) (3.4 , 3.6)

Each value for the averages has its own uncertainty because a standard error method for

calculating uncertainty was used. Because each set of trials has a different standard deviation,

each average also has a slightly different average uncertainty.

The ranges for all 5 external temperatures seems to be about the same, so the spread is

consistent, however the minimum and maximum values differ greatly, especially between 0°C

and 40°C. This shows that higher external temperatures correlate with faster finger lifting

action for the 50 finger lifts.

The rates also correspond to an inclination for faster action at higher temperatures. The

interval is created from the highest and lowest values with the uncertainty calculated in for the

total time. There is no overlap between these intervals, suggesting that there is a significant

different between the external temperatures. Higher rates equate to higher endurance of the

fingers, and less fatigue in the muscles, seen in the higher temperatures like 30°C and 40°C.

Time Elapsed (seconds)








Average Time Elapsed after a Number of Lifts for each Temperature

0 10 20 30 40 50

Number of Finger Lifts






Dr. Funk 4/1/09 2:08 PM

Comment: Raw data is included on a

separate data and should be inserted at this

point in the lab.

A separate table for the processed data is

included. The table has a title and is clearly

labeled. Units are given. In addition,

uncertainties are provided in each box for the

processed data.

Dr. Funk 4/1/09 2:08 PM

Comment: Rates are easy to calculate and

often are very appropriate for explaining the

data. Be sure to include units!

Dr. Funk 4/1/09 2:09 PM

Comment: Data has been clearly analyzed.

Reference to specific data is appropriate.

Dr. Funk 4/1/09 2:10 PM

Comment: The graph is of processed data

only! The title is clear and includes both the IV

and the DV. Axes are labeled and units have

been given. A different color is used to

represent each level of the IV. Error bars are

also included.


This graph visually represents the changes in the slopes for each external temperature

as well as a visual comparison for times at each interval of Number of Finger Lifts (10, 20,

30, 40, and 50). Error bars of many of the closer temperatures seem to overlap. This could

Dr. Funk 4/1/09 2:10 PM

Comment: A solid discussion of the graph.

suggest that these data values are not significantly different; if we look at the extremes in

temperature however, there is no overlap. External temperature does seem to have an effect

on the onset of muscle fatigue in the left index finger of a 17-year-old female.

Slopes of Best-Fit Lines for Each External Temperature

0°C 10°C 20°C 30°C 40°C


(Δtime/Δlifts) 3.94 3.93 3.46 3.06 2.87

Dr. Funk 4/1/09 2:14 PM

Comment: Data was processed in several

ways for this lab. This table shows the slopes

for each line in the graph (with calculations

provided). This data is then included in a graph

which is followed by an explanation of what

this all means and why this calculation was

useful for understanding the data.

Slope (change in time/change in

number of lifts)











Slope Comparison for each External Temperature

0°C 10°C 20°C 30°C 40°C




These slopes represent the inverse of the rate. Temperatures with a higher slope signify that

more time was required to complete the finger lifts, thus showing a build-up of fatigue in the

muscles. Lower temperatures such as 0 and 10 seem to have higher slopes of their lines

meaning that muscle fatigue onset quicker than in lower slopes.



The purpose of this investigation was to explore a factor that affected muscle fatigue.

An independent variable of external environment temperature was applied to a dependant

variable of time taken to complete 50 finger lifts. Specifically, the question asked the effect of

external temperature on the rate of index finger lifts in the left hand of a 17-year-old female.

The hypothesis inferred that with an increase in external temperature there would be

an increase in the rate of index finger lifts. From these data, the hypothesis is supported. The

interval created for the rates of finger lifts for each external environment temperature

increased as the temperature increased, thus showing a positive association between the two

variables. Higher rates signified more activity, indicating a higher level of endurance and

ultimately a later onset of muscle fatigue. Conversely, the slopes of the lines, which signified

the change in time divided by 50, decreased as the temperature increased, a negative

relationship, also supporting the hypothesis – a higher slope indicates slower activity,

implying less endurance, implying an earlier onset of muscle fatigue. From the background

information, the hypothesis asserted that this relationship was caused by primarily the effect

temperature has on the blood circulation of the extremities, like the index finger. It is known

that as temperature dips below desired levels the body restricts blood to the extremities, as

their blood vessels constrict. Less oxygen is available to tissue in areas like this, thus

inhibiting adequate muscle function, and inducing an onset of muscle fatigue earlier than

when there are warmer temperatures because of less ATP to the muscles which inhibits the

myosin heads to release from the actin fiber. Warmer temperatures allow adequate blood flow

to all parts of the body, including extremities such as the index finger. This explanation fits

the data observed in this investigation.

Because muscle endurance and ability is so variable between humans, and even within

the same human, this lab cannot really generalize for a whole population. As a matter of fact,

there are numerous limitations and weaknesses in the design of the investigation. The most

significant error to this lab was the treatment of the external environment. Although a water

bath was suitable for exposing the hand to different temperatures very quickly, whenever the

hand was removed from the water bath to perform the activity heat was either lost or gained to

or from the atmosphere. The external temperature did not remain constant throughout the

trials for this reason, and the data becomes questionable as to its ability to show a relationship

Dr. Funk 4/1/09 2:14 PM

Comment: The conclusion begins with a

restatement of the data followed by the initial

hypothesis for the lab.

Dr. Funk 4/1/09 2:15 PM

Comment: A discussion of whether the

hypothesis was supported or refuted includes

reference to specific data.

Dr. Funk 4/1/09 2:16 PM

Comment: The results of this lab are

justified by research from the literature. Did

you get the results that were expected based on

the background information? If not, what

problems existed in the lab or what factors

contributed to the results.

Dr. Funk 4/1/09 2:18 PM

Comment: A discussion of the limitations

and/or weaknesses in the lab. Each limitation is

identified AND discussed. Why is it a

limitation? What could be done differently?


etween temperature and muscle fatigue onset. To avoid this weakness in further

investigations, one would suggest using methods to actually change the temperature of the

environment surrounding the place of activity. A ice box cooler, or cold day, could offer

lower temperatures while a sunny hot day could offer the warmer temperatures. Although,

problems remain with that kind of set up – one could not accurately change the temperature of

the environment, rather only use what is available. Also, you could not control temperature

anymore, because one would have to wait for that warm day, or cold day. Adequately

controlling the external atmospheric temperature was a major weakness in this investigation.

Another weakness was the method of counting the number of finger lifts. An arbitrary

method of just counting by listening to when the finger hit the table was used, however I

admit that I may have missed a few, or accidently added a few – human error. Because of this,

I would suggest a method in which a computer records the cumber of finger taps performed.

Perhaps a sensor under your finger could detect the pressure changes when lifting the finger

and replacing it. There was also a weakness in regulating the height of the lift. If the test

subject did not lift to the full height, the data produced an underestimate of the true value,

while lifting too high would produce an overestimate. Fixing this would entail placing a

platform at the specific height of the desired lift, and requiring the test subject to touch the

platform each time. Once again, some sort of computerized pressure sensor would offer more

accurate data.

Finally, because this lab was so specified to the abilities of a single finger on a single

hand of a single 17-year-old female, no generalizations could be made. Perhaps comparisons

of age, gender, altitude, or any other constant variables for this experiment would be

worthwhile. While variables like age and gender could speak to muscle capability, a variable

such as altitude could speak to the oxygen differences in habitants of different altitudes.

Dr. Funk 4/1/09 2:23 PM

Comment: Following each limitation, an

improvement is suggested and discussed for

the next time around.

Dr. Funk 4/1/09 2:23 PM


Dr. Funk 4/1/09 2:18 PM

Comment: Several limitations are evaluated.

None of these says, “I messed up!” Do not

include a limitation like this.

Dr. Funk 4/1/09 2:23 PM

Comment: Final thoughts about the lab

would be appropriate here.

Dr. Funk 4/1/09 2:24 PM

Comment: Notice that the entire lab is

written in third person. Do not ever use first or

second person.


Works Cited

1 BiologyMad A-Level Biology. 02 Mar. 2009


Dr. Funk 4/1/09 2:25 PM

Comment: Sources are correctly sited,

including the date they were accessed and the


2 "Human Physiology - Muscle." EKU People. 02 Mar. 2009


3 "Lactic Acid Not The Culprit In Muscle Fatigue." Science News, Research And

Discussion. 02 Mar. 2009


4 "Muscle Fatigue - What Causes Muscle Fatigue and Muscle Pain During Exercise."

Sports Medicine, Sports Performance, Sports Injury - Information About Sports

Injuries and Workouts for Athletes. 02 Mar. 2009


5 "Wikipedia." Standard Deviation. 22 Aug. 2008



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