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.
If…then…because.
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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
given.
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.
Materials:
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
20°C.
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.
2

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
set-up.
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
set-up.
† 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.
3

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)
25
20
15
10
5
0
-5
Average Time Elapsed after a Number of Lifts for each Temperature
0 10 20 30 40 50
Number of Finger Lifts
0°C
10°C
20°C
30°C
40°C
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.
4

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
Slope
(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)
4.5
4
3.5
3
2.5
2
1.5
1
0.5
0
Slope Comparison for each External Temperature
0°C 10°C 20°C 30°C 40°C
Temperature
Slope
Comparison
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.
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Conclusion:
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?
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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
Comment:
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.
7

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
URL.
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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