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,

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.

the energy source for all muscles, is required for a muscle contraction to take place. Usually, ATP is created aerobically, with the presence of O2. If O2 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, Ca2+, 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 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.

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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.

Independent variable: Temperature of external environment 0°C, 10°C, 20°C(control), 30°C, and 40°

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.

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: 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. *

This may require a second person to record time values.

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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.

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, Sx, 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.

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Average Time Elapsed after a Number of Lifts / seconds 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)

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.

# of Lifts

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!

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.

Dr. Funk 4/1/09 2:09 PM Comment: Data has been clearly analyzed. Reference to specific data is appropriate.

Average Time Elapsed after a Number of Lifts for each Temperature

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.

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Time Elapsed (seconds)

20

0°C 15

10°C 20°C

10

30°C 40°C

5 0 0 -5

10

20

30

40

50

Num ber of Finger Lifts

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This graph visually represents the changes in the slopes for each external temperature Dr. Funk 4/1/09 2:10 PM Comment: A solid discussion of the graph.

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 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 Slope (Δtime/Δlifts)

10°C 3.94

20°C 3.93

30°C 3.46

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.

40°C 3.06

2.87

Slope (change in time/change in number of lifts)

Slope Com parison for each External Tem perature 4.5 4 3.5 3 2.5

Slope Comparison

2 1.5 1 0.5 0 0°C

10°C

20°C Tem perature

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.

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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.

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.

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

Dr. Funk 4/1/09 2:15 PM Comment: A discussion of whether the hypothesis was supported or refuted includes reference to specific data.

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

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.

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,

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?

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 6

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

Dr. Funk 4/1/09 2:23 PM Comment: Following each limitation, an improvement is suggested and discussed for the next time around.

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

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

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.

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.

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

Dr. Funk 4/1/09 2:23 PM Comment: Final thoughts about the lab would be appropriate here.

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 2:24 PM Comment: Notice that the entire lab is written in third person. Do not ever use first or second person.

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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 .

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"Lactic Acid Not The Culprit In Muscle Fatigue." Science News, Research And Discussion. 02 Mar. 2009 .

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"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 .

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

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