Stretched to the limit? Strained for a knockout science project? Loosen up and make a plan! (Write A Procedure).

Every year, about 3 million American kids and teens suffer sports-related injuries, according to the American Academy of Pediatrics (AAP). The most common damage: sprains(wounds to the tough, stretchy ligaments that connect bones) and strains (torn or stressed muscles).

Should you hang up your sneakers and become a couch potato? No way. The payoffs of exercise far outweigh the health cost of sports injuries, say the National Institutes of Health. "But if injury prevention is the goal, athletes should increase their warm-up, even before stretching," says sports-medicine expert Dr. Ian Shrier. Doing a warm-up like a slow jog increases the blood flow in your muscles, which warms them and increases their flexibility (ability to stretch).

Wonder how temperature affects your flexibility? Sounds like a science project! Since both muscles and gummy worms are stretchy, spare yourself o potential muscle strain and use gummy worms instead. Not only are the gooey candies easier to experiment on--you can chomp them as you investigate. So, here's your research question: How does temperature affect flexibility? To find the answer, you need a step-by-step procedure. Your first plan might look like the initial procedure (1), left.

(1) INITIAL PROCEDURE

1. Stretch a gummy worm to assess how much resistance (opposing force) it gives you.

2. Roll the gummy worm rapidly between your palms for a minute. Measure its temperature.

3. Stretch the worm again.

Easy project? Not exactly. A good experiment should be easily repeated. Can your friends repeat your experiment just as you did it? Probably not. Sweeten your procedure by adding details. Here's a checklist to help you:

Checklist

[check] What materials will you need? Make a list. Include amounts and measurements.

[check] Test one independent variable (the characteristic you change on purpose) at a time. In this experiment, your independent variables are the temperature of the gummy worm and the amount of time you warm or cool it.

[check] Identify a dependent variable (the characteristic that responds when you change the independent variable). In this case, flexibility is the dependent variable.

[check] Keep all other variables, like the gummy worm brand, constant (unchanged).

[check] Include a control, or standard, to compare against your test variables. Your control could be a room-temperature gummy worm.

[check] Repeat the experiment. Did you get the same results? Glitches in the first trial can skew your data.

Consider these tips, then rewrite your plan. It should be easy to follow, like the improved procedure (2), right. Make sure your plan is safe, accurate, and complete. And when you think your plan is near the finish line, conduct a trial run.

Finally are there ways to improve the experiment?

(2) IMPROVED PROCEDURE

You Need

* 4 identical gummy worms
* 12-inch (30.5 cm) ruler
* thermometer
* ice cubes
* stopwatch or watch with
  second hand
* 2 heat-resistant bowls or
  containers
* 2 small zip-top baggies
* rubber gloves
* paper towels
* paper
* pen or pencil

To Do

1. Create a data (to make one, see p. 24).

2. Place each gummy worm lengthwise on a ruler. Measure its unstretched length in centimeters. Record each length beneath a column labeled "Length Before."

3. Choose one gummy worm to be your control and put it aside. Place two gummy worms in individual zip-top baggies. Squeeze air out of each baggy before sealing.

4. Take your control worm and stretch it alongside the ruler as far as you can without breaking the worm. Record the measurement in the "Length After" column of your data table.

5. Take a second worm and roll it vigorously between your hands for 4 minutes to warm it up. Immediately stretch it along the ruler and record the length of the stretch in the "Length After" column.

6. Carefully fill one container with HOT tap water. Take a bagged worm and place it in the hot water for 4 minutes. Measure and record the temperature of the water in the "Temperature" column on your data table. Taking care not to get the worm wet, remove it from the baggy and stretch it along the ruler as far as you can without breaking the worm. Record the measurement in the "Length After" column.

7. Fill another container with ice water. Submerge the remaining bagged worm in the ice-water bath for 4 minutes. Measure and record the temperature of the water in the "Temperature" column. Taking care not to get the worm wet, remove it from the baggy and stretch it along the ruler as far as you can without breaking the worm. Record the measurement in the "Length After" column.

8. Compare the results in your data table.

Conclusion

How does temperature affect a gummy worm's elasticity? Why? How do you think this experiment relates to your muscles' flexibility?

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