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Superhuman Bodies

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KS3 / Biology / Structure and Function of Living Organisms / The Skeletal and Muscular Systems

Many superheroes are well known for having super strength and stamina. Superman was pictured in his first comic book lifting a whole car! Strength can be a result of training, like Batman, or being given ‘super serum’, like Black Widow. Muscles like biceps in your arms and quadriceps in your legs are known as skeletal muscles because they attach to the skeleton to generate movement. They often work in pairs and are called antagonistic pairs because they work ‘against’ each other. One muscle in the pair will bend a joint in the bones of the skeleton, and the other will straighten it.

Exercise can help muscles to grow and increase in strength, along with eating enough protein as part of a balanced diet. Growth of muscle cells is known as hypertrophy. So, it is possible to become stronger without being exposed to gamma radiation, like the Hulk, or spider bites, like Spiderman!

Can you think of sources of protein you could include in your diet to support muscle growth?

Task: Investigating Muscle Stamina

Strong muscles can move heavy loads and repeat movements without getting tired quickly. They can also recover from doing exercise quickly. Superheroes need to be ready to go at any time!

Your task is to measure if being able to rest between exercise (lifting an object) has an effect on your muscles. When muscles get tired it is called fatigue. If you tried to lift a heavy weight (like Superman lifting the car*) would you be able to do it as well each time you tried?

*Don’t try lifting a car. The record for the greatest number of times the rear of a car has been lifted clear of the ground (i.e. the rear wheels are not touching the ground) in one hour is 580! The car weighed 810 kg.


You will be working scientifically to:

  • Make and record observations and measurements
  • Interpret data and make conclusions



  • 1 kg mass (you can use a 1 litre bottle of water if you don’t have a mass)
  • Stopwatch
  • Protective material (such as a thin cushion, folded up towel or exercise mat)



  1. Rest your elbow on a table and have the protective material underneath where your hand rests on the table.
  2. Hold the 1 kg mass in your hand.
  3. Start the stopwatch and record how many times you can lift the mass in 2 minutes. Your hand must touch the table at the beginning of each lift and touch your shoulder at the end of the lift.
  4. Record the number of lifts for minute 1 and minute 2 without rest.
  5. Repeat again, but lift the mass for 1 minute, rest for 30 seconds, then lift again for 1 minute.
  6. Repeat once more, but lift the mass for 1 minute, rest for 1 minute, then lift again for 1 minute.



Number of times mass lifted

1st minute

2nd minute

Total number of lifts

No rest

30 second rest

1 minute rest

Thinking about your results:

  • Which test showed the greatest level of fatigue? How could you tell this?
  • Describe the pattern in the results from minute 1 to minute 2 with no rest between minutes. Did not having a rest affect your muscles ability to perform the lifts?
  • Describe what pattern you see as the rest period increases. Does it have an effect on your muscles ability to perform the lifts?
  • Can you think of any other variables that might affect how your muscles fatigue?