Question

The chin-up is one exercise that can be used to strengthen the biceps muscle. This muscle can exert a force of approximately 800 N as it contracts a distance of 7.5 cm in a 78 kg male. How much work can the biceps muscles (one in each arm) perform in a single contraction?
1 J
Compare this amount of work with the energy required to lift a 78 kg person 40 cm in performing a chin-up. How much is required?
2 J
Based on this analysis, could the biceps muscle be the only muscle involved in performing a chin-up?

Answer 1

To find the work done by the biceps muscles, we can use the formula W = F x d, where W is the work done, F is the force exerted, and d is the distance over which the force is exerted.

W = 800 N × 0.075 m = 60 J

Since there are two biceps muscles (one in each arm), the total work done by both muscles during a single contraction is:

Total work = 60 J + 60 J = 120 J

Now, let's compare this to the energy required to lift a 78 kg person by 40 cm.

The force required to lift a 78 kg person is equal to their weight, which is the mass times the acceleration due to gravity (9.81 m/s²):

Force = mass × gravity = 78 kg × 9.81 m/s² = 765.18 N

The work required to lift the person by 40 cm (0.4 m) is:

Work = Force × distance = 765.18 N × 0.4 m = 306.072 J

Comparing the work done by the biceps muscles (120 J) to the work required to lift a person (306.072 J) in performing a chin-up, we can see that the work done by the biceps muscles is less than the work required to lift the person.

Therefore, based on this analysis, the biceps muscle cannot be the only muscle involved in performing a chin-up. Other muscles, such as the back and shoulder muscles, also contribute to the necessary force and work needed for this exercise.