In intervention studies, is it required to have a Control group to authenticate the study?

In our study, we are measuring the effect of exercise on muscle fibre size and neural control. The STUDY group (sample size 20) will have certain parameters measured before the exercise and then, the same parameters will be measured after the exercise. Thus the data will consist of pre-exercise values and post exercise values. If the participants are within the normal distribution curve of the population (healthy, adults), is it required to have a CONTROL group?In intervention studies, is it required to have a Control group to authenticate the study?
It's -always' best to have a control group to minimize the effects of any 'hidden' variables within the experiment.





Doug