Effects of 8 weeks of free-weight and machine-based resistance training on knee muscle function

This study is looking for healthy adult men aged between 18 and 35 years old. To join, you should be generally healthy, with no major long-term illnesses like diabetes or heart disease. It's also important that you haven't recently had a serious injury to your back or legs, or any surgery in these areas. Your Body Mass Index (BMI) should be in the healthy to slightly overweight range (18.5 to 29.9).

You won't be able to take part if you've had major leg injuries or surgery in the past, or if you currently have pain, swelling, or problems moving your legs. Conditions like severe arthritis, bone disorders, or nerve conditions that affect muscle control would also prevent you from joining. Similarly, if you have certain heart conditions or are taking medications that might affect the study results, you wouldn't be eligible. The researchers want to make sure everyone in the study is in a similar health condition for fair testing.

If you take part, you'll first be randomly assigned to one of two groups: either the barbell squat group or the leg press group. This means a computer will decide which exercise you do, like flipping a coin. Once assigned, you'll have an initial appointment lasting about two hours. During this session, you'll fill out some questionnaires, and researchers will measure your thigh circumference and muscle thickness using a safe ultrasound scan. They'll also attach small sensors to your skin (which might need a little shaving first) to measure muscle activity during jumps and other movements. You'll also do strength tests to find your maximum lifting weight.

After this initial assessment, you'll start your training. You will visit the University of Birmingham twice a week for eight weeks for supervised workouts, with a rest day or two between sessions. Each training session will involve a warm-up and then 5 sets of 5 repetitions of either barbell squats or leg presses. The weight you lift will gradually get heavier as you get stronger, with a lighter "deload" week every three weeks to help manage tiredness. Throughout the study, you'll have a total of 19 sessions: 12 training sessions, 2 lighter training sessions, 1 practice session, and 4 special sessions where the researchers repeat some of the initial measurements to see how your body has changed. The total duration of your active participation will be 8 weeks of training plus the initial and follow-up assessment sessions.