It depends on your fitness level, but only a few reps are good for beginners.
When you can do 8 reps with a weight easily it's time to add weight to the machine or the bar.
This depends entirely on your own capabilities. A short answer is that you should complete as many as you can with perfect form. When you break form (either due to lifting to heavy of a weight, or doing more reps than necessary) stop working the muscle as effectively and you increase your risk of injury.
To effectively target your core muscles on the abdominal crunch machine, aim to do 3 sets of 10-15 reps with proper form and control.
More reps will build muscle, not more weight, after a while you can add more weight and more reps.
It depends on your desired results. For getting stronger and bigger, use a lot of weight and low repetition. I would recommend 2-3 sets of 8 reps with however much weight you can handle for that amount. For getting more toned and gaining endurance, use low weight and high reps. I would recommend 3-4 sets of 12-15 reps.
The number of plates you should use on the leg press machine for an effective workout depends on your fitness level and goals. Start with a weight that allows you to perform 8-12 reps with proper form, and adjust as needed to challenge yourself without sacrificing technique. It's important to listen to your body and gradually increase the weight as you get stronger.
I bench 190 for 5 reps and 185 for six reps and I weigh 142
With the appropriate weight you should be able to do 3 to 4 set with 6-8 reps.
I was always taught that low weight with high reps is for weight loss and toning, whereas high weight and low reps is for strength training and bulking up.
Generally a good workout weight is the weight at which you can do at least 8 reps but no more than 12 reps. If you are able to do more reps, try going heavier. If you are training for strength, use fewer than 8 reps but go heavier on the weight.
more weight less reps more weight less reps
in each workout you must increase either weight lifted or reps with previous weight or sets, if you want to keep growing...