All of your selected weights should allow you to perform the prescribed repetitions or time while maintaining "good" form.
Once your form is broken, either through a change in the execution quality of the lift or by a significant change in the speed of the lift, you should not continue the set. This is often referred to as leaving one rep in the tank, where you should feel that you could have performed at most one more "good" rep. You should not train to muscular failure, as this has been identified as increasing your risk of injury; however, make sure that you are still using challenging weights!
In the above scenario, where a weight or progression is negatively effecting your form, then it's also an option to lower the weight or choose a regression so you can finish the set/interval.
Keeping a log of your weights and reps is very important so you can track any changes. In fact, your workout templates are designed so that you can easily print out the forms and fill in your weights, creating your own workout journal. For each change in the reps, you should assume a 5-10 pound change, depending on the exercise. Be sure to monitor your fatigue. If you need to keep the weight or even drop the weight on subsequent sets in order to maintain your form, do so.
When the routine calls for bodyweight exercises, the resistance can be adjusted in accordance to the required repetitions in your program by using external loading, such as by using a dip belt during pull-ups (eventually :D), elevating your feet during push-ups, or by changing the tempo to make the exercise more explosive. In addition, you can also regress bodyweight exercises if you need to make them easier for higher-rep sets, such as performing push-ups with your hands elevated.
For unilateral or one-sided exercises, such as lunges or step-ups, the required repetitions can be performed either for each side (ea) without alternating, or alternating in which case I will indicate "total reps" (tot).
You may also see the word "max" written in the rep section of your workout. This indicates that you should perform as many repetitions as possible before a form breakdown.
NOTE: "Form breakdown" can be observed with a decrease in your speed of movement, where your form is still good but it takes you longer to perform the repetition. In other words, it becomes more like grinding through the rep. Always pay attention to how you feel throughout your sets and reps, and adjust your weights as necessary to ensure an effective and safe workout.
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~ Your Coach,