I’m 56 and I do 15 mins on a strider at the local gym to warm up and do some cardio. On one machine my pulse is around 130 - 140 but the other is harder and my pulse tends to get to 150. I do another 10 mins at the end of my set.
I don’t rest or hydrate during my workout. Should I be doing both? I see guys sitting on the machines doing their phones, etc, but I am always stretching. So if I’m doing chest reps, I will do leg stretches between sets. I rarely sit around but I do check my pulse and try to get my pulse under 110 before doing my next set.
Hydration is very important, carry a water bottle when you work out, and listen to your body, it will tell you what you can / cannot do, do not over exert. Monitoring your vitals is a good idea, also consulting your doctor on what you can / cannot do is of the utmost importance. I stagger my workouts so I do not get “too use too them”, and the rest factor (very important).
Hydrate before, during and after exercise in order to prevent dehydration symptoms such as muscle cramping and dizziness.
Here’s an article about hydration. " Sports and Hydration for Athletes: Q&A with a Dietitian" and another about resting between sets “This Is How Long You Should Rest Between Sets According to the Latest Research”… I hope this helps to answer your questions.