How do you keep your tendons from getting stressed, when climbing mutiple times a week?

Tendons take longer to strengthen than do muscles. Hence the adage of only increasing your workload by 10% each week. So build up slow is my answer. The other is exercise the opposing muscles and their tendons and vary your climbing style as much as possible.

Spread your days out between climbing. That way it gives time for your body to recover. Theirs alot to be said about proper diet and having enough protein that your body can recover. Another tidbit, everyone has their opinion on ibuprofen and it can definitely be useful sometimes, but according to a study performed on ultramarathon runners, the ones who used ibuprofen directly after their race experienced more muscular breakdown than those that didn't and had impaired kidney function as well. So...the jury is still out, but this might be an interesting puzzle in the pic.

Try glucosamine if you are an old man like I am. Seems to help me a bit...

Hydration - Tendons are 90% water when properly hydrated.

Massage - work the belly of the muscle not the attachment points, the idea is to relax the muscle so that there is not strain on the tendon in a relaxed state.

Antagonistics - Climbers spend all day working their flexors gripping all types of holds, then 5 minutes doing reverse wrist curls. Then we wonder why we get tendonitis.

Proper warm up - a good warmup increases blood flow and also tendon elasticity. 15 minutes of CV before any strength work is a safe measure.

Mix it up - tell yourself you will try a move 5 times, then move on. Doing the same movement ad naseum is a great way to blow a tendon. Remember we are talking about a muscle bundles smaller than carrots holding our entire body weight. Change grip types often.

from another old-timer-ginger, curcumin, fresh vegetables, keep opposing muscles developed, take time to stretch all those tiny muscles in your forearms-I have found gentle stretching releases the pressure on my tendons and seems to allow them to heal more quickly. You want to prevent your muscles from shortening and constantly stressing their attachments. Also, if you tweak it, back off and let it get better. If you tweak a lot, think about your soul and what you are trying to acheive with climbing, and with your life. Be careful with ibuprufen-it is useful for healing but is an invitation to overuse injury(it masks what you are doing to yourself).