When using preworkouts regularly I believe sensitivity can be a major factor but not in every circumstance. A good example is me using Goku Gains recently. That contains DMHA and it's one of only 2 products I have now that contain it. When I was using DMHA 4-5 days per week Goku Gains felt very ordinary. Nothing spectacular about it but still a solid product. But when using the likes of Excelsior and Reign and adding it in I felt nothing special and it felt quite mild.

Move forward approx 1 month of using mainly caffeine based (no DHMA) pre workouts and I decide to use Goka Gains again. It hit me so hard unlike any caffeine based product (unless you dose super high). One of those times I thought it was too much but once I started training I was gtg. I saw my mate in the gym and he came over and spoke to me and I was so wired I could barely hold a conversation. I have since used Goku Gains twice more and it's effects have lessened each time. Just one example I have showing how sensitivity can play into things.

It's like some of the lower dosed stimulant products on the market. I bet if you used one of those in the middle of a 2 month DMAA/DMHA run it would feel very weak. Add one in after 2 months off all stimulants and it will be totally different. It's also why you have to take a bad stimulant junkies opinion on preworkouts with a grain of salt. Some guys can take 800mg caffeine and not feel much because they abuse stimulants every day. Everyone has a different response but if someone is taking 2 scoops of a strong preworkout and not feeling it you know they probably have a massive tolerance. My tolerance is quite high so many would struggle with 1 scoop of many products I use whereas others may need double. I think once people start needing 1.5+ servings of strong products that's when they should definitely be having breaks to improve sensitivity.

Eria Jarensis is a useful ingredient in many newer preworkouts. Useful but nowhere near the strength of DMHA or one of it's natural forms such as Juglans Regia. I used Musclerage's Limitless recently and it's good but not overly powerful for someone with a higher tolerance. Limitless contains:

Serving Size: 1 Scoop (11.4 grams)

Servings Per Container: 30

L-Citrulline DL Malate - 6g

Beta Alanine - 3.2g

Alpha GPC - 300mg

Caffeine Anydrous - 250mg

Eria Jarensis - 175mg

Di-Caffeine Malate - 100mg

Black Pepper Extract (91% Bioperine) - 10mg

Huperzine A - 200mcg