The 70% rule is a principal based in the healing function of qigong. It says: “For best results, exercise at 70% of your maximum capacity.”
This applies to duration, intensity, and range of movement. How long you practice, how intensely you exert, and how far you stretch, should all be at 70% of your maximum capacity.
100% is your edge. If you get too close to your edge, your body will contract, making practice ineffective, and if you push beyond it, you will damage and exhaust yourself. If you approach it slowly, hanging out in the 70% region, it will gently expand to accommodate you.