Effectiveness is doing the things that get you closer to your goals. Efficiency is performing a given task (whether important or not) in the most economical manner possible. Being efficient without regard to effectiveness is the default mode of the universe.
Tim FerrissWhen you elevate the heels more so than you elevate the sole of the foot, you trigger a cascade of compensations in the knees and hips that cause tight hip flexors, and then those hip flexors cause lower-back pain.
Tim Ferriss