Synephrine is a compound found in bitter orange that binds to β-3 receptors on fat cells to enhance fat release and fat burning—hence its use in many fat burners. Synephrine also has stimulant effects (similar to caffeine), where it increases energy and focus and suppresses appetite. Although synephrine’s fat burning effects are well documented, little is known of its ergogenic potential when taken preworkout.
A recent study published in the Journal of the International Society of Sports Nutrition shows us that synephrine may be more than just a potent fat burner. Using a randomized, double-blinded, and placebo controlled design it was found subjects who took 100 mg of synephrine prior to training performed 6 to11% more repetitions compared to control (no supplement) and placebo conditions respectively. Additionally, the ergogenic benefits of synephrine seemed to be amplified when stacked with low dose caffeine (100 mg), as subjects performed all sets with greater velocity and power.
ACTION POINT: We generally recommend taking 60 mg of synephrine per day, split into 3 doses (i.e., 20 mg per dose). However, based on this study, taking 100 mg of synephrine in a single dose, 45 minutes before training, may boost your training volume. If you want to increase volume and power— try stacking synephrine with 100 mg of caffeine. *Note: As with all stimulants, slowly work your way up to the recommended dose and discontinue use if you feel unwell.
Reference: Ratamess NA, Bush JA1, Kang J, Kraemer WJ, Stohs SJ, Nocera VG, Leise MD, Diamond KB, Faigenbaum AD. The effects of supplementation with P-Synephrine alone and in combination with caffeine on resistance exercise performance. J Int Soc Sports Nutr. 2015 Sep 17;12:35.