More IGF-1 and IGF-2 after heavy training due to supplementation with quercetin
Supplementation with quercetin could speed up recovery from heavy physical exertion. During training, quercetin not only reduces muscle damage, but after the session, quercetin also increases IGF-1 and IGF-2 levels.


Italian endocrinologist Paolo Sgro published a study in Frontiers in Endocrinology in which 12 students participated. Sgro had the students complete a biceps workout on two separate occasions that caused significant damage to this muscle group. The students performed 10 sets, each of 10 eccentric reps.In the preceding 14 days, the students had taken a placebo every day on one occasion. On the other occasion, the students had taken two capsules each day, each containing 500 milligrams of quercetin. In total, the students took one gram of quercetin per day. The students took one capsule with breakfast and the other 12 hours later.
In the week after the biceps training, the concentration of enzymes and an inflammatory protein in the blood of the subjects increased, which indicate muscle damage. This increase was smaller if the subjects had used quercetin in the period prior to the training.

CK = creatine kinase, LDH = lactate dehydrogenase, MB = myoglobin, IL-6 = interleukin-6.
Click on the figure below for a larger version.

In itself, it is not surprising that a daily dose of one gram of quercetin protects muscles against degradation due to heavy training. After all, quercetin is a strong antioxidant and anti-inflammatory. What is remarkable in this study is that quercetin increases the production of IGF-1 and IGF-1 immediately after training.
IGF-1 and perhaps IGF-2 are anabolic hormones. Some of the IGF-1 and IGF-2 hormone in the body is made by muscle tissue. Production of both hormones increases after intense exercise. Quercetin seems to speed up this process.
"Dietary supplementation with quercetin, possibly through its anti-inflammatory and antioxidant properties could be a way to prevent, mitigate and promote a faster recovery of eccentric exercise-induced muscle damage by eccentric training", summarizes Sgro.

Front Endocrinol (Lausanne). 2021 Nov 3;12:745959.