Whey protein concentrate can be up to 80% pure protein by weight. By removing or isolating out much of the carbohydrates, fat and lactose using sophisticated filtering technologies, whey protein isolate is up to 90% pure protein. A study published in Journal of the International Society of Sports Nutrition tested the short-term exercise recovery benefits of this sports nutrition supplement.
After completing 4 sets for 10 reps on leg extension, leg press and leg flexion machines using 120% of maximum capacity, 17 untrained men consumed 1.5 grams of whey protein isolate per kilogram of body weight at intervals spread throughout each day for 2 weeks. Some received a carbohydrate drink instead.
Knee extension strength was higher 3 and 7 days into recovery for subjects who consumed whey protein isolate compared to those who got carbohydrates. This suggests that whey isolate might help reduce the impairment of muscle forces during recovery from eccentric training.