Disclaimer: Research in many areas of exercise science has exploded over the last decade. Some of this is due to increased interest and some of it is due to increased funding. Much of what I learned was at the mercy of the science available at the time.
1. Hypertrophy Only Happens in 8-15 Rep Ranges
What I was taught: Muscle growth (hypertrophy) only happens in this specific rep range, while lower reps build strength and higher reps build endurance.
What we know now: You can build muscle using reps as low as 1 and as high as 50, but the optimal range is 5-30, as long as you push close to failure. Effort and total work matter more than the exact rep range.
2. Icing for Injury
What I was taught: Ice everything to reduce inflammation and recover faster.
What we know now: Inflammation is part of the healing process. Icing can actually slow recovery. Newer methods emphasize movement instead of ice.
3. Energy Systems are Discrete
What I was taught: The body switches between energy systems (ATP-PC, glycolytic, oxidative) depending on how long you’re exercising.
What we know now: Energy systems work together all the time—they don’t switch on and off. It’s more like a dimmer switch than separate lights.
4. Stretching Prevents Injuries
What I was taught: Static stretching helps prevent injuries and helps you perform better.
What we know now: Static stretching before a workout can actually weaken muscles temporarily. Warming up with dynamic movements is better. Using exercises to activate muscles through full ranges of motion promotes long lasting mobility far more than static stretching.
5. Lactic Acid Causes Soreness
What I was taught: Lactic acid builds up in your muscles and makes you sore the next day.
What we know now: Lactate isn’t a waste product—it’s actually a fuel. Soreness (DOMS) comes from tiny tears in your muscles, not lactic acid.
6. Eating Every 2-3 Hours Boosts Your Metabolism
What I was taught: Eating frequently keeps your metabolism “fired up” and prevents your body from storing fat.
What we know now: Meal frequency doesn’t really affect metabolism. Total calories and nutrients matter way more than how often you eat.
7. Running is Bad for Your Knees
What I was taught: Running wears down your knees and causes arthritis.
What we know now: Running, when programmed appropriately, can actually improve knee health for most people, as it strengthens cartilage and connective tissue.
8. Cardio Kills Your Gains
What I was taught: Cardio destroys muscle growth if you’re lifting weights.
What we know now: Too much cardio can hurt strength gains, but the right amount can improve recovery, endurance, and overall performance.