8 Things I Was Taught in School About Exercise That Turned Out to Be Mostly Wrong
The world of exercise science has come a long way in the past decade. A lot of what I learned during my undergrad years and early days in the weight room has been debunked or refined as research evolved. Here are some of the biggest myths I was taught—and what we know now.
1. Hypertrophy Only Happens in the 8–15 Rep Range
What I was taught: Muscle growth (hypertrophy) only happens within this magical rep range, while lower reps build strength and higher reps build endurance.
What we know now: Muscle can grow with reps as low as 1 or as high as 50, as long as you train close to failure. While the optimal range for most people tends to be between 5–30 reps, the key factors are effort, progressive overload, and total volume. Instead of fixating on one rep range, a mix of lower, moderate, and higher reps can maximize muscle growth and strength.
2. Icing for Injury Speeds Up Recovery
What I was taught: Ice everything to reduce inflammation and recover faster.
What we know now: Inflammation is actually a crucial part of the healing process. Icing may temporarily numb the pain which is the main reason to use it and reduce swelling, but it can also delay recovery by slowing down blood flow and disrupting the body’s natural repair mechanisms. Instead, active recovery methods like movement or workouts that are pain free (or under 4 out of 10 on the pain scale) help speed up recovery by increasing blood flow and range of motion, compression, and proper nutrition help injuries heal more effectively.
3. Energy Systems Work Separately
What I was taught: The body switches between energy systems (ATP-PC, glycolytic, oxidative) based on how long you’ve been exercising.
What we know now: Energy systems don’t work like flipping switches; they function on a spectrum. Whether you’re lifting weights or running a marathon, all three energy systems are contributing to some degree. The intensity and duration of your activity simply determine which system is working the hardest at any given time.
4. Stretching Before Workouts Prevents Injuries
What I was taught: Static stretching before exercise reduces injury risk and improves performance.
What we know now: Static stretching before a workout can temporarily reduce strength and power output which can actually lead to more injuries and strains. Instead, dynamic warm-ups that activate muscles through movement (like bodyweight squats, lunges, and arm circles) better prepare the body for exercise.
5. Lactic Acid Causes Muscle Soreness
What I was taught: Lactic acid builds up in muscles and causes soreness the next day.
What we know now: First, it’s not even called lactic acid—it’s lactate. More importantly, lactate isn’t a waste product but a valuable energy source your body recycles. The soreness you feel (Delayed-Onset Muscle Soreness, or DOMS) is actually due to microscopic muscle fiber damage, not lactate buildup. DOMS is a sign of your muscles adapting to a new stimulus, not a result of “acid” lingering in your system.
6. Eating Every 2–3 Hours Boosts Metabolism
What I was taught: Eating frequently keeps your metabolism “stoked” and prevents fat gain.
What we know now: Meal frequency has little impact on metabolism. What truly matters is total daily calorie intake and macronutrient balance. Some people feel better eating every few hours, while others thrive on fewer, larger meals. The key is finding what works best for your energy levels and lifestyle—not forcing yourself to eat constantly in the name of metabolism.
7. Running Destroys Your Knees
What I was taught: Running wears down your knees and leads to arthritis.
What we know now: Running, when done with proper form and volume, can actually strengthen the knees by improving cartilage health, ligament integrity, and overall joint stability. The real issues arise from poor technique, excessive mileage, and lack of strength training. A well-balanced program that includes running, strength work, and mobility training can keep your knees healthy for years.
8. Cardio Kills Muscle Gains
What I was taught: Doing cardio will eat away at your muscles and ruin strength gains.
What we know now: Excessive cardio, especially when combined with a calorie deficit, can interfere with muscle growth. However, moderate amounts of cardio can improve endurance, aid recovery, and even enhance work capacity in the gym. The key is balancing strength training with the right amount of cardio based on your goals.
Final Thoughts: The Science is Always Evolving
The field of exercise science and science in general is constantly changing as we get better research and data. A lot of what I was taught wasn’t “wrong” at the time—it was just based on the best available evidence. The key to long-term success in fitness (and life) is staying curious, questioning old beliefs, and being willing to adapt as new information comes to light.
If you’re looking for real, science-backed strategies for strength, health, and nutrition, we’ve got you covered!
Tim
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