Physical Fitness Stack Exchange is a question and answer site for physical fitness professionals, athletes, trainers, and those providing health-related needs. It only takes a minute to sign up.
Sign up to join this community
I've just started a HIIT training routine and after two workouts my arms (triceps & biceps) grew 1/4 inch. I went to the gym this morning and after I got home 12 hours later measured my arms and they'd shrunk by 1/8th of an inch.
I know that muscles grow when I rest and sleep. But will the gain return in the morning? And is the shrinkage a sign of possible over training? I haven't trained to failure in any of my muscle groups in the last week.
Several things can affect the size and makeup of your muscles:
All that said, you will have some variance in muscle size due to the fact that they are living tissue, and the fact that there is always a margin of error in measurement. I've noticed that my calves and thighs can vary fairly widely (.5 inch) from week to week. I'm mostly interested in strength, so for me this is simply anecdotal.
You likely experienced 'The Pump' - i.e. a temporary swelling of a well-used muscle due to additional blood-flow. It can last for several hours, but after the 12 hour period since your workout, it certainly could have faded.
It's completely normal - don't worry too much about small changes to muscle-size.
You can't determine a difference in muscle size by measurements 12 hours apart. Any difference here is due to fluid levels (blood and water). Depending on how much activity you've had today, the amounts of blood in your muscles will vary. Depending on what you've ate and drank today, the amounts of water in your muscles and skin will vary. Best to measure every month at minimum, when you wake up in the morning, after using the restroom, & prior to eating or drinking anything.
