We’ve all been guilty of skipping a workout… fine, several. Eventually, we make our way back to the gym, but it seems like the treadmills have gotten faster and the weights have gotten heavier. Is it just our guilty consciences psyching us out, or did we truly lose our hard-earned strength? Here, we explain just how long it takes to lose muscle mass and strength, and what to do stop it from happening.

Dude, Where’s My Muscle? — Why It Matters

How to Stay Strong and Prevent Muscle Loss

To understand what’s going on, we need to look inside the body, Ms. Frizzle-style. One study on rats found that just 48 hours after exercise, the body hits a lower steady-state rate of protein synthesis and stops building and repairing muscleProtein metabolism and beta-myosin heavy-chain mRNA in unweighted soleus muscle. Thomason DB, Biggs RB, Booth FW. Department of Physiology and Cell Biology, University of Texas Medical School, Houston, TX. Am J Physiol. 1989 Aug;257(2 Pt 2):R300-5. Sure, rats and humans are different, but the study could have interesting applications to human musculature. Immobilized muscles lie dormant and waiting for use (who knew they could be so lazy?). The muscles aren’t getting any stronger — but they’re not wasting away, either.

There are several factors that can lead to muscle atrophy:

  • Age: Regardless of how often we make it to the gym, the natural process of aging can cause muscle loss. Sarcopenia, or muscle loss due to aging, kicks in as early as age 20Sarcopenia- Age-Related Muscle Wasting and Weakness: Mechanisms and Treatments. Lynch, Gordon S. Springer, 2010. Page 103. The rate of sarcopenia picks up as we age; by the time we get to age 50, a person can lose 0.4 pounds of muscle every yearResistance exercise for the aging adult: clinical implications and prescription guidelines. Peterson MD, Gordon PM. Laboratory for Physical Activity and Exercise Intervention Research, Department of Physical Medicine and Rehabilitation, University of Michigan, Ann Arbor, MI. Am J Med. 2011 Mar;124(3):194-8.
  • Diet: While it’s generally thought not eating enough causes muscle loss, recent studies have found rats that were fed fewer calories over the course of 30 months showed improved protein synthesis and muscle activity compared to their cohorts that were placed on a higher calorie dietCalorie Restriction Improves Skeletal Muscle Hypertrophic Response In Aged Rats Following Functional Overload. Darren Ting-Cheung Hwee and Sue C Bodine. Neurobiology, Physiology, & Behavior, University of California, Davis, One Shields Avenue, Davis, CA. The FASEB Journal. 2007;21:922.1. While calorie restriction might not support optimum performance, this research suggests it could preserve greater function as we age. What you eat also matters, as malnutrition can contribute to sarcopeniaThe role of nutrition in the prevention of sarcopenia. Volkert D. Institute for Biomedicine of Aging, University of Erlangen-Nürnberg, Nürnberg, Germany. Wien Med Wochenschr. 2011 Sep;161(17-18):409-15. Epub 2011 Jul 29.
  • Sleep: Because sleep debt decreases the rate at which the body builds and repairs muscle, skipping sleep to hit the weight room can neutralize resultsSleep and muscle recovery: endocrinological and molecular basis for a new and promising hypothesis. Dattilo M, Antunes HK, Medeiros A, Mônico Neto M, Souza HS, Tufik S, de Mello MT. Centro de Estudos em Psicobiologia e Exercício, São Paulo, Brazil. Med Hypotheses. 2011 Aug;77(2):220-2. Epub 2011 May 7. Full recovery from workouts is critical to making (and maintaining) progress.

Results May Vary? — The Answer/Debate

How much and how fast muscles atrophy, or lose mass, depends on the muscle. Antigravity muscles that hold us up (e.g., hamstrings) atrophy slower than muscles used for specialized sports or exercise, especially when those muscles are severely limited such as in bed rest, limb suspension, or complete immobilizationIn vivo alterations in skeletal muscle form and function after disuse atrophy. Clark BC. Institute for Neuromusculoskeletal Research, Department of Biomedical Sciences, Ohio University College of Osteopathic Medicine, Athens, OH. Med Sci Sports Exerc. 2009 Oct;41(10):1869-75MacIntosh, B. R. Skeletal muscle form and function. 2nd. Champaign, IL: Human Kinetics, 2006. Of course, these results are likely to not be as pronounced for a brief break from training. All muscles atrophy with extreme disuse. Skeletal muscles, which include antigravity muscles, are voluntary muscles used to move the body. These are generally more susceptible than involuntary muscles such as cardiac muscles, which help power the heart even when you’re asleep. This helps explain why muscle loss occurs faster for “highly trained individuals” with more specialized muscle groups than for “exercise newbies” even though they may be in better overall shapePhysiological adaptations to physical training. Wilmore, J., & Costill, D. (1988). In Training for sport and activity, Chapter 11. Dubuque, IA: Wm. C. Brown. There are, fortunately, proven ways to speed recovery regardless of fitness level.

(Also Check Out: Can You Exercise Too Much?)

Taking a break can also impact muscle function. While flexibility and power decrease substantially after just one week of inactivity, endurance will decline after two weeksPhysiological adaptations to physical training. Wilmore, J., & Costill, D. (1988). In Training for sport and activity, Chapter 11. Dubuque, IA: Wm. C. Brown. General muscle strength is usually maintained for at least the first month of inactivity. And even a year after quitting a 12-week strength training program, up to 55 percent of the original strength gain is maintainedThe role of nutrition in the prevention of sarcopenia. Volkert D. Institute for Biomedicine of Aging, University of Erlangen-Nürnberg, Nürnberg, Germany. Wien Med Wochenschr. 2011 Sep;161(17-18):409-15. Epub 2011 Jul 29! Now there’s motivation to try, try, and try again.

One last piece of great news if you’re feeling guilty about taking a break: Muscle memory actually makes it easier to regain strength than it was to build that muscle the first timeMyonuclei acquired by overload exercise precede hypertrophy and are not lost on detraining. Bruusgaard JC, Johansen IB, Egner IM, Rana ZA, Gundersen K. Department of Molecular Biosciences, University of Oslo, 0371 Oslo, Norway. Proc Natl Acad Sci U S A. 2010 Aug 24;107(34):15111-6. Epub 2010 Aug 16. So whether that gym membership expired, you got sick, or a dog ate those gym shoes (eww!), climb back up on that horse and keep on keeping on!

Preventing Atrophy — Your Action Plan

There’s no easy way to prevent loss of muscle mass and strength. Here are some ways to keep up a daily routine and avoid lengthy training breaks.

  • Eat Right: Just like great abs are said to be made in the kitchen, it’s critical to eat healthy foods in the period immediately following a workout. While results are inconclusive as to whether eating more protein, specifically, can prevent muscle loss, a balanced diet helps ensure that muscles get the amino acids, vitamins, and minerals they need to build and stay strongDoes protein supplementation prevent muscle disuse atrophy and loss of strength? Stein TP, Blanc S. Department of Surgery , University of Medicine and Dentistry of New Jersey – SOM , Stratford , NJ. Crit Rev Food Sci Nutr. 2011 Oct-Nov;51(9):828-34.
  • Start Early: We can’t control aging, but a recent study found that recreational athletes who consistently worked out four to five times each week were able to “freeze” levels of muscle mass as they aged — thereby avoiding the brunt of the effects of sarcopeniaChronic exercise preserves lean muscle mass in masters athletes. Wroblewski AP, Amati F, Smiley MA, Goodpaster B, Wright V. Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, PA. Phys Sportsmed. 2011 Sep;39(3):172-8. It’s no cryogenic deep freeze, but generally, the sooner we start an exercise regimen, the sooner our muscles will make like Austin Powers and “freeze.”
  • Work it Hard: When hitting the gym, remember to “go hard or go home” and build those muscles as strong as possible. Because loss occurs gradually, the fitter the muscle, the longer it will take to hit ground zero.

This article has been approved by Greatist Experts Jason Edmonds and Joe Vennare.What are your tips for staying fit even on exercise breaks? Let us know in the comments! [Note: This story was updated on May 25.]