You're getting older
As much as you'd like to believe otherwise, age isn't just a number. While a healthy diet and regular exercise can certainly help keep your body running at optimum levels well into your golden years, there's no fighting the fact that the passage of time is real. And it can really have an effect on your ability to build muscle.
Krissy Kendall, PhD, CSCS*D, CISSN, EP-C, and science editor for Bodybuilding.com says, "From age 20 to age 80, there is about a 30% reduction in muscle mass due to a decline in both muscle fiber size and number. Furthermore, there appears to be a preferential loss of type II fibers -- which are the fibers that are most responsive to growth -- with advancing age."
So if the last time you hit the gym was in your 20s, and now you're in your 40s wondering why your body just isn't responding to strength training like it has in the past, well, your age might be playing a role. Your best bet is to keep at it.
Kendall suggests including three to four days of resistance training per week while following a well-balanced diet, "Include ample amounts of vegetables, high-fiber carbohydrates, and lean protein -- you should aim for 1 to 1.2g of protein per kilogram bodyweight. Supplement with vitamin D, vitamin B12, and folate to help preserve muscle mass and strength while aging."
Sex plays a role
Look, I'm a woman, and I'm loathe to admit it, but where muscle mass is concerned, it's very often the case that men can build more of it, and quicker, than women. This certainly doesn't mean women can't build muscle, increase strength, or develop a svelte physique. Quite the contrary.
What it does mean is that if you're a woman hitting the gym with your guy friends, the dudes are probably going to build muscle faster than you.
Dr. Kendall explains that some of the discrepancy is due to gender differences in the makeup and composition of muscle fibers, "Women have a significantly higher percentage of type I muscle fibers in their quadriceps compared to men. Furthermore, studies have shown greater size of type II fibers in men compared to women, and a greater ratio of type II to I fibers." This is significant because type II fibers are associated with high force and power production, and their ability to experience more significant growth.
But that's not all. You see, guys have a lot more testosterone than gals -- according to Kendall, "Men have an approximately 10-fold higher circulating testosterone concentration compared to women. Although the effects of testosterone on muscle are seen in the absence of exercise, its actions are magnified during resistance training, promoting muscle growth both by increasing the protein synthesis rate and inhibiting protein breakdown."
Unless you want to start taking a testosterone prescription, there's not a whole lot you can do to increase your natural testosterone levels, but you can optimize them.
Here's what Kendall recommends: "Eat a higher-fat diet. Diets that are higher in fat -- generally 40% fat versus 25% -- have been shown to maintain testosterone levels in men. Second, get enough sleep! Testosterone peaks during your first REM cycle, so if you aren't getting quality sleep, there's a good chance your testosterone levels are suffering, too. Finally, lift heavy in the gym. Multi-joint exercises that recruit a large amount of muscle mass are best for stimulating testosterone secretion."
Your diet sucks
If you're subscribing to the SAD diet (that's the standard American diet, full of processed, low-nutrient, sugary food and saturated fats), you're going to end up with sad muscles.
Alysha Coughler, a registered dietitian and sports dietitian with a masters degree in health science, puts it bluntly: "It's physiologically impossible to build muscle tissue without sufficient nutrition, especially protein. When individuals eat enough protein in their diets, protein synthesis exceeds breakdown, resulting in a positive protein balance, and ultimately, muscle growth."
As a good rule of thumb, you should consume about 1 to 1.2g of protein per kilogram bodyweight per day. If that sounds too hard to figure out, Rob Arthur, a NSCA-certified strength and conditioning specialist and Precision Nutrition Level 1 certified coach, suggests you "Try aiming for at least one to two palm-sized portions of protein with every meal."
And even though protein gets all the press, it's not the only macronutrient you should be focused on -- your body needs carbohydrates, too. Arthur says, "Having some carbohydrate along with your protein can help accelerate your progress. The appropriate amount varies depending on your activity level and personal carb tolerance, but a good place to start is with one or two cupped handfuls with the meals preceding and following training. Examples of carbs that can help you fuel and recover include potatoes, rice, beans, and quinoa."
You think you're too good for sleep
Everything in your life is better when you get enough sleep, and that includes your body's response to strength training. Dr. Kendall is quick to clarify: "Missing the occasional 'good night's sleep' won't have much of an impact on muscle growth, but chronic sleep deprivation can have significant effects on hormone levels, physical performance, cognitive function, and immune health -- all of which play an important role when it comes to building muscle."
Sleep deprivation's multi-pronged, muscle-slaying weapon is due, in part, to the hampered testosterone production that takes place when you miss out on solid REM sleep, and in part to an increase in cortisol, which Kendall says, "is a catabolic hormone known for its role in breaking down muscle."
So just how much sleep deprivation is too much? According to Kendall, "There's research showing that submaximal and maximal weightlifting performance is affected by as little as three days of partial sleep deprivation. Reduced levels of anabolic hormones, coupled with lackluster performance in the gym, will definitely have an impact on muscle growth."
Everyone's sleep requirements are different, but aim for eight to nine hours per night. Sleep doesn't just maximize testosterone output while controlling cortisol production; it's your body's opportunity to recover and rebuild.
Your stress is out of control
Remember that whole "cortisol" thing we just touched on? Well, cortisol is a stress hormone, and cortisol is catabolic, two muscle-building strikes against your constant and overwhelming sense of anxiety. But an influx of cortisol into your system isn't the negative effect of poorly managed stress.
According to Arthur, "Stress has been shown to reduce muscular strength, and reduce insulin sensitivity in muscle but not fat, resulting in a shift from a hormonal state favoring muscle growth to a state favoring muscle breakdown and fat storage."
Arthur's quick to admit that it's probably impossible to completely eliminate stress from your life, but learning to manage it effectively can make a big difference in your progress at the gym, "Mindfulness and meditation are two great habits to pick up, and they don't require anything but your mind and a quiet spot." And if sitting quietly by yourself sounds too foreign, Arthur suggests trying the Headspace or Calm apps to get started.
You have "hardgainer" genes
Next time you want to complain to your therapist about your parents, consider bringing up your crappy genes. Arthur says it straight: "Some people just don't respond as positively as others to resistance training. Additionally, some people don't respond to overfeeding like others. The fact is that your body composition and performance are strongly influenced by a variety of genes which you largely have no control over."
Before you throw in the towel or stock up on steroids, don't despair. You can still see improvements, it may just require more conscientious effort and consistent, hard work. Arthur concurs, saying, "Train hard with the right program, eat appropriately for your goals, sleep like a lion, and manage stress consistently, and you'll see gains. They may come a bit slower, and you might not win Mr. Olympia, but you'll get there eventually."