ROAR

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BATTLE OF THE SEXES

ALL THE PHYSIOLOGICAL STUFF THAT MAKES YOU "LIKE A GIRL"

You "throw like a girl." The "like a girl" insult is so ubiquitous, such a strong underlying current in our culture, that a maker of feminine hygiene products took it head-on with the #LikeAGirl campaign, which turns the insult into an inspirational compliment.

Look, I'm not one to sugarcoat anything, so I'll give it to you straight. Yes, in head-to-head objective physical performance comparisons, women have some disadvantages. We also have some distinct advantages, but you never hear about those. So let's set the stage here with a complete look at your female physiology in action.

SUGAR AND SPICE AND EVERYTHING NICE: WHAT WE'RE REALLY MADE OF

No surprise: Women tend to be smaller and lighter and have a higher portion of body fat (hello breasts, hips, and all things childbearing!) than men. But dig a little deeper and the comparisons become more interesting and revealing.

First, let's talk about body mass and how it's distributed. Our mass is the stuff we're made of, which everyone commonly refers to as weight--the number you see on the scale. That's not exactly accurate. For one, technically weight is determined by gravitational pull, so you'd weigh less on the moon and far more on Jupiter, but that's being picky. The more important factor is that the number you see on the scale--your weight-- fluctuates widely depending on fluid intake, what you've eaten during the day, salt intake, and how much glycogen you're storing in your muscles (for every 1 gram of glycogen, you store 3 grams of water; as you get fitter, you become better at glycogen storage, so before a big event, you can gain 5 or more £ds that you will blow through during your event, but you haven't gained or lost any fat). Body mass, by contrast, is the actual stuff you're made of--bone, muscle, fat, and organs--which requires tissue loss or gain and is harder to change.

We'll cover bones in Chapter 9, because a strong skeleton is essential for vibrant living, and women's bones are vulnerable to getting brittle. For now, however, let's focus on muscle and fat.

When researchers take core needles and pull out a column of muscle tissue from the designated muscle of interest (usually the shoulder, biceps, or quadriceps) of men and women, what they find might surprise you. There's not much difference. Men and women generally have the same muscle composition as far as the percentage of type I endurance (aerobic) fibers and type II power (anaerobic) fibers. What is different is that the largest fibers in women's bodies tend to be type I endurance fibers, while in men the type II power fibers take up the lion's share of real estate.

Since type II fibers are used to hoist barbells and push broken-down cars to the roadside, it's not surprising that in head-to-head strength comparisons, women fall a bit short. Studies show that women are about 52 percent as strong as men in their upper bodies and 66 percent as strong as men in their lower bodies. In well-muscled women, those strength differences evaporate a bit. When you look at sheer strength relative to lean body mass, a trained woman's strength shoots up to 70 and 80 percent as strong as men in the arms and legs respectively. Still less powerful, but definitely closer.

Women give men more of a run for their money in the leg-press department because we tend to carry most of our lean muscle tissue below the waist. This is also why women's-specific bikes are designed with geometry that balances our center of gravity over the bottom bracket (where the pedal cranks are attached). Our power comes from our hips and legs.

Then there's fat, which is still a four-letter word for most athletes I work with, even though you can't train, race, or even live without it. Most of us think of fat as the stuffing we see under our skin (usually in places where we don't want to see it). That's our storage fat. Those are energy reserves we accumulate. That fat also acts as padding and generates key hormones such as adiponectin that regulate insulin (the hormone that helps your body use and store blood sugar). We need some, but not an abundance of, storage fat to perform our best. Most of the fat you don't see in the mirror is essential body fat, which is in your nerves, bone marrow, and organs. Essential fat in men is about 4 percent, but in women, it is about 12 percent (because we are designed to reproduce!). As a woman, your breasts are also largely fatty tissue.

How much fat either men or women carry depends largely on lifestyle, but you can't dismiss the fact that there are also very distinct body types. For instance, there are people who are simply endomorphs. They tend to be larger, and they carry more body fat. On the other end of the scale are the wispy ectomorphs, who are naturally slim. And in the middle are mesomorphs, who tend to be lean and naturally muscular. You can also be a blend of the two; for example, a mesomorph with endomorph tendencies. How active you are and the type of activity you do can impact the dominance of one body type over another. Your physical activity directly affects your body-fat levels and distribution.

We'll delve into the topic of body composition in great depth in Chapter 5, but generally speaking, healthy body fat ranges span from 12 to 30 percent in women and 5 to 25 percent in men.

In the athletic world, muscle is usually prized, while fat is shunned. As I see it, however, what you're made of is important, but more important is the impact of what you're made of on what you do and/or want to do. Take two cyclists, for instance. A man may have big pectorals (pecs) and biceps, but those heavy upper-body muscles will only weigh him down when faced with a 10 percent climb. A woman who is lighter in the torso but still powerful in the hips and legs will have a far easier time pedaling her way up the mountain.

Likewise, women often dominate in the sport of open-water swimming. According to Open Water Source, female swimmers often perform better than their male counterparts, especially as the swims get longer. In fact, the average time for women in the Catalina Channel swim--an arduous 20-mile swim from the Southern California coast to Catalina Island--is 7 minutes faster than the average time for men. What's more, women hold the overall records in both directions--mainland to island and island to mainland. (In 1976, Penny Dean set the record from mainland to Catalina in 7:15:55, and Karen Burton set the record from Catalina to mainland in 7:37:31 in 1994.)

And let's not forget that in 2013 Diana Nyad became the first person ever to swim the 110.86 miles between Cuba and Florida in a mind-boggling 52 hours and 54 minutes. Fat is more buoyant than muscle, so that extra padding may be a distinct advantage in the open water.

WOMEN ON THE RUN: OUR CAPACITY FOR CARDIO AND ENDURANCE

Whether you run marathons, cycle gran fondos, compete in triathlons, or just exercise to stay fit and healthy, training works similarly for both sexes. As you train longer and harder, you get fitter. Your body can deliver and use more oxygen (that's your max VO2); you can push the pace to a higher point before your muscles scream uncle (that's your lactate threshold talking); you become stronger and leaner (building muscle, burning fat); and your performance improves.

But that open-water swimming example aside, £d for £d, men still generally outrun, outwalk, and outcycle us. Female world records from the 800 meter to the marathon are about 11 percent slower than those held by men.

Why? Well, for the same reason that a Prius will have to pull some wily moves if it wants to race against a Mustang--we start with a smaller engine. As a woman, you have a smaller heart, smaller heart volume, smaller lungs (25 to 30 percent less capacity than men), and lower diastolic pressure (the pressure in the arteries when the heart is resting between beats and the ventricles fill with blood), which predisposes us to have lower maximum heart rates and greater problems with dehydration in the heat. This also means we pump out less oxygenated blood with every beat-- about 30 percent less cardiac output than men.

Less oxygenated blood means we have to breathe more often, and as a consequence, our respiratory muscles--such as the diaphragm and intercostals between our ribs--need to work harder and use a lot of energy. Like other skeletal muscles, the contracting respiratory muscles require enough bloodflow to meet oxygen demand. If you have a greater oxygen cost of breathing, you also likely dedicate a greater amount of bloodflow toward your respiratory muscles during maximal exercise. When you push the pace and breathe hard, it can be difficult to race against the guys because less bloodflow is going to your legs.

Testosterone also gives men a bit of an edge because the male sex hormone increases the production of red blood cells, which absorb and carry oxygen to working muscles. On average, men have 6 percent more red blood cells and 10 to 15 percent more hemoglobin (which is the molecule in red blood cells that carries the oxygen) concentration than women.

Our combined smaller heart and lungs and lower oxygen-carrying capacity means we have a lower max VO2 (the maximum amount of oxygen your body can use to make fuel) than men, about 15 to 25 percent lower on average, as shown in the chart below. So if two athletes are doing the same amount of work, the woman will have a higher heart rate and need more oxygen to get the job done.

MAXIMUM OXYGEN USE: WOMEN VS. MEN

Because of our hormones, we also use energy differently during aerobic exercise. We'll get into this in much greater detail in the following chapters, but in general, because of our high estrogen levels, we rely less on carbs and more on fat than our male counterparts. That sounds like a good thing, and in some ways it is, since fat is the main fuel for aerobic exercise. But it's not such a good thing when we need to go really hard, because that tendency to spare glycogen (which is really strong during the high-hormone phase of your menstrual cycle right before your period) can make it harder to hit high intensities. We really need those carbs to fuel the anaerobic energy system when we push past our threshold. If you're running low on carbs in your bloodstream, it may mean slamming on the brakes instead of hitting the gas because your body just can't get the glycogen stores it needs to make the energy you want.

Speaking of energy, because men have bigger type II fibers and the energy- producing enzymes that go with them, they have a higher glycolytic capacity than women, which is a fancy way of saying that they can burn through more glucose in the absence of oxygen. That helps them outperform us in short- intense bursts of effort, but it also means they accumulate more lactate (a chemical your body makes and uses for energy during very high-intensity efforts; accumulating more than you can use leads to muscle acidity or "the burn" and forces you to slow down) and need longer recovery time for all- out efforts. Women, on the other hand, have a greater advantage in the endurance world, as our type I fibers are much more efficient at using fat as fuel and sparing glucose.

Finally, women are also more likely to sweat out excess amounts of sodium and are more likely to eat into their muscles for energy. We also have a harder time rebuilding and repairing those muscles after exercise during the high-hormone premenstrual time in the cycle when progesterone levels are high.

What's a woman to do? Well, let's go back to that wily Prius for a moment. Sure, that Mustang is going to beat her in a drag race. Maybe even in a race across New Jersey. But that efficient little vehicle will hum along much longer on less fuel and may even beat the high-horsepower vehicle in the long run.

On the pointy end of the field where the very elite athletes are, the fastest woman probably won't ever break the tape in front of the fastest man because they are too close in body size (top marathoners--male and female--often weigh within 5 £ds of each other). But for the rest of us, it means hanging with and passing or "chicking" the dudes is very much in the realm of possibility, so long as we know and work with our unique physiology. In this case, it's a matter of building up your plasma (the watery part of your blood) volume through training and feeding your body what it needs to keep your metabolism humming, which we'll cover in great depth in the chapters to come.

HORMONES AT A GLANCE

Hormones play a huge role in every physical function of living. You see that very clearly in the sphere of athletics. Here, at a glance, are the major impacts of male and female hormones.

Testosterone (the primary male hormone) leads to:

• Bone formation, larger bones
• Protein synthesis (the biological muscle-building process), larger muscles
• Erythropoietin (EPO) secretion, increased red blood cell production

Estrogen (the primary female hormone) leads to:

• Fat deposition (lipoprotein lipase--the enzyme responsible for taking fatty acids from the blood and putting them into fat tissue; estrogen increases this process)
• Inhibition of anabolic stimuli (harder to make muscle)
• Faster, more brief bone growth
• Shorter stature, lower total body mass
• More fat mass and higher percent body fat

FAST WOMEN: OUR STRENGTH, SPEED, AND POWER

Okay, CrossFit athletes and sprinters, this one's for you. As you saw in the section on body composition, your biggest fibers are your type I fibers, which can help you run a fast 10-K but don't necessarily chip in much for kipping pullups or suicide drills on the soccer field. But that's not to say you can't build your type II fibers through strength training. You most certainly can.

With training, you can honestly get nearly as strong as a man, relatively speaking. For example, when researchers pitted 52 young men against 50 young women in max power tests on a stationary bike, the men frankly smoked the women--generating about 50 percent greater peak power. But the men were significantly heavier. When the researchers looked at how much power they could produce per kilogram of body weight, the difference dropped dramatically to 15 percent. Taking that one step further, when power outputs were adjusted for fat-free mass, the values plummeted to a 2.5 percent difference, or not statistically different--a pretty even match.