Muscle cramps can stop athletes in their tracks. Although they usually self-extinguish within seconds or minutes, the abrupt, harsh, involuntary muscle contractions can cause mild-to-severe agony and immobility, often accompanied by knotting of the affected muscle (Minetto et al. 2013). And cramps are common; 50%–60% of healthy people suffer muscle cramps during exercise, sleep or pregnancy or after vigorous physical exertion (Giuriato et al. 2018). There is no gender difference with skeletal muscle cramps, but they appear to occur more often in endurance athletes and in the elderly (Naylor & Young 1994).

During endurance exercise, muscle cramps correlate with the length and intensity of workouts. Fitness pros and clients frequently talk about muscle cramps, but until recently, little has been known about their actual physiology.

Types of Muscle Cramps

Giuriato et al. categorized muscle cramps into three groups:

1. 1. Nocturnal cramps occur during sleep without any clear trigger.

1. 1. Pathological cramps are a consequence of having diabetes, nerve dysfunctions or metabolic disorders.

1. Exercise-associated muscle cramps occur during or after exertion. The first scientific confirmation of these types of cramps dates to 1908, when they were described in miners working in hot and humid conditions.

Muscle Cramp Risk Factors

With marathon runners, research has found certain risks associated with the occurrence of a muscle cramp (Schwellnus, Derman & Noakes 1997). These risks include a longer history of running, advanced age, higher body mass index, shorter daily stretching time, irregular stretching habits and a family history of cramping. Schwellnus, Derman & Noakes report that the two most important observations from the research are that exercise-associated cramps for marathoners are muscle fatigue (linked to longer runs) and poor stretching habits.

Early Theories About Muscle Cramp Causes

Schwellnus, Derman & Noakes analyzed three early theories on the causes of exercise-associated muscle cramps.

SERUM ELECTROLYTE THEORY

Blood plasma contains electrolytes, such as sodium, potassium, chloride, bicarbonate, calcium and phosphate. Although electrolyte depletion is often blamed for causing cramps, there currently is no solid explanation of how low serum electrolyte concentrations can result in the condition. Schwellnus, Derman & Noakes pointed to two studies that measured serum electrolyte concentrations in endurance runners at prerace, immediate postrace and at 60-minute postexercise recovery. Neither study found a connection between postrace recovery, muscle cramps and changes in serum electrolyte concentrations.

DEHYDRATION THEORY

In the past, studies have suggested treating muscle cramps in workers and firefighters with fluids and electrolytes. But those studies did not measure hydration. More recent studies that have estimated blood volume and plasma volume do not support the theory that dehydration has a direct link to exercise-associated cramps.

ENVIRONMENTAL THEORY

This theory sprang from the condition referred to as “heat cramps.” While exercising in a hot, humid environment may be correlated with the development of muscle cramps, no evidence shows cramps are linked to an increase in core body temperature.

Current Theory on Muscle Cramps

The newest concept of muscle cramps is a neuromuscular theory (Giuriato et al. 2018). This theory has evolved to point to two origins: a central (spinal column) and a peripheral (neuromuscular junction).

The central or spinal origin theory suggests that the involuntary contraction of a muscle occurs when nerve messages to the spinal column are altered, perhaps due to muscle fatigue (see “The Neuromuscular Theory of Skeletal Muscle Cramps,” below). This results in an imbalance of excitatory (from muscle spindles) and inhibitory (from Golgi tendon organs) spinal messages to muscles (see “What are Muscle Spindles and Golgi Tendon Organs?,” below). This neural signaling imbalance leads to enhanced muscle cell excitability and cramping.

With the peripheral origin theory, scientists suggest there is abnormal excitation of the motor nerves terminal branches to the muscle, causing cramping.

The scientific evidence of a neuromuscular theory is mounting. The research appears to show that, in some cases, fatigued muscle can’t fully relax. This condition leads to an imbalance between excitatory signals and inhibitory messages to the muscle. So the most recent research appears to support the central origin theory of the muscle cramp (Giuriato et al. 2018; Scwellnus, Derman & Noakes 1997).

For information on the neuromuscular theory of skeletal muscle cramps; muscle spindles and Golgi tendon organs and muscle cramp prevention, see “Ouch! What Causes Muscle Cramps” from the October 2019 print edition of Fitness Journal. If you cannot access the full article and would like to, please contact the IDEA Inspired Service Team at 800-999-4332, ext. 7.

Protein powders, especially the whey variety, have long been glorified in fitness circles for their muscle-building benefits. “Pump some iron and chug back a protein shake” is a preferred muscle-making formula. But research published in the journal Nature Metabolism, led by scientists from the University of Sydney, suggests that while the essential branched-chain amino acids (BCAAs) leucine, isoleucine and valine—found in high amounts in certain protein powders—can indeed help muscles recover and grow in response to training, excessive consumption of BCAAs may have unwanted side effects if taken at the expense of other amino acids from additional protein sources.

For instance, supplementing with high doses of BCAAs leads to high levels in the blood, potentially triggering competition with another amino acid, tryptophan, for transport to the brain. This can negatively affect mood, as tryptophan is a precursor for the feel-good hormone serotonin. Lower brain levels of serotonin can also stimulate appetite, leading to possible excess consumption of calories and, in the end, weight gain.

The take-home message is that it’s fine to include a scoop of whey protein in your daily diet to support training needs, but it’s best to eat a wide range of protein foods—including those from plant sources like legumes—to get a better balance of amino acids.

Every day, more women are moving from the cardio room to the weight room. It’s a welcome transition; getting stronger can transform their self-esteem, confidence and self-efficacy.

Supporting your female clients’ strength-training ambitions is fundamental to their long-term success. Women and girls enjoy a wealth of benefits from resistance exercise: reduced injury risk, better cardiovascular health, stronger bones, protection against diabetes, and less inflammation, to name a few. As more women flock to strength training, however, fitness professionals face a host of challenges. For starters, the research on weight training for women is relatively new, and there are fewer studies on women than there are on men. Also, the physiological differences between genders is either misrepresented or not discussed.

We aren’t that much different. In equally trained men and women, research finds most strength differences result from differences in muscle size, not gender (Bishop, Cureton & Collins 1987). These findings suggest that a man and a woman with the same muscle size should display the same amount of strength. Thus, we can retire terms like “toned” and “girl pushups”—and the pictures of pink dumbbells—because women should and can do the same exercises your male clients do. You, of course, already know this.

You should consider two crucial points, however:

• Women and men have different muscular fiber type compositions, making women less prone to fatigue (Hunter 2014).
• Female sex hormones, especially those involved in the menstrual cycle, can affect program timing and recovery (Sung et al. 2014).

Understanding these differences is pivotal to building programs that will help your female clients achieve muscle growth, strength gains and training success.

Fiber Types in Women vs. Men

Type I and type II. Generally speaking, the skeletal muscles of men are larger than those of women, and, in men, some muscles possess “a greater proportional area of metabolically and functionally faster muscle fibers,” whereas in women there is “a greater proportional area of the ‘slow’ type I fibers” (Hunter 2014). The higher concentration of type I fibers makes women more resistant to muscle fatigue. Men have a higher glycolytic capacity based on their larger concentration of type II fibers, priming males for quick, explosive activities like sprinting and weightlifting.

While muscle fiber type plays a large role, it is important to remember that the tendency to fatigue depends a lot on task conditions, including contraction type, speed and intensity; the muscle group involved; environmental conditions; and state of arousal (Hunter 2014).

Metabolism. The makeup of muscular tissue affects the energy substrates that each gender uses. Women typically carry 6%–12% more fat than men. Women are also better at handling fat and using it for energy during exercise, which spares muscle glycogen and decreases exertion ratings, again playing into fatigue resistance. Additionally, women are more sensitive to insulin across the entire body and are better able to take up glucose (Lundsgaard & Kiens 2014).

Program design. If muscle growth is a female client’s main goal, keep in mind that she is probably more resistant to fatigue than a male client would be. Programming sets in the 6- to 10-rep range seems to yield maximal muscle growth (Schuenke et al. 2012) and maximal increases in strength.

Because women can theoretically handle more work, your general-population clients might benefit from harder-intensity training sessions with supersets and timed rest periods. Consider challenging them to fatigue a little faster than they normally would, since you need to push them beyond their comfort zone to achieve muscle growth.

Sex Hormone Differences

Menstrual cycle. Women’s menstrual hormones fluctuate throughout their cycle, which usually lasts 28 days (hormonal contraceptives and other issues can alter the cycle). Hormonal fluctuations play a huge role in strength training, a reality only recently discussed in academic literature. By opening up this conversation with your female clients, you can tap into their strengths a little more and use biology in their favor (Sung et al. 2014).

The menstrual cycle has four phases:

• menstrual (days 1–5)
• follicular (days 1–13)
• ovulation (day 14)
• luteal (days 15–28).

The luteal phase triggers sharp hormonal changes—progesterone peaks and then plunges, along with estradiol. Hunger increases, moods change suddenly, core temperature rises, and more calories are burned; in fact, basal metabolic rate has been shown to increase by as much as 9% (Webb 1986). In this phase, symptoms of premenstrual syndrome often discourage interest in going to the gym.

The follicular phase, by contrast, is the time for women to really push themselves in hard workouts because estrogen hits its peak at this time, improving mood, energy and strength.

Estrogen vs. testosterone. These sex hormones have the most impact on the relative strength of women and men. Men have much more testosterone, affecting their baseline strength. Thus, men start out stronger with higher absolute strength, but relative strength gains are about the same for both genders.

Estrogen, on the other hand, has proved to have some anabolic and protective effects against various injuries and diseases. Within muscle, estrogen has been shown to influence contractions and postexercise muscle damage by acting as an antioxidant and a stabilizing membrane and by binding to estrogen receptors (Enns & Tidius 2010). Estrogen also has regenerative properties, which is why combining exercise and hormonal therapies can increase lean tissue mass (Velders & Diel 2013).

Program design. Maintain an open dialogue with your female client: Ask how she is feeling and if she would like to disclose the current phase of her menstrual cycle. Explain that while she doesn’t have to push through the bothersome symptoms of the luteal phase, she will benefit from some type of movement.

In the luteal phase, steer clear of high-intensity interval training and avoid going for personal bests or heavy strength sessions. Save these for the follicular phase. The luteal phase is an optimal time for deloading if the client is on a strength program. It’s also a great time for moderate conditioning or low-intensity cardio training.

Optimize periodization around her cycle. For instance, if she usually does strength training three times a week, you might keep the frequency the same during the luteal phase and ramp it up a session or two during the follicular phase (Sung et al. 2014). See “Sample Program Design,” below, for more.

Putting It All Together

Though men and women are different, your approach to strength training should be similar: Optimize physiological differences to produce peak training performance. As a fitness professional, you need to do three things to avoid alienating female clients by suggesting that their strength training programs are somehow inferior to men’s:

1. Lead by example. Show pictures, videos and articles of women doing what men (and other women) do. Show what these women’s bodies look like, what they are capable of and how they got there, while also (if you are a female trainer) disclosing the importance of strength training in your own life. You have the power to be a role model and a leader. Be the example, and your female clients will follow.
2. Banish biased language. Remove gender-labeled equipment and exercises from your vocabulary: Words like long, lean, toned and girl pushups have no merit or place in this space. This kind of language reinforces the false notion that women require a different type of exercise that will not make them “bulky” or “manly.”
3. Make room for self-discovery. Strength training can be scary and intimidating. Women almost never approach weight training wholeheartedly unless they’ve grown up around it. Let your clients draw their own conclusions about the experience—what they like or dislike. Female clients will appreciate having the space to find what they love about moving their bodies in this way. When the motivation comes from within, they will be more likely to stick with the activity and see the benefits of a strong body and mind throughout their entire lives—inside and outside of the gym.

Did you know that the closer a food is to its natural state, the more nutrient-dense it is? Whole foods give you the best bang for your caloric buck since you are eating the entire food with all its vitamins, minerals and fiber, and the food has not been subjected to potentially damaging processing.

Make a goal this year to include more whole plant–based foods in your diet. You probably already eat berries as whole foods. Try these other suggestions from Lourdes Castro, MS, RDN, adjunct professor at New York University’s department of nutrition, food studies and public health.

1. Beets, Garlic, Sweet Potatoes

Why eat these foods? Roots, tubers and bulbs grow underground and function as a plant’s nutrient-storage system, so it’s no surprise they are packed with vitamins and minerals. They provide antioxidant benefits, such as protection against many chronic diseases and conditions associated with aging.

Whenever possible, use the entire plant from root to leafy greens. Different parts of the plant may require different cooking methods, but the nutrient density is worth it.

Try this at home. Roasted beets with sautéed garlicky beet greens are delicious and easy. Remove the beet tops where stems meet the root, and roughly chop. Quarter the beets and lightly toss with olive oil, salt and pepper. Roast in the oven at 425 degrees Fahrenheit for 35 minutes, or until beets are fork tender. Meanwhile, finely chop 1–2 cloves of garlic and place in a pan with 1 tablespoon olive oil. Place over medium-high heat and add beet greens when the garlic begins to sizzle. Sauté until all greens are wilted. Serve with roasted beets.

Alternative. Roast sweet potatoes and substitute watercress for the beet greens.

2, Lentils, Chickpeas, Fresh Snap Peas

Why eat these foods? Legumes are seeds that grow in pods. The seeds can be fresh or dried, the pods edible or inedible. Legumes are rich in protein, fiber and iron, and they get an extra punch from folate. High folate intake can decrease cardiovascular risk (Willet 2001).

Try this at home. Dried lentils are quick-cooking and versatile. Simmer them in water until tender and then drain and cool. Toss with tomatoes, arugula, corn and carrots, and drizzle with olive oil and a squeeze of lemon. Eat this salad alone or augmented with sliced chicken breast. It also makes great leftovers.

3. Chia Seeds, Walnuts, Ground Flaxseeds

Why eat these foods? All nuts and seeds are rich in healthy monounsaturated fats and help stabilize blood sugar levels. But these foods are especially high in essential omega-3 fatty acids, which lower inflammation throughout the body (Calder 2006). This is especially good for people with arthritis and other inflammatory diseases.

Flaxseeds must be ground to enable your body to absorb all their beneficial nutrients, because the whole seeds pass through the intestines undigested. Chia seeds, on the other hand, do not have to be ground and have a longer shelf life because they can be left whole.

Try this at home. Soaking a table-spoon of chia seeds (or ground flaxseeds) in water will form a gel. Add this gel to your berry purée for a thick smoothie.

Why eat these foods? Sea vegetables (types of seaweed) such as dulse, wakame and hijiki are high in both iron and vitamin C, which make them high-value iron sources because vitamin C is necessary for the absorption of plant-based iron. Sea vegetables are thought to have an anti-inflammatory effect, and regular ingestion has been linked to low blood pressure (Wada et al. 2011).

Try this at home. Crumble dulse or wakame leaves and sprinkle over salads, soups, noodles or rice dishes.