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Age-related decline of muscle power (powerpenia) featured article

Around age 50, muscle strength—the ability to exert force or lift a heavy resistance—drops by about 3% per year, while muscle mass falls by about 1% per year.

The fix to this is simple: Resistance training and an adequate protein intake. Engaging in strength training 2–3 times per week and consuming 1.2–1.6 grams of protein per kilogram of body weight per day can help one maintain—and even build—muscle mass and muscle strength as they age.

It's not inevitable that we lose muscle as we get older. But it takes work.

These drops in muscle strength and mass might seem drastic, but muscle power might experience even more drastic changes.

In fact, muscle power is so important that researchers have proposed a new term for the age-related loss of muscle power: powerpenia (a friendly nod to the more well-known term sarcopenia, which refers to the age-related loss of muscle mass).

[image id='aging and muscle loss'...

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Why It's Never Too Late to Start Building Muscle

Posted on January 21st 2025 (4 months)

In this clip, Dr. Rhonda Patrick highlights muscle's role in aging, metabolic health, and how exercise and protein combat age-related muscle loss.

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The 4 Most Important Players for Muscle Mass - Rhonda Patrick

Posted on January 21st 2025 (4 months)

In this clip, Dr. Rhonda Patrick outlines key factors for building and maintaining muscle mass.

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The Science of Protein and Its Role in Longevity, Cancer, Aging, and Building Muscle

Posted on December 3rd 2024 (6 months)

Dr. Rhonda Patrick dives into the science of protein and discusses intake requirements, its ties to longevity, and debunks several protein-related myths.

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  • Regular infrared sauna use increases blood vessel density in aged muscles by 33%, though muscle size, strength, and protein synthesis remain unchanged. pubmed.ncbi.nlm.nih.gov
    Aging Heat Stress Muscle Sauna Protein

    Scientists have speculated that regular heat exposure, such as that experienced in a sauna, might help aging muscles adapt in ways that preserve strength and mass. A recent study found that older adults who engaged in infrared sauna sessions regularly experienced a 33% increase in the number of small blood vessels surrounding their muscle fibers.

    Researchers asked 14 healthy older adults (65 to 85 years old) to sit in an infrared sauna (60°C, 140°F) for 45 minutes, three times weekly, for eight weeks. They collected muscle biopsies before and after the heat exposure to measure capillarization—the number of capillaries around each muscle fiber—as well as muscle size. They also tracked muscle protein synthesis using amino acid infusions and ultrasound imaging to assess how well blood flowed through muscle tissue after eating. Finally, they measured leg strength using a one-repetition maximum test.

    After eight weeks of heat therapy, participants had 31% to 33% more capillaries surrounding both type I and type II muscle fibers. However, muscle blood flow, protein synthesis rates, leg strength, and muscle size did not improve. Body weight, body composition, and walking speed also stayed the same. The only physical performance measure that improved was handgrip strength, which increased slightly. Interestingly, systolic blood pressure dropped by 2%, while diastolic pressure and resting heart rate were unchanged.

    These findings suggest that passive heat treatment can increase blood vessel density in older muscle tissue, but this change alone doesn’t improve nutrient delivery, muscle building, or strength. Heat exposure might support muscle health in other ways, but it doesn’t appear to be a replacement for resistance or aerobic exercise. Learn more about the benefits of heat exposure in Aliquot #96: Thermal Stress, Part I: The Science Behind Heat Stress and its Positive Effects on Health.

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  • Once-weekly, low-volume resistance training boosts physical functioning, energy, and social engagement in older adults while reducing pain by up to 40% and improving strength by 30%. www.sciencedirect.com
    Exercise Aging Muscle

    Resistance training is a powerful tool for improving the health and well-being of older adults, but many guidelines focus on higher training volumes that may be difficult for some to achieve or maintain. A recent study found that once-weekly, low-volume resistance training boosted physical functioning, energy, and social engagement in older adults, reducing pain by up to 40% and improving strength by 30%.

    Researchers assigned 31 older adults (average age, 66) to one of four groups. Participants trained once a week for six weeks, doing leg press exercises with either a slower, controlled pace or a more explosive effort and using lighter or heavier weekly exercise “doses” (either three or five sets of five repetitions). The researchers assessed the participants' quality of life, functional capacity, strength, and body mass at baseline and weeks 3 and 6.

    They found that participants moved more easily, felt more energetic, and reported less pain after the intervention. Their balance and strength improved, and many participants reported more frequent physical activity—an average increase of 25%—and a 20% improvement in mental health. Most participants (85%) continued exercising after the study, and 95% said they would recommend the program. Many valued the structure and support, with 75% finding the shorter three-by-five routine practical and sustainable.

    These findings suggest that lower-dose, once-weekly resistance training interventions can produce meaningful health improvements in older adults. One of the principal benefits of resistance training is building muscle, which is critical for maintaining health during aging. Learn how it’s never too late to start building muscle in this clip featuring Dr. Rhonda Patrick.

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  • Short-term creatine monohydrate use, even without exercise, may boost lean body mass, particularly in women. www.mdpi.com
    Exercise Muscle Supplements

    Creatine monohydrate—one of the most widely studied and popular supplements—has a well-earned reputation for helping increase lean body mass, but some of those gains may come from changes in body water rather than actual muscle growth. A recent study found that creatine monohydrate alone, even without exercise, can boost lean body mass in the short term—especially in women.

    Researchers randomly assigned 63 healthy adults to take either 5 grams of creatine monohydrate daily or nothing. After a one-week “wash-in” period with the supplement, everyone began a 12-week resistance training program. The researchers measured lean body mass using a body scan before and after the wash-in and after the training program.

    After one week of taking creatine without exercising, those who used the supplement had gained about 0.5 kilograms (roughly 1.1 pounds) more lean body mass than the control group—a difference most apparent in women. Once training began, both groups gained about 2 kilograms (4.4 pounds) of lean body mass over 12 weeks, but creatine users did not gain more than those who did not take it, indicating the supplement gave an early bump in lean body mass but did not enhance long-term gains from resistance training.

    These findings suggest that short-term creatine use can raise lean body mass measurements, likely by increasing body water. The investigators posited that higher doses or different timing strategies may be necessary to see continued benefits beyond that initial increase. Learn more about creatine in this episode featuring Dr. Darren Candow.

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  • Post-exercise infrared sauna use contributes to a 25% increase in jump height and a 6.8% peak power boost in female athletes—a potential tool for enhancing power production. pmc.ncbi.nlm.nih.gov
    Exercise Performance Muscle Sauna

    Infrared saunas are gaining in popularity among athletes as a recovery tool, but their effects on strength training adaptations remain uncertain. While traditional saunas can impair performance, infrared saunas may offer a more effective and comfortable recovery option. A recent study found that using infrared saunas after exercise enhances power production but doesn’t influence muscle growth.

    Forty female team sport athletes participated in the study, with half using an infrared sauna after training sessions for six weeks. Sauna sessions were done three times weekly for 10 minutes at 50°C (122°F) following their training. All participants underwent body composition measurements and physical performance tests, including sprint tests, jumps, and leg press exercises, before and after the training period.

    Both groups improved in neuromuscular performance and muscle size. However, the infrared sauna group showed greater jump height and peak power improvements, with a 25% increase in jump height and a 6.8% increase in peak power. Five-minute sprint times were also faster in the infrared sauna group, though not statistically significant. While both groups gained lean mass, the infrared sauna group experienced small body mass and fat mass increases. There were no marked differences between the groups in muscle hypertrophy or other body composition changes.

    These findings suggest that post-exercise infrared sauna use enhances power output over time but doesn’t affect muscle growth. Learn more about the benefits of infrared and traditional sauna use in our overview article.

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  • Higher muscular strength and cardiorespiratory fitness can help reduce the risk of premature death in cancer patients by up to 46%. bjsm.bmj.com
    Exercise Cancer Muscle Mortality Cardiovascular

    Cancer remains one of the leading causes of death globally, with millions of new cases and deaths each year. Despite treatment advancements, cancer patients are at a greater risk of death due to muscle loss, heart complications, and inadequate physical activity. A recent study found that higher muscle strength and cardiorespiratory fitness reduce the risk of death in cancer patients, with a 31% to 46% lower likelihood of premature death.

    Researchers conducted a systematic review and meta-analysis of 42 studies involving more than 47,000 cancer patients across various types and stages to examine how muscle strength and cardiorespiratory fitness influence survival rates. They sought to determine whether higher fitness levels were associated with better outcomes in terms of overall and cancer-specific death.

    Their analysis revealed that patients with higher muscle strength or cardiorespiratory fitness were 31% to 46% less likely to die prematurely from any cause than those with lower fitness levels. Each increase in muscle strength was associated with an 11% lower risk of all-cause mortality. Furthermore, patients with advanced cancer stages, as well as those with lung and digestive cancers, saw significant reductions in death risks—ranging from 8% to 46% lower for all-cause mortality. Increments in cardiorespiratory fitness were particularly important, with each improvement in cardiorespiratory fitness linked to an 18% reduced risk of dying specifically from cancer.

    These findings suggest that boosting muscle strength and cardiorespiratory fitness can improve cancer patients' survival rates. Given the strong connection between physical fitness and mortality risk, health professionals should prioritize fitness assessments for cancer patients as part of their treatment strategies. Learn more about the role of exercise in cancer prevention and recurrence in this episode featuring Dr. Kerry Courneya.

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  • Combining creatine with dextrose accelerates muscle creatine accumulation and maintains elevated levels, potentially boosting muscle mass and performance. www.degruyter.com
    Exercise Muscle Supplements

    Creatine helps supply energy to muscles during high-intensity exercise and is commonly used to boost performance and muscle mass. However, determining the most effective creatine supplementation protocol has proven challenging. A recent study found that combining creatine with dextrose for five days rapidly increases muscle total creatine, with continued consumption maintaining this high level.

    Researchers provided healthy young men with one of four creatine supplementation protocols: Group 1: Four doses of 5 grams of creatine daily for five days, followed by 5 grams daily for 28 days.
    Group 2: Four doses of 5 grams of creatine plus 95 grams of dextrose daily for five days. Group 3: Split from Group 2 after the initial five days:
    Group 3A: 5 grams of creatine daily for 28 days.
    Group 3B: 5 grams of creatine plus 95 grams of dextrose daily for 28 days. Group 4: Four doses of 5 grams of creatine with 14 grams of protein, 7 grams of phenylalanine, 7 grams of leucine, and 57 grams of dextrose daily for five days, followed by a single daily dose of the same combination for the next 28 days.
    The researchers collected muscle biopsies from the participants at baseline, after five days, and after 33 days.

    They found that muscle total creatine increased in Groups 1, 2, and 4 after five days. The largest increase occurred in Group 2, reaching an average maximum of 150 mmol/kg. However, after 33 days:
    Group 1 total creatine increased further to approximately 150 mmol/kg.
    Group 3A showed a tendency to decline.
    Group 3B remained unchanged from the level observed at five days.
    Group 4 remained unchanged from the level observed at five days and was lower than Group 1. Creatine transporter gene expression changed slightly in all groups. However, the more creatine levels increased after five days, the smaller the change in this gene’s activity.

    These findings suggest that combining creatine with dextrose for five days rapidly increases total muscle creatine. Continued consumption of creatine with dextrose helps maintain this high level. While ingesting creatine alone also boosts total muscle creatine, it takes longer to reach levels similar to those in combination with dextrose. Learn more about creatine in this episode featuring Dr. Rhonda Patrick.

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  • Mechanical stresses and myokines produced by muscles during exercise synergistically promote nerve growth and connectivity. onlinelibrary.wiley.com
    Exercise Muscle Neurodegeneration

    Muscle contraction, the hallmark of exercise, releases signaling molecules called myokines that influence cell function throughout the body. However, the mechanical forces it generates may also play a role. A recent lab study found that biochemical and mechanical signals from contracting muscle work synergistically to promote nerve growth and maturation.

    Researchers grew muscle cells on a specialized gel that mimicked the movements of contracting muscles. Then, by adding tiny magnetic particles, they stretched the cells to simulate exercise. They assessed how these forces and the myokines released by the muscle cells influenced the growth of nerve cells.

    They found that nerve cells grew and migrated more readily when exposed to myokines from contracting muscle cells, with more robust effects at higher levels of muscle activity. Stretching the nerve cells mechanically produced similar growth, but further analysis demonstrated that chemical signals were more effective in activating genes related to nerve growth and forming connections.

    These findings suggest that exercise influences nerve health through biochemical and mechanical pathways, providing new insights into how muscle activity supports the nervous system. Myokines also exert anti-cancer effects. Learn more in this episode featuring Dr. Rhonda Patrick.

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  • High-protein, low-calorie diets—whether animal or plant-based—lead to an average weight loss of ~18 pounds and improved glucose metabolism in people at risk for type 2 diabetes. dom-pubs.pericles-prod.literatumonline.com
    Diet Obesity Diabetes Muscle Protein Weight Loss

    The global obesity epidemic is driving a marked increase in the incidence of type 2 diabetes, and some experts estimate that by 2024, more than 780 million adults worldwide will develop the disease. A recent study found that high-protein, low-calorie diets promote weight loss and improve cardiometabolic markers in people at risk for type 2 diabetes.

    The study involved 117 adults with either prediabetes or type 2 diabetes and a body mass index (BMI) over 27.5—considered overweight or obese. Participants consumed an animal- or plant-based high-protein diet that provided 35% of their total calories for six months. The remainder of their calories came from fat (30%) and carbohydrates (35%).

    Participants in both groups saw similar improvements in body composition, including an average weight loss of approximately 8 kilograms (~18 pounds) and reduced visceral (abdominal) fat. Glucose metabolism indicators, such as fasting glucose and glycated hemoglobin levels, improved equally in both groups, as did lipid levels, liver enzymes, and inflammatory markers.

    These findings suggest that high-protein, low-calorie diets—whether animal- or plant-based—can improve body composition, glucose metabolism, and other cardiometabolic markers in people with prediabetes or type 2 diabetes.

    Dietary protein supports muscle hypertrophy and maintenance—critical aspects of glucose metabolism. Learn how to optimize protein intake to support muscle health when following a plant-based diet in this clip featuring Dr. Luc van Loon.

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  • Magnesium supplementation reduces post-workout muscle soreness and enhances recovery in both recreational runners and elite athletes. translational-medicine.biomedcentral.com
    Exercise Performance Magnesium Muscle

    Muscle contraction relies on a magnesium-dependent calcium transport system. Consequently, magnesium levels drop after exercise, increasing muscle soreness and impairing performance. A recent review found that magnesium supplementation reduces muscle soreness, improves performance, and protects against muscle damage.

    Researchers reviewed the findings of four studies investigating the effects of magnesium supplementation on muscle soreness. The studies included 73 participants (60 males and 13 females) between the ages of 19 and 27. One study focused on muscle soreness, one on running performance, and two on team sports performance.

    They found that 350 milligrams of magnesium glycinate daily reduced muscle soreness and improved recovery after resistance training. Similarly, 500 milligrams of magnesium oxide and stearate taken daily for a week reduced muscle soreness in recreational runners with low dietary magnesium intake. Markers of muscle damage decreased in elite basketball players who took 400 milligrams of magnesium daily throughout the season. Competitive cyclists experienced similar effects at the same dose.

    These findings suggest that magnesium supports muscle health and performance in recreational and competitive athletes. The review’s authors posited that physically active people need 10% to 20% more magnesium than the recommended doses taken two hours before physical activity, even during the off-season. For more information about magnesium, check out our deep-dive podcast and our comprehensive overview article.

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  • Naringenin, a citrus fruit flavonoid, preserves muscle mass in aging while enhancing exercise capacity and aerobic metabolism efficiency (animal study). medicalxpress.com
    Nutrition Aging Muscle Polyphenol

    Muscle mass declines markedly with age, with up to 8 percent muscle mass loss occurring per decade after age 30. Evidence suggests that naringenin, a flavonoid compound found in citrus fruits, maintains muscle mass in aging. Mice that ate a diet supplemented with naringenin showed improved muscle endurance and grip strength.

    Researchers supplemented the diets of young adult mice, middle-aged mice, and mice prone to muscular dystrophy (accelerated muscle loss) with naringenin. Then, they assessed naringenin’s effects on exercise capacity and aerobic metabolic levels in skeletal muscle.

    They found that young adult and middle-aged mice receiving naringenin could run farther than those that did not. Middle-aged mice also showed improved grip strength and increased calf muscle size. Mice prone to developing muscular dystrophy ran farther and showed improved grip strength.

    The researchers attributed these improvements in muscle endurance to naringenin’s capacity to increase the number of oxidative myofibers (muscle fibers that use oxygen) and improve the overall efficiency of aerobic metabolism in the body. They found that Sp1, a transcription factor that influences gene expression in muscle, likely mediated naringenin’s effects.

    These findings indicate that naringenin may preserve muscle mass in aging and disease. Other dietary components, such as omega-3 fatty acids, influence muscle maintenance, too. Learn more in this episode featuring Dr. Chris McGlory.

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  • Vitamin D increases muscle strength and mass without altering body weight in mice. www.biorxiv.org
    Vitamin D Obesity Aging Metabolism Hormones Muscle

    Vitamin D, best known for maintaining calcium balance and bone health, is critical in many physiological processes, including blood pressure regulation, immune function, and cell growth. Evidence now suggests vitamin D also influences body composition and muscle strength. A recent study in mice showed that high vitamin D intake increased muscle strength and mass without altering body weight.

    Researchers fed mice one of three diets, providing low, normal, and high doses of vitamin D for four weeks to achieve deficient, insufficient, and sufficient vitamin D concentrations, respectively. At the end of the fourth week, they assessed the animals' grip strength (a measure of muscle function) and body composition.

    They found that compared to low or normal vitamin D intake, high intake increased grip strength and lean mass and decreased fat mass without altering the animals' weights. High intake also impaired myostatin production and increased the animals' leptin sensitivity and energy expenditure without altering their activity levels.

    Leptin is a satiety hormone that signals the brain to balance energy. When body fat increases or decreases, blood concentrations of leptin change accordingly. Higher leptin levels signal the brain to reduce hunger and boost energy use. However, in obesity, the body becomes less responsive to leptin, dulling its effects on appetite and energy expenditure.

    These findings suggest that vitamin D influences body composition and metabolism by preferentially allocating calories toward muscle development and overall growth rather than fat storage. They also highlight the intricate relationship between obesity and vitamin D status. Learn more about vitamin D in our comprehensive overview article.

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  • Hydrolyzed collagen increases knee joint strength and tendon stiffness by 18 percent. www.frontiersin.org
    Muscle Bone Supplements

    A new study shows that hydrolyzed collagen strengthens knee tendons in female soccer players. Those who took supplemental collagen experienced an 18 percent gain in knee tendon stiffness, potentially reducing their risk for injury during play.

    The study involved 17 elite teenage female soccer players. Half of the players consumed a hydrolyzed collagen supplement plus vitamin C three times a week for ten weeks. The other half consumed a placebo. Both groups participated in a training regimen designed to strengthen the knee and thigh muscles. A team of researchers measured various parameters of the players' knee tendon thickness and strength before and after the intervention.

    They found that the players who consumed the supplemental hydrolyzed collagen experienced an 18 percent increase in their knee tendon stiffness. However, they experienced little change in tendon thickness, suggesting that the increase in stiffness was due to changes in the tendon’s material properties subsequent to collagen intake.

    Female soccer players are more likely to experience knee injuries than male players, due in part to greater knee joint laxity. These findings suggest that supplemental hydrolyzed collagen support training regimens to bolster knee strength in female athletes.

    Hydrolyzed collagen is a mixture of peptides derived from the protein collagen. Evidence suggests that supplemental hydrolyzed collagen consumption improves skin aging, decreases arthritis-induced pain, increases bone mineral density, and decreases hypertension. Learn more about hydrolyzed collage in our overview article.

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  • Study shows that high protein does not affect kidney function across a wide variety of metrics. journals.humankinetics.com
    Muscle Protein

    “We’ve got 40 years’ worth of data with people on [protein supplementation] now. And we’re not seeing some sort of rife wave of people who used it getting various forms of cancer, etc., which you would expect. Forty years is enough to see the effect.” - Stuart Phillips, Ph.D. on high protein supplementation

    High protein intake is often believed to be harmful to kidney function, but robust evidence indicates that this concern is unfounded. A 2000 study demonstrated that athletes with high protein consumption do not have an increased risk for kidney dysfunction.

    Researchers asked bodybuilders and other athletes to keep detailed dietary records for one week after following their normal dietary patterns for one month. Then the researchers assessed the participants' kidney function via blood tests and urinalysis. They also measured their nitrogen balance – an assessment of the net balance of protein metabolism in the body drawn from estimates of nitrogen losses that occur via urine, feces, sweat, and other means.

    They found that, on average, daily protein intake was approximately 1.97 grams per kilogram of body weight among the bodybuilders and 1.35 grams per kilogram of body weight among the other athletes. Despite their high protein intake, the participants' urinary output of creatinine, urea, and albumin was normal, as were other kidney health parameters. Both the bodybuilders and the other athletes achieved nitrogen balance when their daily protein intake exceeded 1.26 grams per kilogram of body weight.

    The current recommended dietary allowance for protein intake is 0.8 grams per kilogram of body weight (~0.36 grams per pound) per day – about 68 grams for a 150-pound adult. Nutrition experts established this guideline several decades ago, based on evidence from nitrogen balance studies, which are often inaccurate due to problems with collection and overestimation of losses. Based on findings from more recent stable isotope studies, which more accurately assess muscle protein anabolism and catabolism, evidence suggests that eating 1.2 to 1.6 grams of protein per kilogram of body weight is likely optimal for muscle protein synthesis, especially as one ages. Learn more in this episode featuring Dr. Stuart Phillips.

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  • Short-term aerobic conditioning prior to resistance training augments muscle hypertrophy and satellite cell content in healthy young men and women pubmed.ncbi.nlm.nih.gov
    Exercise Muscle Aerobic

    Aerobic exercise pre-conditions muscles for optimal returns from resistance exercise.

    Skeletal muscle contains a designated population of adult stem cells called satellite cells. These cells are typically inactive, but if the muscle is injured or stressed (as in exercise), they can be recruited to participate in the regeneration of muscle fibers. As such, satellite cells play important roles in muscle maintenance, repair, and hypertrophy, the increase in muscle size that accompanies exercise. Findings from a new study suggest that engaging in aerobic exercise prior to resistance training increases satellite cell numbers and promotes muscle hypertrophy via increased muscle capillarization.

    Muscle capillarization refers to the formation of capillaries in muscle tissue. Capillarization facilitates the delivery of oxygen, nutrients, and various signaling and growth factors to muscle tissues and plays critical roles in muscle maintenance and growth. Previous research indicates that muscle capillarization decreases with age.

    The study involved 14 healthy, recreationally active young adults (average age, 22 years). Using a specially adapted exercise bike that challenged only one leg, participants engaged in 45 minutes of progressively difficult aerobic exercise conditioning three times a week for six weeks. Previous research has demonstrated that six to eight weeks of conditioning is sufficient to promote muscle capillarization.

    Two weeks after completing the conditioning program, the participants began a 10-week resistance training program using both legs and primarily targeting the muscles of the thighs. Immediately after each resistance training session, participants received a whey protein supplement that contained leucine, a branched-chain amino acid that promotes muscle protein synthesis, which is essential for muscle gains. The investigators collected muscle tissue samples from the participants' legs before and after the interventions to assess muscle capillarization, fiber size, and satellite cell content and activity.

    They found that aerobic conditioning promoted muscle capillarization in the conditioned leg, amplifying muscle hypertrophy in response to resistance training. They noted that the number of satellite cells increased in the conditioned leg relative to the non-conditioned one. In addition, they observed a significant relationship between the degree of capillarization and hypertrophy.

    These findings suggest that engaging in aerobic exercise prior to resistance training promotes muscle capillarization, which in turn increases satellite cell numbers and promotes muscle protein synthesis and hypertrophy. Learn about other factors that promote muscle hypertrophy in this episode featuring Dr. Stuart Phillips.

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  • The secret to staying young: New research highlights power of life long exercise to keep muscles healthy www.sciencedaily.com
    Exercise Aging Muscle

    Lifelong exercise protects older adults from losing muscle mass and function with age.

    With age, muscles shrink in size and lose strength, a process called sarcopenia that can increase frailty and reduce the quality of life for older adults. In people with sarcopenia, muscle fibers contain fewer satellite cells (i.e., muscle stem cells) and progressively lose their connections to nerves, a process called denervation. Findings of a new report show that lifelong exercisers have more youthful muscles that resist denervation.

    Satellite cells are stem cells that proliferate, fuse together, and form the long tubular structures than comprise muscle fibers. Satellite cells are necessary for muscle repair and growth after exercise, a process called hypertrophy, due to their connection with cells that produce growth factors and deliver nutrients. Previous research demonstrates that exercise interventions that last several weeks can reverse muscle denervation in older adults with frailty; however, the preventive effects of lifelong exercise have yet to be investigated.

    The authors recruited 15 moderately active young men (average age, 26 years), 16 older men who were lifelong exercisers (average age, 73 years), and 15 older men who lived a sedentary lifestyle (average age, 73 years). On their first visit to the lab, participants completed a bout of heavy resistance training on only one side of their body so that the researchers could compare the effects of exercise and sedentary behavior in each person. The researchers also measured maximum muscle strength and body composition and collected a blood sample. Participants provided another blood sample two days and six days after the exercise challenge and provided a muscle biopsy sample six days after.

    Lifelong exercisers had muscles that were more resistant to fatigue during exercise compared to sedentary young and older adults. Compared with sedentary older adults, lifelong exercisers had more satellite cells in their muscles connected to type 2 myofibrils, which are important for fast-twitch muscle movement, but no difference in connection to type 1 slow-twitch myofibrils. Muscles from lifelong exercisers also expressed high levels of mRNA for acetylcholine receptors, which are necessary for preventing denervation.

    These results show that lifelong exercisers maintained a more youthful muscle profile due to increased connections with muscle- and nerve-supporting satellite cells. People who started life with a sedentary lifestyle can still reap the longevity-promoting benefits of exercise. Starting a new aerobic exercise habit, even at age 70, cuts heart disease death in half.

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  • Whole-body hyperthermia activates muscle hormone irisin and increases neuroprotective factors. www.sciencedirect.com
    Exercise Brain Muscle Sauna BDNF Neurodegeneration

    Exposure to high heat while sauna bathing causes mild hyperthermia – an increase in the body’s core temperature – that induces a thermoregulatory response to restore homeostasis and condition the body for future heat stressors. These adaptations to high temperatures involve increased production of brain derived neurotrophic factor (BDNF), a promoter of neuroplasticity, and irisin, a biomarker of exercise. Findings of a new report demonstrate that whole-body hyperthermia increases BDNF and irisin in healthy young adults.

    Whole-body hyperthermia is a therapeutic strategy used to treat various diseases, including cancer and depression. Previous research has shown that use of a hyperthermia chamber increases BDNF to a greater extent than light intensity exercise. Some research has suggested that BDNF production is stimulated by irisin, a hormone secreted from muscle in response to exercise. Irisin may mediate some of the beneficial effects of exercise and sauna use in humans, but additional research is needed.

    The authors recruited 20 male participants (average age, 22 years) and assessed their baseline heat tolerance using a hyperthermia protocol. Participants reclined in a hyperthermia chamber while the researchers increased the temperature of the chamber by 50 degrees F every ten minutes until the participant reached their personal heat threshold. Next, participants completed ten hyperthermia sessions tailored to their baseline conditioning, during which the hyperthermia chamber was set to a temperature of 150 to 175 degrees F. Following a three-week wash-out period, they completed ten sham treatments over two weeks, during which the hyperthermia chamber was set to a temperature of 75 to 77 degrees F.

    Participants had an average core body temperature of 102 degrees F at the end of each whole-body hyperthermia treatment. Following ten whole-body hyperthermia treatments, participants had a significant increase in circulating irisin levels (6.3 micrograms per milliliter) compared to their baseline levels (5.0 micrograms per milliliter) and compared to their irisin levels following the sham treatment (5.4 micrograms per milliliter). Whole-body hyperthermia treatment also significantly increased BDNF levels (28.3 picograms per liter) compared to baseline (25.9 picograms per liter).

    In healthy young adults, ten whole-body hyperthermia significantly increased irisin and BDNF levels. The authors noted that future studies should explore the effects of whole-body hyperthermia on adipose tissue, which also produces irisin.

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  • Time-restricted eating improves athletic performance. www.mdpi.com
    Exercise Fasting Fat Muscle Time-Restricted Eating

    Time-restricted eating involves restricting the timing of food intake to certain hours of the day (typically within an 8- to 12-hour time window) without an overt attempt to reduce caloric intake. Increasing the amount of time spent fasting each day has been used to treat metabolic diseases such as type 2 diabetes and high cholesterol, increase muscle mass, decrease fat mass, and improve exercise performance. Findings of a recent report demonstrate the beneficial effects of time-restricted eating on exercise performance in power athletes.

    Increasing muscle mass and decreasing fat mass is an important goal for many athletes because increasing their strength-to-mass ratio improves performance. While time-restricted eating is one strategy to improve body composition, previous research has shown that other types of intermittent fasting (e.g., religious fasting during Ramadan) decrease power output and endurance. Another study involving intermittent fasting with caloric restriction found similar deficits in athletic performance. The effects of long-term time-restricted eating without caloric restriction are unknown.

    The researchers recruited healthy young males who were currently practicing a power-sport at least three times per week and had been practicing for at least three years. Twelve participants (average age, 22 years) completed four weeks of time-restricted eating and four weeks of a standard meal pattern in random order with two weeks of wash-out in between. During the time-restricted eating period, participants consumed all of their food within an eight-hour window. The researchers measured body composition using X-ray and athletic performance using the Wingate test, a cycling challenge that measures power and total work.

    Time-restricted eating produced a significant increase in total work (a measure of force over a set distance) and average power output (a measure of work over time). These improvements translated to a one second reduction in sprinting time. The participants achieved this change after four weeks of time-restricted eating, but not after one week. Time-restricted eating did not improve peak power, endurance, or body composition.

    Time-restricted eating, along with regular training, improved exercise performance in athletes. Given that the difference between the current and former 400 meter running world records is only 15 hundredths of one second, the one second decrease in sprinting time produced by time-restricted eating is meaningful.

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  • Depression is associated with muscle loss in older adults. journals.plos.org
    Aging Depression Muscle Dementia

    Sarcopenia, the loss of muscle mass with age, is related to falling, poor oral health, and chronic disease. Sarcopenia is a progressive disorder, but early interventions with diet and exercise may improve health outcomes. Authors of a new report investigated the relationship between sarcopenia progression, depression, dementia, and hypertension.

    Body composition shifts across the lifespan, with a progression toward lower muscle mass and increased fat mass after age of 60. Because fat and muscle participate in whole-body metabolism and hormone signaling, this shift in body composition contributes to the development of age-related diseases. Previous research has reported a link between sarcopenia, cognitive impairment, and depressive symptoms in older Korean men, but research is needed in additional demographic groups.

    The authors collected data from more than 750 adults aged 60 years and older living in Japan. Participants completed surveys to measure depression and dementia status and underwent a physical examination that included the measurement of blood pressure, height, muscle mass, grip strength, and walking speed. The investigators classified participants as having sarcopenia if they had low skeletal muscle index (i.e., the ratio of the muscle in a person’s arms and legs to their height), poor grip strength, and slower walking speed. They defined pre-sarcopenia as having a low skeletal muscle index with normal grip strength and walking speed. Finally, they classified participants with a normal skeletal muscle index as robust.

    Sarcopenia was associated with increased age and depression severity, but reduced hypertension. Compared to robust participants, those with pre-sarcopenia were more likely to have depression and hypertension. However, sarcopenia was not associated with dementia, which the authors noted may have been due to the small number of participants (only 49) with dementia.

    The authors suggested that future research should explore strategies for management of depression, dementia, and hypertension in the prevention of sarcopenia.

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  • Body fat increases the risk of death, while muscle mass decreases it. academic.oup.com
    Aging Muscle

    Body mass index (BMI) is a measure of body size that is calculated by dividing a person’s weight by their height. A wealth of research has demonstrated that having a body mass index outside of the normal range (18.5 to 25) increases the risk of death. However, body mass index does not differentiate fat and muscle mass. Authors of a new report investigated the effects of body composition on risk of death.

    Extra body fat has been shown to increase the risk of developing a number of chronic lifestyle diseases, while increased muscle (fat-free) mass has been shown to decrease disease risk. Previous research has demonstrated mixed results for the effect of body composition and risk of death, likely due to differences in study design.

    The authors combined data from seven studies with over 16,000 participants between the ages of 20 and 93 years collected between 1994 and 2008. Researchers measured body composition using bioelectrical impedance and adjusted for age and sex. They also interviewed participants about their health, lifestyle, and socioeconomic factors and tracked them for an average of 14 years.

    After adjusting for a number of demographic and lifestyle factors, the researchers found that having body fat below or above the normal range increased risk of death among the participants. Those with high body fat (37 kilograms) had a 56 percent greater risk of death, while those with highest fat-free mass had a 30 percent lower risk of death.

    The authors concluded that fat mass and fat-free mass have opposite effects on the risk of death. They noted that their study included a large number of participants and a long follow-up period, which strengthened the quality of their results.

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  • Different forms of vitamin D have distinct impacts on muscle mass and strength. www.medicalnewstoday.com
    Vitamin D Muscle

    The loss of muscle mass and strength, known as sarcopenia, is a significant problem in aging, affecting both healthspan and quality of life. Findings from a recent study suggest that vitamin D affects muscle function through diverse metabolic pathways.

    Clinicians determine a person’s vitamin D status by measuring 25-hydroxyvitamin D3, or 25(OH)D3 — the inactive circulating form of vitamin D. However, a new technique, high-throughput liquid chromatography-tandem mass spectrometry (LC-MS/MS), allows researchers to quantify additional vitamin D metabolites. While these other metabolites, part of what is termed the vitamin D metabolome, are present in low concentrations in the blood, they can perform critical functions in tissues, such as muscles.

    Previous research has examined the relationship between vitamin D and muscle function yielding inconsistent results; however, these studies have mainly focused on 25(OH)D3. The current study investigated whether other vitamin D metabolites are associated with muscle function.

    The cross-sectional study involved 116 healthy adults who performed handgrip and lower limb strength tests, while a subset of 85 participants consented to thigh muscle biopsies. The authors assessed the participants' vitamin D status using LC-MS/MS, steroid metabolites from urine samples, and the expression of 92 genes from the muscle biopsies. The authors also measured lean body mass and body fat percentages.

    Only 14 percent of participants had normal vitamin D levels, while 28 percent had insufficient levels, and 58 percent were found to be deficient. Subjects with a higher percent body fat had lower vitamin D levels. Participants with higher muscle mass had higher active vitamin D levels. Those with higher active, but not inactive vitamin D levels scored better on the muscle strength tests. The authors observed that the expression of 24 skeletal muscle genes correlate with levels of serum 25(OH)D3.

    These findings highlight the complex relationship between vitamin D, gene expression, and muscle function. They suggest that the maintenance of muscle mass and strength is complicated, and it may be more appropriate to measure other vitamin D forms rather than just 25(OH)D3.

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  • Whole-body heat exposure alters skeletal muscle signaling and mitochondrial biogenesis in humans. www.frontiersin.org
    Muscle Sauna

    Muscle loss can occur as part of a disease process, trauma, or aging. Although exercise can prevent muscle loss, some medical conditions or physical limitations can make exercise difficult or even impossible. Findings from a new study indicate that hyperthermia may preserve or increase muscle mass and increase mitochondrial biogenesis.

    Hyperthermia is a state of elevated core body temperature that activates molecular mechanisms that mitigate protein damage and drive the body’s in-house repair systems. Mitochondrial biogenesis is the process by which new mitochondria are made inside cells. Many factors can activate mitochondrial biogenesis including exercise, hyperthermia, and others.

    The study involved nine healthy young men (average age, 35 years) who underwent two 60-minute sessions of passive heat treatment, separated by one week. One session was a whole-body treatment at 44˚C to 50˚C (111˚F to 122˚F) and 50 percent humidity. The other session was a single-leg treatment using a water-perfused suit at approximately 50˚C (122˚F). The authors of the study monitored core, skin and quadriceps muscle temperatures throughout the sessions and took muscle biopsies before, 30 minutes after, and three hours after the heat treatments.

    The whole-body heat treatment switched on the activity of molecules involved in the Akt/mTOR biological pathway, a critical regulator in maintaining skeletal muscle mass. It also increased the expression of heat shock proteins and Nrf2. Nrf2 is a cellular protein that regulates the expression of antioxidant and stress response proteins. Its activity is an indicator of mitochondrial biogenesis. These changes were not evident when the participants received single-leg heat treatment, suggesting that whole-body hyperthermia elicits systemic improvements involved in muscle maintenance and mitochondrial health.

    Interestingly, whole-body heat inhibited the activity of some FOXO proteins and switched on the activity of some genes involved in atrophy. Further study is needed to determine the full effects of whole-body hyperthermia on muscle atrophy.

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