How Resistance Training Helps To “Rejuvenate” Aging Skin
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The benefits of exercise on human health are numerous, but how different types of training can impact the health of our skin isn’t yet clear. A new study by scientists at Ritsumeikan University in Kyoto, Japan, suggests that resistance training (RT) can improve skin elasticity and dermal thickness in women. The research is published in Scientific Reports.
Skin health and exercise
Beyond esthetics, taking care of our skin is critical for our overall health. The largest organ in the human body, the skin senses our external environment and acts as an important barrier for our internal systems, helping to fend off infection and disease. The continually growing skincare industry is projected to generate approximately $182 billion U.S. dollars by 2027. Topical serums, lotions and treatments can be effective at tackling skin deterioration and aging from the outside in, but what can we do to protect our skin from the inside out?
The structure of skin
Skin has three main layers:
- The epidermis – the elastic outer layer of skin that is constantly regenerating. It comprises cells such as keratinocytes and melanocytes, the latter of which produces melanin and contributes to skin tone.
- The dermis – sits below the epidermis and contains connective tissue, sweat glands, hair follicles and sebaceous glands.
- Subcutaneous tissue – beneath the dermis, this layer is made of fat and connective tissue.
Aging is associated with a deterioration of the dermis – the middle skin layer – which can disrupt the beneficial functions that skin serves in maintaining our health. Why dermis deterioration occurs is a complex question – a multitude of factors can affect the extracellular matrix (ECM) and mitochondrial metabolism in tissue, leading the skin to age and weaken. Environmental effects, such as UV or environmental pollution, hormonal changes and an increase in circulating inflammatory cells such as cytokines, are known contributors.
The beneficial effects of physical activity on human health are well-known. Making time for 150 minutes of moderate physical activity per week can reduce our risk of heart disease and stroke. Regular movement helps to counteract diabetes and metabolic syndrome risk, encourages stronger bones and can positively affect our mental health. But what about skin health?
Skeletal muscle as an endocrine organ
Skeletal muscle can act as an endocrine organ, whereby the contracting of muscle fibers causes changes in circulating hormones and cytokines levels, which may be the “molecular mediators” of exercise’s positive effects on human health.
In 2015, Professor Mark Tarnopolsky, a physician and director of the Neuromuscular and Neurometabolic Clinic at McMaster University, Canada, published a study suggesting that endurance exercise can help to regulate skin metabolism and aging. Analyzing skin biopsies from the buttocks – a region less exposed to the external environment – Tarnopolsky found that endurance exercise reduced age-associated changes in the skin. The mediator of this change was identified as the inflammatory cytokine interleukin-15 (IL-15), the research team describes: “We show that exercise controls IL-15 expression in part through skeletal muscle AMP-activated protein kinase (AMPK), a central regulator of metabolism, and that the elimination of muscle AMPK causes a deterioration of skin structure.”
Endurance training generally refers to training that activates the aerobic system, also known as aerobic training or AT. Aerobic training might include swimming, running, cycling or brisk walking. Exercise scientist Satoshi Fujita at Ritsumeikan University questioned whether RT, commonly known as “weight training”, might induce a different effect on skin aging. “We performed a 16-week, randomized study in 61 healthy sedentary middle-aged Japanese women and measured circulating levels of various factors in blood samples taken from participants before and after the training intervention. In parallel, plasma samples were added to normal human primary dermal fibroblasts (NHDFs), and the expression of dermal ECM-related genes was quantified,” Fujita and colleagues say.
Resistance training increases skin elasticity and dermal thickness
Half of Fujita and colleagues’ participants were assigned to cycle for 30 minutes twice per week, while the other half were assigned to undertake a RT program for the same period of time and at the same frequency. In addition to exploring the molecular effects of RT training, the researchers used ultrasound and other techniques to assess skin thickness, elasticity and structure. All measures were obtained at baseline and after 16 weeks of training. “At baseline, no significant differences were found between the AT and RT groups in participant characteristics such as age, dietary intake, skin aging property, body composition and physical capacity,” Fujita and team report.
Across both groups of women, skin elasticity and dermal structure were significantly improved after 16 weeks of training. When assessing changes in gene expression, the researchers found that AT and RT induced changes in dermal ECM-related genes, including genes encoding collagen and proteoglycans. In the RT group specifically, dermal thickness increased, associated with increased expression of proteoglycan-related genes, including biglycan (BGN).
What are proteoglycans?
Proteoglycans are the main component of the ECM in animals. They form complexes with hyaluronic acid, collagen and other proteoglycans to “fill in the gaps” between an organism’s cells, supporting firmness in the skin.
To understand why RT training increased dermal thickness, the researchers focused on BGN: “BGN-knockout mice were reported to show a thinned dermis phenotype, and biglycan levels were found to decrease with aging and sun-exposure; taken together, these findings suggest that increased BGN expression could lead to increased dermal thickness,” they describe. Compared to AT training, RT training led to a decrease in the circulating levels of molecules that are known to suppress BGN expression, including CCL28, N,N-dimethylglycine and CXCL4.
Youthful skin a bonus of exercising
Collectively, the data suggest that this mechanism results in an increased dermal thickness after AT training. Why AT training didn’t produce the same effect isn’t yet clear: “The study clarified only the mechanism by which RT counteracts age-associated dermal thinning, and the other mechanisms of AT- and RT-driven skin rejuvenation remain to be elucidated,” Fujita and colleagues say.
Before you rush off to join a gym or add a kettlebell to your online shopping cart, it’s worth noting that there are several limitations to this study that impact how applicable the results are to the wider population. It’s a short study – 16 weeks in length – the scientists cannot definitively state how RT or AT affects skin long-term based on this data alone. A control group was not included, and the research was conducted in a specific population: middle-aged Japanese women. Whether the same effects would be observed in a male population, or a group of participants in a different age bracket, needs to be determined.
Limitations aside, this is the first study to report on the different effects of AT and RT on skin aging, according to the researchers. It’s a step in the right direction to understanding how different physical activity programs might produce beneficial effects for our skin health. Given that AT and RT are associated with numerous health benefits, if you’re already active, perhaps consider the possibility of healthy and youthful-looking skin as an added bonus.
Reference: Nishikori S, Yasuda J, Murata K, et al. Resistance training rejuvenates aging skin by reducing circulating inflammatory factors and enhancing dermal extracellular matrices. Sci Rep. 2023;13(1):10214. doi: 10.1038/s41598-023-37207-9