The benefits of exercise on the skin.

Satoshi FUJITA and his colleagues compared the effects of aerobic training and resistance training on skin ageing over a 16-week period in 61 women. They measured the circulating levels of various factors in blood samples taken from the participants before and after the training. Concurrently, plasma samples were added to human dermal fibroblasts to quantify the expression of genes related to the dermal extracellular matrix (collagen, elastin...).

Both exercises have significantly improved skin elasticity and the structure of the upper dermis compared to the time before the exercise, moving from an elasticity recovery rate of about 0.31 to around 0.37. Resistance training also improved the thickness of the dermis with an increase of 0.05 mm. After training, the expression of genes related to the dermal extracellular matrix increased in normal human primary dermal fibroblasts. Finally, resistance training increased dermal biglycan, a skin glycoprotein, from 1 to 1.10.

All these results indicate a positive effect of physical exercise on reducing skin ageing. Studies have shown that exercise couldincrease the biogenesis of mitochondria, and therefore maintain the structure of the skin. Moreover, during exercise, blood circulation increases, stimulating the skin's fibroblastic cells and the production of collagen is promoted, a fundamental dermal fibre for skin elasticity.

In a study, Aibara HIROMI and her team sought to measure the impact of exercise habits on skin hydration function. To do this, they surveyed 86 participants about their level of physical activity using a questionnaire. They also examined their skin hydration function, by measuring the hydration levels of the stratum corneum and transepidermal water loss (TEWL).

Comparisons of participants' activity levels, hydration of the stratum corneum, and Transepidermal Water Loss (TEWL), taking into account differences in sex and age, revealed that increased activity is associated with a significantly higher skin hydration. The higher the activity levels, the higher the hydration, moving from a hydration score of 34.4 for the least active individuals to 46.5 for the most active. No difference was observed regarding TEWL. The results do suggest, however, that exercise habits can prevent skin dryness.

Researchers believe that the decline in skin functions, such as skin hydration and barrier function, is due to pronounced deletions of mitochondrial DNA caused by the impact of UV rays, for example. This then leads to an increased production of free radicals, which are responsible for cellular damage that disrupts the cells' ability to maintain good skin hydration through homeostasis. It would therefore be necessary to stimulate mitochondrial biosynthesis to maintain the cellular ability to regulate hydration. Endurance exercise induces the production of the cytokine IL-5, which promotes mitochondrial biosynthesis. As a result, the skin's structure improves, associated with better skin hydration.

Furthermore, a study conducted by Li LI found that after measuring the pH and hydration of the skin's corneal layer in individuals at rest and those engaging in physical activity, perspiration could potentially increase skin hydration. Indeed, hydration increased by almost 50% during exercise compared to rest. With metabolism being more active, the content of α-hydroxy acids, such as lactic acid and hydroxybutyric acid, increases. These are naturally present in sweat and are part of the natural moisturising factors (NMFs) that could enhance the hydration of the corneal layer by binding to it.

However, it is not precisely known which type of exercise (endurance, strength, etc.) is most effective in achieving this goal. Any potential differences between the effects need to be studied.

Abrar A. QURESHI and his team sought to evaluate the association between physical activity and psoriasis, a common inflammatory skin disease, within a cohort of women in the United States. They also assessed the association between the type of physical activity, for example, walking or vigorous exercise, and the risk of psoriasis. The population studied included 86,655 American nurses who reported having been diagnosed with psoriasis and who completed detailed questionnaires about their physical activity in 1991, 1997 and 2001.

After adjusting for age, smoking, and alcohol consumption, an increase in physical activity was inversely associated with the risk of psoriasis. The quintile of women who were most physically active had a lower relative risk (RR) of psoriasis (0.72) than the least active quintile (1.06). Walking was not associated with the risk of psoriasis. Furthermore, in a subset of 550 confirmed psoriasis cases, a more significant reduction in the risk of psoriasis was observed with intense physical activity (0.64).

It is biologically plausible that intense activity could modulate the state of chronic inflammation or immune activation that predisposes to psoriasis. An over-expression of pro-inflammatory cytokines compared to anti-inflammatory molecules plays a significant role in the pathogenesis of psoriasis, and conditions marked by increased chronic inflammation, such as obesity, can heighten the risk of psoriasis. It is known that physical activity decreases this chronic inflammation and specifically reduces the levels of pro-inflammatory mediators, such as the TNF-α, IL-6 and leptin. Physical activity can increase the levels of anti-inflammatory cytokines, including adiponectin. Furthermore, physically active women have lower levels of C-reactive protein (CRP), an inflammatory marker.

Another significant finding from the study is that walking and intense physical activity do not confer similar reductions in the risk of psoriasis; only intense activity reduces it. This observation can be explained by the more substantial effects of moderate to vigorous activity on systemic inflammation. In the context of an interventional trial, a 12-week programme of low to moderate intensity aerobic exercises did not alter the serum levels of TNF-α, IL-6 and CRP in obese women. However, vigorous intensity aerobic exercises may reduce the levels of inflammatory markers and thus reduce the risk of developing inflammatory skin conditions such as psoriasis.

However, further studies on the subject are necessary to confirm these results.

• LI L. & al. Effect of exercise-induced sweating on facial sebum, stratum corneum hydration, and skin surface pH in normal population. Skin Research and Technology (2012).

• QURESHI A.A. & al. The association between physical activity and the risk of incident psoriasis. Archives of Dermatological Research (2012).

• BIRCH-MACHIN M. and STOUT R. Mitochondria’s role in skin ageing. Biology (2019).

• HIROMI A. & al. The association between activity levels and skin moisturising function in adults. Dermatology Reports (2021).

• FUJITA S. & al. Resistance training rejuvenates aging skin by reducing circulating inflammatory factors and enhancing dermal extracellular matrices. Scientific Reports (2023).

• RALLIS E. & al. The effect of exercise on the quality of the skin. Review of Clinical Pharmacology and Pharmacokinetics (2024).