Fit instead of wrinkle-free? How intensive physical activity could influence the efficacy of botulinum toxin - findings from a controlled single-blind study

 

Introduction:

The process of facial ageing is complex and multifaceted, comprising soft tissue atrophy, bone resorption and remodelling, muscle changes (hypertrophy) and an imbalance between muscle groups. Factors such as smoking, sun damage, poor health and depression can exacerbate this process. The aesthetic consequences of the ageing process in the upper face include wrinkles, pronounced forehead lines, which may be accompanied by drooping eyebrows, and deeper glabellar lines.

 

Injection of botulinum toxin type A (BoNT-A) for the treatment of facial wrinkles is the most frequently performed minimally invasive procedure in the EU, the USA and Brazil. The most commonly treated areas are the forehead and the glabellar complex, as the treatment achieves very good results and is safe. Although there is consensus and there are clinical studies on BoNT-A, data on factors influencing the duration of effect are limited.

 

The duration of effect of BoNT-A can be up to 6 months, depending on the preparation. The waning of the effect is mainly related to functional regeneration and the regrowth of nerve endings. There are many factors that can influence the durability of the BoNT-A effect, such as handling of the medicinal product, dosage and intervals between applications, and skin type.

 

It has been observed that the effect of BoNT-A lasts for a shorter time in people with high levels of physical activity. Studies in mice have shown that repeated motor training can stimulate certain neuronal pathways to promote functional reorganisation in the spinal cord. Clinical studies have shown that individualised exercise programmes can improve motor recovery in people with spinal cord injuries.

 

It is therefore assumed that high physical activity can influence muscle reinnervation and thus negatively affect the duration of effect of BoNT-A. The aim of the study described here was therefore to investigate the influence of activity level on the duration of effect of BoNT-A in the muscles of the upper face.

 

Study design:

This is a single-centre, controlled, single-blind study. Brazilian women aged 25 to 50 years who either practised CrossFit or did not (control group) took part in the study. The participants had moderate to severe dynamic forehead and glabellar lines according to the Merz 5-point scale. The subjects must not previously have received BoNT-A injections in the face for aesthetic or therapeutic purposes, nor undergone any other aesthetic anti-wrinkle procedures. Exclusion criteria were tetanus vaccination or chemical peeling in the last 6 months, procedures that could affect the forehead and glabellar regions in the last 12 months, autoimmune diseases and/or current use of medications acting at neuromuscular junctions.

 

Four types of activity – walking, sitting, moderate-intensity activities and high-intensity activities – were assigned to the subjects.

BoNT-A (100 U, Botox®, Allergan, Irvine, CA, USA) was reconstituted with 1.0 ml of preservative-free saline so that 0.1 ml corresponded to 10 U of the product. The doses applied in the muscles followed the prescribing information for OnabotulinumtoxinA (Botox®). The regions treated were the glabellar and forehead lines. No touch-up treatments were performed.

 

The subjects were examined at four time points (baseline, 30, 60 and 90 days) over a period of three months. At all evaluation time points, the results were assessed by a researcher who had not previously been involved in the study. The results were evaluated by means of electromyographic (EMG) activity: forehead wrinkling (surprised facial expression), glabellar frowning (angry facial expression in the upper area), and the subjects were asked to complete a questionnaire.

 

What did the study find?

A significant reduction in electrical activity was found in all muscles after BoNT-A injections up to the first month of follow-up in all groups, with the low physical activity group showing a greater reduction at the one-month assessment than the other two groups.

From the second month onwards, the groups with moderate and high physical activity showed a higher prevalence of “severe” and “very severe” lines in the forehead and glabellar region compared with the low physical activity group. The low physical activity group, by contrast, had fewer “severe and very severe lines” in both areas from the 2nd and 3rd month onwards. Patients in the low and moderate physical activity groups were also more satisfied with the treatment of lines between the eyebrows, with patients in the low physical activity group being the most satisfied. The high physical activity group already showed muscle recovery in the second month. This group also had a smaller reduction in electrical activity and a higher prevalence of severe lines compared with the low physical activity group at all measurement time points for all muscles.

 

Conclusion:

Based on the results of this study, it can be concluded that higher levels of physical activity could have a negative influence on the duration of effect of BoNT-A.

 

Reference:

Morhy et al. Toxins (Basel) . 2023 Jul 19;15(7):463. doi: 10.3390/toxins15070463.