GLP-1 receptor agonists such as semaglutide (Ozempic, Wegovy) and tirzepatide (Mounjaro) are FDA-approved drugs for type 2 diabetes and are popular weight loss tools. They work by mimicking incretin hormones, primarily glucagon-like peptide-1 (GLP-1), which regulate appetite and blood sugar levels. GLP-1 drugs suppress appetite by delaying gastric emptying to promote feelings of fullness and by increasing insulin secretion in response to food intake. These effects result in lower blood glucose levels and decreased caloric intake, leading to weight loss. While GLP-1 drugs have been shown to induce substantial weight loss, clinical trials have indicated that 10-40% of the weight lost can be lean body mass, or muscle. This large amount of muscle loss is concerning because muscle plays a crucial role in metabolism, strength, balance, and overall physical function, especially in older adults. While these drugs may benefit some individuals, there is concern that muscle loss may negatively affect long-term health.
The goal of this research is to determine whether GLP-1 drug use affects muscle performance by comparing muscle activation and fatigue in individuals taking these drugs for weight loss with matched controls who are not using them. The primary focus of this study is the gastrocnemius and soleus muscles during static calf raise holds, which are functionally relevant for balance and lower-limb stability. Hand-grip strength will also be considered as an additional marker of overall muscle strength.
Preliminary work and trials have focused on developing signal processing tools and refining experimental protocols. MATLAB code was created to calculate Maximum Voluntary Contraction (MVC) using the Root Mean Square (RMS) of sEMG signals and to assess muscle fatigue using Fast Fourier Transform (FFT) analysis. Initial testing was conducted on participants using repeated 30-second calf raise holds with standardized rest intervals. Additional fatigue trials involved prolonged static calf raise holds to evaluate frequency shifts in EMG signals associated with fatigue. We hypothesize that individuals taking GLP-1 receptor agonists will demonstrate reduced MVC and earlier onset of fatigue compared with matched controls. Future trials will recruit participants on GLP-1 drugs to further investigate how GLP-1-associated muscle loss may influence lower-limb muscle activation and functional strength.