Glycolytic Phenotype (vLapeak) and Magnitude of Skeletal Muscle Hypertrophy After Resistance Training

Overview

The HyperLa study investigates whether a person's "glycolyticness"-the efficiency with which their body uses glycolysis for energy-can predict how much their muscles will grow (hypertrophy) in response to resistance training. Participants will undergo a specialized "vLapeak" test, which measures the maximal rate of lactate accumulation during a 10-second all-out cycling sprint, to determine their individual glycolytic power. Following this initial assessment, participants will complete eight weeks of standardized, twice-weekly resistance training focused on the lower body. The study aims to determine if individuals with higher initial vLapeak values experience greater increases in muscle size compared to those with lower values. This research may help explain why people respond differently to exercise and support the development of personalized training programs.

This multicentre, prospective, single-arm interventional cohort study aims to link metabolic phenotypes with physical adaptations. * Primary Assessment: Glycolytic power is quantified via the vLapeak test, defined as the peak rate of blood lactate accumulation during a 10-second isokinetic or sprint-configured cycle ergometry test. * Intervention: The 8-week resistance training program consists of two supervised sessions per week. Exercises include the leg press (or Smith-machine squat) and leg extensions, performed for 4 sets of 8-12 repetitions. Intensity progresses from an RPE of 6 to voluntary muscular failure by the third week. * Measurements: Muscle hypertrophy is primarily assessed via ultrasound measurement of muscle thickness and cross-sectional area (CSA) of the thigh muscles before and after the intervention. * Secondary Objectives: The study also evaluates changes in the plasma metabolome via venous blood samples and, at select sites, analyzes muscle biopsies for glycolytic enzyme activity and fiber type composition to further validate the vLapeak results.