Effects of Core Strength Training on Maximal Trunk Muscle Strength and Cycling Economy in Female Mountain Bikers

Background Performance in cross-country mountain biking (MTB) is primarily determined by athletes’ aerobic capacity. With the reduction of race duration to 80 minutes, anaerobic capacity, along with muscle strength and power gained importance as key performance determinants. Adequate trunk muscle strength (TMS) is essential in MTB for effective force transfer between the lower and upper extremities, particularly during starts, inclines and finishes. Cycling economy (CE)—the oxygen cost and mechanical efficiency of cycling at a given workload—is a key performance factor and may benefit from TMS training. This study examined the effects of global TMS training on TMS and CE in MTB athletes. Methods Twenty-four female highly-trained (Tier 2–3) mountain bikers aged 14–22 years were paired-matched by age and randomly assigned to a TMS training or an active control (CON) group. Over eight weeks in the off-season, the TMS group performed three-weekly sessions of 30 minutes global TMS training while CON completed standard strength training excluding trunk-specific exercises. Both groups had similar training volumes. Pre- and post-training assessments included maximal isometric TMS and TMS endurance for ventral, dorsal and lateral trunk muscles. CE was measured during a twelve-minute MTB racecourse simulation on a treadmill, including physiological parameters (i.e., O₂/CO₂ per min/kg) and mechanical metrics (e.g., lateral bike displacement, torque effectiveness during pedaling). Results Group-by-time interactions were found for maximal isometric trunk flexor (p < 0.0001, d = 1.1) and extensor (p < 0.0001, d = 1.7) strength, with larger gains in the TMS group (flexors + 47.5%; extensors + 39.7%). Lateral trunk endurance improved more in the TMS group (p = 0.03, d = 0.74, + 22.2%). For mechanical CE, lateral bike displacement decreased significantly in the TMS group (p = 0.01, d = 0.9, -19.6%). No significant differences were found in physiological CE parameters (O₂/CO₂). Conclusions Eight weeks of global TMS training improved maximal isometric trunk flexor, extensor strength, lateral TMS endurance and mechanical CE in female MTB athletes. Despite the relatively small sample size (N = 24) and narrow age range, these findings suggest that targeted strength training for the global trunk muscles during the off-season may enhance MTB-specific performance. Further studies are needed to confirm generalizability to broader MTB populations.