Lipolytic, Hormonal, and Muscle Quality Differences of Female Endurance Athletes with Higher vs Lower Body Fat

Introduction: The popularity of endurance events has grown recently with an increased number of participants who have an elevated body fat percentage. The influence of chronic endurance training on adipose tissue physiology in these recreational athletes is unknown. The purpose of this investigation was to determine the effect of chronic endurance training on lipolytic rate and measurements of muscle quality (MQ) between two groups of female endurance athletes with two different levels of body fatness. Methods: Female endurance athletes (N=14) with >8 yrs of training experience were divided based on body fat % into lower body fat (LBF; N=5, age=32.1±8.2yrs, BF%=19.4±4.7%, BMI=21.8±1.7kg/m2) or higher body fat (HBF; N=9, age=36.1±8.3 yrs, BF%=31.1±3.1%, BMI=23.9±3.2 kg/m2) groups based upon a BF cut-off of the 30th percentile. Two visits were completed: 1) anthropometrics, BF%, fitness, strength, and MQ testing. US histogram analysis and isokinetic force production of the rectus femoris were used to quantify MQ (IMF% and N-m/cm2), and 2) SCAAT lipolysis was measured 1 hr before, during cycling at ~70% VO2peak for 45 min, and after exercise for 2h. Results: SCAAT lipolysis was not significantly different pre-exercise or not post-exercise (p > 0.05). However, there was a significant difference during exercise F(1,12) =15.01, p=.002, ƞ2=.556 (LBF=3090.6±1394.1µM, HBF=1003.2±654.3µM) between groups. There were no significant differences between groups in insulin or growth hormone (p > 0.05). There were no significant differences between groups in muscle quality with IMF% (p > 0.05). Conclusion Chronic endurance exercise training of recreational female athletes appears to alleviate the expected decrements in muscle quality due to excess adiposity among individuals in the EBF group; however, there remains a lower resting and exercise-induced lipolysis in the HBF than LBF group. Further investigations should consider possible mechanisms or lifestyle factors contributing to these observed differences