Faculty Proceedings, Presentations, Speeches and Lectures


The Relationship between the ACTN3 Genotype and Measures of Stress, Exercise Performance and Body Composition

Event Location / Date(s)

Phoenix, Arizona

Document Type

Conference Proceeding

Presentation Date


Conference Name / Publication Title

Proceedings of the Fourteenth International Society of Sports Nutrition (ISSN) Conference and Expo





Alpha-Actinin-3 is a Z-disc protein expressed in fast-twitch or Type II skeletal muscle fibers. A polymorphism in the ACTN3 gene (R577X) results in the XX genotype (i.e., lack of alpha-actinin-3). The purpose of this study was to assess the relationship between the expression of the ACTN3 gene (RR homozygous or RX heterozygous) and measures of stress, bench press strength and endurance, and body composition.


One-hundred and ten male and female athletes volunteered for this study (mean±SD: age 30.2±9.2 years; height 171.3±9.6 cm; % body fat 21.6±7.0; male n=55, female n=55). Body composition was assessed via a DEXA scan. Strength and muscle endurance was determined via a 1-RM for the bench press and repetitions to failure on the bench press at 60% of the 1-RM weight. Saliva was collected before and after the exercise test to determine salivary cortisol concentration as well as for ACTN3 genotyping. Genomic DNA extraction was performed using the QIAamp DNA Investigator kit, following the manufacturer instructions (QIAGEN, Valencia, CA). After isolation, amplification was conducted by polymerase chain reaction (PCR) using allele specific fluorescent primers.


There were no significant differences in body composition between XX and R/- (carriers of ACTN3) for body weight, lean body mass, fat mass or percentage body fat. However, R/- demonstrated significantly greater bone mineral content and density. Self-reported stress (pre- and post-exercise testing) showed no differences between XX and R/-. Baseline cortisol was significantly greater in the R/- group; however, no differences were found post-exercise testing. Furthermore, there were no significant differences between the XX and R/- groups for 1-RM bench press strength or repetitions to failure.


In exercise-trained individuals, the presence of the ACTN3 genotype did not confer an advantage with muscular strength/endurance, lean body mass or fat mass. However, carriers of the gene (R/-) demonstrated greater bone mineral content and density. Furthermore, the stress response (i.e., self-reported and salivary cortisol) was not different between groups post-exercise.