Background: D-aspartic acid may enhance athletic performance by regulating the hypothalamus-pituitarygonadal
axis to increase plasma testosterone. Increasing testosterone via D-aspartic acid, may lead to improved
muscle function and concurrent improvements in athletic performance.
Purpose: To determine the effect of D-aspartic acid supplementation on athletic performance in young male
Methods: After screening for ACSM low risk, 15 healthy male athletes (average age=20.9 years, body
weight=79.1 kg and body fat=9.2%) were randomized to two groups for supplementation using a double blinded
parallel arm experimental design. They ingested either 3 grams of d-aspartic acid (DAA, n=9) or a Placebo (PL,
n=6) for 14 days supplied in capsule form. Subjects recorded and replicated previous 3 days diets prior to testing.
Blood was collected for testosterone determination before and after the supplementation. Physical assessments were
performed prior to and after supplementation and included a peak VO2 test by cycle ergometer, 1 maximal repetition
bench press and 1 maximal repetition squat (average values ± SEM before supplementation were 41.7 ± 6.4 ml/kg/
min, 108.1 ± 3.5 kg and 138.7 ± 5.4 kg, respectively).
Results: The DAA group had a significant increase in the 1 maximal repetition squat by 8.5 ± 10.5 kg (p=0.013)
and a positive trend in performance during the 1 maximal repetition bench press by 3.5 ± 6.8 kg (p=0.06). DAA
improved performance in VO2 peak test increasing maximum workload by 48.8 ± 15.9 W (p<0.01) and time to peak
1.4 ± 0.5 min (p<0.05) following supplementation. No change in performance measures were observed in the
Placebo group. There was no change in testosterone levels in the control group: 2.5 ± 70.4 ng/dL or in the
experimental group: -0.76 ± 72.8 ng/dL. Body composition did not change for either group.
Conclusion: D-aspartic acid supplementation leads to improved upper and lower body muscle performance but
does not increase testosterone levels after 14 days of supplementation.