Author(s): TAKAHIRO, F., RYOYA, O., CHEN, Y.C., YOSHIHIRO, N., HIROYUKI, T., Institution: NATIONAL INSTITUTE OF FITNESS AND SPORTS IN KANOYA, Country: JAPAN, Abstract-ID: 1412

INTRODUCTION:
Muscular endurance is a key determinant of sports performance, as it prolongs exercise duration and delays fatigue accumulation. Cinnamaldehyde has been suggested to promote energy metabolism and exhibit antioxidant properties, potentially enhancing endurance. While its precise effects remain unclear, its known antioxidant and anti-inflammatory actions may help reduce oxidative stress, a major contributor to muscle fatigue. However, direct research on its impact on muscular endurance is limited.
METHODS:
Male Fischer 344 rats (6-7 weeks of age, n=12) were divided into two groups: a cinnamaldehyde-treated (CN) group and a control (Cont) group. Cinnamaldehyde was administered intraperitoneally twice per week for eight weeks at a dose of 20-50 mg/kg body weight. Following the intervention, muscular endurance and maximal isometric force of the tibialis anterior (TA) muscle were assessed in vivo using an electrical stimulator and force transducer. Time-course changes in unfused (50 Hz) and fused (143 Hz) tetanic forces were recorded at stimulation intensities corresponding to maximal force (16-25 V). Following force measurements, TA muscles were excised, subjected to NADH-TR staining, and analyzed for myofiber cross-sectional area using light microscopy and an image analysis system.
RESULTS:
There was no significant difference in maximal force between the CN and Cont groups. The force-time curves for both unfused and fused tetanic contractions were greater throughout the stimulation period in the CN group than in the Cont group. The force-time integral (FTI) during the first 10 seconds of both tests was significantly greater in the CN group. The cross-sectional areas of myofibers with intense or light NADH-TR staining did not significantly differ between groups.
CONCLUSION:
These findings suggest that cinnamaldehyde administration may enhance muscular endurance, particularly during the initial phase (0-10 s) of unfused and fused tetanic contractions, without inducing hypertrophy or altering fiber composition. This effect may be attributed to its antioxidant properties, which could reduce oxidative stress during sustained contractions.