Decreases in resting plasma beta-endorphin and depression scores after endurance training.

That endurance training changes resting plasma beta-endorphin (BE) at the same time that there are improvements in non-clinical depression was tested in medically healthy middle-aged men (40-60 years). Subjects were self-selected based on compliance into treatment (T, n = 10) and placebo (P, n = 6) groups. T attended an eight month fitness program. P had less than 50% attendance in the program. Treadmill tests at the pre and post program were used to estimate the Physical Fitness Score (PFS). The Minnesota Multiphasic Personality Inventory (MMPI) was used to measure depression. All psychological scores were within non-pathological, normal limits. BE was measured with the subjects fasting and resting in the early morning. BE, detected by radioimmunoassay, decreased (p less than .005) from pre 48.53 +/- 3.32 (SE) to post 31.73 +/- 4.43 pg/ml in T. The MMPI depression score also decreased in T (p less than .05) from pre 58.90 +/- 2.81 (SE) to post 53.20 +/- 1.48 T-score units. In contrast, the PFS increased in T (p less than .005) from pre 254.57 +/- 18.62 (SE) to post 304.94 +/- 15.95 PFS units. No pre to post program changes were detected in P. In conclusion, endurance training of eight months duration appeared to decrease the resting plasma BE concentrations and the MMPI depression scores of the middle-aged men in the present study.