Plasma volume during weight lifting.

The magnitude and pattern of the hematocrit (Hct), hemoglobin (Hb), and plasma volume (PV) responses during and upon recovery from two resistance training protocols based on either a ten-repetition maximum (10 RM) or five-repetition maximum (5 RM) resistance was examined. Twelve college-aged male resistance exercise trainers were equally divided between the protocols and performed at least four workouts prior to testing to determine the 10 RM or 5 RM for each exercise set. Each protocol included three sets of nine exercises. The 10-RM session used one-minute rest periods between sets, and two minutes between exercises. The 5-RM session employed three-minute rest periods between sets and exercises. A catheter inserted in the forearm allowed for venous blood sampling after twenty minutes supine rest, the last set of each exercise, and at fifteen and thirty minutes of recovery. Control conditions were included for posture (P) and limb motion (U). Loaded exercise (L) was significantly different from U and P controls for Hct, Hb, and PV responses. For 10 RM and 5 RM respectively, the mean change from rest was 6.2 (+/- 0.9) and 3.5 (+/- 0.4) % for Hct, 2.2 (+/- 0.2) and 1.2 (+/- 0.1) gm . dl (-1) for Hb, and - 22.6 (+/- 2.3) and - 13.0 (+/- 1.2) % for PV. The main effect for protocol was significant for Hct (p = 0.0006) and Hb (p = 0.0033), with 10-RM changes being greater than 5 RM. The greatest increase in Hct and Hb occurred after the first set for both protocols. An increase in Hct and Hb during the protocol was observed for the 10 RM, but not the 5 RM. During recovery, Hct and Hb were elevated above rest for 10 RM, but not 5 RM. PV decreases mirrored Hct and Hb in pattern of change and significance. The data demonstrate that magnitude and pattern of Hct, Hb, and PV was dependent on the type of resistance training protocol.