Blood lactate and ventilatory responses to interval-and endurance-training in recreational runners

The purpose of the present study was to compare threshold levels of blood lactate and ventilation after two different training programs of 9 weeks, that is, interval-run (IR) and endurance-run (ER). Twenty (20) recreational male runners from local running clubs volunteered to this study and completed maximal ramp cycle tests to determine maximal aerobic power (VO_2max) and blood lactate concentrations. Maximal cycle testing involved progressing in increments of 25 watts (W) every 2 minutes following a 4-min warm-up period at 0 W. The subjects were requested to maintain a pedaling frequency of 60 rpm. The test was continued till the subjects reached a point of exhaustion. After baseline tests, subjects were matched in terms of the VO_2max and placed in one of two training groups, an interval-run group (IR, mean age 40 years), and an endurance-run group (ER, mean age 41.7 years). Gas analysis was carried out every 20 sec for minute ventilation, oxygen consumption, carbon dioxide production using Metamax system. Calculation of ventilatory threshold (VT) employed the V-slope method. Blood samples were collected during exercise from the brachial vein for analyses of blood lactate using YSI 1500 Sport Lactate analyzer. The value of blood lactate concentrations corresponding to 4 mmol/L for determining the lactate threshold (LT) was chosen. After training, there were significant increases in VO_2max, the estimated LT-4 mmol/L, and VT in both groups. In addition, faster running performance of 10 km after a 9-week training program was observed in the IR and ER groups with no significant differences between the groups. However, the magnitude of the aforementioned improvements was greater in the IR than ER groups. Blood lactate concentrations in both groups lowered significantly at all given work rates after 100 W during the incremental graded exercise. However, the lactate concentrations at higher work rates were significantly lower in the IR than ER groups. It was concluded that both aerobic interval-training and endurance-training produce increases in performance and physiological parameters. However, it seemed that, for runners who are already trained, notable improvements in endurance performance can be achieved only through high-intensity interval training