Effect of training status and relative exercise intensity on physiologicalresponses in men

Purpose: This study examined the effect of training status and relative exe rcise intensity an physiological responses to endurance exercise in humans, Methods: Seven endurance trained (TR: peak oxygen uptake [(V) over dot O(2 )peak] = 65.8 +/- 2.4 mL.kg(-1).min(-1)) and six untrained (UT:(V) over dot O(2)peak = 46.2 +/- 1.9 mL.kg(-1).min(-1)) men cycled for 60 min, either a t a work rate corresponding to similar to 70% (V) over dot O(2)peak or simi lar to 95% lactate threshold (LT). Results: The work rate and relative exer cise intensity (i.e., (V) over dot O(2)peak) for UT 95% LT were lower (P < 0.01) than for all of the other trials. Although the work rate for UT 70% ( V) over dot O(2)peak was lower (P < 0.001) than for TR 70% (V) over dot O(2 )peak and TR 95% LT, average heart rate (HR) for the trial was higher (P < 0.01) throughout exercise in UT 70% (V) over dot O(2)peak compared with all of the other trials. Plasma lactate and ammonia concentrations were greate r (P < 0.01) during exercise in UT 70% (V) over dot O(2)peak compared with all of the other trials. There was a tendency (P = 0.077) for plasma hypoxa nthine to be greater at 60 min in UT 70% (V) over dot O(2)peak compared wit h the other trials. At no time were any of the plasma metabolite concentrat ions different between the UT 95% LT. TR 95% LT and TR 70% (V) over dot O(2 )peak trials. Conclusions: These data demonstrate that HR and plasma marker s of metabolic stress were greater in UT compared with TR when exercise was performed at 70% (V) over dot O(2)peak but were similar during exercise at 95% LT.