Reduced sensations of intensity of breathlessness enhances maintenance of intense intermittent exercise

Abstract

To identify the effect of normal breathlessness sensation elicited during intense intermittent exercise at exhaustion on limitation of exercise maintenance (Ex), the contribution of the flow-resistive unloading effect of normoxic helium-oxygen breathing on the breathlessness sensation to the change in the Ex was examined. Seven men repeatedly performed 12-s exercise at 160% maximal aerobic power output followed by passive recovery for 18-s under normal (CON) and unloaded (UL) breathing conditions until exhaustion. In UL, Ex was enhanced [mean (SD) 127.2 (11.8)% CON] concomitantly with reduction in averaged peak inhaled mouth pressure (PPmi) of recorded breathing cycles that reflected approximate true inspiratory muscle force output. At the iso-time point of CON exhaustion, the reduction in PPmi to [75.7(10.2)% CON] in UL was concomitant with the reductions in the rating of perceived breathlessness (RPB) [87.5 (13.1)% CON] and in the slope of time course for RPB (RPB/2-min period) [82.1 (17.2)% CON]. It was also concomitant with increases in ventilation and total oxygen consumption. However, the augmented oxygen consumption did not result in lowering of subjects' metabolic stress that was indicated by accumulations of blood lactate and plasma ammonia and uric acid. Nevertheless, the reductions in the RPB and RPB/2-min period, which reflected the breathlessness intensity, were correlated to the CON Ex enhancement in UL (RPB r=-0.57, RPB/2-min period r=-0.83; P<0.05). These findings implied that the normal noxious breathlessness sensation elicited during intense intermittent exercise at exhaustion might contribute to the limitation of subjects' exercise maintenance.

Effect of specific inspiratory muscle warm-up on intense intermittent run to exhaustion

“…Such findings implied that the addition of the specific IM warm-up, preferably the one in IMW, to a whole-body warm-up protocol could subsequently improve the tolerance of the intense intermittent run by lessening of the exercise-induced noxious breathlessness sensation. Further, the findings enriched our notion reported in previous studies that the noxious breathlessness sensation elicited during intense intermittent exercise at exhaustion in normal active persons plays a part in limiting the exercise maintenance (Tong et al 2003a(Tong et al , 2004. In the previous studies, the mode of exercise selected was cycling.…”

“…However, the findings in the present study revealed that such mechanical advantage of the upright bodily position in breathing did not attenuate the limitation of the noxious breathlessness sensation elicited during intense intermittent run in exercise tolerance. In light of the current findings and those in our previous studies (Tong et al 2003a(Tong et al , 2004, it was noted that the noxious breathlessness sensation elicited during intense intermittent exercise at exhaustion in normal active persons may play a role in limiting the exercise tolerance regardless of whether the exercise was cycling or running.…”

“…Redline et al (1991) noted that the perceived intensity of breathlessness sensation in normal persons could reflect the proportion of the maximum force utilized by IM in breathing. Such relationship was shown not to be affected either by augmenting the capacity of IM force output via IM strength training or by reducing the IM tension for inhalation during intense exercise with HeÀO 2 breathing (Redline et al 1991;Tong et al 2004). In the present study, we found that the D RPB/4i in IMW and IMW P was negatively correlated to the DP 0 and D MRPD (r 2 =0.23 and 0.29, respectively, n=20).…”

“…Recently, the breathlessness sensation elicited during intense intermittent exercise at exhaustion in normal active persons was shown to play a part in limiting the exercise maintenance (Tong et al 2001a(Tong et al , 2003a(Tong et al , 2004. It was also noted that the intensity of breathlessness sensation during the exercise was proportional to the magnitude of IM force output relative to the maximum dynamic force utilized by the muscles (Tong et al 2004).…”

“…It was also noted that the intensity of breathlessness sensation during the exercise was proportional to the magnitude of IM force output relative to the maximum dynamic force utilized by the muscles (Tong et al 2004). Romer et al (2002aRomer et al ( , 2002b reported that improving the maximum dynamic IM function could reduce the intensity of breathlessness sensation during maximal incremental exercise and sub-maximal shuttle run.…”