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Bogdanis, GC, Mallios, VJ, Katsikas, C, Fouseki, T, Holman, I, Smith, C, and Astorino, TA. Effects of exercise structure and modality on physiological and perceptual responses to exercise. J Strength Cond Res XX(X): 000-000, 2021-This study examined the effect of exercise mode and intensity on physiological and perceptual responses to exercise. Twelve active adults (6 men and 6 women, age = 21.7 ± 1.6 years) initially performed incremental testing on the treadmill (TM) and cycle ergometer (CE) to assess maximal oxygen uptake (V[Combining Dot Above]O2max) and ventilatory threshold (VT). During the next 4 visits in a randomized order, subjects performed 20 minutes of moderate-intensity continuous exercise (MICE) at an intensity 20% below VT on the TM (TMMICE) and cycle ergometer (CEMICE) as well as time-matched high-intensity interval exercise (HIIE; 10 1-minute bouts at workload equal to 20% above VT followed by 1-minute active recovery) on both modes (TMHIIE and CEHIIE). During exercise, gas exchange data, blood lactate concentration, and perceptual responses (rating of perceived exertion, affective valence, and enjoyment) were assessed. Heart rate (p < 0.001) and V[Combining Dot Above]O2 (p < 0.001) were higher in response to TMHIIE vs. CEHIIE as well as TMMICE vs. CEMICE. Blood lactate concentration was higher (p = 0.003) in response to CEHIIE vs. TMHIIE. The rating of perceived exertion was significantly higher (p < 0.001) in TMMICE compared with CEMICE which showed the most positive affective valence (p = 0.009). Enjoyment was similar across all bouts (p = 0.11). Treadmill-based HIIE leads to higher heart rate and V[Combining Dot Above]O2 vs. CEHIIE, although there was no difference in affective valence or enjoyment. Practitioners aiming to optimize the cardiorespiratory response to moderate or interval exercise in their clientele should recommend TM running rather than cycling.

Previous studies have shown the existence of an ideal respiratory rate (fR) for a given ventilation at which the respiratory work rate (J.s-1) is minimum. The purpose of the present study was to measure the effect of fR, tidal volume and breathing pattern on the respiratory work per breath and respiratory work rate during exercise on a cycle ergometer. Three work rates on the cycle ergometer were used and at each work rate the ventilation was kept constant. Two different breathing patterns were applied at each ventilation. Nine male trained cyclists [mean (SD) maximum oxygen consumption, 57 (5.47) ml.kg-1.min-1] participated in this study. The results indicated that there was a significant difference in the respiratory work per breath, with different breathing patterns at a given ventilation and for all levels of ventilation. There was no significant difference in the respiratory work rate with different breathing patterns at a given ventilation and for all levels of ventilation. In addition, the respiratory work per breath and respiratory work rate were increased with increasing ventilation. Thus, the data indicated that the manipulation of tidal volume, respiratory rate and breathing pattern had no significant effect on the energy cost of breathing for a given ventilation. The absence of this significant effect on respiratory work rate was observed across a range of ventilation from 24 to 72 l.min-1. These findings suggest that the breathing pattern is predominantly an expression of the function of the higher respiratory brain center instead of energy economy, at least within this range of ventilation.

Muscarinic cholinergic receptors (mAChRs) within the pontine brain stem play a key role in generating rapid eye movement (REM) sleep. Using an in vitro autoradiographic technique that permits selective labeling of mAChR subtypes by radioligand binding, this study provides the first quantitative map of mAChR subtypes in cat brain stem areas important for REM sleep generation. M1, M2 and M3 mAChR subtypes were distributed heterogeneously throughout the brain stem. For all 3 mAChR subtypes, the greatest levels of binding were found in the dorsal raphe and locus coeruleus, and the least amount of binding was in the reticular formation. These findings are consistent with data from in vivo studies showing that multiple mAChR subtypes are involved in REM sleep generation.