Jonathon L. Stickford

Comments on Point: Counterpoint: Hypobaric hypoxia induces/does not induce different responses from normobaric hypoxia.

112:1788-1794, 2012. ; J Appl Physiol Joshua C. Weavil, Peter Bartsch and Charles F. Nelatury Samuel Verges, Patrick Levy, Eric M. Snyder, Bruce D. Johnson, Jonathon L. Stickford, Y. Millet, Benjamin D. Levine, James H. Wessel III, Bernard Wuyam, Renaud Tamisier, MacInnis, Michael S. Koehle, Thomas Rupp, Marc Jubeau, Stephane Perrey, Guillaume Laymon, Jack A. Loeppky, Matiram Pun, Kai Schommer, Mary C. Vagula, Martin J. S. Chapman, Johnny Conkin, Hugo Nespoulet, Darren P. Casey, Bryan J. Taylor, Abigail Olivier Girard, Michael S. Koehle, Jordan A. Guenette, Samuel Verges, Robert F. normobaric hypoxia induces/does not induce different responses from Comments on Point:Counterpoint: Hypobaric hypoxia

Effect of weight loss on operational lung volumes and oxygen cost of breathing in obese women

Background:The effects of moderate weight loss on operational lung volumes during exercise and the oxygen (O2) cost of breathing are unknown in obese women but could have important implications regarding exercise endurance.Methods:In 29 obese women (33±8 years, 97±14 kg, body mass index: 36±4 kg m−2, body fat: 45.6±4.5%; means±s.d.), body composition, fat distribution (by magnetic resonance imaging), pulmonary function, operational lung volumes during exercise and the O2 cost of breathing during eucapnic voluntary hyperpnea (([Vdot ]O2) vs ([Vdot ]E) slope) were studied before and after a 12-week diet and resistance exercise weight loss program.Results:Participants lost 7.5±3.1 kg or ≈8% of body weight (P<0.001), but fat distribution remained unchanged. After weight loss, lung volume subdivisions at rest were increased (P<0.05) and were moderately associated (P<0.05) with changes in weight. End-expiratory lung volume (percentage of total lung capacity) increased at rest and during constant load exercise (P<0.05). O2 cost of breathing was reduced by 16% (2.52±1.02–2.11±0.72 ml l−1; P=0.003). As a result, O2 uptake of the respiratory muscles ([Vdot ]O2Resp), estimated as the product of O2 cost of breathing and exercise ([Vdot ]E) during cycling at 60 W, was significantly reduced by 27±31 ml (P<0.001), accounting for 46% of the reduction in total body ([Vdot ]O2) during cycling at 60 W.Conclusions:Moderate weight loss yields important improvements in respiratory function at rest and during submaximal exercise in otherwise healthy obese women. These changes in breathing load could have positive effects on the exercise endurance and adherence to physical activity.

Verification of Maximal Oxygen Uptake in Obese and Nonobese Children

Purpose The purpose of this study was to examine whether a supramaximal constant-load verification test at 105% of the highest work rate would yield a higher V˙O2max when compared with an incremental test in 10- to 12-yr-old nonobese and obese children. Methods Nine nonobese (body mass index percentile = 57.5 ± 23.2) and nine obese (body mass index percentile = 97.9 ± 1.4) children completed a two-test protocol that included an incremental test followed 15 min later by a supramaximal constant-load verification test. Results The V˙O2max achieved in verification testing (nonobese = 1.71 ± 0.31 L·min−1 and obese = 1.94 ± 0.47 L·min−1) was significantly higher than that achieved during the incremental test (nonobese = 1.57 ± 0.27 L·min−1 and obese = 1.84 ± 0.48 L·min−1; P < 0.001). There was no significant group (i.e., nonobese vs obese)–test (i.e., incremental vs verification) interaction, suggesting that there was no effect of obesity on the difference between verification and incremental V˙O2max (P = 0.747). Conclusion A verification test yielded significantly higher values of V˙O2max when compared with the incremental test in obese children. Similar results were observed in nonobese children. Supramaximal constant-load verification is a time-efficient and well-tolerated method for identifying the highest V˙O2 in nonobese and obese children.

Aerobic exercise training without weight loss reduces dyspnea on exertion in obese women.

Dyspnea on exertion (DOE) is a common symptom in obesity. We investigated whether aerobic exercise training without weight loss could reduce DOE. Twenty-two otherwise healthy obese women participated in a 12-week supervised aerobic exercise training program, exercising 30 min/day at 70-80% heart rate reserve, 4 days/week. Subjects were grouped based on their Ratings of Perceived Breathlessness (RPB) during constant load 60 W cycling: +DOE (n=12, RPB≥4, 37±7 years, 34±4 kg/m(2)) and -DOE (n=10, RPB≤2, 32±6 years, 33±3 kg/m(2)). No significant differences between the groups in body composition, pulmonary function, or cardiorespiratory fitness were observed pre-training. Post-training,peak was improved significantly in both groups (+DOE: 12±7, -DOE: 14±8%). RPB was significantly decreased in the +DOE (4.7±1.0-2.5±1.0) and remained low in the -DOE group (1.2±0.6-1.3±1.0) (interaction p<0.001). The reduction in RPB was not significantly correlated with the improvement in cardiorespiratory fitness. Aerobic exercise training improved cardiorespiratory fitness and DOE and thus appears to be an effective treatment for DOE in obese women.

Ventilation and Locomotion in Humans: Mechanisms, Implications, and Perturbations to the Coupling of These Two Rhythms

Abstract To best sustain endurance activity, two systems must be effectively coordinated: ventilation and locomotion. Evidence has long suggested that these two mammalian rhythms are linked, yet determinants and implications of locomotor–respiratory coupling (LRC) continue to be investigated. Two general areas explaining the potential mechanisms underlying LRC are (1) neural interactions between central and peripheral controllers of locomotion and respiration, and (2) mechanical interactions between locomotor dynamics and respiratory mechanics. Additional suggested explanations for/consequence of the existence of LRC in mammals include an improved energetic cost of locomotion and a reduced sensation of breathlessness. As such, any perturbation to LRC, via alterations in breathing or kinematic patterns, could have negative performance implications to both athlete and patient populations.