Inter-individual differences in breathing pattern at high levels of incremental cycling exercise in healthy subjects

Differential control of respiratory frequency and tidal volume during exercise

The lack of a testable model explaining how ventilation is regulated in different exercise conditions has been repeatedly acknowledged in the field of exercise physiology. Yet, this issue contrasts with the abundance of insightful findings produced over the last century and calls for the adoption of new integrative perspectives. In this review, we provide a methodological approach supporting the importance of producing a set of evidence by evaluating different studies together-especially those conducted in 'real' exercise conditions-instead of single studies separately. We show how the collective assessment of findings from three domains and three levels of observation support the development of a simple model of ventilatory control which proves to be effective in different exercise protocols, populations and experimental interventions. The main feature of the model is the differential control of respiratory frequency (f_R) and tidal volume (V_T); f_R is primarily modulated by central command (especially during high-intensity exercise) and muscle afferent feedback (especially during moderate exercise) whereas V_T by metabolic inputs. Furthermore, V_T appears to be fine-tuned based on f_R levels to match alveolar ventilation with metabolic requirements in different intensity domains, and even at a breath-by-breath level. This model reconciles the classical neuro-humoral theory with apparently contrasting findings by leveraging on the emerging control properties of the behavioural (i.e. f_R) and metabolic (i.e. V_T) components of minute ventilation. The integrative approach presented is expected to help in the design and interpretation of future studies on the control of f_R and V_T during exercise.

Breath Tools: A Synthesis of Evidence-Based Breathing Strategies to Enhance Human Running

Running is among the most popular sporting hobbies and often chosen specifically for intrinsic psychological benefits. However, up to 40% of runners may experience exercise-induced dyspnoea as a result of cascading physiological phenomena, possibly causing negative psychological states or barriers to participation. Breathing techniques such as slow, deep breathing have proven benefits at rest, but it is unclear if they can be used during exercise to address respiratory limitations or improve performance. While direct experimental evidence is limited, diverse findings from exercise physiology and sports science combined with anecdotal knowledge from Yoga, meditation, and breathwork suggest that many aspects of breathing could be improved via purposeful strategies. Hence, we sought to synthesize these disparate sources to create a new theoretical framework called “Breath Tools” proposing breathing strategies for use during running to improve tolerance, performance, and lower barriers to long-term enjoyment.

The effect of pedalling cadence on respiratory frequency: passive vs. active exercise of different intensities

PURPOSE

Pedalling cadence influences respiratory frequency (f_R) during exercise, with group III/IV muscle afferents possibly mediating its effect. However, it is unclear how exercise intensity affects the link between cadence and f_R. We aimed to test the hypothesis that the effect of cadence on f_R is moderated by exercise intensity, with interest in the underlying mechanisms.

METHODS

Ten male cyclists performed a preliminary ramp incremental test and three sinusoidal experimental tests on separate visits. The experimental tests consisted of 16 min of sinusoidal variations in cadence between 115 and 55 rpm (sinusoidal period of 4 min) performed during passive exercise (PE), moderate exercise (ME) and heavy exercise (HE). The amplitude (A) and phase lag (φ) of the dependent variables were calculated.

RESULTS

During PE, f_R changed in proportion to variations in cadence (r = 0.85, P < 0.001; A = 3.9 ± 1.4 breaths·min^-1; φ = - 5.3 ± 13.9 degrees). Conversely, the effect of cadence on f_R was reduced during ME (r = 0.73, P < 0.001; A = 2.6 ± 1.3 breaths·min^-1; φ = - 25.4 ± 26.3 degrees) and even more reduced during HE (r = 0.26, P < 0.001; A = 1.8 ± 1.0 breaths·min^-1; φ = - 70.1 ± 44.5 degrees). No entrainment was found in any of the sinusoidal tests.

CONCLUSION

The effect of pedalling cadence on f_R is moderated by exercise intensity-it decreases with the increase in work rate-and seems to be mediated primarily by group III/IV muscle afferents, at least during passive exercise.

Influence of high-intensity interval training on ventilatory efficiency in trained athletes

The aim of this study was to investigate the effects of 3 weeks high-intensity interval training (HIIT) on ventilatory efficiency (V_E/VCO₂ slope) in endurance athletes. Sixteen male well-trained (67.72 ml kg min^-1) athletes participated in this study. Each participant performed an incremental exercise test with gas analysis (i.e. V_E, VO₂) and a 400 m running field test (T400m) before and after the 3 weeks intervention period. HIIT group (HIITG) performed 11 HIIT sessions consisting of four 4-min interval bouts at an exercise intensity of 90-95% of the VO_2max, separated by 4-min active recovery periods (work/rest ratio = 1:1). No significant differences were found in the parameters studied. Ventilatory efficiency (up to VT₂ and up to exhaustion) did not show any change in HIITG after training intervention (ES = 0.24 HIITG; ES = 0.21 CG). No significant changes were observed on ventilation (V_Emax; ES = 0.38). VO_2max and T400 m did not show a significant improvement after the training period (no interaction time × group, p < .05) (ES = 0.43 and ES = 0.75 respectively). These results do not support the hypothesis that 3 weeks of HIIT could modify the ventilatory efficiency response in well-trained athletes. Furthermore, they show the lack of relationship between ventilatory efficiency and sport performance.