The effects of sinusoidal linear drifts on the estimation of cardiorespiratory dynamic parameters during sinusoidal workload forcing: a simulation study

Girardi, Michele; Gattoni, Chiara; Mauro, Lorenzo; Capelli, Carlo

doi:10.1016/j.resp.2021.103652

“…This is another consequence of operating within a continuously oscillating exercise transient, as pointed out above, during which an oxygen deficit is built in the rising phase and an oxygen debt is paid in the declining phase of the sinusoid. Recently, Girardi et al ( 2021a ) conducted a theoretical analysis of the effects of T on AMP. For T equal to 4 min, they predicted AMP of some 70% of the that is necessary to sustain a power corresponding to the mechanical AMP.…”

Section: Discussionmentioning

confidence: 99%

“…To simulate workload oscillations under controlled laboratory conditions, Wigertz ( 1970 ) proposed to study exercises in which the mechanical power varied continuously following a sinusoidal function. When we investigate sinusoidal exercise patterns with a sufficiently long sinusoid period ( T ), we should observe a sinusoidal response, with a time lag with respect to the mechanical sinusoidal pattern equal to the time constant of the primary phase of the kinetics (Casaburi et al 1977 ; Girardi et al 2021a ; Ferretti 2023 ). In spite of this, the number of studies so far devoted to an analysis of the cardiorespiratory and metabolic responses to sinusoidal exercise has been relatively small (Wigertz 1970 ; Casaburi et al 1977 ; Bakker et al 1980 ; Fukuoka and Ikegami 1990 ; Haouzi et al 1993 ; Fukuoka et al 1997 ; Nicolò et al 2018 ; Girardi et al 2021b ).…”

Section: Introductionmentioning

confidence: 99%

“…In particular, only two studies have investigated the response to sinusoid-wave work rates in two different exercise domains, one in healthy humans (Haouzi et al 1993 ), the other in patients affected by chronic obstructive pulmonary disease (Porszasz et al 2013 ). Some studies analyzed the effects of varying the T on the patterns followed by cardiorespiratory and metabolic variables during sinusoidal work rate in homogeneously aerobic exercise (light-moderate exercise domain) only, either by simulation (Girardi et al 2021a ) or experimentally (Casaburi et al 1977 ; Bakker et al 1980 ; Fukuoka and Ikegami 1990 ).…”

Section: Introductionmentioning

confidence: 99%

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Energetics of sinusoidal exercise below and across critical power and the effects of fatigue

Borrelli,

Shokohyar,

Rampichini

et al. 2024

Eur J Appl Physiol

1

0

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Purpose Previous studies investigating sinusoidal exercise were not devoted to an analysis of its energetics and of the effects of fatigue. We aimed to determine the contribution of aerobic and anaerobic lactic metabolism to the energy balance and investigate the fatigue effects on the cardiorespiratory and metabolic responses to sinusoidal protocols, across and below critical power (CP). Methods Eight males (26.6 ± 6.2 years; 75.6 ± 8.7 kg; maximum oxygen uptake 52.8 ± 7.9 ml·min−1·kg−1; CP 218 ± 13 W) underwent exhausting sinusoidal cycloergometric exercises, with sinusoid midpoint (MP) at CP (CPex) and 50 W below CP (CP-50ex). Sinusoid amplitude (AMP) and period were 50 W and 4 min, respectively. MP, AMP, and time-delay (tD) between mechanical and metabolic signals of expiratory ventilation ($${\dot{V}}_{E}$$ V ˙ E ), oxygen uptake ($${\dot{V}}_{{{\text{O}}}_{2}}$$ V ˙ O 2 ), and heart rate ($${f}_{H}$$ f H ) were assessed sinusoid-by-sinusoid. Blood lactate ([La−]) and rate of perceived exertion (RPE) were determined at each sinusoid. Results $${\dot{V}}_{{{\text{O}}}_{2}}$$ V ˙ O 2 AMP was 304 ± 11 and 488 ± 36 ml·min−1 in CPex and CP-50ex, respectively. Asymmetries between rising and declining sinusoid phases occurred in CPex (36.1 ± 7.7 vs. 41.4 ± 9.7 s for $${\dot{V}}_{{{\text{O}}}_{2}}$$ V ˙ O 2 tD up and tD down, respectively; P < 0.01), with unchanged tDs. $${\dot{V}}_{{{\text{O}}}_{2}}$$ V ˙ O 2 MP and RPE increased progressively during CPex. [La−] increased by 2.1 mM in CPex but remained stable during CP-50ex. Anaerobic contribution was larger in CPex than CP-50ex. Conclusion The lower aerobic component during CPex than CP-50ex associated with lactate accumulation explained lower $${\dot{V}}_{{{\text{O}}}_{2}}$$ V ˙ O 2 AMP in CPex. The asymmetries in CPex suggest progressive decline of muscle phosphocreatine concentration, leading to fatigue, as witnessed by RPE.

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“…The smaller PS values for B f and the larger PS value for VT were specifically characterized under the SL fix condition. The increased muscle contraction of sinusoidal cadence may thus be competitively related to the faster ventilatory drive to breathe ( Takano, 1988 ; Caterini et al, 2016 ; Girardi et al, 2021 ). Notably, this specific adaptation was to the PS rather than the magnitude ( Casaburi et al, 1977 ; 1978; Wells et al, 2007 ).…”

Section: Discussionmentioning

confidence: 99%

Influence of Step Frequency on the Dynamic Characteristics of Ventilation and Gas Exchange During Sinusoidal Walking in humans

Fujita

¹

,

Kamibayashi

²

,

Aoki

³

et al. 2022

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We tested the hypothesis that restricting either step frequency (SF) or stride length (SL) causes a decrease in ventilatory response with limited breath frequency during sinusoidal walking. In this study, 13 healthy male and female volunteers (mean ± SD; age: 21.5 ± 1.8 years, height: 168 ± 7 cm, weight: 61.5 ± 8.3 kg) participated. The walking speed was sinusoidally changed between 50 and 100 m⋅min–1 with periods from 10 to 1 min. Using a customized sound system, we fixed the SF at 120 steps⋅min–1 with SL variation (0.83–0.41 m) (SFfix) or fixed the SL at 0.7 m with SF variation (143–71 steps⋅min–1) (SLfix) during the subjects’ sinusoidal walking. Both the subjects’ preferred locomotion pattern without a sound system (Free) and the unprompted spontaneous locomotor pattern for each subject (Free) served as the control condition. We measured breath-by-breath ventilation [tidal volume (VT) and breathing frequency (Bf)] and gas exchange [CO2 output (V.CO2), O2 uptake (V.O2)]. The amplitude (Amp) and the phase shift (PS) of the fundamental component of the ventilatory and gas exchange variables were calculated. The results revealed that the SFfix condition decreased the Amp of the Bf response compared with SLfix and Free conditions. Notably, the Amp of the Bf response under SFfix was reduced by less than one breath at the periods of 5 and 10 min. In contrast, the SLfix condition resulted in larger Amps of Bf and V.E responses as well as Free. We thus speculate that the steeper slope of the V.E-V.CO2 relationship observed under the SLfix might be attributable to the central feed-forward command or upward information from afferent neural activity by sinusoidal locomotive cadence. The PSs of the V.E, V.O2, and V.CO2 responses were unaffected by any locomotion patterns. Such a sinusoidal wave manipulation of locomotion variables may offer new insights into the dynamics of exercise hyperpnea.

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“…Similarly, quantitative analysis of ventilatory and gas exchange kinetics during exercise is commonly used to understand underlying metabolic and ventilatory control mechanisms (43,49) and are modified in patients with chronic disease (50,51). This is particularly true for the investigation of the control mechanisms of V ̇E, where analysis of V ̇E and V ̇CO 2A kinetics can provide important physiological information (52)(53)(54)(55)(56).…”

Section: *Figure 6 Near Here*mentioning

confidence: 99%

Current definitions of the breathing cycle in alveolar breath-by-breath gas exchange analysis

Girardi

¹

,

Gattoni

²

,

Stringer

³

et al. 2023

American Journal of Physiology-Regulatory, Integrative and Comp

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Identification of the breathing cycle forms the basis of any breath-by-breath gas exchange analysis. Classically, the breathing cycle is defined as the time interval between the beginning of two consecutive inspiration phases. Based on this definition, several research groups have developed algorithms designed to estimate the volume and rate of gas transferred across the alveolar membrane ("alveolar gas exchange"); however, most algorithms require measurement of lung volume at the beginning of the ith breath ( VLi-1 - i.e., the end-expiratory lung volume of the preceding ith breath). The main limitation of these algorithms is that direct measurement of VLi-1 is challenging and often unavailable. Two solutions avoid the requirement to measure VLi-1 by redefining the breathing cycle. One method defines the breathing cycle as the time period between two equal fractional concentrations of lung expired oxygen ( FO2) (or carbon dioxide; FCO2), typically in the alveolar phase, whereas the other uses the time period between equal values of the FO2/FN2 (or FCO2/ FN2) ratios. Thus, these methods identify the breathing cycle by analyzing the gas fraction traces rather than the gas flow signal. In this review, we define the traditional approach and two alternative definitions of the human breathing cycle and present the rationale for redefining this term. We also explore the strengths and limitations of the available approaches and provide implications for future studies.

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The effects of sinusoidal linear drifts on the estimation of cardiorespiratory dynamic parameters during sinusoidal workload forcing: a simulation study

Cited by 4 publications

References 28 publications

Energetics of sinusoidal exercise below and across critical power and the effects of fatigue

Energetics of sinusoidal exercise below and across critical power and the effects of fatigue

Influence of Step Frequency on the Dynamic Characteristics of Ventilation and Gas Exchange During Sinusoidal Walking in humans

Current definitions of the breathing cycle in alveolar breath-by-breath gas exchange analysis

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