An integrated view on the oxygenation responses to incremental exercise at the brain, the locomotor and respiratory muscles

Abstract

In the past two decades oxygenation responses to incremental ramp exercise, measured non-invasively by means of near-infrared spectroscopy at different locations in the body, have advanced the insights on the underpinning mechanisms of the whole-body pulmonary oxygen uptake ([Formula: see text]) response. In healthy subjects the complex oxygenation responses at the level of locomotor and respiratory muscles, and brain were simplified and quantified by the detection of breakpoints as a deviation in the ongoing response pattern as work rate increases. These breakpoints were located in a narrow intensity range between 75 and 90 % of the maximal [Formula: see text] and were closely related to traditionally determined thresholds in pulmonary gas exchange (respiratory compensation point), blood lactate measurements (maximal lactate steady state), and critical power. Therefore, it has been assumed that these breakpoints in the oxygenation patterns at different sites in the body might be equivalent and could, therefore, be used interchangeably. In the present review the typical oxygenation responses (at locomotor and respiratory muscle level, and cerebral level) are described and a possible framework is provided showing the physiological events that might link the breakpoints at different body sites with the thresholds determined from pulmonary gas exchange and blood lactate measurements. However, despite a possible physiological association, several arguments prevent the current practical application of these breakpoints measured at a single site as markers of exercise intensity making it highly questionable whether measurements of the oxygenation response at one single site can be used as a reflection of whole-body responses to different exercise intensities.

Metabolic and performance‐related consequences of exercising at and slightly above MLSS

“…The physiological mechanisms underlying these different patterns of behavior of the VL and RF muscles in regulating the delivery and utilization of O 2 are a current topic of debate . What is important in relation to the findings of the present study is that these behavior patterns might be reflective of the metabolic changes occurring when transitioning from the heavy‐to‐severe exercise intensity domain.…”

Validation of a novel wearable, wireless technology to estimate oxygen levels and lactate threshold power in the exercising muscle

“…Interest in examining muscle oxygen saturation (SmO 2 ) has been growing due to its ability to provide a localized measurement continuously and noninvasively using nearinfrared spectroscopy (NIRS) (Chance et al 1992;Belardinelli et al 1995;Hamaoka et al 1996Hamaoka et al , 2011Bhambhani et al 1997;Grassi et al 1999Grassi et al , 2003Wang et al 2006;Soller et al 2008;Bailey et al 2009;Ihsan et al 2013;Racinais et al 2014;Boone et al 2016;van der Zwaard et al 2016;Baker et al 2017;Hammer et al 2018;Perrey and Ferrari 2018). NIRS techniques work by delivering light (in the 650-900 nm wavelength range) into the tissue and measuring the diffused light to estimate the absorption and scattering properties of the measured tissue volume (Yodh and Chance 1995).…”

Examining Work-to-Rest Ratios to Optimize Upper Body Sprint Interval Training

“…At the onset of exercise, there is an increase in blood volume to the working muscle carrying oxygenated hemoglobin (Hb) to meet the energy demands of the activity. As exercise continues to intensify, such as a ramp incremental graded exercise protocol, oxygenated hemoglobin tends to drop off and deoxygenated Hb tends to rise (Boone, Vandekerckhove, Coomans, Prieur, & Bourgois, 2016). This rise is a natural consequence of oxygen being extracted from the red blood cells into the muscle's mitochondria as per the oxygen-dissociation curve, which continues until there is a plateau due to limits imposed by oxygen extraction and utilization (Boone et al, 2016).…”

“…As exercise continues to intensify, such as a ramp incremental graded exercise protocol, oxygenated hemoglobin tends to drop off and deoxygenated Hb tends to rise (Boone, Vandekerckhove, Coomans, Prieur, & Bourgois, 2016). This rise is a natural consequence of oxygen being extracted from the red blood cells into the muscle's mitochondria as per the oxygen-dissociation curve, which continues until there is a plateau due to limits imposed by oxygen extraction and utilization (Boone et al, 2016). This plateau is synonymous with deoxygenation threshold or break point [HHb]BP which delineates the point at which maximal oxygen extraction, by the working muscle, has been achieved (Boone et al, 2016).…”

“…This rise is a natural consequence of oxygen being extracted from the red blood cells into the muscle's mitochondria as per the oxygen-dissociation curve, which continues until there is a plateau due to limits imposed by oxygen extraction and utilization (Boone et al, 2016). This plateau is synonymous with deoxygenation threshold or break point [HHb]BP which delineates the point at which maximal oxygen extraction, by the working muscle, has been achieved (Boone et al, 2016). Continued exercise following [HHb]BP in a ramp protocol elicits exhaustion within minutes as the supply cannot keep up with the demand.…”