Juan M. Murias

Critical power testing or self-selected cycling: Which one is the best predictor of maximal metabolic steady-state?

Critical power (CP) demarcates the boundary between heavy and very heavy exercise intensity domains, and therefore, the power output (PO) that can be sustained at the maximal metabolic steady-state during constant-PO exercise (i.e., maximal lactate steady-state (MLSS)). However, the estimated CP does not always reflect a sustainable intensity of exercise, where blood lactate concentration ([La]) and oxygen uptake (V˙O2) reach a plateau.nnnOBJECTIVESnTo test cyclists ability to predict their highest PO associated with metabolic steady-state based on their own perception of effort.nnnDESIGNnRepeated measures.nnnMETHODSnThirteen healthy young cyclists (26±3years; 69.0±9.2kg; 174±10cm) were tested. Five time-to-exhaustion trials were used to derive CP based on a 2-parameter hyperbolic model (CPHYP). Participants performed two 30-min rides at a self-selected PO that they considered their highest sustainable exercise intensity (CPSELF). Additionally, MLSS was determined as the highest PO at which variation in [La] ≤1.0mmolL-1 between the 10th and 30th min was observed during a 30-min ride.nnnRESULTSnMean PO at CPSELF (233±42W) was similar (p>0.05) to MLSS (233±41W), whereas CPHYP (253±44W) consistently overestimated (p<0.05) the PO associated to metabolic steady-state. The limits of agreement (LOA) between MLSS and CPSELF were -20 to +20W (bias=0W, p>0.05), whereas the LOA between CPHYP and CPSELF were -40 to 0W (bias=-20W, p<0.05). CPSELF and MLSS presented similar (p>0.05) metabolic response (i.e., V˙O2, [La], and HR).nnnCONCLUSIONSnCompared to CPHYP, CPSELF may offer a more precise approach to predict the constant-PO associated with maximal physiological steady-state.

Effects of short‐term training and detraining on VO2 kinetics: Faster VO2 kinetics response after one training session

This study examined the time course of short‐term training and detraining‐induced changes in oxygen uptake ( V ˙ O 2 ) kinetics. Twelve men (24u2009±u20093 years) were assigned to either a 50% or a 70% of V ˙ O 2 m a x training intensity (nu2009=u20096 per group). V ˙ O 2 was measured breath‐by‐breath. Changes in deoxygenated‐hemoglobin concentration (Δ[HHb]) were measured by near‐infrared spectroscopy. Moderate‐intensity exercise on‐transient V ˙ O 2 and Δ[HHb] were modeled with a mono‐exponential and normalized (0–100% of response) and the [ H H b ] / V ˙ O 2 ratio was calculated. Similar changes in time constant of V ˙ O 2 ( t V ˙ O 2 ) were observed in both groups. The combined group mean for t V ˙ O 2 decreased ∼14% (32.3 to 27.9u2009s, Pu2009<u20090.05) after one training session with a further ∼11% decrease (27.9 to 24.8u2009s, Pu2009<u20090.05) following two training sessions. The t V ˙ O 2 p remained unchanged throughout the remaining of training and detraining. A significant “overshoot” in the [ H H b ] / V ˙ O 2 ratio was decreased (albeit not significant) after one training session, and abolished (Pu2009<u20090.05) after the second one, with no overshoot observed thereafter. Speeding of V ˙ O 2 kinetics was remarkably quick with no further changes being observed with continuous training or during detraining. Improve matching of local O2 delivery to O2 utilization is a mechanism proposed to influence this response.

The near-infrared spectroscopy-derived deoxygenated haemoglobin breaking-point is a repeatable measure that demarcates exercise intensity domains

OBJECTIVESnA breaking-point in the near-infrared spectroscopy (NIRS)-derived deoxygenated haemoglobin ([HHb]) profile towards the end of a ramp incremental (RI) cycling test has been associated to the respiratory compensation point (RCP). Despite the physiological value of this measure, its repeatability remains unknown. The aim was to examine the repeatability of the [HHb] breaking-point ([HHb]BP) and its association to RCP during a RI cycling test.nnnDESIGNnA repeated measures design was performed on 11 males (30.5±8.4 year; 76.5±8.4kg) and 4 females (30.5±5.9 year; 61.9±4.4 Kg).nnnMETHODSnGas exchange and NIRS [HHb] data were collected during RI tests performed on two different days separated by 48h. The [HHb]BP and the RCP were determined and compared for each trial.nnnRESULTSnThe [HHb]BP and the respiratory compensation point (RCP) occurred at the same VO2 in test 1 and test 2 ([HHb]BP: 3.49±0.52Lmin-1 test 1; 3.48±0.45Lmin-1 test 2; RCP: 3.38±0.40Lmin-1 test 1; 3.38±0.44Lmin-1 test 2) (P>0.05). The VO2 associated with the [HHb]BP and the VO2 at RCP were not significantly different from each other either in test 1 as well as in test 2 (P>0.05). Neither test 1 nor test 2 showed significant mean average error between the VO2 at the [HHb]BP and RCP using Bland & Altman plots.nnnCONCLUSIONSnThe [HHb]BP is a repeatable measure that consistently occurs towards the end of a RI test. The association between the [HHb]BP and the RCP reinforces the idea that these parameters may share similar mechanistic basis.

The relationship between oxygen uptake kinetics and neuromuscular fatigue in high-intensity cycling exercise

PurposeIn theory, a slow oxygen uptake (

The plateau in the NIRS-derived [HHb] signal near the end of a ramp incremental test does not indicate the upper limit of O2 extraction in the vastus lateralis

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Fitness level and not aging per se, determines the oxygen uptake kinetics response

V˙O2) kinetics leads to a greater accumulation of anaerobic by-products, which can, in turn, induce more neuromuscular fatigue. However, the existence of this relationship has never been tested.MethodsAfter two sessions to measure peak

Near-infrared spectroscopy assessment of microvasculature detects difference in lower limb vascular responsiveness in obese compared to lean individuals

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