Very Early Lactate Threshold in Healthy Young Men as Related to Oxygen Uptake Kinetics

Imahashi

et al. 2020

Preprint

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Background: The gas exchange threshold (GET) is determined during incremental exercise (Inc-Ex) testing. It is generally considered to be a safe training intensity, with little or no elevation in blood lactate (BLa). However, actual exercise training at GET is carried out primarily as a constant load exercise (CL-Ex). The dynamics of BLa during CL-Ex at GET have not been studied. This study was conducted particularly among the elderly population. Methods: We recruited 20 healthy elderly individuals (H: age 69.4±6.8 years) and 10 patients with cardiovascular diseases or under medication for cardiovascular risk factors (P: age 73.0±8.8 years). On day 1, we determined GET during symptomatic maximal Inc-Ex. On day 2, CL-Ex at GET intensity was performed for 20 min. Arterialized blood lactate levels were determined. Results: The mean BLa at GET during Inc-Ex was 1.51±0.29 mmol/L in H and 1.78±0.42 mmol/L in P (p < 0.05). During CL-Ex, BLa increased significantly more than that at GET, reaching a steady state level of 2.65±1.56 (H) and 2.53±0.95 (P) mmol/L (ns), with a mean respiratory exchange ratio (RER) of 0.94±0.05 (H) and 0.93±0.05 (P) (ns). Oxygen uptake (VO2) also reached a steady state in all participants. All participants were able to complete CL-Ex with mean perceived exertion ratings (Borg/20) of 11.8±1.3 (H) and 12.2±1.3 (P) (ns). Conclusions: CL-Ex at GET occurred at distinctly increased BLa levels; however, BLa reached a steady state, together with VO2 and RER, indicating that exercise intensity was metabolically moderate.

Section: Discussionsupporting

confidence: 92%

Section: Blood Lactatementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Constant Load Exercise at Gas Exchange Threshold is Accompanied by a Distinct Elevation in Blood Lactate Level

Kominami

Imahashi

et al. 2020

Preprint

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“…When more than one such parallel lines were observed, the first one was always taken as S1, the end of which is the VAT. The VAT thus determined best agreed with the lactate threshold in the study we previously reported [7]. Ventilatory equivalent and end-tidal gas concentration plots were also utilized, primarily for the detection of hyperventilation, which breaks the V-slope leftward and may be interpreted as a VAT point.…”

Section: Methodssupporting

confidence: 63%

New method for the mathematical derivation of the ventilatory anaerobic threshold: a retrospective study

BMC Sports Sci Med Rehabil

Kominami

Kondo

et al. 2019

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Background Ventilatory anaerobic threshold (VAT) is a useful submaximal measure of exercise tolerance; however, it must be visually determined. We developed a new mathematical method to objectively determine VAT. Methods We employed two retrospective population data sets (A/B). Data A (from 128 healthy subjects, patients with cardiovascular risk factors, and cardiac subjects at institution A, who underwent symptom-limited cardiopulmonary exercise testing) were used to develop the method. Data B (from 163 cardiac patients at institution B, who underwent pre−/post-rehabilitation submaximal exercise testing) were used to apply the developed method. VAT (by V-slope) was visually determined (vVAT), assuming that the pre-VAT segment is parallel to the respiratory exchange ratio (R) = 1 line. Results First, from data A, exponential fitting of ramp V-slope data yielded the equation y = ba x , where a is the slope of the exponential function: a smaller value signified a less steep curve, representing less VCO 2 against VO 2 . Next, a tangential line parallel to R = 1 was drawn. The x-axis value of the contact point was the derived VAT, termed the expVAT (VCO 2 ) (calculated as LN (1/[ b *LN( a )]/LN( a ). This point represents an instantaneous ΔVCO 2 /ΔVO 2 of 1.0. Second, in a similar way, the relation of VO2 vs. VE (minute ventilation) was fitted exponentially. The tangent line that crosses zero was drawn and the x-axis value was termed expVAT (VE) (calculated as 1/LN( a ). For data A, the correlation coefficients (r) of vVAT versus VAT (CO 2 ), and VAT (VE) were 0.924 and 0.903, respectively ( p < 0.001), with no significant difference between mean values with the limits of agreement (1.96*SD of the pair difference) being ±276 and ± 278 mL/min, respectively. expVAT (VCO 2 ) and expVAT (VE) significantly correlated with VO 2 peak ( r = 0.971, r = 0.935, p < 0.001). For data B, after cardiac rehabilitation, expVAT (CO 2 ) and exp. (VE) (mL/min) increased from 641 ± 185 to 685 ± 201 and from 696 ± 182 to 727 ± 209, respectively ( p < 0.001, p < 0.008), while vVAT increased from 673 ± 191 to 734 ± 226 ( p < 0.001). During submaximal testing, expVAT (VCO 2 ) underestimated VAT, whereas expVAT (VE) did not. Conclusions Two new mathematically-derived estimates to determine...

“…The hypothesis that the S1 is parallel to the diagonal R = 1 was tested as described [ 10 ]. After all of the VAT points and S1 data points (those visually interpreted as being located on or around the hypothetical S1 line parallel to R = 1) had been finalized, the mean of the S1 slopes was tested against the slope of 1.0.…”

Section: Methodsmentioning

confidence: 99%

Quantification and physiological significance of the rightward shift of the V-slope during incremental cardiopulmonary exercise testing

BMC Sports Sci Med Rehabil

Kondo

Yonezawa

et al. 2017

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BackgroundVentilatory anaerobic threshold (VAT) is frequently used as a measure of exercise tolerance, with the V-slope method being the standard; however, this needs to be visually determined. Over the years, we have observed that the V-slope itself often appears to shift rightward before the appearance of the VAT (RtShift: rightward shift of V-slope). This phenomenon has long been known to occur during the first 1–2 min of steady-state exercise and disappears thereafter; it is attributed to CO2 storage, presumably in active muscle. However, during incremental exercise, we have observed that the RtShift persists; furthermore, it seems to be related to the level of VAT. Therefore, we attempted to objectively quantify the RtShift, and to confirm its relationship to an index of exercise tolerance (VAT).MethodsThis study was based on a retrospective analysis of data from 100 cardiopulmonary ramp exercise tests (submaximal) performed by patients with cardiac disease. VAT was determined with the visual V-slope method. The horizontal distances between the diagonal R = 1 line and each data point on the V-slope plot to the right of R = 1 were measured; the average of these measurements was used as an objectively determined estimate of RtShift.ResultsThe predominant portion of RtShift occurred earlier than VAT. The mean RtShift was 33.9 ± 25.0 mL⋅min−1 VO2, whereas the mean VAT was 635 ± 220 mL⋅min−1. RtShift positively correlated with VAT (r = 718, p < 0.001), confirming previous visual observations. It also significantly correlated with ΔVO2/Δwork rate, a marker of oxygen uptake efficiency (r = 0.531, p < 0.001).ConclusionsWe identified that among patients with cardiac disease, V-slope is shifted rightward to varying degrees. The objectively quantified rightward shift of V-slope is significantly correlated with an index of exercise tolerance (VAT). Furthermore, it appears to occur at even lower work rates. This may offer a new objective means of estimating exercise tolerance; however, its exact biological basis still needs to be elucidated.Electronic supplementary materialThe online version of this article (doi:10.1186/s13102-017-0073-1) contains supplementary material, which is available to authorized users.