A new objective method for determining exercise gas exchange thresholds by respiratory frequency in middle-aged men.

PURPOSE: To evaluate the agreement between the two Gas Exchange Thresholds (GETs = GET1 and GET2), identified by the conventional V-Slope method, and two Respiratory Frequency Thresholds (fRTs = fRT1 and fRT2) obtained from a novel, low-cost, and simple method of breakpoint determination. METHODS: Fifty middle-aged males (age: 50-58 years; V ˙ o2peak: 37.5 ± 8.6 mL·Kg-1·min-1), either healthy or with chronic illnesses, underwent an incremental cycle exercise test to determine maximal oxygen uptake ( V ˙ o2max/ V ˙ o2peak), GETs and fRTs. RESULTS: There were no statistical differences [P > 0.05; ES: 0.17 to 0.32, small] between absolute and relative (56-60% V ˙ o2peak) oxygen uptake ( V ˙ o2) values at GET1 with those obtained at fRT1, nor between V ˙ o2 values at GET2 with those at fRT2 (76-78% V ˙ o2peak). Heart rate (HR) at fRT1, and V ˙ o2 and HR at fRT2 showed very large correlations (r = 0.75-0.82; P < 0.001) and acceptable precision (SEE < 7-9%) in determination of their corresponding values at GET1 and GET2. The precision in the estimation of V ˙ o2 at GET1 from fRT1 was moderate (SEE = 15%), while those of power output at GET1 (SEE = 23%) and GET2 (SEE = 12%) from their corresponding fRTs values were very poor to moderate. CONCLUSION: HR at fRT1 and V ˙ o2 and HR at fRT2, determined using a new objective and portable approach, may potentially serve as viable predictors of their respective GETs. This method may offer a simplified, cost-effective, and field-based approach for determining exercise threshold intensities during graded exercise.

Creatine supplementation and VO2max: a systematic review and meta-analysis.

Although creatine supplementation is well-known to increase exercise performance in acute high-intensity exercises, its role in aerobic performance based on VO2max is more controversial. Thus, we performed a systematic review and meta-analysis on the effects of creatine supplementation on VO2max. PubMed, Cochrane, Embase, and ScienceDirect were searched for randomized controlled trials (RCTs) reporting VO2max in creatine supplementation and placebo groups before and after supplementation. We computed a random-effects meta-analysis on VO2max at baseline, within groups following supplementation, on changes on VO2max between groups, and after supplementation between groups. Sensitivity analyses and meta-regression were conducted. We included 19 RCTs for a total of 424 individuals (mean age 30 years old, 82% men). VO2max did not differ at baseline between groups (creatine and placebo). Participants in both groups were engaged in exercise interventions in most studies (80%). Using changes in VO2max, VO2max increased in both groups but increased less after creatine supplementation than placebo (effect size [ES] = -0.32, 95%CI = -0.51 to -0.12, p = 0.002). Comparisons after creatine supplementation confirmed a lower VO2max in the creatine group compared to the placebo group (ES= -0.20, 95%CI = -0.39 to -0.001, p = 0.049). Meta-analysis after exclusion from meta-funnel resulted in similar outcomes in a subgroup of young and healthy participants. Meta-regressions on characteristics of supplementation, physical training, or sociodemographic were not statistically significant. Creatine supplementation has a negative effect on VO2max, regardless of the characteristics of training, supplementation, or population characteristics.Supplemental data for this article is available online at https://doi.org/10.1080/10408398.2021.2008864 .

Validation of a non-linear index of heart rate variability to determine aerobic and anaerobic thresholds during incremental cycling exercise in women.

Studies highlight the usage of non-linear time series analysis of heart rate variability (HRV) using the short-term scaling exponent alpha1 of Detrended Fluctuation Analysis (DFA-alpha1) during exercise to determine aerobic and anaerobic thresholds. The present study aims to further verify this approach in women. Gas exchange and HRV data were collected from 26 female participants with different activity levels. Oxygen uptake (VO2) and heart rate (HR) at first (VT1) and second ventilatory thresholds (VT2) were compared with DFA-alpha1-based thresholds 0.75 (HRVT1) and 0.50 (HRVT2). Results: VO2 at VT1 and VT2 were 25.2 ml/kg/min (± 2.8) and 31.5 ml/kg/min (± 3.6) compared with 26.5 ml/kg/min (± 4.0) and 31.9 ml/kg/min (± 4.5) for HRVT1 and HRVT2, respectively (ICC3,1 = 0.77, 0.84; r = 0.81, 0.86, p < 0.001). The mean HR at VT1 was 147 bpm (± 15.6) and 167 bpm (± 12.7) for VT2, compared with 152 bpm (± 15.5) and 166 bpm (± 13.2) for HRVT1 and HRVT2, respectively (ICC3,1 = 0.87, 0.90; r = 0.87, 0.90, p < 0.001). Bland-Altman analysis for VT1 vs. HRVT1 showed a mean difference of - 1.3 ml/kg/min (± 2.4; LoA: 3.3, - 6.0 ml/kg/min) for VO2 and of - 4.7 bpm (± 7.8; LoA: 10.6, - 20.0 bpm) for HR. VT2 vs. HRVT2 showed a mean difference of - 0.4 ml/kg/min (± 2.3; LoA: 4.1, - 4.9 ml/kg/min) for VO2 and 0.5 bpm (± 5.7; LoA: 11.8, - 10.8 bpm) for HR. DFA-alpha1-based thresholds showed good agreement with traditionally used thresholds and could be used as an alternative approach for marking organismic transition zones for intensity distribution in women.

Cardiac output and arteriovenous oxygen difference contribute to lower peak oxygen uptake in patients with fibromyalgia.

BACKGROUND: Patients with fibromyalgia (FM) exhibit low peak oxygen uptake ([Formula: see text]O2peak). We aimed to detect the contribution of cardiac output to ([Formula: see text]) and arteriovenous oxygen difference [Formula: see text] to [Formula: see text] from rest to peak exercise in patients with FM. METHODS: Thirty-five women with FM, aged 23 to 65 years, and 23 healthy controls performed a step incremental cycle ergometer test until volitional fatigue. Alveolar gas exchange and pulmonary ventilation were measured breath-by-breath and adjusted for fat-free body mass (FFM) where appropriate. [Formula: see text] (impedance cardiography) was monitored. [Formula: see text] was calculated using Fick's equation. Linear regression slopes for oxygen cost (∆[Formula: see text]O2/∆work rate) and [Formula: see text] to [Formula: see text]O2 (∆[Formula: see text]/∆[Formula: see text]O2) were calculated. Normally distributed data were reported as mean ± SD and non-normal data as median [interquartile range]. RESULTS: [Formula: see text]O2peak was lower in FM patients than in controls (22.2 ± 5.1 vs. 31.1 ± 7.9 mL∙min-1∙kg-1, P < 0.001; 35.7 ± 7.1 vs. 44.0 ± 8.6 mL∙min-1∙kg FFM-1, P < 0.001). [Formula: see text] and C(a-v)O2 were similar between groups at submaximal work rates, but peak [Formula: see text] (14.17 [13.34-16.03] vs. 16.06 [15.24-16.99] L∙min-1, P = 0.005) and C(a-v)O2 (11.6 ± 2.7 vs. 13.3 ± 3.1 mL O2∙100 mL blood-1, P = 0.031) were lower in the FM group. No significant group differences emerged in ∆[Formula: see text]O2/∆work rate (11.1 vs. 10.8 mL∙min-1∙W-1, P = 0.248) or ∆[Formula: see text]/∆[Formula: see text]O2 (6.58 vs. 5.75, P = 0.122) slopes. CONCLUSIONS: Both [Formula: see text] and C(a-v)O2 contribute to lower [Formula: see text]O2peak in FM. The exercise responses were normal and not suggestive of a muscle metabolism pathology. TRIAL REGISTRATION: ClinicalTrials.gov, NCT03300635. Registered 3 October 2017-Retrospectively registered. https://clinicaltrials.gov/ct2/show/NCT03300635 .

The effect of saddle setback and cycling intensity on saddle pressures and comfort in male and female recreational cyclists.

Cycling is a recreational activity that helps to prevent different diseases. The practice of this popular worldwide sport requires the cyclist to maintain a particular posture in contact with the pedals, handlebars, and saddle for long periods of time. Therefore, the study of the pressure exerted on the saddle is of great importance as it is directly related to the reduction of perineal injuries and pathologies. The present research aims to study the effect on comfort and saddle pressures when performing a cycloergometer test using 3 saddle positions: own setback position (P1), forward [-10% (P2)], backward [+10% (P3)] at two exercise intensities (Ventilatory Threshold: VT1 and VT2). 34 amateur cyclists (14 women, 20 men) were analysed. The results showed that comfort was significantly reduced in P3 (p < 0.01) and significantly increased for some items in the VT1 condition and for men in P1 regarding overall comfort (p < 0.01, ES = 0.105). In addition, the average and maximum pressure in the pubic region were significantly higher at P3 (p < 0.001) and men show higher values for average pressure compared to women (p = 0.006, ES = 0.235). In conclusion, backward saddle setback positions increase pressure and discomfort to recreational cyclists in comparison with the forward and own setback position, which could increase the risk of injury.

Body composition, cardiorespiratory fitness, and neuromuscular adaptations induced by a home-based whole-body high intensity interval training.

Background/objective: Bodyweight exercises performed at home could be a complementary approach to improve health-related fitness in people having little spare time and during stay-at-home periods. This study then investigated body composition, cardiorespiratory fitness, and neuromuscular adaptations to a home-based, video-directed, whole-body high-intensity interval training (WB-HIIT). Methods: Fourteen subjects participated to an 8-week WB-HIIT (6 females, 23 ± 1 years) and fourteen were included in a non-exercise control group (CTL; 6 females, 24 ± 4 years). All took part to pre- and post-intervention assessments of body composition, peak oxygen uptake (VO2peak) and first ventilatory threshold (VT1; index of aerobic capacity), dynamic (leg press 3-repetition maximum) and isometric strength (knee extensors maximal isometric contractions with assessment of voluntary activation), and muscle endurance during an isometric submaximal contraction maintained till exhaustion. WB-HIIT consisted in 30-s all-out whole-body exercises interspaced with 30 s of active recovery. Training sessions were performed at home by means of videos with demonstration of exercises. Heart rate was monitored during sessions. Results: WB-HIIT increased VO2peak (5%), VT1 (20%), leg lean mass (3%), dynamic (13%) and isometric strength (6%), and muscle endurance (28%; p < 0.05), while they did not improve in CTL. VO2peak increase was correlated (r = 0.56; p < 0.05) with the time spent above 80% of maximal heart rate during training sessions. Isometric strength increase was correlated with change in voluntary activation (r = 0.74; p < 0.01). Conclusion: The home-based WB-HIIT induced concomitant cardiorespiratory fitness and neuromuscular improvements. The predominant effect was observed for aerobic capacity and muscle endurance which could improve exercise tolerance and reduce fatigability.

Effect of a novel 90-second "Gear" exercise programme on markers of inflammation and cardiorespiratory fitness measurements in person at risk of cardiovascular disease.

The study compared the effect of the novel "Gear" exercise programmes on inflammatory markers and cardiorespiratory fitness measurements. The participants mean age was 38 ± 5.74 years, with a mean body mass of 83 ± 16.93kg. Participants were randomly assigned to either the "Gear" exercise programme repeated at different times during the day (GEP-DT): cycled for 90 seconds, repeated three times per day, three days per week; the "Gear" exercise programme repeated at one point in time (GEP-OT): cycled for 90 seconds followed by four minutes and 30 seconds rest, repeated three times at one point in time, three days per week; moderate-intensity continuous exercise group (MICE): cycled for 30 minutes at 55-69% of HRmax or the control group (CTRL): did not exercise. The GEP-DT demonstrated a moderate increase in load at ventilation threshold (VT-L) (MD = 8.18 ± 12.30, % Δ = 14.53, d = 0.77, d (95% CI): (-0.17, 1.64)). The GEP-OT group demonstrated a large effect size for VT-L (MD = 11.79 ± 18.77, % Δ = 18.86, d = 0.81, d (95% CI): (-0.02, 1.63)). The GEP-DT and GEP-OT raised the VT-L, which prevented premature fatigue and improved the efficiency of the cardiorespiratory system.

A Preliminary Investigation into the Frequency Dose Effects of High-Intensity Functional Training on Cardiometabolic Health.

The objective of this study was to explore the effects of three weekly frequency doses of high-intensity functional training (HIFT) on an array of cardiometabolic markers in adults with metabolic syndrome (MetS). Twenty-one men and women, randomized into one (HIFT1), two (HIFT2), or three (HIFT3) days per week of HIFT, completed 3-weeks of familiarization plus a 12-week progressive training program. Pre- and post-intervention, several cardiometabolic, body composition, oxygen consumption, metabolic syndrome severity, and perceptions of fitness measurements were assessed. Additionally, an exercise enjoyment survey was administered post-intervention. A Cohen's d was used to demonstrate within-group change effect size. Although this study was not fully powered, a one-way and two-way ANOVA were used to compare the dose groups to provide provisional insights. No differences were found when frequency dose groups were compared. Many cardiometabolic, body composition, and fitness improvements were seen within each group, with clinically meaningful improvements in the metabolic syndrome severity score (MSSS) (HIFT1: -0.105, d = 0.28; HIFT2: -0.382, d = 1.20; HIFT3: -0.467, d = 1.07), waist circumference (HIFT1: -4.1cm, d = 3.33; HIFT2: -5.4cm, d = 0.89; HIFT3: -0.7cm, d = 0.20), and blood glucose (HIFT1: -9.5mg/dL, d = 0.98; HIFT2: -4.9mg/dL, d = 1.00; HIFT3: -1.7mg/dL, d = 0.23). All three groups similarly reported high exercise enjoyment and likeliness to continue after the intervention. In conclusion, HIFT performed once, twice, or thrice a week elicits improvements in MetS and is considered enjoyable. HIFT, even at a low weekly dose, therefore represents a potential strategy to reduce the global MetS burden.

The Effects of a Single Session of High Intensity Functional Training on Energy Expenditure, VO2, and Blood Lactate.

High intensity functional training (HIFT) provides a potential option to meet public exercise recommendations for both cardiorespiratory and strength outcomes in a time efficient manner. To better understand the potential for HIFT as an exercise approach, energy expenditure (EE) and relative intensity need quantifying. In thirteen sedentary men and women with metabolic syndrome (MetS), we used both indirect calorimetry and blood lactate levels to calculate EE of a single session of HIFT. The HIFT session included four, 6-minute sets of consecutive functional exercises. Examples of the exercises involved were squats, deadlifts, suspension rows, suspension chest press, and planks. Intensity is described relative to individual ventilatory thresholds. The total group EE was 270.3 ± 77.3 kcal with approximately 5% attributed anaerobic energy production. VO2 ranged between 88.8 ± 12.3% and 99 ± 12% of the second ventilatory threshold (VT2), indicating a vigorous effort. After each work interval, peak blood lactate ranged between 7.9 ± 1.9 and 9.3 ± 2.9 mmol, and rate of perceived exertion between 6.9 ± 1.0 and 8.7 ± 0.8 arbitrary units from 1-10. These were achieved in approximately 46 minutes of exercise per participant. In conclusion, HIFT elicits the energy expenditure and effort requisite to result in the adaptive responses to produce the known suite of benefits of exercise for individuals with MetS.

The Effects of Standardised versus Individualised Aerobic Exercise Prescription on Fitness-Fatness Index in Sedentary Adults: A Randomised Controlled Trial.

A poor Fitness Fatness Index (FFI) is associated with type 2 diabetes incidence, other chronic conditions (Alzheimer's, cancer, and cardiovascular disease) and all-cause mortality. Recent investigations have proposed that an individualised exercise prescription based on ventilatory thresholds is more effective than a standardised prescription in improving cardiorespiratory fitness (CRF), a key mediator of FFI. Thus, the aim of the current study was to determine the effectiveness of individualised versus standardised exercise prescription on FFI in sedentary adults. Thirty-eight sedentary individuals were randomised to 12-weeks of: (1) individualised exercise training using ventilatory thresholds (n = 19) or (2) standardised exercise training using a percentage of heart rate reserve (n = 19). A convenience sample was also recruited as a control group (n=8). Participants completed CRF exercise training three days per week, for 12-weeks on a motorised treadmill. FFI was calculated as CRF in metabolic equivalents (METs), divided by fatness determined by waist to height ratio (WtHR). A graded exercise test was used to measure CRF, and anthropometric measures (height and waist circumference) were assessed to ascertain WtHR. There was a difference in FFI change between study groups, whilst controlling for baseline FFI, F (2, 42) = 19.382 p < .001, partial η2 = 0.480. The magnitude of FFI increase from baseline was significantly higher in the individualised (+15%) compared to the standardised (+10%) (p = 0.028) and control group (+4%) (p = <.001). The main finding of the present study is that individualised exercise prescription had the greatest effect on improving FFI in sedentary adults compared to a standardised prescription. Therefore, an individualised based exercise prescription should be considered a viable and practical method of improving FFI in sedentary adults.

The anaerobic threshold: 50+ years of controversy.

The anaerobic threshold (AT) remains a widely recognized, and contentious, concept in exercise physiology and medicine. As conceived by Karlman Wasserman, the AT coalesced the increase of blood lactate concentration ([La- ]), during a progressive exercise test, with an excess pulmonary carbon dioxide output ( V̇CO2 ). Its principal tenets were: limiting oxygen (O2 ) delivery to exercising muscle→increased glycolysis, La- and H+ production→decreased muscle and blood pH→with increased H+ buffered by blood [HCO3- ]→increased CO2 release from blood→increased V̇CO2 and pulmonary ventilation. This schema stimulated scientific scrutiny which challenged the fundamental premise that muscle anoxia was requisite for increased muscle and blood [La- ]. It is now recognized that insufficient O2 is not the primary basis for lactataemia. Increased production and utilization of La- represent the response to increased glycolytic flux elicited by increasing work rate, and determine the oxygen uptake ( V̇O2 ) at which La- accumulates in the arterial blood (the lactate threshold; LT). However, the threshold for a sustained non-oxidative contribution to exercise energetics is the critical power, which occurs at a metabolic rate often far above the LT and separates heavy from very heavy/severe-intensity exercise. Lactate is now appreciated as a crucial energy source, major gluconeogenic precursor and signalling molecule but there is no ipso facto evidence for muscle dysoxia or anoxia. Non-invasive estimation of LT using the gas exchange threshold (non-linear increase of V̇CO2 versus V̇O2 ) remains important in exercise training and in the clinic, but its conceptual basis should now be understood in light of lactate shuttle biology.

Heat acclimation during low-intensity exercise increases V̇O2max and Hsp72, but not markers of mitochondrial biogenesis and oxidative phosphorylation, in skeletal tissue.

NEW FINDINGS: What is the central question of this study? Heat acclimation increases tolerance to exercise performed in the heat and may improve maximal oxygen uptake (VO2 max) and performance in temperate environments. However, it is unknown if HA affects the expression of proteins related to mitochondrial biogenesis and oxidative capacity in skeletal muscle. What is the main finding and its importance? We showed that heat acclimation increased VO2 max in a temperate environment but did not change markers of mitochondrial biogenesis and oxidative phosphorylation in the skeletal muscle. ABSTRACT: Heat acclimation (HA) increases tolerance to exercise performed in the heat and may improve maximal oxygen uptake ( V̇O2max ) in temperate environments. However, it is unknown if HA affects the expression of proteins related to mitochondrial biogenesis and oxidative capacity in skeletal muscle. The purpose of this study was to investigate the effect of HA on skeletal muscle markers of mitochondrial biogenesis and oxidative phosphorylation in recreationally trained adults. Thirteen (7 males and 6 females) individuals underwent 10 days of HA. Participants performed two 45 min bouts of exercise (walking at 30-40% maximal velocity at 3% grade) with 10 min rest per session in a hot environment (∼42°C and 30-50% relative humidity). V̇O2max , ventilatory thresholds (VT), and protein expression of peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α), mitochondrial transcription factor A (TFAM), calcium/calmodulin-dependent protein kinase (CaMK), electron transport chain (ETC) complexes I-IV, and heat shock protein 72 (Hsp72) in skeletal muscle were measured pre- and post-HA. Comparing day 1 to day 10, HA was confirmed by lower resting core temperature (Tcore ) (P = 0.026), final Tcore (P < 0.0001), mean heart rate (HR) (P = 0.002), final HR (P = 0.003), mean ratings of perceived exertion (RPE) (P = 0.026) and final RPE (P = 0.028). Pre- to post-HA V̇O2max (P = 0.045) increased but VT1 (P = 0.263) and VT2 (P = 0.239) were unchanged. Hsp72 (P = 0.007) increased, but skeletal muscle protein expression (PGC-1α, P = 0.119; TFAM, P = 0.763; CaMK, P = 0.19; ETC I, P = 0.629; ETC II, P = 0.724; ETC III, P = 0.206; ETC IV, P = 0.496) were not affected with HA. HA during low-intensity exercise increased V̇O2max in a temperate environment and Hsp72 but it did not affect markers of mitochondrial biogenesis and oxidative phosphorylation in the skeletal muscle.

Estimation of the second ventilatory threshold through ventricular repolarization profile analysis.

Under the hypothesis that sympathetic control of ventricular repolarization may change once the second ventilatory threshold (VT2) has been reached, a novel methodology for non-invasive VT2 estimation based on the analysis of the T wave from the electrocardiogram (ECG) is proposed, and potential underlying physiological mechanisms are suggested. 25 volunteers (33.4 ± 5.2 years) underwent an incremental power cycle ergometer test (25 W/minute). During the test, respiratory gas exchange and multi-lead ECG were acquired. The former was employed to determine VT2, used here as a reference, whereas the latter was used to compute the temporal profiles of an index of ventricular repolarization instability (dT) and its low-frequency (LF) oscillations (LFdT). The sudden increases observed in dT and LFdT profiles above an established heart rate threshold were employed to derive VT2 estimates, referred to as VT2d T and VT2LF d T , respectively. Estimation errors of -4.7 ± 25.2 W were obtained when considering VT2d T . Errors were lower than the one-minute power increment of 25 W in 68% of the subjects and lower than 50 W in 89.5% of them. When using VT2LF d T , estimation error was of 15.3 ± 32.4 W. Most of the subjects shared common characteristic dT and LFdT profiles, which could be reflecting changes in the autonomic control of ventricular repolarization before and after reaching VT2. The analysis of ventricular repolarization dynamics during exercise allows non-invasive ECG-based estimation of VT2, possibly in relation to changes in the autonomic control of ventricular electrical activity when VT2 is reached.

The importance of ventilatory thresholds to define aerobic exercise intensity in cardiac patients and healthy subjects.

BACKGROUND: Although structured exercise training is strongly recommended in cardiac patients, uncertainties exist about the methods for determining exercise intensity (EI) and their correspondence with effective EI obtained by ventilatory thresholds. We aimed to determine the first (VT1 ) and second ventilatory thresholds (VT2 ) in cardiac patients, sedentary subjects, and athletes comparing VT1 and VT2 with EI defined by recommendations. METHODS: We prospectively enrolled 350 subjects (mean age: 50.7±12.9 years; 167 cardiac patients, 150 healthy sedentary subjects, and 33 competitive endurance athletes). Each subject underwent ECG, echocardiography, and cardiopulmonary exercise testing. The percentages of peak VO2 , peak heart rate (HR), and HR reserve were obtained at VT1 and VT2 and compared with the EI definition proposed by the recommendations. RESULTS: VO2 at VT1 corresponded to high rather than moderate EI in 67.1% and 79.6% of cardiac patients, applying the definition of moderate exercise by the previous recommendations and the 2020 guidelines, respectively. Most cardiac patients had VO2  values at VT2 corresponding to very-high rather than high EI (59.9% and 50.3%, by previous recommendations and 2020 guidelines, respectively). A better correspondence between ventilatory thresholds and recommended EI domains was observed in healthy subjects and athletes (90% and 93.9%, respectively). CONCLUSIONS: EI definition based on percentages of peak HR and peak VO2  may misclassify the effective EI, and the discrepancy between the individually determined and the recommended EI is particularly relevant in cardiac patients. A ventilatory threshold-based rather than a range-based approach is advisable to define an appropriate level of EI.

Bicycle spiroergometry: comparison of standardized examination protocols for adolescents: is it necessary to define own standard values for each protocol?

PURPOSE: To compare performance data of adolescents collected with five different bicycle spiroergometry protocols and to assess the necessity for establishing standard values for each protocol. METHODS: One-hundred-twenty adolescents completed two bicycle spiroergometries within 14 days. One of the two tests was performed based on our institutional weight-adapted protocol (P0). The other test was performed based on one out of four exercise protocols widely used for children and adolescents (P1, 2, 3 or 4) with 30 persons each. The two tests were performed in a random order. Routine parameters of cardiopulmonary exercise tests (CPET) such as VO2peak, maximum power, O2 pulse, OUES, VE/VCO2 slope as well as ventilatory and lactate thresholds were investigated. Agreement between protocols was evaluated by Bland-Altman analysis, coefficients of variation (CV) and intra-class correlation coefficients (ICC). RESULTS: None of the CPET parameters were significantly different between P0 and P1, 2, 3 or 4. For most of the parameters, low biases between P0 and P1-P4 were found and 95% confidence intervalls were narrow. CV and ICC values largely corresponded to well-defined analytical goals (CV < 10% and ICC > 0.9). Only maximal power (Pmax) showed differences in size and drift of the bias depending on the length of the step duration of the protocols. CONCLUSION: Comparability between examination protocols has been shown for CPET parameters independent on step duration. Protocol-dependent standard values do not appear to be necessary. Only Pmax is dependent on the step duration, but in most cases, this has no significant influence on the fitness assessment.

Influence of Artefact Correction and Recording Device Type on the Practical Application of a Non-Linear Heart Rate Variability Biomarker for Aerobic Threshold Determination.

Recent study points to the value of a non-linear heart rate variability (HRV) biomarker using detrended fluctuation analysis (DFA a1) for aerobic threshold determination (HRVT). Significance of recording artefact, correction methods and device bias on DFA a1 during exercise and HRVT is unclear. Gas exchange and HRV data were obtained from 17 participants during an incremental treadmill run using both ECG and Polar H7 as recording devices. First, artefacts were randomly placed in the ECG time series to equal 1, 3 and 6% missed beats with correction by Kubios software's automatic and medium threshold method. Based on linear regression, Bland Altman analysis and Wilcoxon paired testing, there was bias present with increasing artefact quantity. Regardless of artefact correction method, 1 to 3% missed beat artefact introduced small but discernible bias in raw DFA a1 measurements. At 6% artefact using medium correction, proportional bias was found (maximum 19%). Despite this bias, the mean HRVT determination was within 1 bpm across all artefact levels and correction modalities. Second, the HRVT ascertained from synchronous ECG vs. Polar H7 recordings did show an average bias of minus 4 bpm. Polar H7 results suggest that device related bias is possible but in the reverse direction as artefact related bias.

Using an Electromyography Method While Measuring Oxygen Uptake to Appreciate Physical Exercise Intensity in Adolescent Cyclists: An Analytical Study.

Background and Objectives: During physical exercise, the electrical signal of the muscle fibers decreases due to repeated muscle contractions held at different intensities. The measured signal is strongly related to the motor unit activation rate, which is dependent on the chemical mediators and the available energy. By reducing the energy availability, adenosine triphosphate (ATP) production will decrease and therefore the muscle fibers activation rate will be negatively affected. Such aspects become important when taking into account that the training intensity for many young athletes is rather controlled by using the heart rate values. Yet, on many occasions, we have seen differences and lack of relationship between the muscle activation rate, the heart rate values and the lactate accumulation. Materials and Methods: We conducted a prospective analytical study conducted during a 4-month period, on a sample of 30 participants. All study participants underwent an incremental exercise bike test to measure maximum aerobic capacity as well as the muscle activation rate in the vastus lateralis by using an electromyography method (EMG). Results: With age, the EMG signal dropped, as did the electromyography fatigue threshold (EMGFT) point, as seen through p = 0.0057, r = -0.49, CI95% = -0.73 to -0.16, and electromyography maximum reached point (EMGMRP) (p = 0.0001, r = -0.64, CI95% = -0.82 to -0.36), whereas power output increased (p = 0.0186, r = 0.427). The higher the power output, the lower the signal seen by measuring active tissue EMGFT (p = 0.0324, r = -0.39) and EMGMRP (p = 0.0272, r = -0.40). Yet, with changes in median power output, the power developed in aerobic (p = 0.0087, r = 0.47), mixed (p = 0.0288, r = 0.39), anaerobic (p = 0.0052, r = 0.49) and anaerobic power (p = 0.004, r = 0.50) exercise zones increased. Conclusions: There has been reported a relationship between aerobic/anaerobic ventilatory thresholds (VT1 and VT2) and EMGFT, EMGMRP, respectively. Each change in oxygen uptake increased the power output in EMGFT and EMGMRP, improving performances and therefore overlapping with both ventilatory thresholds.

Plasma free metanephrine and normethanephrine levels correlated to plasma catecholamine after acute running in amateur runner.

BACKGROUND: Catecholamine is a typical index of exercise intensity, but it is difficult to detect. Plasma metanephrine (MN) and normethanephrine (NMN) levels are more stable than those of catecholamines. This study aimed to investigate plasma MN and NMN levels during acute exercise running in amateur runners. METHODS: Samples were collected from eight healthy male participants. They were either sedentary or running at low or high intensity for 30 min. Blood samples were collected under these conditions. Measurements taken included plasma adrenaline, noradrenaline, MN, and NMN. RESULTS: Plasma adrenaline levels increased after high-intensity exercise compared with sedentary subjects. Plasma noradrenaline, MN, and NMN levels increased after both low- and high-intensity exercise compared with sedentary subjects. In addition, these levels were also significantly higher at high intensity than at low intensity. Plasma adrenaline and noradrenaline levels were positively correlated with plasma free MN and NMN levels after acute running, respectively. CONCLUSION: This study revealed that plasma MN and NMN levels transiently increased depending on exercise intensity in amateur runners. In addition, plasma NMN levels are better markers than plasma MN levels because of their stronger correlation with plasma catecholamine levels.

[Discussion on the application of ventilatory threshold in classification of physical workload in plateau].

Objective: To explore the application of the first ventilatory threshold (VT1) and the second ventilatory threshold (VT2) in the classification of physical workload for plateau workers, to provide reference for formulating the classification in plateau. Methods: In August 2018, 88 male workers from substations at different altitudes (500 m, 2000 m, 3000 m and 4000 m) of a company were selected as study subjects by cluster sampling. They were divided into plain group and plateau groups.The intensities of workload were simulated by power bicycle, and physiologic parameters, including VO(2), heart rate (HR) and energy metabolic rate per body surface area (E/BSA) , were recorded in test system when reaching VT1, VT2 and peak oxygen uptake (VO(2)Peak) . The ratios of VT1, VT2 and VO(2)Peak to the quiet and work potential at different altitudes were compared. Results: In a quiet state, compared with the plain group, the HR and E/BSA of the workers in the 2000 m and 3000 m groups increased, and the differences were statistically significant (P<0.05) . At VT2, compared with the plain group, the HR of the workers in the 4000 m group decreased, the difference was statistically significant (P<0.05) . VO(2) and E/BSA of workers in each plateau group were lower than those in the plain group at VO(2)Peak, and the differences were statistically significant (P<0.05) . At VT2 and VO(2)Peak, the ratios of VO(2), HR, and E/BSA relative to the quiet state of the workers in each plateau group were lower than those of the plain group, and the differences were statistically significant (P<0.05) . In the quiet state and VT1, compared with the plain group, the remaining percentages of VO(2) and E/BSA of workers in each plateau group decreased, and the differences were statistically significant (P<0.05) . Taking VT1, VT2 and VO(2)Peak as cut-off points and VO(2), HR and E/BSA as indicators, the physical workload in plateau could be divided into four levels, namely medium, heavy, extremely heavy and extreme physical workload. Conclusion: It is practicable to use ventilatory threshold to classification of physical workload. VT1 and VT2 can be applied to the classification in plateau to supplement and optimize current national standard of physical workload.

Exercise intensity prescription in cancer survivors: ventilatory and lactate thresholds are useful submaximal alternatives to VO2peak.

PURPOSE: Most studies with cancer survivors use percentages of peak oxygen uptake (VO2peak) for intensity prescription. Lactate or ventilatory thresholds might be useful submaximal alternatives, but this has never been investigated. Therefore, we aimed at comparing three training sessions prescribed using %VO2peak (reference), lactate thresholds, and ventilatory thresholds in terms of meeting the vigorous-intensity zone, physiological, and psychological responses. METHODS: Twenty breast (58 ± 10 years) and 20 prostate cancer survivors (68 ± 6 years), 3.6 ± 2.4 months after primary therapy, completed a maximal cardiopulmonary exercise test and three vigorous training sessions in randomized order: 38 min of cycling at 70% VO2peak (M-VO2peak), 97% of individual anaerobic lactate threshold (M-IAT), and 67% between ventilatory thresholds 1 and 2 (M-VT). Heart rate (HR), blood lactate concentration (bLa), perceived exertion, and enjoyment were assessed. RESULTS: Cancer survivors exercised at 75 ± 23, 85 ± 18, and 79 ± 19 W during M-VO2peak, M-IAT, and M-VT (p > .05). Sessions could not be completed in 3, 8, and 6 cases. Session completers showed HR of 82 ± 7, 83 ± 9, and 84 ± 8 %HRpeak and bLa of 3.7 ± 1.9, 3.9 ± 0.9, and 3.9 ± 1.5 mmol·l-1, which was not different between sessions (p > .05). However, variance in bLa was lower in M-IAT compared to M-VO2peak (p = .001) and to M-VT (p = .022). CONCLUSION: All intensity prescription methods on average met the targeted intensity zone. Metabolic response was most homogeneous when using lactate thresholds. IMPLICATIONS FOR CANCER SURVIVORS: Submaximal thresholds are at least as useful as VO2peak for intensity prescription in cancer survivors. Overall, slightly lower percentages should be chosen to improve durability of the training sessions.