Incremental Treadmill Exercise Research Articles

Validation Of A Wrist-mounted Heart Rate Monitor During Maximal Graded Exercise Testing

The electrocardiogram (ECG) serves as the gold standard of heart rate (HR) monitoring but is rarely used outside of a clinical environment. Newly developed wearable technology is more usable outside of a clinical setting, but has not been validated against this gold standard. PURPOSE: The purpose of this study is to determine the validity of a wrist-mounted photoplethysmography (PPM) device used for measuring HR during incremental treadmill exercise using ECG as the criterion HR measurement. METHODS: Twenty-two subjects (13 men, 9 women; 35.8 ± 6.3 yr, 14.6 ± 7.5 % body fat, VO2max: 55.5 ± 0.49 ml·kg-1·min-1) performed a Bruce treadmill protocol graded exercise test. HR was recorded at rest and at the end of each minute with the Mio Alpha PPM device and ECG simultaneously. HR was compared between methods across the entire testing session (rest and exercise values) and separately for each exercise test stage using paired-samples t-tests and the Bonferroni correction. Validity coefficients were determined using the Pearson correlation. RESULTS: HR across the entire intensity range (rest to maximal exercise) exhibited a significant correlation between methods (r = 0.97, p < 0.001) and was similar between ECG and Mio after the Bonferroni correction was applied, requiring p < 0.008 (overall mean HR: ECG = 124 ± 39 b·min-1, Mio = 123 ± 37 b·min-1, t359 = -2.504, p = 0.013). Significant correlations were observed at rest and each exercise test stage, with r values ranging from 0.67 to 0.96 (all p < 0.001). HR was similar between methods at rest and each exercise test stage except for stage 4 (ECG = 168 ± 13 b·min-1, Mio = 164 ± 14 b·min-1, p = 0.004). CONCLUSIONS: Correlational analyses indicated a strong agreement between HR methods overall, as well as individually at rest and during each exercise test stage. However, mean comparisons observed a significant difference between methods at stage 4 and mean differences between methods became larger as intensity increased. From a practical standpoint, the mean difference between methods did not exceed 3 b·min-1 except for stage 5. Therefore, a PPM device seems valid for HR monitoring during low-to-moderate-intensity but not high-intensity treadmill exercise.

Hit Effects On Substrates Oxidation Rates Of Women In Different Phases Of Monthly Ovarian Cycle

The metabolic inflexibility (limitation to respond or adapt to conditional changes in metabolic demand due to dietary patterns, energy availability, or circulating energy substrates) may be associated with variations in estrogen concentrations observed during the monthly ovarian cycle, whereas that apparently healthy women of childbearing age exhibit variation in substrates oxidation rates that may lead to overweight, type II diabetes and other associated conditions. PURPOSE: The aims of this study were to verify and compare the influence of eight treadmill high-intensity interval training (HIT) sessions on carbohydrate and lipid oxidation rates (CHOox and LIPox, respectively) and intensities of ventilatory anaerobic thresholds (VATs) of women in different phases of monthly ovarian cycle. METHODS: Eleven irregularly active women performed incremental treadmill exercise testing followed by submaximal work-rate running for 45min to determine VATs, VO2peak, peak velocity (Vpeak), and substrate oxidation rates, before and after training period, in different phases of their monthly ovarian cycle (“Follicular” phase group, FPG, n=6; “Luteal” phase group, LPG, n=5). The training period consisted of eight HIT sessions, composed each one of eight sets of 60s running at 100%Vpeak interspersed by 75s recovery, every 48h. RESULTS: Our results showed no significant differences in VATs intensities between groups. The comparison between groups showed significant differences in relative energy derived from CHOox pre-post training of the -61.4% and -59.3% respectively, and LIPox pre-post training of the 27.5% and 34.4% respectively. The relative energy derived from CHOox after the training period were 18.9% and 25.5% higher to FPG and LPG, respectively; consequently, the relative energy derived from LIPox after the training period were 8,45% and 3.46% lower to FPG and LPG, respectively. Over the training period, Vpeak was ~13.5 km/h, which produced the relative intensities of ~89%VO2peak e ~93%HRpeak for both groups. CONCLUSION: The monthly ovarian cycle phases promote significant changes on substrates oxidation rates leading to decrease of CHOox. High intensity interval training can minimize the differences observed and constitute an alternative intervention.

High-intensity training in normobaric hypoxia enhances exercise performance and aerobic capacity in Thoroughbred horses: A randomized crossover study.

We examined the effects of high‐intensity training in normobaric hypoxia on aerobic capacity and exercise performance in horses and the individual response to normoxic and hypoxic training. Eight untrained horses were studied in a randomized, crossover design after training in hypoxia (HYP; 15.0% inspired O2) or normoxia (NOR; 20.9% inspired O2) 3 days/week for 4 weeks separated by a 4‐month washout period. Before and after each training period, incremental treadmill exercise tests were performed in normoxia. Each training session consisted of 1 min cantering at 7 m/s and 2 min galloping at the speed determined to elicit maximal oxygen consumption ( V˙O2max) in normoxia. Hypoxia increased significantly more than NOR in run time to exhaustion (HYP, +28.4%; NOR, +10.4%, p = .001), V˙O2max (HYP, +12.1%; NOR, +2.6%, p = .042), cardiac output ( Q˙; HYP, +11.3%; NOR, −1.7%, p = .019), and stroke volume (SV) at exhaustion (HYP, +5.4%; NOR, −5.5%, p = .035) after training. No significant correlations were observed between NOR and HYP for individual changes after training in run time (p = .21), V˙O2max (p = .99), Q˙ (p = .19), and SV (p = .46) at exhaustion. Arterial O2 saturation during exercise in HYP was positively correlated with the changes in run time (r = .85, p = .0073), Q˙ (r = .72, p = .043) and SV (r = .77, p = .026) of HYP after training, whereas there were no correlations between these parameters in NOR. These results suggest that high‐intensity training in normobaric hypoxia improved exercise performance and aerobic capacity of horses to a greater extent than the same training protocol in normoxia, and the severity of hypoxemia during hypoxic exercise might be too stressful for poor responders to hypoxic training.

Higher Maximal Cardiorespiratory Fitness is Associated with Lower Cerebrovascular Stiffness in Healthy Mid‐Life and Older Adults

BackgroundAge‐related impairments in cerebrovascular function likely contribute to cognitive decline with aging. In particular, cerebral artery stiffening with aging leads to transmission of damaging, pulsatile blood flow to the microcirculation, causing suboptimal tissue perfusion and cerebrovascular dysfunction. Conversely, physically active older adults with higher cardiorespiratory fitness (CRF) often have greater cerebrovascular function, as evidenced by greater cerebrovascular reactivity, than sedentary peers. This suggests that either regular physical activity, higher CRF, or both has beneficial effects on the cerebrovasculature and may contribute to preserved cognitive function with aging. However, little is known about the relations between physical activity, as assessed by leisure time physical activity (LTPA), or CRF and cerebrovascular stiffness.PurposeTo determine if cerebrovascular stiffness is related to LTPA, CRF or both among healthy mid‐life and older adults, and if individuals with higher levels of LTPA and/or CRF have greater cerebrovascular stiffness reactivity in response to a vasodilatory stimulus and/or better cognitive function.MethodsCerebrovascular stiffness (pulsatility index, PI), LTPA, CRF and cognitive function were assessed in 27 mid‐life/older adults (12F/15M; 67±1 years) free from chronic diseases and dementia. Middle cerebral artery velocity (MCAv) was measured with a 2‐MHz Doppler probe during 5 minutes of normocapnia and hypercapnia (breathing 5% CO2). PI was defined as (MCAvsystolic‐MCAvdiastolic)/MCAvmean measured over the final 60 seconds of each phase. LTPA was calculated using the Modifiable Activity Questionnaire. CRF was determined by assessing maximal oxygen consumption (VO2max) during incremental treadmill exercise to exhaustion. The cognitive domains of executive function, processing speed, working memory, and language were assessed with the NIH Toolbox Cognition Domain and composite scores for fluid, crystallized, and total cognition were calculated.ResultsPI was inversely related to CRF under both normocapnic (r=0.41, p=0.04) and hypercapnic (r=0.46, p=0.02) conditions, indicating lower cerebrovascular stiffness in those with greater CRF. However, there was no relation between LTPA and PI under normocapnic (r=0.04, p=0.86) or hypercapnic (r=0.12, p=0.55) conditions. There were no relations between the change in PI from normocapnia (baseline) to hypercapnia and CRF (r=0.06, p=0.23) or LTPA (r=0.041, p=0.84). Finally, there were no relations between any measures of cognitive function and PI under either normocapnic or hypercapnic conditions (all p&gt;0.05).ConclusionsThese preliminary results suggest cerebrovascular stiffness is inversely related to CRF, but unrelated to LTPA, among healthy mid‐life/older adults. However, the change in cerebrovascular stiffness in response to a vasodilatory stimulus was not related to CRF, suggesting that absolute cerebrovascular stiffness may be more strongly associated with CRF than functional reactivity. Cognitive performance was not related to CRF or LTPA, likely because subjects were healthy and without cognitive impairments.Support or Funding InformationAHA 18POST33990034

Effects of Oral Branched-Chain Amino Acids (BCAAs) Intake on Muscular and Central Fatigue During an Incremental Exercise.

The aim of this study was to investigate the effects of oral branched-chain amino acids (BCAAs) intake on muscular (creatine kinase and myoglobin) and central (serotonin) fatigue during an incremental exercise protocol and to determine the time to exhaustion. Sixteen male long-distance runners (25.7 ± 2.0 yrs) performed two trials, 14 days apart. Using a double-blind, placebo-controlled, randomised crossover design, participants ingested either 20 g of BCAAs (BCAA trial) or a placebo 1 hour prior to performing an incremental exercise session on a treadmill. The starting speed was 8 km/h and this was increased by 1 km/h every 5 minutes until volitional exhaustion. Blood analysis indicated that plasma levels of serotonin were lower in the BCAA trial (259.3 ± 13.5 ng/ml) than the placebo trial (289.1 ± 14.5 ng/ml) (p < 0.05). There was a similar pattern of results for free fatty acid (p < 0.05). The creatine kinase level was higher in the BCAA trial (346.1 ± 33.7 U/L) than the placebo trial (307.3 ± 30.2 U/L). No significant difference between trials was observed regarding the level of myoglobin (p = 0.139). Time to exhaustion was longer in the BCAA trial (50.4 ± 2.3 min) than the placebo trial (46.6 ± 3.2 min). In conclusion, oral intake of 20 g of BCAAs 1 hour prior to an incremental treadmill exercise session increased time to exhaustion, probably due to the reduction in serotonin concentration. As myoglobin levels were within the normal range in both trials, we conclude that the participants did not reach muscular fatigue.

Nrf2 Activation Enhances Muscular MCT1 Expression and Hypoxic Exercise Capacity.

Skeletal muscle is the major producing and metabolizing site of lactic acid. A family of monocarboxylate transporter (MCT) proteins, especially MCT1 and MCT4, are involved in the lactate-pyruvate exchange and metabolism. Nuclear factor erythroid 2-related factor 2 (Nrf2) is a pivotal coordinator of antioxidant response and energy metabolism, and has been reported to associate with the physiological functions of the skeletal muscle. In this study, C57BL/6 J mice were administrated with an Nrf2 activator, sulforaphane (SFN) before taking incremental treadmill exercise to exhaustion under hypoxia; then the effects of SFN on exercise endurance and molecular/biochemical makers of the skeletal muscle were evaluated. The results indicated that SFN pretreatment enhanced the exercise endurance under hypoxia. SFN not only increased the expressions of antioxidant genes and activity of antioxidant enzymes, but also significantly increased the mRNA and protein levels of MCT1 and CD147, but not MCT4. Moreover, the expressions of LDH-B and LDH activity of converting lactate into pyruvate, as well as citrate synthase activity were significantly higher, whereas the LDH activity of converting pyruvate into lactate and blood lactate level were remarkably lower in the SFN-exercise mice than those of the phosphate-buffered saline-exercise group. Furthermore, Atf3Δzip2 (the alternatively spliced isoform of activating transcription factor-3) mRNA was increased by the exercise and further potentiated by SFN. These results show, for the first time, that SFN increases MCT1 expression in the skeletal muscle under acute hypoxic exercise and suggest that Nrf2 activation is a promising strategy to enhance exercise performance under hypoxia.

Change in Lactate, Ammonia, and Hypoxanthine Concentrations in a 1-Year Training Cycle in Highly Trained Athletes: Applying Biomarkers as Tools to Assess Training Status.

Włodarczyk, M, Kusy, K, Słomińska, E, Krasiński, Z, and Zieliński, J. Change in lactate, ammonia, and hypoxanthine concentrations in a 1-year training cycle in highly trained athletes: applying biomarkers as tools to assess training status. J Strength Cond Res 34(2): 355-364, 2020-The aim was to determine changes in biomarker (LA, NH3, purine metabolites) blood concentration during graded exercise and recovery throughout an annual training cycle in highly trained athletes of different training profiles. The study included 12 sprinters (SP, 21-30 years), 11 triathletes (TR, 20-31 years), 12 futsal players (FU, 19-31 years), and 13 amateur runners (AM, 20-33 years). Purine metabolite (hypoxanthine, xanthine, uric acid), ammonia (NH3), and lactate (LA) concentrations were determined at rest, during an incremental treadmill exercise test (every 3 minutes), and during recovery (5, 10, 15, 20, and 30 minutes postexercise) in 4 phases of an annual training cycle. Purine metabolite concentration was determined from plasma, whereas LA and NH3 from whole blood. For LA during exercise and recovery, certain significant differences between training phases within groups were observed for FU, TR, and SP but not for AM. For NH3, the greatest differences between examination points were observed for SP and TR near maximal exercise and in the first few stages of recovery. For hypoxanthine (Hx), the largest amount of differences between examination points was observed for FU, TR, and FU throughout the entire exercise spectrum. Biomarker concentration dynamics change during an incremental exercise test and postexercise in an annual training cycle. Biomarker responses differ depending on training type and magnitude of training loads used in various phases of an annual training cycle. When assessing training status using an incremental exercise test throughout an annual training cycle, NH3 and Hx concentration changes are more sensitive compared with LA.

Hypoxia preconditioning promotes endurance exercise capacity of mice by activating skeletal muscle Nrf2

Elite endurance athletes are used to train under hypoxic/high-altitude conditions, which can elicit certain stress responses in skeletal muscle and helps to improve their physical performance. Nuclear factor erythroid 2-related factor 2 (Nrf2) regulates cellular redox homeostasis and metabolism in skeletal muscle, playing important roles in adaptation to various stresses. In this study, Nrf2 knockout (KO) and wild-type (WT) mice were preconditioned to 48 h of hypoxia exposure (11.2% oxygen), and the effects of hypoxia preconditioning (HP) on exercise capacity and exercise-induced changes of antioxidant status, energetic metabolism, and mitochondrial adaptation in skeletal muscle were evaluated. Nrf2 knockout (KO) and wild-type (WT) mice were exposed to normoxia or hypoxia for 48 h before taking incremental treadmill exercise to exhaustion under hypoxia. The skeletal muscles were collected immediately after the incremental treadmill exercise to evaluate the impacts of HP and Nrf2 on the exercise-induced changes. The results indicate the absence of Nrf2 did not affect exercise capacity, although the mRNA expression of certain muscular genes involved in antioxidant, glycogen and fatty acid catabolism was decreased in Nrf2 KO mice. However, 48-h HP enhanced exercise capacity in WT mice but not in Nrf2 KO mice, and the exercise capacity of WT mice was significantly higher than that of Nrf2 KO mice. These findings suggest HP promotes exercise capacity of mice with the participation of the Nrf2 signal in skeletal muscle.NEW & NOTEWORTHY Hypoxia preconditioning (HP) activated the nuclear factor erythroid 2-related factor 2 (Nrf2) signal, which was involved in HP-elicited adaptation responses to hypoxia, oxidative, and metabolic stresses in skeletal muscle. On the other hand, Nrf2 deficiency abolished the enhanced exercise capacity after the 48-h HP. Our results indicate that Nrf2 plays an essential role in the exercise capacity-enhancing effect of HP, possibly by modulating muscular antioxidative responses, the mRNA expression of muscular genes involved in glycogen and fatty acid metabolism, as well as mitochondrial biogenesis, and through the cross talk with AMPK and hypoxia-inducible factor-1α signaling.

Reliability of NIRS portable device for measuring intercostal muscles oxygenation during exercise

ABSTRACTThis study assessed the intra-individual reliability of oxygen saturation in intercostal muscles (SmO2-m.intercostales) during an incremental maximal treadmill exercise by using portable NIRS devices in a test-retest study. Fifteen marathon runners (age, 24.9 ± 2.0 years; body mass index, 21.6 ± 2.3 kg·m−2; V̇O2-peak, 63.7 ± 5.9 mL·kg−1·min−1) were tested on two separate days, with a 7-day interval between the two measurements. Oxygen consumption (V̇O2) was assessed using the breath-by-breath method during the V̇O2-test, while SmO2 was determined using a portable commercial device, based in the near-infrared spectroscopy (NIRS) principle. The minute ventilation (VE), respiratory rate (RR), and tidal volume (Vt) were also monitored during the cardiopulmonary exercise test. For the SmO2-m.intercostales, the intraclass correlation coefficient (ICC) at rest, first (VT1) and second ventilatory (VT2) thresholds, and maximal stages were 0.90, 0.84, 0.92, and 0.93, respectively; the confidence intervals ranged from −10.8% – +9.5% to −15.3% – +12.5%. The reliability was good at low intensity (rest and VT1) and excellent at high intensity (VT2 and max). The Spearman correlation test revealed (p ≤ 0.001) an inverse association of SmO2-m.intercostales with V̇O2 (ρ = −0.64), VE (ρ = −0.73), RR (ρ = −0.70), and Vt (ρ = −0.63). The relationship with the ventilatory variables showed that increased breathing effort during exercise could be registered adequately using a NIRS portable device.

The effect of general duty police ensemble on graded exercise and simulated work performance.

This 2-part study examined the impact of general duty police ensemble on selected cardiopulmonary responses during incremental treadmill exercise and on simulated work performance in 25 healthy young male and female participants. Part I comprised randomly ordered treadmill tests in 2 experimental conditions: physical training (PT; undergarments, shorts, t-shirt, and running shoes) and police duty ensemble (PDE; undergarments, body armour, patrol uniform, boots, duty belt with required equipment, radio, and weapons). The PDE added 10.3 kg (SD 0.4) or 14% (SD 2) body mass. Participants walked at 5.6 km·h-1, starting at 0% grade with 2% increases in grade every 2 min. The 4% stage was 6 min in duration to achieve physiological steady state. Subsequently, the 2-min increments continued to exhaustion. Part II evaluated performance time on a recognized job-related work simulation circuit, in 3 experimental conditions: (i) PT, (ii) weighted belt (WB; PT plus a 7.5 kg weighted belt), and (iii) PDE. In Part I, physiological responses (e.g., oxygen uptake, ventilation, heart rate) were elevated (p < 0.05) with PDE during submaximal exercise but peak values were unchanged. Test duration and peak power output were significantly reduced with PDE. In Part II, circuit completion time was increased in PDE but not WB when compared with PT (p < 0.05). Heart rate and perceived exertion were similar in all conditions and perceived dyspnea was higher in PDE. Novelty Police duty ensemble negatively affected exercise performance more than would be expected due to load mass alone. Specificity must be considered when simulating occupational load carriage.

The Inorganic NItrate For eXercise In Heart Failure (INIX-HF) Trial: Rationale, Design, And Preliminary Data

Peak oxygen uptake (VO2peak) and muscle contractile function are both impaired in patients with heart failure with reduced ejection fraction (HFrEF), with these deficits significantly contributing to the diminished quality of life and possibly even early mortality of such individuals. In previous pilot studies, however, we have reported that these deleterious changes can be ameliorated by acute ingestion of nitrate (NO3-), which in vivo can be converted to nitric oxide (NO) via the enterosalivary NO3- → nitrite (NO2-) → NO pathway. PURPOSE Based on these studies, the INIX-HF trial is a proposed multi-center (i.e., 8 site), randomized control trial of the effects of acute (i.e., single dose) and chronic (i.e., 2 wk) dietary NO3- supplementation (in the form of KNO3) on VO2peak and muscle contractility in patients with HFrEF. We are presently performing the work that is necessary and sufficient to set up this trial, including determining the optimal dose of KNO3 to utilize. METHODS Using a double-blind, crossover design, six patients with HFrEF (5 men, 1 woman; age = 49±4 y; EF = 32±3%) were studied 2-3 h after acute ingestion of either 10 or 20 mmol KNO3. On each occasion, VO2peak was measured during an incremental treadmill exercise test (modified Naughton protocol) and muscle function was determined using isokinetic dynamometry. RESULTS The increase in plasma NO3- was greater following ingestion of 20 vs. 10 mmol KNO3 (Δ = 430±51 vs. 218±19 μmol/L; P=0.002). However, plasma NO2- increased to a similar degree in both trials (Δ = 0.219±0.078 vs. 0.169±0.044 μmol/L; P=0.67). Presumably as a result, VO2peak did not differ between treatments (i.e., 18.0±1.5 vs. 17.7±1.3 mL.min-1.kg-1; P=0.74). There was also no difference in maximal knee extensor power (4.52±0.56 vs. 4.25±0.59 W/kg; P=0.69) across trials. 27% of subjects experienced moderate-to-severe nausea and/or vomited after ingesting the higher dose KNO3, vs. only 9% after the lower dose. CONCLUSION There was no difference in the efficacy of 10 vs. 20 mmol KNO3 in influencing VO2peak or muscle power in patients with HFrEF. The higher dose, however, was associated with a greater frequency of gastrointestinal distress. Based on these preliminary data, it appears that 10 mmol KNO3 is the preferred dose for a larger, multicenter trial. Supported by award R34HL138253 from the NHLBI

Six Hit Treadmill Training Sessions Improves Lipid Oxidation and Ventilatory Thresholds Intensities

The high-intensity interval training (HIT) has been used as alternative to cardiorespiratory training performed continuously with submaximal intensity and prolong time. PURPOSE: The aims of this study were to propose a treadmill HIT protocol and verify the influence of six HIT sessions on intensities of ventilatory anaerobic thresholds (VATs) and substrate oxidation rates during submaximal continuous exercise (SCE). METHODS: Fifteen irregularly active men performed incremental treadmill exercise testing followed by submaximal work-rate running for 45min to determine VATs, VO2peak, peak velocity (Vpeak), and substrate oxidation rates, before and after training period. The training period consisted of six HIT sessions, composed each one of eight sets of 60s running at 100%Vpeak interspersed by 75s recovery, every 48h. RESULTS: Our results showed increases in VATs intensities of 4.4% for VAT1 and 8.8% for VAT2, reduction of 12.8% for carbohydrate oxidation (CHOox) and increase of 23.7% for lipid oxidation (LIPox); as a result, the relative energy derived from LIPox was 20.3% higher after the training period. Vpeak was ~15 km/h, which produces the relative intensities of ~84%VO2peak e ~91%FCpeak during the training period. CONCLUSION: The proposed protocol promoted similar adaptations and intensities which were described by the literature; but unlike others, it can be applied in irregularly active individuals.

Changes in Blood Concentration of Adenosine Triphosphate Metabolism Biomarkers During Incremental Exercise in Highly Trained Athletes of Different Sport Specializations.

Włodarczyk, M, Kusy, K, Słomińska, E, Krasiński, Z, and Zieliński, J. Changes in blood concentration of adenosine triphosphate metabolism biomarkers during incremental exercise in highly trained athletes of different sport specializations. J Strength Cond Res 33(5): 1192-1200, 2019-We hypothesized that (a) high-level specialized sport training causes different adaptations that induce specific biomarker release dynamics during exercise and recovery and (b) skeletal muscle mass affects biomarker release. Eleven sprinters (21-30 years), 16 endurance runners (18-31 years), 12 futsal players (18-29 years), and 12 amateur runners as controls (22-33 years) were examined. Hypoxanthine (Hx), xanthine (X), uric acid (UA), ammonia (NH3), and lactate (LA) concentrations were determined at rest, during an incremental treadmill exercise test (every 3 minutes), and during recovery (5, 10, 15, 20, and 30 minutes after exercise). Hx, X, and UA concentration was determined from plasma, while LA and NH3 from whole blood, and muscle mass was assessed using dual X-ray absorptiometry method. At rest, during incremental exercise, and up to 30 minutes into the postexercise recovery period, sprinters had lowest Hx, X, and UA concentrations, and endurance athletes had lowest NH3 concentrations. For LA during exercise, the lowest concentrations were noted in endurance athletes, except when reaching maximum intensity, where the differences between groups were not significant. There were no significant correlations observed between skeletal muscle mass and biomarker concentration at maximal intensity and recovery in any group. In conclusion, the magnitude of exercise-induced biomarker concentration is only related to training adaptations through specific training profile but not to muscle mass. In addition, the results suggest that combined measuring of LA, NH3, and Hx concentration in blood is useful in indirectly reflecting key changes in exercise- and training-induced energy status. Further research should focus on studying how specific training sessions affect individual biomarker response in highly trained athletes.

Effects of Inspiratory Muscle Strength Training on Cardiorespiratory Fitness in Middle‐Aged to Older Adults

BackgroundCardiorespiratory fitness declines with aging and is a strong independent risk factor for future morbidity and mortality. Conventional aerobic exercise improves cardiorespiratory fitness in middle‐aged and older (MA/O) adults, but is associated with relatively low adherence, due, in part, to significant time requirements (150 min/week). High‐resistance, short‐duration inspiratory muscle strength training (IMST) requires only 30 min/week and is associated with excellent adherence, but effects on cardiorespiratory fitness are unknown. We assessed whether high‐resistance, short‐duration IMST improves cardiorespiratory fitness assessed under maximal exercise (VO2max, exercise tolerance) and standardized submaximal exercise conditions.MethodsHealthy, recreationally active MA/O adults (50–79 years) were recruited. Subjects were randomly assigned to perform 6‐weeks of IMST (30 breaths/day; 6 days/week; 75% maximum inspiratory pressure [PIMAX]) (n=7 age: 68 ± 2 years) or sham (15% PIMAX) training (n=7; age: 67 ± 3 years) in a randomized, double‐blind, placebo‐controlled study. Oxygen uptake (VO2) and other responses were measured throughout incremental treadmill exercise to exhaustion using a modified Balke Protocol pre‐ and post‐intervention.ResultsAdherence, defined as percentage of prescribed training sessions completed, was high in both the IMST (100%) and sham (98%) groups. PIMAX increased in the IMST group (pre: 57 ± 5, post: 70 ± 4 mmHg; p=0.048) but not sham group (pre: 54 ± 2, post: 60 ± 1 mmHg; p=0.5). VO2max did not change with training in either group (p&gt;0.05), but exercise time to exhaustion increased by 15% in the IMST group (pre: 629 ± 64, post: 726 ± 50 seconds; p=0.009) and decreased in the sham group (pre: 583 ± 74, post: 500 ± 77 seconds; p=0.02). At maximal exercise, most markers of voluntary effort (minute ventilation, VE, heart rate, HR, and rating of perceived exertion, RPE) were unchanged pre vs. post training in both groups (all p&gt;0.05), but peak respiratory exchange ratio, a measure of hyperventilation, was higher in the IMST group after training (pre: 1.08 ± 0.03, post: 1.14 ± 0.03; p=0.05; sham group: pre: 1.06 ± 0.02, post: 1.05 ± 0.04; p=0.96). At a fixed submaximal workload (~80% of initial VO2max), VO2 (pre: 23.3 ± 1.8, post: 21.3 ± 1.5 ml/kg/min; p=0.01) and HR (pre: 131 ± 7, post: 127 ± 7; p=0.07) were lower after vs. before IMST, but unchanged with sham training. VE and RPE during submaximal exercise were unchanged with training in both groups (all p&gt;0.05).ConclusionHigh‐resistance short‐duration IMST increases exercise time to exhaustion (exercise tolerance), improves submaximal exercise economy, and lowers HR during submaximal exercise in healthy, recreationally active, MA/O adults. Thus, high resistance, short‐duration IMST improves exercise performance in healthy MA/O adults, and may hold even greater promise for older adults with functional limitations and/or chronic disease.Support or Funding InformationAHA 18POST33990034, T32 DK007135, UL1 TR002535This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Lactate and glucose thresholds and heart rate deflection points for Beagles during intense exercise.

OBJECTIVE To determine whether the lactate threshold of dogs could be determined by a visual method and to assess the extent of agreement and bias among treadmill velocities for the lactate threshold as determined by visual (LTv) and polynomial (LTp) methods, glucose threshold as determined by visual (GTv) and polynomial (GTp) methods, and heart rate deflection point (HRdp) as a method for estimating the aerobic capacity of dogs. ANIMALS 18 healthy adult Beagles. PROCEDURES Each dog underwent a standardized incremental treadmill exercise test once. The test ended when the dog began to show signs of fatigue. Plasma lactate and glucose concentrations and heart rate (HR) were plotted against exercise intensity (treadmill velocity) for the duration of the test, and the LTv, GTv, and HRdp were determined visually. The LTp and GTp were determined by means of a second-order polynomial function. One-way ANOVA, Pearson correlation, Bland-Altman analyses, and ordinary least products regression were used to assess the extent of agreement and bias among the various threshold velocities. RESULTS Mean velocity did not differ significantly among the thresholds evaluated. There was a strong positive correlation between the LTv velocity and the velocity for GTv (r = 0.91), LTp (r = 0.96), GTp (r = 0.94), and HRdp (r = 0.95). CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that LTv could be determined for dogs undergoing intense exercise on a treadmill, and the treadmill velocity corresponding to the LTv was associated with the velocity for the other hallmarks of endurance. Thus, that method may be useful for prescription and evaluation of conditioning programs for dogs.

Alteration of Metabosensitive Afferent Response With Aging: Exercised versus Non-exercised Rats

This study was designed to evaluate the effect of aging on the activity of metabosensitive afferent fibers (thin muscle afferents from group III and IV) and to determine if physical activity performed at old age may influence the afferent discharge. Afferents from tibialis anterior and soleus muscles were recorded on non-exercised rats aged of 3, 6, 12, and 20 months and on animals aged of 12 and 20 months performing a daily incremental treadmill exercise protocol during the last 8 weeks preceding the recordings. Metabosensitive afferent fibers were activated with potassium chloride (KCl) and lactic acid (LA) injections into the blood stream or by muscle electrically-induced fatigue (EIF). Results indicated that aging is associated to a decrease in the magnitude of the responses to chemical injections and EIF. Unfortunately, physical activity did not allow restoring the metabosensitive afferents responses. These results indicate an alteration of the thin afferent fibers with aging and should be taken into account regarding the management of muscle fatigue and potential alterations of exercise pressor reflex (EPR) occurring with aging.

Increased prevalence of expiratory flow limitation during exercise in children with bronchopulmonary dysplasia.

Evidence regarding the prevalence of expiratory flow limitation (EFL) during exercise and the ventilatory response to exercise in children born preterm is limited. This study aimed to determine the prevalence of EFL as well as contributing factors to EFL and the ventilatory response to exercise in preterm children with and without bronchopulmonary dysplasia (BPD).Preterm children (≤32 weeks gestational age) aged 9–12 years with (n=64) and without (n=42) BPD and term controls (n=43), performed an incremental treadmill exercise test with exercise tidal flow–volume loops.More preterm children with BPD (53%) had EFL compared with preterm children without BPD (26%) or term controls (28%) (p<0.05). The presence of EFL was independently associated with decreased forced expiratory volume in 1 s/forced vital capacity z-score and lower gestational age (p<0.05). There was no difference in peak oxygen uptake between preterm children with BPD and term controls (48.0 versus 48.4 mL·kg−1·min−1; p=0.063); however, children with BPD had a lower tidal volume at peak exercise (mean difference −27 mL·kg−1, 95% CI −49– −5; p<0.05). Children born preterm without BPD had ventilatory responses to exercise similar to term controls.Expiratory flow limitation is more prevalent in children born preterm with BPD and is associated with airway obstruction and a lower gestational age.

The effects of recovery duration on physiological and perceptual responses of trained runners during four self-paced HIIT sessions

ObjectivesThis study aimed to examine the effects of different recovery durations on self-selected running velocities, physiological responses, and ratings of perceived exertion (RPE) in a commonly used high intensity interval training (HIIT) protocol. Design & methodsTwelve trained runners performed an incremental treadmill exercise test to determine maximal oxygen uptake (V˙O2max) and heart rate (HRmax). In four subsequent visits, participants performed a HIIT session comprising six 4-min work intervals, in which the recovery duration between work intervals equalled either a fixed (1MIN, 2MIN, 3MIN) or a self-selected duration (ssMIN). HIIT sessions were run on a non-motorized treadmill, and were performed under isoeffort conditions. ResultsMean running velocity was significantly higher in 3MIN compared with all other protocols, and higher in ssMIN compared with 2MIN. No significant differences in time spent ≥90% and 95% V˙O2max, or ≥90% and 95% HRmax were evident between the four protocols. RPE responses were similar across and within the protocols showing a gradual increase with each progressive interval. ConclusionIn a self-paced HIIT session of six 4-min work intervals, the length of recovery durations had a limited effect on the total physiological strain endured in the training. However, running velocities were higher when participants received the longest recovery period (3MIN). Longer recovery durations may facilitate a higher external training load (faster running), whilst maintaining a similar internal training load (physiological stimulus), and may therefore allow for greater training adaptations.

Exercise-induced arterial hypoxemia in aerobic and anaerobic trained athletes during incremental exercise

Purpose: The purpose of this study was to examine and compare the occurrence of exercise-induced arterial hypoxemia (EIAH) in aerobic and anaerobic trained athletes during an incremental treadmill exercise test. Material: International level male junior skiers including ten cross-country skiers and ten alpine skiers took part in the study. All participants performed an incremental treadmill exercise test to determine maximal oxygen uptake (VO2max), and oxyhemoglobin saturation (SaO2) was continuously measured using a pulse oximetry. Maximal minute ventilation (VEmax), maximal heart rate (HRmax), ventilatory equivalent for oxygen (VE/VO2) and carbon dioxide (VE/VCO2) were determined during the last stage of the incremental exercise test. EIAH was assumed to have developed when SaO2 decreased by at least 4% (ΔSaO2 ≤ −4%) from the baseline values. Results: VO2max, VE, maximal running speed and test time were higher in the cross-country skiers than in the alpine skiers (p &lt; 0.01), whereas HRmax, VE/VO2 and VE/VCO2 showed similar values in both group (p &gt; 0.05). All the athletes in both groups exhibited EIAH. SaO2 was significantly decreased from 97.5 ± 0.9% at rest to 89 ± 2% at exhaustion in alpine skiers and from 97.8 ± 0.7% at rest to 88.1 ± 2.4% at exhaustion in cross-country skiers (p &lt; 0.001). There were no differences in resting and lowest %SaO2 values between two groups (p &gt; 0.05). Conclusions: EIAH may occur in endurance athletes as well as anaerobic trained athletes. Well-trained athletes who have different aerobic fitness levels may exhibit similar EIAH during the incremental maximal exercise.

Different Training Modalities Improve Energy Cost and Performance in Master Runners.

Purpose: The aim of this study was to compare the effects of continuous moderate-intensity and discontinuous high-intensity training on running performance in master runners.Methods: Thirty-four male master runners (47.2 ± 7.4 years) were assigned to three different groups: continuous moderate-intensity training (CMIT), discontinuous high-intensity training (DHIT), and control group (CON). CMIT and DHIT performed 8-week of supervised training (3 session·wk−1; ~35 km·wk−1) while CON maintained their normal training habits (3–4 session·wk−1; ~50 km·wk−1). Peak oxygen consumption (O2peak) and peak running speed (vpeak) during incremental treadmill exercise, gas exchange threshold (GET), speed at GET, energy cost of running (Cr), and 5-km performance were evaluated before and after training.Results: Following the training period, both CMIT and DHIT significantly reduced Cr (−4.4 and −4.9%, respectively, P < 0.05), increased speed at GET (3.4 and 5.7%, P < 0.05) and improved 5-km time-trial performance (3.1 and 2.2%, P < 0.05) whereas no differences were found for O2peak and GET (as %O2peak). After training, vpeak improved only for DHIT (6%, P < 0.05). No differences were found in any variable for CON.Conclusions: This study indicates that both CMIT and DHIT may positively affect running performance in middle-aged master runners. This improvement was achieved despite a significant reduction of the amount of weekly training volume.