Incremental Cycling Test Research Articles

Surgical shortening of lengthened iliac arteries in endurance athletes: Short-term and long-term satisfaction

ObjectiveEndurance athletes are prone to develop flow limitations in iliac arteries (FLIA). Especially in cyclists and ice speed skaters, excessive hemodynamic loading coupled with hip hyperflexion may cause kinking in lengthened iliac arteries necessitating surgical correction. This study investigated the short-term (≤1.5 years) and long-term (≥5 years) satisfaction of operative shortening of the iliac artery in endurance athletes. MethodsAll patients who were diagnosed and operated for FLIA owing to lengthened and kinked iliac arteries between 1997 and 2015 in one center were analyzed. Short-term follow-up consisted of an incremental maximal cycling test, ankle-brachial index with flexed hips, echo-Doppler examination with peak systolic velocity measurements and contrast-enhanced magnetic resonance angiography before and 6 to 18 months after surgery. Both short- and long-term satisfaction were assessed using questionnaires. ResultsA total of 83 patients (90 operated legs; 96.7% males; median age of 34 years at the time of surgery; interquartile range [IQR], 29-47) were analyzed. In the short-term, 87.5% reported symptom reduction with an 86.4% overall satisfaction rate. Symptom-free cycling improved from 272 ± 84 W to 384 ± 101 W (P < .001), whereas the maximal workload increased from 419 ± 72 W to 428 ± 67 W (P = .01). The ankle-brachial index with flexed hips increased from 0.55 (IQR, 0.45-0.65) to 0.62 (IQR, 0.52-0.74; P = .008), and the peak systolic velocity measured with hips flexed decreased from 2.50 m/s (IQR, 1.77-3.13 m/s) to 1.57 m/s (IQR, 1.20-2.04 m/s; P < .001). After a median of 12 years (IQR, 9.0-15.4 years), symptoms were still decreased in 84.1% of patients with an 81.2% overall satisfaction rate (79.5% response rate). Three patients needed a reintervention (recurrent FLIA, n = 2; failure, n = 1). ConclusionsOperative shortening of a lengthened and kinked iliac artery causing FLIA is successful both in the short- and long-term.

Does The Countermovement Jump Accurately Assess Lower-limb Neuromuscular Fatigue?

Neuromuscular fatigue is monitored in athletes following intense exercise to inform future training prescription and to improve performance. Temporal analysis of the countermovement jump (CMJ) is frequently used to assess fatigue in athletes but is infrequently compared directly to low-frequency fatigue (LFF), a long-lasting fatigue typically assessed in the laboratory. LFF may be present in athletes. PURPOSE: To determine the time-course of changes in CMJ and lower limb LFF following an exhaustive cycling test and the relationship between LFF and temporal CMJ variables. METHODS: LFF and CMJ were assessed in seven active adults (24±2 years, 78±14 kg) prior to and following (0, 8, 15, 30, 60 mins and 24 and 48 hours) an incremental cycling test to exhaustion. Cycling began at 100 W and increased 25 W every 2 min until exhaustion. Temporal analysis of CMJ for peak power (PP), jump height (JH), and concentric contraction duration (CCD) were calculated from bilateral force plates. Low-frequency (10 Hz) force (F10) was elicited from transcutaneous femoral nerve stimulation prior to a maximal voluntary contraction (MVC). LFF was quantified as the F10:MVC ratio. The order of CMJ or LFF was randomized across time points. Changes in LFF and CMJ variables were assessed from two-way repeated measures analysis of variance (measure x time). RESULTS: Maximal aerobic power was 234±67 W (96±4% HRmax). A significant measure x time interaction (p<0.0001) and significant main effects of time (p=0.05) and method (p=0.02) were found. Compared to baseline, significant reductions in LFF (i.e., greater fatigue) were seen at 0-, 8-, 15- and 30-mins post-exercise (all p<0.02). No significant changes in any of the CMJ variables were observed post-exercise (p = 1.0). Furthermore, changes in LFF during exercise recovery was not correlated to changes in any of CMJ variables (r2<0.04, p>0.20), whereas all CMJ variables were significantly correlated with each other (0.22<r2<0.42, p<0.001). CONCLUSION: These results show that following exhaustive exercise, LFF persists for at least 30 mins whereas no change in CMJ performance variables were seen. These results call into question the practical utility of interpreting neuromuscular fatigue in athletes using the CMJ, even within 30 minutes of exhaustive exercise.

Power Of Breathing In Heart Failure With Preserved Ejection Fraction During Exercise

Heart failure patients with preserved ejection fraction (HFpEF) exhibit impaired exercise tolerance, while the underlying mechanisms are unclear. HFpEF patients exhibit alterations to the pulmonary system at rest; however, it is unknown if these alterations translate to a higher power of breathing (POB) during exercise, which may contribute to exercise intolerance. PURPOSE: To compare the total POB and its components (inspiratory elastic and resistive and expiratory resistive POB) in HFpEF and healthy controls at matched ventilations (VE). We hypothesized that HFpEF compared to healthy controls (CTL) would exhibit greater total POB as a result of greater inspiratory elastic and resistive POB and expiratory resistive POB. METHODS: HFpEF (n = 10; age: 73 ± 7 yrs; BMI: 32 ± 4 kg/m2; EF: 62 ± 4%) and CTL (n = 10; age: 71 ± 8 yrs; BMI: 28 ± 3 kg/m2) were recruited for this study. All performed an incremental cycling test to volitional fatigue. Esophageal pressure and ventilatory variables were measured at matched VE (i.e. 30 and 50 L/min) during exercise. Inspiratory elastic and resistive as well as expiratory resistive POB were quantified using the Otis method. RESULTS: At VE of 30 and 50 L/min, HFpEF exhibited smaller tidal volumes and greater breathing frequencies compared to CTL (all, p < 0.05). HFpEF compared to CTL had greater total POB at VE of 30 (37 ± 13 vs. 20 ± 9 J/min) and 50 L/min (71 ± 13 vs. 45 ± 13 J/min, p < 0.05 for both). At VE of 30 and 50 L/min, HFpEF compared to CTL had greater inspiratory resistive POB (30 L/min: 13 ± 5 vs. 7 ± 4 J/min; 50 L/min: 27 ± 4 vs.15 ± 4 J/min) and expiratory resistive POB (30 L/min:15 ± 10 vs. 2 ± 2 J/min; 50 L/min: 26 ± 11 vs. 8 ± 12 J/min, all, p < 0.05). Inspiratory elastic POB was not different between groups at VE of 30 and 50 L/min (both, p > 0.05). CONCLUSIONS: These data demonstrate that the HFpEF syndrome is associated with pulmonary alterations eliciting a greater POB during exercise due to greater inspiratory and expiratory resistive POB. These findings suggest that the respiratory muscles may necessitate an increased blood flow demand in HFpEF compared to healthy controls for a given VE during exercise.

Locomotor Muscle Afferent Inhibition Augments Activation Of Locomotor Muscles In Heart Failure Patients During Exercise

Exercise intolerance is a hallmark feature of heart failure with reduced ejection fraction (HFrEF). Locomotor muscle afferent feedback contributes to exercise intolerance in patients with HFrEF. Locomotor muscle afferent inhibition via intrathecal fentanyl, compared to the sham condition (SHAM), results in increased peak workload, cardiac output, and leg oxygen delivery during maximal exercise. To date, the impact of locomotor muscle afferent feedback inhibition on locomotor muscle activation responses during exercise in patients with HFrEF have not been investigated. PURPOSE: To determine the effect of intrathecal fentanyl on vastus lateralis (VL) muscle activation during incremental exercise in patients with HFrEF. METHODS: Patients with HFrEF (n = 7, EF: 35 ± 13%, age: 60 ± 9 yrs, BMI 28.7 ± 5.5 kg/m2) performed an incremental cycle test to task failure with lumbar intrathecal fentanyl (FENT) or SHAM (in randomized order). Electromyography (EMG) of the VL was measured and the root-mean square (RMS) of 10 contractions were averaged at 30 W, 50 W, 70 W, and peak workload. Changes in RMS were normalized as a percent of the SHAM response (unloaded = 0%; peak workload = 100%). RESULTS: Peak workload was significantly greater with FENT compared to SHAM (129 ± 30 vs. 114 ± 31 W, p = 0.04). VL RMS was not different at 30 W between FENT and SHAM (FENT: 44 ± 22 vs. SHAM: 17 ± 33%, p = 0.06). However, VL RMS was greater with FENT compared to SHAM at 50 W (FENT: 82 ± 61 vs. SHAM: 31 ± 24%), 70 W (FENT: 96 ± 56 vs. SHAM: 45 ± 29%), and peak workload (FENT: 167 ± 55 vs. SHAM: 92 ± 10%) (all, p < 0.04). There was no significant relationship between the change in peak workload and VL RMS with FENT with both normalized as a percent of the SHAM response (p = 0.09). CONCLUSION: These data suggest that locomotor muscle afferent feedback may contribute to exercise intolerance via inhibition of locomotor muscle activation during exercise in patients with HFrEF.

Intensified training before Olympic-distance triathlon in recreational triathletes: "Less pain, more gain".

To examine 1) the contribution of physiological performance variables to Olympic-distance (OD) triathlon performance, and 2) the links between an 8-wk intensified training plus competition preceding the main OD triathlon race and the changes in the physiological status in triathletes. An observational longitudinal study. Endurance performance variables during maximal incremental running and cycling tests, and average velocity during an all-out 400-m swimming performance test (V400) were assessed before (T1) and after (T2) the intensified training in 7 recreational-level triathletes. Overall main OD triathlon time was extremely largely (r = -0.94; P = 0.01) correlated with peak running velocity (PRV). Best correlation magnitude between exercise modes' partial race times and the corresponding specific physiological criterion tests was observed for swimming (r = -0.97; P<0.001). Improvement in V400 (2.9%), PRV (1.5%) and submaximal running blood lactate concentration (17%) was observed along the training period, whereas no changes were observed in the cycling endurance performance variables. Higher volume of training plus competition at high intensity zones during cycling, running and swimming were associated with lower improvements or declines in their corresponding exercise mode-specific criterion performance variables (r = 0.81-0.90; P = 0.005-0.037). Results indicate that: 1) PRV is highly associated with overall OD triathlon performance, and 2) spending much time at high relative intensities during swimming, cycling or running may lead, in a dose-response manner, to lower improvements or decreases on those exercise-specific physiological performance variables. This may favor the emergence of overreaching or diminished performance.

Impact of Ageing on Female Metabolic Flexibility: A Cross-Sectional Pilot Study in over-60 Active Women

BackgroundAgeing affects metabolic flexibility, although physical status could influence this relationship. This cross-sectional study aims to describe and analyse the metabolic flexibility/inflexibility in a group of active older women, together with the impact of ageing and physical status on their oxidation rates and maximal fat oxidation (MFO).MethodsFifteen volunteers (69.00 ± 6.97 years)—from 24 women—completed an incremental cycling test until the second ventilatory threshold. Intensity increased 10 W each 3 min 15 s, starting at 30 W. Gas exchange, heart rate, rate of perceived effort, pain scale and muscle power were registered, together with lactate. VO2 and VCO2 were considered for fat and carbohydrate oxidation (FATox and CHOox; Frayn’s equation) at intensities 60%, 80% and 100% from the peak power in the test (P100). Psychophysiological parameters were compared at MFO/FATmax and P100, together with the energy expenditure calculations around MFO (included FAT and CHO contributions), and the main correlation analyses, with and without P100 and VO2 as covariates.ResultsFATox was low at MFO (0.13; 95% CI [0.09–0.17] mg/min/kgFFM; 3.50; 95% CI [2.49–4.50] mg/min/kgFFM), with short oxidation-rate curves shifting down and leftward. CHOox and FATox were both low for reduced power with age (77.14 ± 18.58 W and 39.29 ± 9.17 W at P100 and MFO, respectively), all accompanied by a fall in energy expenditure (5.44 ± 2.58 kcal/min and 3.32 ± 1.55 kcal/min at P100 and MFO, respectively). Power appears as a determinant factor, given its strong and negative significant association with age (r = − 0.85, p < 0.005; R2 = 0.72) and moderate with MFO (r = − 0.54, p = 0.04; R2 = 0.29). In turn, energy expenditure shows a positive and moderate association with muscle power (r = 52, p = 0.04).ConclusionsDespite the drop in substrates oxidation with age, physical status (i.e. larger muscular power and energy expenditure) suggests a key role in the preservation of metabolic health with ageing in active women.

Low Vitamin D Status Relates to the Poor Response of Peripheral Pulse Wave Velocity Following Acute Maximal Exercise in Healthy Young Men.

The primary objective of this study was to determine the effects of vitamin D levels on peripheral pulse wave velocity (pPWV) following acute maximal exercise in healthy young adults. Fifty male healthy adults from National Chung Cheng University participated in the study. Participants were divided into the 25-hydroxyvitamin D (25(OH)D) sufficiency group (n = 28, 25(OH)D ≥ 50 nmol/L) and deficiency group (n = 22, 25(OH)D < 50 nmol/L). The acute maximal exercise was performed using an incremental cycling test to exhaustion. Additionally, the pPWV and blood pressure were obtained at rest and 0, 15, 30, 45, 60 min after acute maximal exercise. The results show that 25(OH)D deficiency group had higher pPWV at post-exercise (5.34 ± 0.71 vs. 4.79 ± 0.81 m/s, p < 0.05), post-exercise 15 min (5.13 ± 0.53 vs. 4.48 ± 0.66 m/s, p < 0.05) and post-exercise 30 min (5.26 ± 0.84 vs. 4.78 ± 0.50 m/s, p < 0.05) than the sufficiency group. Furthermore, there was a significant inverse correlation between 25(OH)D levels and pPWV following acute maximal exercise. Our study demonstrated that low vitamin D status relates to the poor response of pPWV following maximal exercise in healthy young men. Vitamin D deficiency may increase the risk of incident cardiovascular events after acute exhaustive exercise, even in healthy and active adults.

Maintenance of cardiorespiratory fitness, body composition, and a physically active lifestyle after structured exercise interventions in individuals with overweight and obesity: A mixed-method follow-up study

ObjectivesThe aim of this mixed-method study was to explore maintenance of physical activity and health effects one year after completion of exercise interventions in transport and leisure-time domains of everyday life. We hypothesised that routinisation of active commuting would lead to better maintenance of physical activity and health effects compared with leisure-time exercise. Study designMixed-methods follow-up study. MethodsIndividuals with overweight/obesity, who completed a 6-month exercise intervention (active commuting by bike (BIKE), moderate (MOD) or vigorous intensity leisure-time exercise (VIG)), were after one year invited to participate in a follow-up visit which included measurements of cardiorespiratory fitness during an incremental bicycle test and body composition using dual-energy X-ray absorptiometry. Variability in maintenance practices was assessed in a sub-sample of participants who experienced the greatest improvements (‘VO2peak improvers’) and reductions (‘VO2peak reducers’), respectively, in cardiorespiratory fitness. Semi-structured interviews were conducted (15–30 min) and analysed using systematic text condensation to identify barriers and facilitators associated with maintenance of physical activity. ResultsOut of the 74 participants completing an exercise intervention, 46 (62%) completed follow-up (BIKE: n = 14; MOD: n = 14; VIG: n = 18). Improvements in VO2peak and reductions in fat mass were maintained in BIKE and VIG. Body weight decreased in BIKE and fat free mass increased in VIG. Changes in VO2peak and anthropometry at follow-up did not differ between BIKE and MOD + VIG. Fat mass decreased and recreational physical activity increased in ‘VO2peak improvers’. Findings from the interviews suggested that self-monitoring, collective exercising, and new personal exercise challenges facilitate maintenance of a physically active lifestyle. ConclusionCompletion of a structured exercise intervention consisting of 6 months of active commuting or vigorous intensity leisure-time exercise was associated with long-term maintenance of improvements in VO2peak and body composition, whereas moderate intensity leisure-time exercise was not. In contrast to our hypothesis, active commuting was not associated with better maintenance of physical activity and health effects after the intervention compared with leisure-time exercise.

A high carbohydrate diet with a low glycaemic index improves training effects in male endurance athletes

The present study investigated the effect of a 4-week high fat low carbohydrate (HFLC-G) versus high carbohydrate low glycaemic (LGI-G) or high glycaemic (HGI-G) diet on power output at lactate thresholds, peak oxygen uptake and peak performance during an incremental cycle test in 28 male endurance athletes. All participants showed improved levels of power output at the lactate thresholds with a more pronounced effect in the HFLC-G and LGI-G. In the HFLC-G peak performance (−11.6 ± 16.3 W) decreased, while in the LGI-G (9.20 ± 13.8 W) and HGI-G (9.89 ± 12.8 W) peak performance increased (p = 0.009). In summary, the LGI-G showed comparable training adaptations as the HFLC-G at submaximal intensities without limiting the ability to perform at high intensities. Compared to a HFLC and HGI diet, the LGI diet in this study seemed to be advantageous during submaximal and high intensities resulting from an improved metabolic flexibility.

Blood oxidative stress biomarkers in women: influence of oral contraception, exercise, and N-acetylcysteine

PurposeTo compare physiological responses to submaximal cycling and sprint cycling performance in women using oral contraceptives (WomenOC) and naturally cycling women (WomenNC) and to determine whether N-acetylcysteine (NAC) supplementation mediates these responses.MethodsTwenty recreationally trained women completed five exercise trials (i.e., an incremental cycling test, a familiarisation trial, a baseline performance trial and two double-blind crossover intervention trials). During the intervention trials participants supplemented with NAC or a placebo 1 h before exercise. Cardiopulmonary parameters and blood biochemistry were assessed during 40 min of fixed-intensity cycling at 105% of gas-exchange threshold and after 1-km cycling time-trial.ResultsWomenOC had higher ventilation (β [95% CI] = 0.07 L·min−1 [0.01, 0.14]), malondialdehydes (β = 12.00 mmol·L−1 [6.82, 17.17]) and C-reactive protein (1.53 mg·L−1 [0.76, 2.30]), whereas glutathione peroxidase was lower (β = 22.62 mU·mL−1 [− 41.32, − 3.91]) compared to WomenNC during fixed-intensity cycling. Plasma thiols were higher at all timepoints after NAC ingestion compared to placebo, irrespective of group (all p < 0.001; d = 1.45 to 2.34). For WomenNC but not WomenOC, the exercise-induced increase in malondialdehyde observed in the placebo trial was blunted after NAC ingestion, with lower values at 40 min (p = 0.018; d = 0.73). NAC did not affect cycling time-trial performance.ConclusionsBlood biomarkers relating to oxidative stress and inflammation are elevated in WomenOC during exercise. There may be an increased strain on the endogenous antioxidant system during exercise, since NAC supplementation in WomenOC did not dampen the exercise-induced increase in malondialdehyde. Future investigations should explore the impact of elevated oxidative stress on exercise adaptations or recovery from exercise in WomenOC.

Estimation of Tidal Volume during Exercise Stress Test from Wearable-Device Measures of Heart Rate and Breathing Rate

Tidal volume (TV), defined as the amount of air that moves in or out of the lungs with each respiratory cycle, is important in evaluating the respiratory function. Although TV can be reliably measured in laboratory settings, this information is hardly obtainable under everyday living conditions. Under such conditions, wearable devices could provide valuable support to monitor vital signs, such as heart rate (HR) and breathing rate (BR). The aim of this study was to develop a model to estimate TV from wearable-device measures of HR and BR during exercise. HR and BR were acquired through the Zephyr Bioharness 3.0 wearable device in nine subjects performing incremental cycling tests. For each subject, TV during exercise was obtained with a metabolic cart (Cosmed). A stepwise regression algorithm was used to create the model using as possible predictors HR, BR, age, and body mass index; the model was then validated using a leave-one-subject-out cross-validation procedure. The performance of the model was evaluated using the explained variance (R2), obtaining values ranging from 0.65 to 0.72. The proposed model is a valid method for TV estimation with wearable devices and can be considered not subject-specific and not instrumentation-specific.

Effects of the addition of high- vs. low-intensity resistance training on top of endurance training in patients with heart failure: preliminary results from a randomized clinical trial

Abstract Funding Acknowledgements Type of funding sources: Public Institution(s). Main funding source(s): Hasselt University Background Adding resistance training on top of endurance training is recommended in the rehabilitation of patients with heart failure. However, it is unknown which intensity of resistance training should be preferred. Purpose To compare the effects of the addition of high- vs. low-intensity resistance training on top of endurance training in patients with heart failure. Methods Nineteen patients with heart failure were block randomized (by gender and sex) in a combined high-intensity resistance and endurance group (HIG; n=8, age=61±12y, 7 males, LVEF=38±10%) vs. combined low-intensity resistance and endurance group (LIG; n=9, age=68±21y, 8 males, LVEF=38±13%). Patients trained 3x/week for 45 sessions. The resistance exercises were volume-matched between groups and consisted of three sets of leg press, pull down and dip exercises, separated by 30s of rest, done at 55-70% 1RM in HIG vs. 35-40% 1RM in LIG. Both groups did moderate-intense endurance training on a bicycle, cross-trainer, treadmill and arm ergometer for 30 min per training. Maximal oxygen consumption was evaluated with an incremental cardiopulmonary cycling test and muscle strength by 1-RM testing, while quality of life was assessed with the Minnesota questionnaire, and walking distance by a 6-minute walking test. Mann-Whitney U test was used for analyzing differences between groups in all variables and Wilcoxon signed-rank test for evaluating pre-post difference of the entire sample. P values &amp;lt;0,05 (2-tailed) were considered statistically significant. Results Training adherence was similar in both groups (LIG vs HIG: 41±6 vs 37±9 sessions, p=0,370; Table 1). Overall, the intervention improved maximal oxygen consumption, walking capacity and muscle strength (p&amp;lt;0,05), but the between-group changes in maximal oxygen consumption (LIG vs HIG: 3±2 vs 3±4 ml/kg/min, p=0,963), quality of life (LIG vs HIG: -8±23 vs -1±5 points, p=0,931) and muscle strength (LIG vs HIG: Dip 34±34 vs 18±20kg, p=0,481; Leg press, 66±87 vs 47±53kg, p=0,486; Pull down, 9±6 vs 9±7kg, p=0,574) were similar. Conclusion Adding either high- or low-intensity resistance training on top of endurance training seems equally effective for improving aerobic capacity and walking performance in patients with heart failure. The study is ongoing.

High‐intensity Interval Training Combined With Blood‐flow Restriction Predominantly Alters Anaerobic Capacity in Endurance‐trained Athletes

Blood‐flow restriction (BFR) training has gained popularity amongst athletes and sport practitioners to enhance training adaptations and performance. However, BFR has typically been associated with low‐intensity exercise, and there is still limited evidence of its impact when combined with high‐intensity training. This study investigated the impact of high‐intensity interval training (HIIT) with concurrent BFR on anaerobic and aerobic physical capacities and key physiological responses. In a pre‐post, parallel‐groups design, fifteen endurance‐trained males (VO2max 65.0±4.8 mL/min/kg) included three sessions of HIIT per week (sets of 15 s ON/15 s OFF at 100% maximal aerobic power) into their usual training for three weeks either with (BFR group, n=9) or without restriction (CTL group, n=6). In BFR, cuffs were worn proximal on both quadriceps and inflated progressively from 50 to 70% of arterial occlusion pressure across training weeks. Before and after training, athletes completed a maximal incremental step cycling test, a Wingate anaerobic test (WAnT) and a 5‐km cycling time trial. Blood samples were drawn during the time trials. Maximal aerobic power increased in BFR (364.8±60.7 vs 383.4±61.4 watts, p=0.003, Cohen’s effect size ES 0.27) but not in CTL (381.2±62.1 vs 385.5±64.4 watts, p=0.45, ES 0.05). Concomitantly, mean power output achieved during the WAnt also increased with BFR (23.8±4.0 vs 24.6±4.1 kJ, p=0.08, ES 0.28) but not in CTL (23.4±2.5 vs 23.4±2.4 kJ, p=0.95, ES 0.01). However, there was no change between groups in VO2max (BFR: 0.86% vs CTL: 1.77%, ES ‐0.15) and in both the mean power output (BFR: 1.81% vs CTL: 6.51%, ES ‐0.21) and completion time (BFR: ‐0.69% vs CTL: ‐2.55%, ES ‐0.21) of the 5‐km time trial. During the time trial, BFR also induced greater changes in pH (BFR: ‐0.05 vs CTL: ‐0.03 units, ES ‐0.43) and base excess (BFR: ‐1.55 vs CTL: ‐0.70 units, ES ‐0.37), and lowered the potassium ion concentration (BFR: ‐0.55 vs CTL: 0.44 mmol/L, ES ‐0.63). There was no change between groups in lactate production from pre‐ to post‐training. These findings suggest that short‐term HIIT combined with BFR improved anaerobic capacity in endurance‐trained athletes without meaningful effect on endurance exercise performance.

Effect of a High Fat Diet vs. High Carbohydrate Diets With Different Glycemic Indices on Metabolic Parameters in Male Endurance Athletes: A Pilot Trial.

Consuming low glycemic carbohydrates leads to an increased muscle fat utilization and preservation of intramuscular glycogen, which is associated with improved flexibility to metabolize either carbohydrates or fats during endurance exercise. The purpose of this trial was to investigate the effect of a 4-week high fat low carbohydrate (HFLC-G: ≥65% high glycemic carbohydrates per day; n = 9) vs. high carbohydrate low glycemic (LGI-G: ≥65% low glycemic carbohydrates daily; n = 10) or high glycemic (HGI-G: ≥65% fat, ≤ 50 g carbohydrates daily; n = 9) diet on fat and carbohydrate metabolism at rest and during exercise in 28 male athletes. Changes in metabolic parameters under resting conditions and during cycle ergometry (submaximal and with incremental workload) from pre- to post-intervention were determined by lactate diagnostics and measurements of the respiratory exchange ratio (RER). Additionally, body composition and perceptual responses to the diets [visual analog scale (VAS)] were measured. A significance level of α = 0.05 was considered. HFLC-G was associated with markedly decreased lactate concentrations during the submaximal (−0.553 ± 0.783 mmol/l, p = 0.067) and incremental cycle test [−5.00 ± 5.71 (mmol/l) × min; p = 0.030] and reduced RER values at rest (−0.058 ± 0.108; p = 0.146) during the submaximal (−0.078 ± 0.046; p = 0.001) and incremental cycle test (−1.64 ± 0.700 RER × minutes; p < 0.001). In the HFLC-G, fat mass (p < 0.001) decreased. In LGI-G lactate, concentrations decreased in the incremental cycle test [−6.56 ± 6.65 (mmol/l) × min; p = 0.012]. In the LGI-G, fat mass (p < 0.01) and VAS values decreased, indicating improved levels of gastrointestinal conditions and perception of effort during training. The main findings in the HGI-G were increased RER (0.047 ± 0.076; p = 0.117) and lactate concentrations (0.170 ± 0.206 mmol/l, p = 0.038) at rest. Although the impact on fat oxidation in the LGI-G was not as pronounced as following the HFLC diet, the adaptations in the LGI-G were consistent with an improved metabolic flexibility and additional benefits regarding exercise performance in male athletes.

Mechanisms of Neuromuscular Fatigability in People with Cancer-Related Fatigue.

Cancer-related fatigue (CRF) is a debilitating symptom that affects around one-third of people for months or years after cancer treatment. In a recent study, we found that people with posttreatment CRF have greater neuromuscular fatigability. The aim of this secondary analysis was to examine the etiology of neuromuscular fatigability in people with posttreatment CRF. Ninety-six people who had completed cancer treatment were dichotomized into two groups (fatigued and nonfatigued) based on a clinical cut point for fatigue. Alterations in neuromuscular function (maximal voluntary contraction peak force, voluntary activation, potentiated twitch force, and EMG) in the knee extensors were assessed across three common stages of an incremental cycling test. Power outputs during the fatigability test were expressed relative to gas exchange thresholds to assess relative exercise intensity. The fatigued group had a more pronounced reduction in maximal voluntary contraction peak force and potentiated twitch force throughout the common stages of the incremental cycling test (main effect of group: P < 0.001, ηp2 = 0.18 and P = 0.029, ηp2 = 0.06, respectively). EMG was higher during cycling in the fatigued group (main effect of group: P = 0.022, ηp2 = 0.07). Although the relative intensity of cycling was higher in the fatigued group at the final common stage of cycling, this was not the case during the initial two stages, despite the greater impairments in neuromuscular function. Our results suggest that the rapid impairments in neuromuscular fatigability in people with CRF were primarily due to disturbances at the level of the muscle rather than the central nervous system. This could affect the ability to tolerate daily physical activities.

Aerobic Fitness Is Associated with Cerebral μ-Opioid Receptor Activation in Healthy Humans.

Central μ-opioid receptors (MORs) modulate affective responses to physical exercise. Individuals with higher aerobic fitness report greater exercise-induced mood improvements than those with lower fitness, but the link between cardiorespiratory fitness and the MOR system remains unresolved. Here we tested whether maximal oxygen uptake (V̇O2peak) and physical activity level are associated with cerebral MOR availability and whether these phenotypes predict endogenous opioid release after a session of exercise. We studied 64 healthy lean men who performed a maximal incremental cycling test for V̇O2peak determination, completed a questionnaire assessing moderate-to-vigorous physical activity (MVPA; in minutes per week), and underwent positron emission tomography with [11C]carfentanil, a specific radioligand for MOR. A subset of 24 subjects underwent additional positron emission tomography scan also after a 1-h session of moderate-intensity exercise and 12 of them also after a bout of high-intensity interval training. Higher self-reported MVPA level predicted greater opioid release after high-intensity interval training, and both V̇O2peak and MVPA level were associated with a larger decrease in cerebral MOR binding after aerobic exercise in the ventral striatum, orbitofrontal cortex, and insula. That is, more trained individuals showed greater opioid release acutely after exercise in brain regions especially relevant for reward and cognitive processing. Fitness was not associated with MOR availability. We conclude that regular exercise training and higher aerobic fitness may induce neuroadaptation within the MOR system, which might contribute to improved emotional and behavioral responses associated with long-term exercise.

Effects of workload level on the timing of concentric-eccentric contractions during cycling.

The mechanical energy required to drive the cranks during cycling depends on concentric and eccentric muscle actions. However, no study to date provided clear evidence on how workload levels affect concentric and eccentric muscle actions during cycling. Therefore, the aim of this study was to investigate the workload effects on the timing of lower limb concentric and eccentric muscle actions, and on joint power production. Twenty-one cyclists participated in the study. At the first session, maximal power output (PO<inf>max</inf>) and power output at the first (PO<inf>VT1</inf>) and second (PO<inf>VT2</inf>) ventilatory thresholds were determined during an incremental cycling test. At the second session, cyclists performed three trials (2 min/each) in the workloads determined from their PO<inf>max</inf>, PO<inf>VT1</inf> and PO<inf>VT2</inf>, acquiring data of lower limb muscle activation, pedal forces and kinematics. Concentric and eccentric timings were computed from muscles' activations and muscle-tendon unit excursions along with hip, knee and ankle joints' power production. Longer rectus femoris eccentric activation (62%), vastus medialis concentric (66%) and eccentric activation (26%), and biceps femoris concentric (29%) and eccentric (133%) activation at PO<inf>max</inf> were observed compared to PO<inf>VT1</inf>. Longer positive (12%) and shorter negative (12%) power were observed at the knee joint for PO<inf>max</inf> compared to PO<inf>VT1</inf>. We conclude that, to sustain higher workload levels, cyclists improved the timing of power transmission from the hip to the knee joint via rectus femoris eccentric, vastus medialis concentric and eccentric and biceps femoris concentric and eccentric contractions.

Increased Fat Oxidation During Arm Cycling Exercise in Adult Men With Spinal Cord Injury Compared With Noninjured Controls.

People with spinal cord injury (SCI) tend to be more sedentary and increase fat accumulation, which could have a negative influence on metabolic flexibility. The aim of this study was to investigate the capacity to oxidize fat in a homogenous sample of men with thoracic SCI compared with healthy noninjured men during an arm cycling incremental test. Forty-one men, 21 with SCI and 20 noninjured controls, performed an incremental arm cycling test to determine peak fat oxidation (PFO) and the intensity of exercise that elicits PFO (Fatmax). PFO was expressed in absolute values (g/min) and relative to whole-body and upper-body lean mass ([mg·min-1]·kg-1) through three different models (adjusting by cardiorespiratory fitness and fat mass). Gross mechanical efficiency was also calculated. PFO was higher in SCI than in noninjured men (0.27 ± 0.07 vs. 0.17 ± 0.07g/min; 5.39 ± 1.30 vs. 3.29 ± 1.31 [mg·min-1]·kg-1 whole-body lean mass; 8.28 ± 2.11 vs. 5.08 ± 2.12 [mg·min-1]·kg-1 upper-body lean mass). Fatmax was found at a significantly higher percentage of VO2peak in men with SCI (33.6% ± 8.2% vs. 23.6% ± 6.4%). Differences persisted and even increased in the fully adjustment model and at any intensity. Men with SCI showed significantly higher gross mechanical efficiency at 35 and 65W than the noninjured group. Men with SCI showed higher fat oxidation when compared with noninjured men at any intensity, even increased after full adjustment for lean mass, fat mass, and cardiorespiratory fitness. These findings suggest that SCI men could improve their metabolic flexibility and muscle mass for greater efficiency, not being affected by their fat accumulation.

Peer Presence Increases Session Ratings of Perceived Exertion.

This study aimed to examine the effect of peer presence on session rating of perceived exertion (RPE) responses. Fourteen males, with mean (SD) age 22.4 (3.9) years, peak oxygen uptake 48.0 (6.6)mL·kg-1·min-1, and peak power output 330 (44)W, completed an incremental cycling test and 3 identical experimental sessions, in groups of 4 or 5. Experimental sessions involved 24 minutes of cycling, whereby the work rate alternated between 40% and 70% peak power output every 3 minutes. During cycling, heart rate was collected every 3 minutes, and session-RPE was recorded 10 minutes after cycling, in 3 communication contexts: in written form unaccompanied (intrapersonal communication), verbally by the researcher only (interpersonal communication), and in the presence of the training group. Session-RPE was analyzed using ordinal regression and heart rate using a linear mixed-effects model, with models fit in a Bayesian framework. Session-RPE was voted higher when collected in the group's presence compared with when written (odds ratio = 4.26, 95% credible interval = 1.27-14.73). On average, the posterior probability that session-RPE was higher in the group setting than when written was .53. Session-RPE was not different between the group and verbal, or verbal and written collection contexts. This study suggests that contextual psychosocial inputs influence session-RPE and highlights the importance of session-RPE users controlling the measurement environment when collecting votes.

Abstract 12146: Acute Nitroglycerin Treatment Improves Exercise Hemodynamics, but Not Ventilation-Perfusion Matching in Patients With Heart Failure With Preserved Ejection Fraction

Introduction: Heart failure with preserved ejection fraction (HFpEF) patients exhibit a marked rise in PCWP during exercise, which may contribute to ventilation-perfusion (V/Q) mismatch and manifest as an increase in alveolar dead space (alveolar V D ) and alveolar-arterial PO 2 difference (AaPO 2 ). Nitrates reduce PCWP during exercise in HFpEF, but whether nitrates also reduce V/Q mismatch during exercise is unknown. Hypothesis: The increase in PCWP and V/Q mismatch during exercise would be attenuated with acute nitroglycerin (NTG) treatment compared with placebo in HFpEF patients. Methods: 13 patients performed a 6min cycling test at 20W and an incremental cycling test (with right-heart and arterial catheterization) with placebo and NTG treatment. The physiologic dead space to tidal volume (V D /V T ) was calculated using the Enghoff modification of the Bohr equation. Alveolar V D was calculated as: V D /V T x V T - anatomic dead space (anatomic V D , estimated as 2mL/kg lean body mass). AaPO 2 was calculated using the alveolar gas equation. Data were analyzed using a 2-way ANOVA. Results: PCWP decreased with NTG at 20W (placebo: 21.1±6.2 vs. NTG: 16.5±6.1mmHg, p=0.02) and peak exercise (placebo: 33.7±7.1 vs. NTG: 26.2±5.6mmHg, p&lt;0.01). However, alveolar V D did not differ between treatments at rest (placebo: 0.11±0.07 vs. NTG:0.12±0.06L/breath, p=0.91), 20W (placebo: 0.22±0.09 vs. NTG: 0.24±0.10L/breath, p=0.62), or peak exercise (placebo: 0.34±0.14 vs. NTG:0.36±0.16L/breath, p=0.83). Nor did AaPO 2 differ between treatments at rest (placebo: 17.6±4.3 vs. NTG: 18.3±5.7mmHg, p=0.76), 20W (placebo: 22.0±6.9 vs. NTG: 22.1±8.1mmHg, p=0.99), or peak exercise (placebo: 25.1±9.1 vs. NTG: 27.8±9.9mmHg, p=0.41). No significant exercise-by-treatment interaction was detected for V D /V T (p=0.80). Conclusions: This study showed that NTG attenuated the increase in PCWP, but had no effect on the increase in alveolar V D or AaPO 2 during exercise. These findings suggest that the exercise-induced increase in V/Q mismatch may not be exclusively related to abnormal exercise hemodynamics. Further study is required to determine the clinical consequences and the mechanism(s) responsible for the progressive increase in V/Q mismatch during exercise in HFpEF patients.