Incremental Cycle Research Articles

The Effect Of Sex And Exercise Intensity On Hunger Ratings In Adults: A Pilot Study

Acute exercise transiently suppresses appetite, oftentimes in an intensity dependent manner. However, the majority of prior work only included young adult males, and did not explore the effects of sex on exercise-induced appetite measures. PURPOSE: To determine the effect of exercise intensity and sex on appetite responses in middle-age adult males and females. METHODS: Untrained males (n = 5; age: 46.8 ± 5.8 y; BMI; 22.5 ± 0.84 kg/m2 VO2peak: 34.7 ± 6.7 mL/kg/min) and females (n = 4; age: 43.8 ± 5.4 y; BMI 22.2 ± 0.94 kg/m2;VO2peak: 28.15 ± 2.3 mL/kg/min) completed 3 conditions in a randomized, crossover design: control (C), moderate intensity exercise (at the lactate threshold (LT); MOD), or high intensity (75% of the difference between LT and VO2 peak; HI) exercise. Exercise intensity was determined from a maximal incremental cycle ergometer test. Venous blood was sampled at the end of each 3-min stage and analyzed for lactate. Visits occurred in the morning after an overnight fast. All exercise sessions were calorically matched within subjects. Subjective appetite parameters were assessed via visual analogue scales (VAS) during each condition at: 0 minutes, 60 minutes, 90 minutes, 120 minutes. Area-under-the curve values were calculated using the trapezoidal method for each VAS component. RESULTS: Preliminary inspection of data suggest perception of hunger (units = mm*120 min-1; males: C: 491.1 ± 291.7 MOD: 355.8 ± 107.8, HI: 351.6 ± 129.2;females: C: 539.6 ± 69.5, MOD: 419.6 ± 106.9, HI: 409.5 ± 67.5) satisfaction (males: C: 420.6 ± 174.9, MOD: 293.7 ± 187.65, HI: 395.3 ± 197.05; females: C: 279.0 ± 239.7 MOD: 342.4 ± 159.6, HI: 382.0 ± 146.4), fullness (males: C: 393.6 ± 154.3, MOD: 266.1 ± 163.8, HI: 398.6 ± 176.5; females: C: 247.5 ± 241.2, MOD: 264.4 ± 215.5, HI: 411.5 ± 159.9), and how much you think you can eat (males: C: 653.7 ± 225.9, M: 573.9 ± 239.2, HI: 460.2 ± 248.9; females: CON: 684.4 ± 192.1, MOD: 545.6 ± 107.4, HIGH: 731.0 ± 150.2), are affected in an intensity dependent manner with differing responses between middle aged males and females. CONCLUSIONS: Both exercise intensity and sex may impact subjective ratings of appetite. Supported by The University of Virginia School of Education and Human Development, and National Institute of Diabetes and Digestive and Kidney Diseases (1R01DK12950-01)

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.

Cortisol response under low intensity exercise during cognitive-behavioral therapy is associated with therapeutic outcome in panic disorder-an exploratory study.

Patients with Panic Disorder (PD) show an abnormal stress-induced functioning of the Hypothalamic-Pituitary-adrenal (HPA)-axis. Different protocols for stress induction are of rather low relevance for the psychotherapeutic treatment. In practice, interoceptive exposure is often realized as Low Intensity Exercise (LIE), as compared to an incremental cycle exercise test to exhaustion. Currently, it is not known, whether LIE displays an effective interoceptive stressor 1.) leading to a significant anxiety induction; 2.) a comparable HPA- and Sympathetic-Adreno-Medullar (SAM)-axis response in both patients and healthy controls; 3.) stress responses under LIE are associated with treatment outcomes. N = 20 patients with PD and n = 20 healthy controls were exposed to ten minutes of LIE on an exercise bike. LIE was applied as part of the interoceptive exposure, during an intensive Cognitive-Behavioral Therapy (CBT) in a day clinic. Heart rate was monitored and salivary cortisol samples collected. Before and after the LIE, state anxiety/ arousal were assessed. In order to evaluate psychopathology, the Panic and Agoraphobia Scale, Mobility Inventory, Agoraphobic Cognitions Questionnaire and Body Sensations Questionnaire were applied, before (T1) and after five weeks (T2) of an intensive CBT. LIE led to a significant and similar heart rate increase in both groups. Cortisol decreased over time in both groups, especially in male patients. A higher psychopathology before, and after CBT, was associated with a significantly lower cortisol response under LIE. In the present study, LIE led to a divergent stress response: while there was a significant heart rate increase, cortisol decreased over time, particularly in male patients. A lower reactivity of the HPA-axis seems to be associated with a lower treatment outcome, which may affect extinction based learning. The findings suggest, that interoceptive stimuli should be designed carefully in order to be potent stressors.

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.

Acute high-intensity interval exercise is less pro-oxidative/thrombotic compared to isovolumic moderate-intensity steady-state exercise.

While high-intensity interval training (HIIT) has emerged as a more time-efficient alternative to moderate-intensity steady-state exercise (MISS), the impact on systemic free radical formation and link to activated coagulation remains unknown. We recruited sixteen healthy males aged 21 ± 3 y who performed incremental cycle ergometry to determine peak oxygen uptake ([Formula: see text] PEAK). Participants were randomly assigned single blind to two separate groups (MISS: n = 8; HIIT: n = 8) matched for [Formula: see text] PEAK. HIIT participants completed five exercise cycles, each consisting of 3min at 80%[Formula: see text] PEAK alternating with 3min at 40% [Formula: see text] PEAK, whereas MISS participants performed an isovolumic bout of 30min at 60% [Formula: see text] PEAK. Cephalic venous blood was assayed for ascorbate free radical (A•-, electron paramagnetic resonance spectroscopy) and clot fractal dimension (df, rheometry) at rest every hour over a 6-h period to determine critical difference (CD) and before/after submaximal/peak exercise. Submaximal MISS increased A• - and df to a greater extent compared to HIIT (P = 0.039 to 0.057) although elevations generally fell within CD boundaries (54.2% and 5.5% respectively). No further elevations were observed during peak exercise (P = 0.508 to 0.827) and no relationships were observed between A•- and df (r = 0.435 to - 0.121, P = 0.092 to 0.655). Collectively, these findings suggest that HIIT is less pro-oxidative/thrombotic compared to more traditional MISS, advocating its prescription in patients given the potential for superior vascular adaptive benefit.

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.

Efficacy of 12weeks oral beta-alanine supplementation in patients with chronic obstructive pulmonary disease: a double-blind, randomized, placebo-controlled trial.

BackgroundBeta‐alanine (BA) supplementation increases muscle carnosine, an abundant endogenous antioxidant and pH buffer in skeletal muscle. Carnosine loading promotes exercise capacity in healthy older adults. As patients with chronic obstructive pulmonary disease (COPD) suffer from elevated exercise‐induced muscle oxidative/carbonyl stress and acidosis, and from reduced muscle carnosine stores, it was investigated whether BA supplementation augments muscle carnosine and induces beneficial changes in exercise capacity, quadriceps function, and muscle oxidative/carbonyl stress in patients with COPD.MethodsIn this double‐blind, randomized, placebo (PL)‐controlled trial (clinicaltrials.gov identifier: NCT02770417), 40 patients (75% male) with COPD (mean ± standard deviation: age 65 ± 6 years; FEV1% predicted 55 ± 14%) were assigned to 12 weeks oral BA or PL supplementation (3.2 g/day). The primary outcome, i.e. muscle carnosine, was quantified from m. vastus lateralis biopsies obtained before and after intervention. Co‐primary outcomes, i.e. incremental and constant work rate cycle capacity, were also assessed. Linear mixed model analyses were performed. Compliance with and side effects of supplement intake and secondary outcomes (quadriceps strength and endurance, and muscle oxidative/carbonyl stress) were also assessed.ResultsBeta‐alanine supplementation increased muscle carnosine in comparison with PL in patients with COPD (mean difference [95% confidence interval]; +2.82 [1.49–4.14] mmol/kg wet weight; P < 0.001). Maximal incremental cycling capacity (VO2peak: +0.5 [−0.7 to 1.7] mL/kg/min; P = 0.384, Wpeak: +5 [−1 to 11] W; P = 0.103) and time to exhaustion on the constant work rate cycle test (+28 [−179 to 236] s; P = 0.782) did not change significantly. Compliance with supplement intake was similar in BA (median (quartile 1–quartile 3); 100 (98–100)%) and PL (98 (96–100)%) (P = 0.294) groups, and patients did not report side effects possibly related to supplement intake. No change was observed in secondary outcomes.ConclusionsBeta‐alanine supplementation is efficacious in augmenting muscle carnosine (+54% from mean baseline value) without side effects in patients with COPD in comparison with PL. However, accompanied beneficial changes in exercise capacity, quadriceps function, and muscle oxidative/carbonyl stress were not observed.

Effect of caffeine intake on fat oxidation rate during exercise: is there a dose-response effect?

The effect of caffeine to enhance fat utilisation as fuel for submaximal aerobic exercise is well established. However, it is unknown whether this effect is dose dependent. The aim of this study was to investigate the effect of 3 and 6mg of caffeine per kg of body mass (mg/kg) on whole-body substrate oxidation during an incremental cycling exercise test. In a double-blind, randomised, and counterbalanced experiment, 18 recreationally active males (maximal oxygen uptake [VO2max] = 56.7 ± 8.2mL/kg/min) performed three experimental trials after ingesting either 3mg/kg of caffeine, 6mg/kg of caffeine or a placebo (cellulose). The trials consisted of an incremental exercise test on a cycle ergometer with 3-min stages at workloads from 30 to 80% of VO2max. Energy expenditure, fat oxidation rate, and carbohydrate oxidation rate were continuously measured by indirect calorimetry. During exercise, there was significant effect of substance (F = 7.969; P = 0.004) on fat oxidation rate. In comparison to the placebo, the rate of fat oxidation was higher with 3mg/kg of caffeine at 30, 40, 50 and 70% of VO2max [all P < 0.050, effect sizes (ES) from 0.38 to 0.50] and with 6mg/kg of caffeine at 30, 40, 50, 60 and 70% of VO2max (all P < 0.050, ES from 0.28 to 0.76). Both 3mg/kg (0.40 ± 0.21g/min, P = 0.021, ES = 0.57) and 6mg/kg of caffeine (0.40 ± 0.17g/min P = 0.001, ES = 0.60) increased the maximal rate of fat oxidation during exercise over the placebo (0.31 ± 0.15g/min). None of the caffeine doses produced any significant effect on energy expenditure or heart rate during exercise, while both caffeine doses reduced perceived fatigue at 80% of VO2max (all P < 0.050, ES from 0.71 to 1.48). The effect of caffeine to enhance fat oxidation during submaximal aerobic exercise is of similar magnitude with 3 and 6mg of caffeine per kg of body mass. Thus, a dose of 3mg of caffeine per kg of body mass would be sufficient to enhance fat utilisation as fuel during submaximal exercise.

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.

Neuromuscular Fatigue Responses of Endurance- and Strength-Trained Athletes during Incremental Cycling Exercise.

This study explored the development of neuromuscular fatigue responses during progressive cycling exercise. The sample comprised 32 participants aged 22.0 ± 0.54 years who were assigned into three groups: endurance-trained group (END, triathletes, n = 10), strength-trained group (STR, bodybuilders, n = 10) and control group (CG, recreationally active students, n = 12). The incremental cycling exercise was performed using a progressive protocol starting with a 3 min resting measurement and then 50 W workload with subsequent constant increments of 50 W every 3 min until 200 W. Surface electromyography (SEMG) of rectus femoris muscles was recorded during the final 30 s of each of the four workloads. During the final 15 s of each workload, participants rated their overall perception of effort using the 20-point rating of the perceived exertion (RPE) scale. Post hoc Tukey’s HSD testing showed significant differences between the END and STR groups in median frequency and mean power frequency across all workloads (p < 0.001 and p < 0.01, respectively). Athletes from the END group had significantly lower electromyogram amplitude responses than those from the STR (p = 0.0093) and CG groups (p = 0.0006). Increasing RPE points from 50 to 200 W were significantly higher in the STR than in the END group (p < 0.001). In conclusion, there is a significant variation in the neuromuscular fatigue profiles between athletes with different training backgrounds when a cycling exercise is applied. The approximately linear trends of the SEMG and RPE values of both groups of athletes with increasing workload support the increased skeletal muscle recruitment with perceived exertion or fatiguing effect.

Effect of incremental intensities on the spinal morphology and core muscle activation in competitive cyclists

ABSTRACT Cycling is a sport where cyclists predominantly adopt a sitting posture, with the trunk tilted forward. This posture requires a high volume of training and duration in several intensities of effort. This study aims to: 1) evaluate the behaviour of the thoracic and lumbar spine flexion and sacral inclination in the sagittal plane, the thoracic and lumbar spine flexion in the frontal plane, and the trunk torsion in the transverse plane; 2) compare the activation of the core muscles as the intensity of effort increases during an incremental test in cycling, and 3) identify which core muscle has a greater activation in each intensity zone. The spinal posture and the activation of the eight core muscles were evaluated in twelve competitive cyclists during incremental cycling intensities. Thoracic and lumbar spine flexion and sacral inclination statistically increased as the intensity of effort increased (Start < VT1 < VT2 < VO2max). A significant increase in muscle activation was observed in all core muscles evaluated as the intensity increased. The rectus abdominis showed statistically significant greater muscle activation than the other core muscles evaluated. In conclusion, as the intensity of effort in cycling increases, cyclists significantly increase the thoracic and lumbar spine flexion, the sacral inclination in the sagittal plane, the thoracic and lumbar spine flexion in the frontal plane, trunk rotation in the transverse plane, as well as the activation of the core muscles.

Experimental study on deformational resilience of longitudinal joint in shield tunnel lining

Resilience is a functional attribute of shield tunnels to ensure continued serviceability. From the performance-based perspective, the concept of deformational resilience is proposed and defined as the ability to resist deformation development (robustness) and the ability to recover from pre-existing deformation (recoverability). This work aims to measure the deformational resilience of shield tunnel lining structure, targeting at its most vulnerable part—longitudinal joint. For this purpose, a series of full-scale tests are carried out to perform 1) the failure process to simulate external surcharge loads, 2) the recovery process to simulate the effects of unloading and tunnel bilateral soil grouting, and 3) the cyclic loading process to simulate incremental cycling loading and unloading conditions. The assessment of deformational resilience is based on joint opening from the tests and related structural energy analysis. The test results demonstrate that the capability of tunnel longitudinal joint to resist deformation deteriorates with increasing overload level, and the recovery efficiency of joint opening presents nonlinear degradation with the increase of pre-existing deformation. The deformational resilience of longitudinal joint revealed in this research can facilitate the selection of appropriate timing and optimal design of technical parameters related to recovery measures for over-deformed shield tunnels.

Marked improvements in cardiac function in postmenopausal women exposed to blood withdrawal plus endurance training

ABSTRACT The cardiac phenotype of a substantial fraction of the population, i.e., mature women, is mainly unresponsive to endurance training (ET), the most effective intervention to improve cardiorespiratory fitness. This study assessed whether a novel intervention comprising additional haemodynamic stimuli may overcome the generalized limitations to modify the cardiac phenotype of middle-aged and older women. Fifteen healthy postmenopausal women (52–75 yr) were recruited. Transthoracic echocardiography and central haemodynamics were assessed during incremental cycle ergometry (i) in baseline conditions, (ii) after standard (10%) blood withdrawal and (iii) subsequent 8-week ET. Main outcomes such as left ventricular (LV) function and structure and blood volume (BV) were determined. Phlebotomy induced a 0.5 ± 0.1 l reduction of BV, which was re-established after ET. Decrements in LV end-systolic volume (−27%) and increments in LV ejection fraction (+8%) during exercise as well as improved E/A ratio were detected after ET compared with baseline. In parallel, ET induced a 10% increment in LV mass without a concomitant increase in LV size. In conclusion, postmenopausal women exhibit large improvements in cardiac systolic and diastolic functions along with LV concentric remodelling in response to the sequenced combination of blood withdrawal and ET.

Performance fatigability and recovery after dynamic multi-joint maximal exercise in elbow flexors versus knee extensors.

Elbow flexors (EFs) and knee extensors (KEs) have shown differences in performance fatigability and recovery of neuromuscular function after isometric and isotonic single-joint fatiguing contractions. However, dynamic multi-joint movements are more representative of real-world activities. The aim of the study was to assess central and peripheral mechanisms of fatigability after either arm-cranking or cycling. Ten physically active men performed maximal incremental arm-cranking and cycling until task failure. Maximal voluntary isometric contraction (MVIC) and electrically evoked forces of both EF and KE were assessed before (PRE) and 1 (POST) and 20 (POST20) min after exercise. At POST, MVIC decreased similarly to 76 ± 8% and 81 ± 7% (both P < 0.001) of PRE for EF and KE, respectively. MVIC force remained lower than PRE at POST20 for both EF and KE (85 ± 8% vs. 95 ± 3% of PRE, P ≤ 0.033), having recovered less in EF than in KE (P = 0.003). Electrically evoked forces decreased similarly from PRE to POST in EF and KE (all P > 0.05). At POST20, the ratio of low-to-high frequency doublets was lower in EF than in KE (75 ± 13% vs. 85 ± 10% of PRE; P ≤ 0.034). Dynamic maximal incremental exercise acutely induced similar magnitudes of MVIC and evoked force loss in EF and KE. However, at POST20, impaired MVIC recovery and lower ratio of low-to-high frequency doublets in EF than in KE suggest the recovery of neuromuscular function after dynamic maximal exercises is specific to and dependent on changes within the muscles investigated.

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.

Associations of resting and peak fat oxidation with sex hormone profile and blood glucose control in middle-aged women

Background and aimsMenopause may reduce fat oxidation. We investigated whether sex hormone profile explains resting fat oxidation (RFO) or peak fat oxidation (PFO) during incremental cycling in middle-aged women. Secondarily, we studied associations of RFO and PFO with glucose regulation. Method and resultsWe measured RFO and PFO of 42 women (age 52–58 years) with indirect calorimetry. Seven participants were pre- or perimenopausal, 26 were postmenopausal, and nine were postmenopausal hormone therapy users. Serum estradiol (E2), follicle-stimulating hormone, progesterone, and testosterone levels were quantified with immunoassays. Insulin sensitivity (Matsuda index) and glucose tolerance (area under the curve) were determined by glucose tolerance testing. Body composition was assessed with dual-energy X-ray absorptiometry; physical activity with self-report and accelerometry; and diet, with food diaries. Menopausal status or sex hormone levels were not associated with the fat oxidation outcomes. RFO determinants were fat mass (β = 0.44, P = 0.006) and preceding energy intake (β = −0.40, P = 0.019). Cardiorespiratory fitness (β = 0.59, P = 0.002), lean mass (β = 0.49, P = 0.002) and physical activity (self-reported β = 0.37, P = 0.020; accelerometer-measured β = 0.35, P = 0.024) explained PFO. RFO and PFO were not related to insulin sensitivity. Higher RFO was associated with poorer glucose tolerance (β = 0.52, P = 0.002). ConclusionAmong studied middle-aged women, sex hormone profile did not explain RFO or PFO, and higher fat oxidation capacity did not indicate better glucose control.

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.