Increasing Exercise Intensity Research Articles

Monitoring skeletal muscle oxygen saturation kinetics during graded exercise testing in NCAA division I female rowers.

The purpose of this study was to analyze changes in skeletal muscle oxygen saturation (SmO2) kinetics during exercise in female rowers both acutely and longitudinally in relation to blood lactate (BLa). We also aimed to determine the agreement and statistical equivalence between physiological thresholds derived from SmO2 and BLa kinetics. Twenty-three female NCAA Division I rowers were tested throughout the 2023-2024 academic year. Of these, 11 athletes completed at least two near-infrared spectroscopy (NIRS)-equipped GXTs, with physiological data analyzed for longitudinal changes. A 7x4-min discontinuous GXT protocol was performed by all athletes. First and second SmO2 breakpoints (SmO2BP1 and SmO2BP2) were estimated via piecewise linear regression modeling, and BLa thresholds (LT1 and LT2) were calculated using ADAPT software. Paired-samples t-tests assessed differences, and equivalence was tested using two one-sided tests (TOST). Agreement was determined using Bland-Altman analysis yielding mean differences (MD) and 95% limits of agreement (LoA). Intraclass correlation coefficients (ICC2,1) were also calculated. No difference was found between SmO2BP2 and LT2 (MD = -5.76W [95% LoA = -38.52 to 22.25W], p = 0.134), moderate-to-good levels of agreement (ICC2,1 = 0.67 [95% CI: 0.36-0.85], p < 0.001), and no statistical equivalence (p = 0.117). This was not the case for SmO2BP1 and LT1, with NIRS significantly underestimating LT1 (MD = -8.14W [95% LoA = -38.90 to 27.37W], p = 0.026), poor-to-moderate agreement (ICC2,1 = 0.24 [95% CI: -0.13-0.58], p = 0.10), and no statistical equivalence (p = 0.487). Additionally, SmO2 recovery kinetics (SmO2resat) during 1-min rest intervals increased in response to graded increases in exercise intensity (p < 0.001, η2 p = 0.71), with higher intensities appearing to blunt this effect (step 6 - step 7: MD = -0.16%⋅s-1, p = 0.69). No statistically significant changes were observed in LT's or SmO2BP's throughout the 2023-2024 season. In female collegiate rowers, NIRS may be a tool that compliments BLa testing when determining the second lactate threshold (i.e., LT2). However, significant inter-individual variablility exists between SmO2BP2 and LT2 paired with a lack of statistical equivalence suggest the two are not interchangeable. While not a standalone replacement, if used in combination with traditional BLa testing methods NIRS may be a complimentary tool that helps inform individual athlete training zone prescription.

Validity of heart rate measurements in wrist-based monitors across skin tones during exercise.

To evaluate the accuracy of a wrist-based heart rate (HR) monitor at different exercise intensities across different skin tones. Using a cross-sectional design, we compared HR measures from the wrist-based photoplethysmography Fitbit Charge 5 to the Polar H10 chest strap at rest and during the YMCA Protocol using a recumbent cycle ergometer. Participant were grouped into three skin tone categories: light (Fitzpatrick Scale Skin Types 1+2), medium (Types 3+4), and darker skin tone (Types 5+6). HR measures using the Polar chest strap during the exercise test were categorized as <40%, 40-60%, or >60% HR reserve (HRR). Absolute error in beats per minute (bpm) between the two devices was calculated for each measure. A linear mixed effects model was used to assess interaction effects between skin tone and exercise intensity, with participants as the random effect. Bland-Altman plots were used for visual analyses. Twenty-five participants [mean (SD): 25.8 (1.9) years old; 64% female] were included with 495 observations of simultaneous Fitbit and Polar HR recordings collected during exercise. During exercise, we observed a statistically significant interaction effect between skin tone and exercise intensity. Compared with light skin tone at <40% HRR, mean error was greater for medium skin tone at >60% HRR [mean error (95%CI): 11.8 (5.6-17.9) bpm, p<0.001] and darker skin tone at 40-60% HRR [7.6 (1.7-13.5) bpm, p = 0.011] and >60% HRR [11.7 (5.3-18.0) bpm, p<0.001]. HR measurement error using a wrist-based device was greater with increasing exercise intensity for people with darker skin tones.

Steady Moderate Exercise Confers Resilience Against Neurodegeneration and Neuroinflammation in a Mouse Model of Parkinson's Disease.

Intensive aerobic exercise slows the progression of movement disorders in Parkinson's disease (PD) and is therefore recommended as an important component of treatment for PD patients. Studies in animal models of PD have shown that vigorous exercise has neuroprotective effects, and emerging evidence suggests that it may be a disease-modifying treatment in humans. However, many people with PD may not be able to participate in vigorous exercise because of multiple medical conditions that severely limit their physical activity. In this study, we have shown that chronic MPTP treatment in sedentary mice resulted in loss of dopaminergic neurons in the SNpc, decreased levels of neurotrophins, BDNF and GDNF, and increased levels of inflammatory markers and pro-inflammatory changes in immunocompetent cells. Moderate exercise, initiated both before and after chronic MPTP treatment, significantly attenuated the loss of dopaminergic neurons and increased BDNF and GDNF levels even above those in sedentary control mice. No signs of inflammation were observed in MPTP-treated mice, either when training began before or after MPTP treatment. Training induced beneficial changes in the dopaminergic system, increased levels of neurotrophins and suppression of inflammation were similar for both steady moderate (present data) and intense training (our previously published data). This suggests that there is a kind of saturation when the percentage of rescued dopaminergic neurons reaches the highest possible value, and therefore further increases in exercise intensity do not enhance neuroprotection. In conclusion, our present results compared with the previous data show that increasing exercise intensity beyond the level used in this study does not increase the neuroprotective effect of aerobic training in a mouse model of Parkinson's disease.

Acute Effects of Passive Stretching with and Without Vibration on Hip Range of Motion, Temperature, and Stiffness Parameters in Male Elite Athletes.

Objectives: Increasing exercise intensity and performance output with superimposed vibration gains interest, especially in high-performance training. However, the additional benefit of vibration in passive stretching exercises and its mechanisms remain unclarified. Methods: Passive stretching with (ST+V) and without (ST) vibration (20 Hz) was performed in male Olympic youth skiing athletes (n = 8, age: 17.9 ± 1.0 years) using a single-blinded randomized cross-over design. Acute hip abduction, hip anteversion, knee extension, and hamstrings (stand and reach straight leg raise) range of motion (ROM) were assessed using a digital goniometer, while stiffness was examined via MyotonPRO. The skin temperature of the whole leg was captured with infrared thermography and analyzed in different segments. Results: Both stretching interventions increased ROM compared to the control group (CG) (p < 0.001-0.033, d = 1.0-1.6) without differences between ST+V and ST (p = 0.202-0.999). While skin temperature decreased in the CG and ST, ST+V maintained a constant temperature in the lower legs. Stiffness was not affected by both stretching interventions. Conclusions: The stretching intervention leads to significant increases in flexibility, while additional vibration did not further enhance the ROM.

Habitual preexercise caffeine supplementation prevents exercise training-induced attenuation of exercising systolic blood pressure and double product.

We examined the effect of habitual preexercise caffeine supplementation on training-induced adaptations to exercising systolic blood pressure (SBP), diastolic blood pressure (DBP), pulse pressure (PP), heart rate (HR), and double product (DP). Young women (means ± SD; 24 ± 7 yr) were randomized to a caffeine (120 mg) supplement (CAF; n = 17) or placebo (PLA; n = 16) group, completed 6 wk of high-intensity exercise training on three nonconsecutive days per week, and supplemented with CAF or PLA 30-60 min before exercise or else upon waking. Before (PRE) and after (POST) the intervention, SBP, DBP, and HR were measured and PP and DP were calculated, at rest and during fixed-power exercise at 50 and 75 W. Statistical analyses included three-way mixed-factorial ANOVAs with post hoc comparisons as necessary. Group × intensity × time interactions were observed for SBP (P = 0.0105) and DP (P = 0.003). SBP and DP increased with increasing exercise intensity at PRE and POST in both groups. However, although SBP and DP decreased PRE to POST at 50 and 75 W in PLA, SBP and DP did not change at any intensity from PRE to POST in CAF. An intensity × time interaction was observed for DBP (P = 0.006) indicating no change in resting DBP, but reductions from PRE to POST at 50 and 75 W that were independent of group. Main effects of intensity (P < 0.0001) and time (P = 0.03) were observed for HR, and a main effect of intensity was observed for PP (P < 0.0001). Habitual caffeine supplementation blunted training-induced reductions in exercising SBP and DP. Individuals may wish to avoid preexercise supplementation if seeking to maximize the BP-lowering benefits of exercise.NEW & NOTEWORTHY Habitual preexercise caffeine consumption prevented reductions in exercising systolic blood pressure and double product induced by 6 wk of high-intensity exercise in women. Therefore, our findings indicate that habitual preexercise caffeine supplementation may impede beneficial hemodynamic adaptations of exercise training in healthy, young women.

The association between stent design and patient exercise intensity: structural coupling effects and hemodynamic analysis.

In-stent restenosis remains a significant challenge in coronary artery interventions. This study aims to explore the relationship between exercise intensity and stent design, focusing on the coupled response of the stent structure and hemodynamics at different exercise intensities. A coupled balloon-stent-plaque-artery model and a fluid domain model reflecting structural deformation were developed to investigate the interaction between coronary stents and stenotic vessels, as well as their impact on hemodynamics. The study examines the influence of stent connectors on the mechanical response of both the plaque and the coronary artery, with hemodynamic analyses conducted under three exercise intensities: rest, moderate exertion, and maximal exertion. The model effectively simulates the gradual expansion of the stent, plaque, and artery, as well as the recoil behavior post-expansion. The gradual adaptation of the stent to the plaque during the initial expansion phase helps mitigate the adverse effects of the dog-boning phenomenon. Areas of low time-averaged wall shear stress (TAWSS) and high relative residence time (RRT) are observed at both ends and near the stent, with a general decreasing trend as exercise intensity increases. Additionally, the study quantifies the changes in hemodynamic characteristics across different physiological states. Specifically, the areas of low TAWSS and high RRT are significantly reduced during moderate exertion, with no further substantial reduction observed at maximal exertion. These findings provide valuable insights for the design of stent connectors and offer guidance on optimal exercise intensity for patients undergoing stent interventions. Future research, combining dynamic vascular wall deformation and advanced imaging techniques, could lead to more precise and effective stent designs tailored to individual patients.

Development of an active-control foot press trainer and comparison of lower limb muscle activity by exercise type and intensity

Background Addressing lower limb disabilities in stroke survivors is crucial for enhancing gait patterns and overall mobility. Objective This study aimed to develop an active-control foot press trainer (AFPT) to strengthen lower extremity muscles to improve rehabilitation outcomes. Methods This study utilized AFPT to examine the effects of different exercise types (forefoot exercise, FFE; Rearfoot Exercise, RFE) and intensities (30 and 15 repetition maxima) on lower limb muscle activity. Ten healthy women participated in the evaluation of muscle activation during ankle exercises in the standing position. Results The FFE primarily activated the Tibialis Anterior (TA), Gastrocnemius Medialis (GM), and Gastrocnemius Lateralis (GL), whereas the RFE engaged the Rectus Femoris (RF). Increased exercise intensity led to higher activity in the GM and GL in the FFE and TA in the RFE, indicating the potential for tailored exercise protocols. Conclusions AFPT is a valuable tool for personalized rehabilitation, allowing variable exercise methods and intensities. Further research is needed to assess the efficacy of AFPT in a broader population, including stroke survivors. Moreover, enhancing AFPT technology and developing diverse training programs are crucial as these advancements will significantly support the rehabilitation of individuals requiring lower limb and gait training, including stroke survivors.

Exercise cardiovascular magnetic resonance shows improved diastolic filling by atrioventricular area difference in athletes and controls.

Hydraulic force, a novel mechanism shown to aid diastolic filling, can be calculated by assessing the geometrical relationship between the left ventricular and atrial short-axis areas (atrioventricular area difference, AVAD) (Maksuti E, Carlsson M, Arheden H, Kovács SJ, Broomé M, Ugander M. Sci Rep 7: 43505-43510, 2017; Steding-Ehrenborg K, Hedström E, Carlsson M, Maksuti E, Broomé M, Ugander M, Magnusson M, Smith JG, Arheden H. J Appl Physiol (1985) 130: 993-1000, 2021). During exercise both ventricular and atrial volumes change due to altered loading conditions compared with rest, but it is unknown to what extent this affects AVAD. The aim of this study was to investigate whether AVAD differs when going from rest to exercise in sedentary controls and athletes. We included 13 sedentary controls and 20 endurance athletes to undergo cardiovascular magnetic resonance (CMR) imaging at rest and during moderate and vigorous exercise using a CMR-compatible ergometer. AVAD was calculated as the largest ventricular short-axis area minus the largest atrial short-axis area in end-diastole (ED) and end-systole (ES) as measured from CMR short-axis images. AVAD in ED increased during moderate exercise in both sedentary controls and athletes, thus aiding diastolic filling, but did not increase further during vigorous exercise. AVAD in ES was negative in both groups at rest and decreased further with increasing exercise intensity in sedentary controls, whereas athletes remained unchanged. In conclusion, results from AVAD in ED indicate the net hydraulic force to further augment diastolic filling during moderate exercise when compared with rest, providing new insights into the mechanism by which diastolic function increases during exercise.NEW & NOTEWORTHY This study is the first to assess hydraulic force during exercise, a novel mechanism shown to augment diastolic filling at rest. Our results indicate hydraulic force to further aid in diastolic filling during moderate exercise compared with rest in athletes and sedentary controls, providing new insights into the mechanism by which the left ventricle increases diastolic function during exercise.

Carbohydrate storage in cells: a laboratory activity for the assessment of glycogen stores in biological tissues.

Carbohydrates and fats constitute our primary energy sources. The importance of each of these energy substrates varies across cell types and physiological conditions. For example, the brain normally relies almost exclusively on glucose oxidation, whereas skeletal muscle shifts from lipids toward higher carbohydrate oxidation rates as exercise intensity increases. Understanding how carbohydrates are stored in our cells and which tissues contain significant carbohydrate stores is crucial for health professionals, especially given the role of carbohydrate metabolism in various pathophysiological conditions. This laboratory activity uses a simple and low-cost iodine binding method to quantify glycogen in mouse skeletal muscle and liver samples. By integrating the results of this activity with literature data, students can determine overall glycogen storage in the human body. The primary goal of the activity is to enhance students' understanding of the importance and limitations of glycogen stores in energy metabolism.NEW & NOTEWORTHY Carbohydrates are one of the primary energy sources utilized by our cells. Liver and skeletal muscle glycogen, which are the main carbohydrate reserves in the body, play a central role in energy metabolism, especially during periods of fasting and exercise. In this laboratory activity, students measure glycogen levels in tissues to gain insights into how carbohydrates are stored in our cells and understand the role and limitations of liver and muscle carbohydrate stores.

Unraveling the role of exercise in cancer suppression: insights from a mathematical model

Recent experimental studies have shown that physical exercise has the potential to suppress tumor progression. Such suppression has been reported to be mediated by the exercise-induced activation of natural killer (NK) cells through the release of IL-6, a cytokine. Aimed at shedding light on how exercise-induced NK cell activation helps in the suppression of cancer, we developed a coarse-grained mathematical model based on a system of ordinary differential equations describing the interaction between IL-6, NK-cells, and tumor cells. The model is then used to study how exercise duration and exercise intensity affect tumor suppression. Our results show that increasing exercise intensity or increasing exercise duration leads to greater and sustained tumor suppression. Furthermore, multi-bout exercise patterns hold promise for improving cancer treatment strategies by adjusting exercise intensity and frequency. Thus, the proposed mathematical model provides insights into the role of exercise in tumor suppression and can be instrumental in guiding future experimental studies, potentially leading to more effective exercise interventions.

Evidence that mitral and/or tricuspid regurgitation diminishes stroke volume increase during exercise

Abstract Background and Purpose The severity of heart failure can be evaluated by peak oxygen consumption (VO2). Cardiac output is one of the major essential factors to determine the VO2. Therefore, cardiac output increases linearly as the exercise intensity increases. However, in mitral regurgitation, effective stroke volume decreases due to some blood flowing back into the left atrium from the left ventricle. This reduction may compromise oxygen delivery to working muscles and diminish oxygen uptake. Peak VO2/HR is known to indicate the stroke volume at the peak exercise, but since c(A-V)O2 difference shows almost a similar change pattern during a ramp protocol, VO2/HR during the load is also reported to be an indicator of stroke volume (SV) at that work rate. However, there are no investigations that have examined the extent to which the increase in cardiac output during stress is affected by the severity of mitral regurgitation. Therefore, we investigated the influence of the degree of regurgitant volume in mitral regurgitation (MR) and tricuspid regurgitation (TR) affects the SV increasing response to exercise load. Additionally, we examined whether blunted SV increase influences on the peak VO2. Methods Among 525 patients who underwent cardiopulmonary exercise test (CPX) at our institution from January 2023 to October 2023, 518 patients (143 females, 375 males, mean age 65.2±15.0 years old) where precise analyses of CPX was possible. CPX was performed using breath-by-breath gas analysis, and an incremental load test (10watts/min) was administered until exhaustion. The rate of increase in VO2/HR per watt during an incremental loading (Δ(VO2/HR)/ΔWR) was used as an indicator of the degree of increase in SV. Typically, SV increases up to 60% of maximum load, around AT, after which it stops increasing and plateaus. Therefore, the slope of Δ(VO2/HR)/ΔWR was examined from the initiation of ramp loading to AT. The degree of reflux was evaluated by echocardiography and classified as none/trivial, mild and moderate/severe. The number of people in each group of None/trivial, mild, moderate/severe was, 392, 83, 30 for MR, and 416, 64, 24 for TR. Δ(VO2/HR)/ΔWR was evaluated for each degree of reflux, using ANOVA to determine whether there was a difference between groups. Results As shown in the Figure1, Δ(VO2/HR)/ΔWR decreased as the reflux flow rate increased for both MR and TR. Concurrently, peak VO2 also decreased in the moderate/severe group compared to the non/trivial-reflux group for both MR and TR (MR: 17.5±5.4 mL/min/kg vs. 14.9±3.5 mL/min/kg, TR: 17.2±5.3 mL/min/kg vs. 13.6±3.8 mL/min/kg). Conclusion The Δ(VO2/HR)/ΔWR obtained through CPX has been shown to be an index that can evaluate the severity of reflux. Additionally, it was also demonstrated that as regurgitation flow increased, true stroke volume decreases, which is correlated with a reduction in peak VO2.

The Rate of Leg Fat Oxidation Is Not Attenuated During Incremental Intensity One-Leg Knee Extensor Exercise.

It is not clear if fat oxidation is attenuated at higher exercise intensities, when exercising with a small muscle mass, and therefore, we studied leg fat oxidation during graded one-leg exercise. Ten males (age: 27 ± 2 years, body mass: 82 ± 3 kg, BMI: 24 ± 1 kg m-2, V̇O2max: 49 ± 2 mL min-1 kg-1) performed one-leg exercise at 25% of maximal workload (Wmax) for 30 min, followed by 120-min exercise at 55% Wmax with the contralateral leg, and finally 30-min exercise at 85% Wmax with the first leg. Blood was sampled from an artery and both femoral veins, and blood flow was determined using Doppler ultrasound. Muscle biopsies were obtained before and after 30 min at each workload. One-way RM ANOVA was applied to determine the impact of exercise intensity. Data are expressed as mean ± SEM. From rest through exercise average blood flow (0.4 ± 0.1, 2.1 ± 0.1, 2.6 ± 0.2, 3.7 ± 0.2 L min-1) and oxygen uptake across the leg (0.03 ± 0.01, 0.23 ± 0.02, 0.35 ± 0.03, 0.53 ± 0.04 L min-1) increased with exercise intensity (p < 0.001). Leg RQ (0.76 ± 0.04, 0.86 ± 0.02,0.87 ± 0.01, 0.92 ± 0.01, p < 0.001), leg plasma FA uptake (2 ± 2, 46 ± 8,83 ± 9, 114 ± 16 μmol min-1; p < 0.001) and rate of leg fat oxidation (0.016 ± 0.005, 0.062 ± 0.012, 0.075 ± 0.011, 0.084 ± 0.018 g min-1, p < 0.007) increased with exercise intensity. Muscle-free carnitine content was unchanged from rest at 25% Wmax and decreased after 30 min exercise at 55% and 85% Wmax (17.4 ± 1.6, 16.6 ± 0.7, 14.5 ± 1.2, 10.5 ± 1.0 mmol/kg dry muscle, respectively; p < 0.006). During incremental one-leg exercise, the rate of leg fat oxidation was not attenuated with increasing exercise intensity, probably due to an insufficient muscle metabolic stress response.

Effect of exercise intensity on growth performance, serum biochemistry parameters, liver antioxidant capacity, and intestinal health of common carp (Cyprinus carpio) in recirculating aquaculture system

Effect of exercise intensity on growth performance, serum biochemistry parameters, liver antioxidant capacity, and intestinal health of common carp (Cyprinus carpio) in recirculating aquaculture system

Breathing variability during running in athletes: The role of sex, exercise intensity and breathing reserve

Breathing variability during running in athletes: The role of sex, exercise intensity and breathing reserve

Combined Impact of Heart Rate Sensor Placements with Respiratory Rate and Minute Ventilation on Oxygen Uptake Prediction.

Oxygen uptake (V˙O2) is an essential metric for evaluating cardiopulmonary health and athletic performance, which can barely be directly measured. Heart rate (HR) is a prominent physiological indicator correlated with V˙O2 and is often used for indirect V˙O2 prediction. This study investigates the impact of HR placement on V˙O2 prediction accuracy by analyzing HR data combined with the respiratory rate (RESP) and minute ventilation (V˙E) from three anatomical locations: the chest; arm; and wrist. Twenty-eight healthy adults participated in incremental and constant workload cycling tests at various intensities. Data on V˙O2, RESP, V˙E, and HR were collected and used to develop a neural network model for V˙O2 prediction. The influence of HR position on prediction accuracy was assessed via Bland-Altman plots, and model performance was evaluated by mean absolute error (MAE), coefficient of determination (R2), and mean absolute percentage error (MAPE). Our findings indicate that HR combined with RESP and V˙E (V˙O2HR+RESP+V˙E) produces the most accurate V˙O2 predictions (MAE: 165 mL/min, R2: 0.87, MAPE: 15.91%). Notably, as exercise intensity increases, the accuracy of V˙O2 prediction decreases, particularly within high-intensity exercise. The substitution of HR with different anatomical sites significantly impacts V˙O2 prediction accuracy, with wrist placement showing a more profound effect compared to arm placement. In conclusion, this study underscores the importance of considering HR placement in V˙O2 prediction models, with RESP and V˙E serving as effective compensatory factors. These findings contribute to refining indirect V˙O2 estimation methods, enhancing their predictive capabilities across different exercise intensities and anatomical placements.

(Invited) Wearable Flexible Microfluidic Biosensor for Sweat Monitoring

As we enter the post-pandemic era, our lives have certainly become more convenient than before, due to the advancement and elimination of technologies that became practical or widespread during the pandemic. Among these, technologies related to non-invasive bioinstrumentation, which can be used at an individual level to access one's own health information, have become increasingly important. Non-invasive bioinstrumentation can be broadly divided into the measurement of physical information (shape, activity and so on) and the measurement of chemical information, i.e. the components of the body. For example, facial shape is widely used for personal identification, while weight and energy expenditure related to activity are easily managed by smartphones. In contrast, chemical sensing, which is often difficult to sample and requires a wet environment for measurement, still requires breakthroughs to be used by individuals with the same ease as physical sensing.In the research field of non-invasive biomedical measurements, the technology is often developed in the form of wearable systems. Wearable microfluidic devices have been intensively studied for the measurement of body components. We focused on sweat, which contains a variety of biomarkers, and have developed a wearable microfluidic biosensing system that measures sweat components in real-time. Sweat is secreted from sweat glands on the skin of the entire body, making it easily accessible and less mentally demanding to collect. On the other hand, there are problems with sampling methods for reliable measurement, such as large fluctuations in the sweat rate and evaporation from the skin surface during secretion. We overcame this problem by using a wearable microfluidic device to transport the full amount of sweat from the sweat gland to a downstream biosensor by carrier flow, and developed a wristwatch biosensing system to monitor the constituents released as sweat independent of sweat rate.The wristwatch sweat sensor consists of a PDMS sweat sampling device, a biosensor, a fluid controller and a wireless control circuit with Bluetooth Low Energy and external analogue I/O. Communication with the mobile device is via Bluetooth Low Energy. Our method has the advantage that secretions are transported by dissolution in the carrier stream and can therefore be reliably monitored even at very low sweat levels. The pump is controlled by an microcontroller unit, so the flow rate can be controlled in real time according to the sweat rate and target substances, and the sensitivity can be improved at the expense of temporal resolution by running the pump intermittently, i.e. allowing secretions to accumulate in the carrier flow for a certain time before measurement.We monitored changes in sweat lactic acid in response to exercise load using an ergometer. The results showed an increase in sweat lactate with increasing exercise intensity, with a dependence on sweat rate. By measuring sweat at rest, we found that the lactate accumulated in the sweat glands and on the skin's surface were dissolved by the biosensor in the early stages of measurement, while the signals from the sweat glands became dominant after these had been sufficiently decreased. These results suggest that our system appropriately reflects the physiological phenomena associated with sweating. The presentation will also include the behaviour of lactic acid in sweat, which was detected by our system for the first time.

Effects of Different Exercise Intensities on the Rat Model of Heart Failure

Heart failure (HF) is a clinical syndrome caused by the progression of various cardiac diseases to severe stages, and exercise training plays a positive role in the development of HF. This study aimed to investigate the impact of different intensities of exercise training on HF rats.In this study, we established two HF rat models by intraperitoneal injection of isoproterenol at 2.5 mg/kg/day and abdominal aortic coarctation. After exercise training for 4 weeks, the heart weight/body weight ratio and echocardiography results were measured. Moreover, the regulatory effect of different exercise intensities on myocardial function in HF model rats was verified using tissue staining, western blotting, and reagent kits.Exercise training had a bidirectional adjust effect on HF. A running training program of 20 minutes/time had the most significant effect on improving myocardial function in HF rats, whereas exercise intensity of 40 minutes/time or 50 minutes/time did not significantly improve myocardial function in HF rats. Moreover, exercise intensities of 20 minutes/time and 30 minutes/time could reduce the expression levels of the HF markers NT-proBNP and BNP in rats, but the effect was more significant at a duration of 20 minutes/time. We also found that compared with other exercise intensities, 20 minutes/time exercise intensity could significantly improve myocardial fibrosis, promote cardiomyocyte autophagy, and reduce apoptosis in combating HF.Furthermore, an exercise intensity of 20 minutes/time can significantly ameliorate the progression of HF. However, the degree of significance of increasing exercise intensity in improving HF progression is weakened or has no significant effect.

Menstrual cycle disorders as an early symptom of energy deficiency among female physique athletes assessed using the Low Energy Availability in Females Questionnaire (LEAF-Q)

Physique competitions are weight-sensitive sports in which stage presentation, aesthetic appearance and posing ability of the athletes are judged rather than physical performance. The aim of this study was to assess low energy availability among female physique athletes by using the LEAF-Q. The study involved 104 females who were physique athletes. Monthly cycle disorders were reported in 58.65% of the women, that is periods stopped for three consecutive months or longer (amenorrhea). This situation occurred before the research was conducted in 43.27% of athletes and during the research in 15.38%. The physique athletes claimed that menstruation changes occurred when there was an increased exercise intensity, frequency or duration. Absence from training due to injury was reported by 27.88% of the women. The LEAF-Q identified 46.15% of the physique athletes as at risk (score ≥ 8) of low energy availability and the physiological consequences related to RED-S. Women who had menstrual cycle disorders were younger and did more training per week. Among women with menstrual disorders, cramps or stomach ache which cannot be related to menstruation occurred more frequently (p = 0.004). Absence from training or lack of participation in competition due to injuries occurred more frequently in the score ≥ 8 group (p = 0.024) thank the ≤ score 8 group. In the score ≥ 8 group menstruation changes, that is less bleeding or cessation of menstruation (p = 0.035), occurred more frequently when there was an increase in exercise intensity, frequency or duration (p = 0.002).

Selenoprotein P in a Rodent Model of Exercise; Theorizing Its Interaction with Brain Reward Dysregulation, Addictive Behavior, and Aging.

Exercise promotes health and wellness, including its operation as a protective factor against a variety of psychological, neurological, and chronic diseases. Selenium and its biomarker, selenoprotein P (SEPP1), have been implicated in health, including cancer prevention, neurological function, and dopamine signaling. SEPP1 blood serum levels were compared with a one-way ANOVA between sedentary (SED), moderately exercised (MOD) [10 m/min starting at 10 min, increasing to 60 min], and high-intensity interval training (HIIT) exercised rats [30 min in intervals of 2-min followed by a 1-min break, speed progressively increased from 10 to 21 m/min]. HIIT rats showed significantly higher serum SEPP1 concentrations compared to MOD and SED. More specifically, HIIT exercise showed an 84% increase in SEPP1 levels compared to sedentary controls. MOD rats had greater serum SEPP1 concentrations compared to SED, a 33% increase. The results indicated that increased exercise intensity increases SEPP1 levels. Exercise-induced increases in SEPP1 may indicate an adaptive response to the heightened oxidative stress. Previous studies found a significant increase in dopamine D2 receptor (D2R) binding in these same rats, suggesting a potential association between SEPP1 and dopamine signaling during exercise. Modulating antioxidants like SEPP1 through personalized therapies, including exercise, has broad implications for health, disease, and addiction.

Selective recruitment of the triceps surae muscles in plantar flexion assessed by diffusion weighted magnetic resonance imaging

Introduction: The triceps surae muscles, including medial and lateral gastrocnemius (MG, LG) and soleus (SOL), play a major role in supporting walking activities. Up to now, the potential selective recruitment of the muscles in walking of different intensities has not been investigated quantitatively. Such knowledge and its in vivo assessment would enable precise monitoring of subject’s performance in therapy. In this study, we measured apparent diffusion coeffcient (ADC) in the muscles of healthy subjects after plantar flexion of different intensities, and hypothesized that the different muscles would be selectively recruited in the exercises. Methods: 8 subjects were recruited. In a 3T MRI, subject performed straight-leg plantar flexion with load of 15 lbs for 3 minutes (moderate intensity), and the same exercise with load of 30 lbs until exhaustion (high intensity). Before and after each exercise, DWI of the right calf was performed: b values 0, 400 s/mm2, TE 70 ms, TR 4000 ms, 12 directions. In post-processing, ADC (unit: 10−6 mm2/s) was averaged for MG, LG and SOL. Results: In MG, ADC of 1580±12.3 before exercise increased to 1910±18.8 (p&lt;0.01) and 2010±13.5 (p&lt;0.01) after the moderate-and the high-intensity exercise, respectively. In LG, ADC of 1600±11.8 before exercise increased to 1900±14.8 (p&lt;0.01) after the moderate-intensity exercise, and stayed stable at 1940±27.8 (P=0.30) after the high-intensity one. In SOL, ADC remained stable after the moderate-intensity exercise (from 1660±80.2 to 1660±11.5, P=0.26), and significantly increased to 1790±25.1 (p&lt;0.01) after the high-intensity exercise. Discussion: The findings with MG and LG agree with expectation that muscle is more water-diffused with increased exercise intensity, and the association diminishes as exercise intensity increases. The higher ADC in MG than in LG at high intensity may be attributed to how the two heads attach to the Achilles tendon differently. The more linear attachment of MG to the tendon could enable higher effciency in achieving high torque. Attaching to tibia and fibula, SOL is not supposed to support straight-leg plantar flexion, as verified in its response after the moderate-intensity exercise. Surprisingly, SOL’s ADC increased after the high-intensity exercise. Besides the increased cardiac output as a possible cause, anatomical features of SOL may enable it to truly assist the exercise. First, similar to MG, SOL attaches to the Achilles tendon linearly, making its torque transfer effcient. Second, with more slow-twitch fibers than gastrocnemius, SOL’s activation is more economical in prolonged exercise. In conclusion, this study provided evidence that the triceps surae muscles are selectively recruited in straight-leg plantar flexion of different intensities, presumably to achieve maximal metabolic effciency. This work was supported by National NSF of China (#82171924, JLZ). No conflicts of interest, financial or otherwise, are declared by the authors. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.