Post-exercise Changes Research Articles

Post-exercise myofibrillar protein synthesis rates do not differ following 1.5 g essential amino acids compared to 15 and 20 g of whey protein in young females.

Optimal adaptation to resistance exercise requires maximal rates of myofibrillar protein synthesis (MyoPS), which can be achieved by postexercise consumption of >20 g of protein or ~2 g of the essential amino acid (EAA) leucine. These nutritional recommendations are based on studies in males. The aim of the present study was to compare the postexercise MyoPS response to nutrition in young females. Twenty-eight healthy, females (age: 28±8 y; BMI: 24±3 kg⋅m2) received a primed-continuous infusion of L-[ring-2H5]-phenylalanine and completed a bout of unilateral resistance exercise before ingesting a drink containing either 1.5 g EAA (n=10), 15 g (n=10) or 20 g (n=8) whey protein, containing 0.6, 1.5, and 2.0 g leucine, respectively. Blood and muscle samples were collected pre- and post-exercise and drink ingestion to assess MyoPS and gene expression. Drink ingestion increased plasma leucine concentrations following 15 and 20 g whey protein compared with 1.5 g EAA (P<0.0001). Exercise and drink ingestion increased basal (0.060±0.026, 0.063±0.034, 0.051±0.023%·h-1) MyoPS rates between 0-2 h to 0.117±0.028, 0.098±0.051 and 0.116±0.034%·h-1 (P<0.0001) and between 2-4 h to 0.110±0.028, 0.074±0.038, and 0.082±0.061%·h-1 (P=0.009) for 1.5, 15, and 20 g drinks, respectively, with no differences observed between drinks (P=0.416). The postexercise changes in muscle mRNA expression of genes involved in protein turnover, substrate utilization, remodeling and inflammation, did not differ between drinks (P>0.050). Post-exercise MyoPS did not differ following ingestion of 1.5, 15 and 20 g drinks, hence 0.6 g leucine may be sufficient to stimulate post-exercise MyoPS in young females.

Direct effects of remote ischemic preconditioning on post-exercise-induced changes in kynurenine metabolism.

Tryptophan (TRP) degradation through the kynurenine pathway is responsible for converting 95% of free TRP into kynurenines, which modulate skeletal muscle bioenergetics, immune and central nervous system activity. Therefore, changes in the kynurenines during exercise have been widely studied but not in the context of the effects of remote ischemic preconditioning (RIPC). In this study, we analyzed the effect of 14-day RIPC training on kynurenines and TRP in runners after running intervals of 20 × 400 m. In this study, 27 semi-professional long-distance runners were assigned to two groups: a RIPC group performing 14 days of RIPC training (n = 12), and a placebo group, SHAM (n = 15). Blood was collected for analysis before, immediately after, and at 6 h and 24 h after the run. After the 14-day RIPC/SHAM intervention, post hoc analysis showed a significantly lower concentration of XANA and kynurenic acid to kynurenine ratio (KYNA/KYN) in the RIPC group than in the SHAM group immediately after the running test. Conversely, the decrease in serum TRP levels was higher in the RIPC population. RIPC modulates post-exercise changes in XANA and TRP levels, which can affect brain health, yet further research is needed.

Acute impact of autoregulation of applied blood flow restriction pressures on bilateral single-joint upper limb resistance exercise

ABSTRACT To investigate the acute effects of 4 sets of autoregulated (AR-BFR) versus non-autoregulated (NAR-BFR) applied pressures during blood flow restriction (BFR) resistance exercise to volitional failure compared with low-load exercise without BFR. A randomized crossover design study was conducted on 32 healthy adults (20.8 ± 2.3 years; 11 females). Outcome measures were as follows: (1) arterial stiffness, (2) peak perceptual responses and likelihood to perform again, and (3) performance. Results: Post-exercise changes in central and brachial diastolic blood pressure were decreased in all groups. Post-exercise supine systolic blood pressure in no-BFR increased (mean difference (MD) = 4 ± 1 mmHg, 95% CI (1–7), p = 0.003, η2 = 0.13). Total repetitions performed and volume workload were similar between BFR conditions but less than no-BFR. AR-BFR reported significantly higher exertion (MD = 0.53 ± 0.2, 95% CI (0.04–1.0), p = 0.03, η2 = 0.19) than other conditions, and induced greater discomfort (MD = 2.50 ± 0.36, 95% CI (1.63–3.37), p < 0.001, η2 = 0.28) than no-BFR. Conclusion: Biceps curl exercise to volitional failure appears to induce negligible arterial stiffness or blood pressure changes regardless of the application of autoregulation, yet autoregulation appears to enhance the perceptual response to BFR exercise compared to NAR-BFR without impacting exercise performance.

Submaximal Verification Test to Exhaustion Confirms Maximal Oxygen Uptake: Roles of Anaerobic Performance and Respiratory Muscle Strength.

Background: The incremental exercise test is commonly used to measure maximal oxygen uptake (VO2max), but an additional verification test is often recommended as the "gold standard" to confirm the true VO2max. Therefore, the aim of this study was to compare the peak oxygen uptake (VO2peak) obtained in the ramp incremental exercise test and that in the verification test performed on different days at submaximal intensity. Additionally, we examined the roles of anaerobic performance and respiratory muscle strength. Methods: Sixteen physically active men participated in the study, with an average age of 22.7 ± 2.4 (years), height of 178.0 ± 7.4 (cm), and weight of 77.4 ± 7.3 (kg). They performed the three following tests on a cycle ergometer: the Wingate Anaerobic Test (WAnT), the ramp incremental exercise test (IETRAMP), and the verification test performed at an intensity of 85% (VER85) maximal power, which was obtained during the IETRAMP. Results: No significant difference was observed in the peak oxygen uptake between the IETRAMP and VER85 (p = 0.51). The coefficient of variation was 3.1% and the Bland-Altman analysis showed a high agreement. We found significant correlations between the total work performed in the IETRAMP, the anaerobic peak power (r = 0.52, p ≤ 0.05), and the total work obtained in the WAnT (r = 0.67, p ≤ 0.01). There were no significant differences in post-exercise changes in the strength of the inspiratory and expiratory muscles after the IETRAMP and the VER85. Conclusions: The submaximal intensity verification test performed on different days provided reliable values that confirmed the real VO2max, which was not limited by respiratory muscle fatigue. This verification test may be suggested for participants with a lower anaerobic mechanical performance.

Rheological and Biochemical Properties of Blood in Runners: A Preliminary Report

Purpose: Physical activity induces numerous modifications in the morphological, rheological, and biochemical properties of blood. The purpose of this study was to evaluate changes in blood rheological and biochemical indicators among runners. Also, we assessed how the rheological and biochemical properties of blood in people who practised running characterised the range and direction of exercise modifications and allowed for the diagnosis of transient adaptive effects. Methods: This study included 12 athletes who regularly trained in middle- and long-distance running (6–8 times a week) and presented a high sports level (national and international class). The athletes performed a 30 min warm-up consisting of 15 min of jogging and exercises. After a 10 min rest, they completed a 3 km run with submaximal effort. Blood samples were collected at baseline and after the effort. Results: No statistically significant changes were revealed in erythrocyte, leukocyte, platelet, iron, ferritin, transferrin, erythropoietin, or C-reactive protein concentrations in the examined runners. The same applied to the elongation index at a shear stress within the range of 0.30–60.00 Pa, amplitude and total extent of aggregation, aggregation half-life, and aggregation index. A significant increase (within standard limits) was only observed in fibrinogen concentration after running. Conclusions: The lack of post-exercise changes in blood rheological and biochemical indicators in the investigated runners points at an efficient haemorheological system. This, in turn, reflects well-executed training and remarkably well-trained adaptive systems responsible for regeneration.

Relationship of peak capillary blood lactate accumulation and body composition in determining the mechanical energy equivalent of lactate during sprint cycling

AimA 15-s all-out sprint cycle test (i.e., νLamax-test) and the post-exercise change in capillary blood lactate concentration is an emerging diagnostic tool that is used to quantify the maximal glycolytic rate. The goal of this study was to determine the relation between 15 s-work, change in capillary blood lactate concentration (∆La) and body composition in a νLamax-test.MethodFifty cyclists performed a 15 s all-out sprint test on a Cyclus2 ergometer twice after a previous familiarization trial. Capillary blood was sampled before and every minute (for 8 min) after the sprint to determine ∆La. Body composition was determined employing InBody720 eight-electrode impedance analysis.ResultSimple regression models of fat-free mass (FFM) and also the product of FFM and ∆La showed similar ability to predict 15 s-work (R2 = 0.79; 0.82). Multiple regression combining both predictors explains 93% of variance between individuals. No differences between males and females were found regarding 15 s-work relative to the product of fat-free mass and ∆La. Considering pairs of similar FFM, a change 1 mmol/l of ∆La is estimated to be equal to 12 J/kg in 15 s-work (R2 = 0.85).DiscussionFifteen s-work is both closely related to FFM and also the product of ∆La and lactate-distribution space approximated by FFM. Differences in 15 s-work between males and females disappear when total lactate production is considered. Considering interindividual differences, the mechanical energy equivalent of blood lactate accumulation seems a robust parameter displaying a clear relationship between ∆La and 15 s-work relative to FFM.

Monitoring Bar Velocity to Quantify Fatigue in Resistance Training.

We analyzed the effects of load magnitude and bar velocity variables on sensitivity to fatigue. Seventeen resistance-trained men (age=25.7±4.9 years; height=177.0±7.2 cm; body mass=77.7±12.3 kg; back-squat 1RM=145.0±33.9 kg; 1RM/body mass=1.86) participated in the study. Pre- and post-exercise changes in the mean propulsive velocity (MPV) and peak velocity (PV) in the back-squat at different intensities were compared with variations in the countermovement jump (CMJ). CMJ height decreased significantly from pre- to post-exercise (∆%=-7.5 to -10.4; p<0.01; ES=0.37 to 0.60). Bar velocity (MPV and PV) decreased across all loads (∆%=-4.0 to -12.5; p<0.01; ES=0.32 to 0.66). The decrease in performance was similar between the CMJ, MPV (40% and 80% 1RM; p=1.00), and PV (80% 1RM; p=1.00). The magnitude of reduction in CMJ performance was greater than MPV (60% 1RM; p=0.05) and PV (40% and 60% 1RM; p<0.01) at the post-exercise moment. Low systematic bias and acceptable levels of agreement were only found between CMJ and MPV at 40% and 80% 1RM (bias=0.35 to 1.59; ICC=0.51 to 0.71; CV=5.1% to 8.5%). These findings suggest that the back-squat at 40% or 80% 1RM using MPV provides optimal sensitivity to monitor fatigue through changes in bar velocity.

Comparison of Postexercise Ankle Brachial Index in at Risk versus Diagnosed Peripheral Arterial Disease Population

Abstract Background: Peripheral arterial disease (PAD) is characterized by stenosis or occlusion in the arteries of the limb causing limitation in the distal blood flow. Out of the various risk factors identified, diabetes and cigarette smoking are the strongest predictors of PAD. PAD results from atherosclerosis of the vessel wall. Patients with lower extremity PAD have clinical presentation of intermittent claudication and atypical leg pain. In patients with arterial stenosis, there is a drop in pressure and flow across stenosis. Asymptomatic PAD approximately 20%–50% of total patients diagnosed with PAD. Ankle brachial index (ABI) is clinically widely used modality which helps to identify the disease. ABI test is the ratio of systolic ankle blood pressure and highest systolic brachial blood pressure. Population at risk with normal resting ABI may still have PAD. For such population, postexercise ABI is recommended. This study evaluated and compared ABI postexercise in normal healthy individuals without risk of PAD, at risk of PAD. Materials and Methods: This study is an observational study. Population with age more than 35 years were selected. Framingham Risk Score was taken for normal and at-risk population. Subjects were recruited in three groups: A, B, and C. ABI at rest was assessed. Individuals performed exercise treadmill test. Immediately, after completing the exercise, postexercise ABI was taken. Absolute systolic blood pressure values and postexercise ABI values were obtained in all three groups and then were compared. Data were analyzed using the SPSS software version 26. Results: The results of this study showed that for all the three groups, there was a significant difference in ABI at rest, postexercise ABI, and difference in systolic ankle pressure as P value was &lt;0.001. When the Chi-squared test was done for postexercise ABI and postsystolic ankle pressure in between Group B and Group C, there was no significant difference found as the P value was &gt;0.05. Conclusion: On comparison with at risk and normal individuals, no significant difference was found in terms of postexercise ABI and change in systolic ankle pressure.

Post-exercise management of exertional hyperthermia in dogs participating in dog sport (canicross) events in the UK

Exercise is a common trigger of heat-related illness (HRI) events in dogs, accounting for 74% of canine HRI cases treated under primary veterinary care in the United Kingdom. However, few empirical studies have evaluated the effectiveness of differing cooling methods for dogs with exertional hyperthermia or HRI. This study aimed to prospectively evaluate effects of ambient conditions and post-exercise management practices (cooling methods and vehicular confinement) on the post-exercise temperature change of dogs participating in UK canicross events. Canine temperature was recorded at three intervals post-exercise: as close as possible to 0- (immediately post-exercise), 5-, and 15-min post-exercise. Ambient conditions and post-exercise management were recorded for 115 cooling profiles from 52 dogs. In 28/115 (24.4%) profiles, the dog's temperature increased during the first 5-min post-exercise. Overall, 68/115 (59.1%) profiles included passive cooling (stood or walked outside), 35 (30.4%) active cooling (cold-water immersion or application of a cooling coat), and 12 (10.4%) involved no cooling and were immediately housed in vehicles. No dogs developed hypothermia during the study and no adverse effects were observed from any cooling method. In hyperthermic dogs, overall post-exercise body temperature change was significantly negatively associated (i.e. the dogs cooled more) with 0-min post-exercise body temperature (β = −0.93, p < 0.001), and not being housed in a vehicle (β = −0.43, p = 0.013). This study provides evidence cold-water immersion (in water at 0.1–15.0 °C) can be used to effectively and safely cool dogs with exertional hyperthermia. Progressive temperature increases in many dogs - even after exercise has terminated - supports the message to “cool first, transport second” when managing dogs with HRI. When transporting dogs post-exercise or with HRI even after active cooling, care should be taken to cool the vehicle before entry and promote air movement around the dog during transport to facilitate ongoing cooling and prevent worsening of hyperthermia during travel.

The effects of short-term, progressive exercise training on disease activity in smouldering multiple myeloma and monoclonal gammopathy of undetermined significance: a single-arm pilot study.

High levels of physical activity are associated with reduced risk of the blood cancer multiple myeloma (MM). MM is preceded by the asymptomatic stages of monoclonal gammopathy of undetermined significance (MGUS) and smouldering multiple myeloma (SMM) which are clinically managed by watchful waiting. A case study (N = 1) of a former elite athlete aged 44 years previously indicated that a multi-modal exercise programme reversed SMM disease activity. To build from this prior case study, the present pilot study firstly examined if short-term exercise training was feasible and safe for a group of MGUS and SMM patients, and secondly investigated the effects on MGUS/SMM disease activity. In this single-arm pilot study, N = 20 participants diagnosed with MGUS or SMM were allocated to receive a 16-week progressive exercise programme. Primary outcome measures were feasibility and safety. Secondary outcomes were pre- to post-exercise training changes to blood biomarkers of MGUS and SMM disease activity- monoclonal (M)-protein and free light chains (FLC)- plus cardiorespiratory and functional fitness, body composition, quality of life, blood immunophenotype, and blood biomarkers of inflammation. Fifteen (3 MGUS and 12 SMM) participants completed the exercise programme. Adherence was 91 ± 11%. Compliance was 75 ± 25% overall, with a notable decline in compliance at intensities > 70% V̇O2PEAK. There were no serious adverse events. There were no changes to M-protein (0.0 ± 1.0g/L, P =.903), involved FLC (+ 1.8 ± 16.8mg/L, P =.839), or FLC difference (+ 0.2 ± 15.6mg/L, P =.946) from pre- to post-exercise training. There were pre- to post-exercise training improvements to diastolic blood pressure (- 3 ± 5 mmHg, P =.033), sit-to-stand test performance (+ 5 ± 5 repetitions, P =.002), and energy/fatigue scores (+ 10 ± 15%, P =.026). Other secondary outcomes were unchanged. A 16-week progressive exercise programme was feasible and safe, but did not reverse MGUS/SMM disease activity, contrasting a prior case study showing that five years of exercise training reversed SMM in a 44-year-old former athlete. Longer exercise interventions should be explored in a group of MGUS/SMM patients, with measurements of disease biomarkers, along with rates of disease progression (i.e., MGUS/SMM to MM). https://www.isrctn.com/ISRCTN65527208 (14/05/2018).

Estimation of Validity of A-Mode Ultrasound for Measurements of Muscle Thickness and Muscle Quality.

This study aimed to determine whether amplitude modulation (A-mode) ultrasound (US) provides accurate and reliable measurements comparable to those obtained using brightness modulation (B-mode) US under diverse conditions. Thirty healthy participants (15 women and 15 men) underwent measurements of subcutaneous fat thickness (SFT), muscle thickness (MT), and muscle quality (MQ) in the trapezius and biceps brachii muscles using both US modes before and after exercises designed to stimulate the respective muscles. Among the three key indices, the results demonstrated the high validity of the A-mode, with minimal mean differences (MDs) between the two devices less than 0.91 mm and intra-class correlation coefficients (ICCs) exceeding 0.95 for all measures. In addition, the correlation coefficients between the error scores and average scores for the trapezius and biceps brachii suggested no evidence of systematic error. The trapezius MT and MQ significantly increased, and the biceps brachii MT significantly increased after the exercises (p < 0.05). Notably, both the A- and B-modes exhibited the same trend in these post-exercise changes in the muscle. This study suggests that low-cost and low-resolution A-mode US provides measurements of SFT, MT, and MQ similar to the more expensive, high-resolution B-mode imaging. A-mode US is an affordable and portable alternative for muscle assessment.

Resistance-only and concurrent exercise induce similar myofibrillar protein synthesis rates and associated molecular responses in moderately active men before and after training.

Aerobic and resistance exercise (RE) induce distinct molecular responses. One hypothesis is that these responses are antagonistic and unfavorable for the anabolic response to RE when concurrent exercise is performed. This thesis may also depend on the participants' training status and concurrent exercise order. We measured free-living myofibrillar protein synthesis (MyoPS) rates and associated molecular responses to resistance-only and concurrent exercise (with different exercise orders), before and after training. Moderately active men completed one of three exercise interventions (matched for age, baseline strength, body composition, and aerobic capacity): resistance-only exercise (RE, n = 8), RE plus high-intensity interval exercise (RE+HIIE, n = 8), or HIIE+RE (n = 9). Participants trained 3 days/week for 10 weeks; concurrent sessions were separated by 3 h. On the first day of Weeks 1 and 10, muscle was sampled immediately before and after, and 3 h after each exercise mode and analyzed for molecular markers of MyoPS and muscle glycogen. Additional muscle, sampled pre- and post-training, was used to determine MyoPS using orally administered deuterium oxide (D2 O). In both weeks, MyoPS rates were comparable between groups. Post-exercise changes in proteins reflective of protein synthesis were also similar between groups, though MuRF1 and MAFbx mRNA exhibited some exercise order-dependent responses. In Week 10, exercise-induced changes in MyoPS and some genes (PGC-1ɑ and MuRF1) were dampened from Week 1. Concurrent exercise (in either order) did not compromise the anabolic response to resistance-only exercise, before or after training. MyoPS rates and some molecular responses to exercise are diminished after training.

Mind over muscle? Time manipulation improves physical performance by slowing down the neuromuscular fatigue accumulation.

While physical performance has long been thought to be limited only by physiological factors, many experiments denote that psychological ones can also influence it. Specifically, the deception paradigm investigates the effect of psychological factors on performance by manipulating a psychological variable unbeknownst to the subjects. For example, during a physical exercise performed to failure, previous results revealed an improvement in performance (i.e., holding time) when the clock shown to the subjects was deceptively slowed down. However, the underlying neurophysiological changes supporting this performance improvement due to deceptive time manipulation remain unknown. Here, we addressed this issue by investigating from a neuromuscular perspective the effect of a deceptive clock manipulation on a single-joint isometric task conducted to failure in 24 healthy participants (11 females). Neuromuscular fatigue was assessed by pre- to post-exercise changes in quadriceps maximal voluntary torque (Tmax ), voluntary activation level (VAL), and potentiated twitch (TTW ). Our main results indicated a significant performance improvement when the clock was slowed down (Biased: 356 ± 118 s vs. Normal: 332 ± 112 s, p = .036) but, surprisingly, without any difference in the associated neuromuscular fatigue (p > .05 and BF < 0.3 for Tmax , VAL, and TTW between both sessions). Computational modeling showed that, when observed, the holding time improvement was explained by a neuromuscular fatigue accumulation based on subjective rather than actual time. These results support a psychological influence on neuromuscular processes and contribute significantly to the literature on the mind-body influence, by challenging our understanding of fatigue.

Cognitive and biomarker responses in healthy older adults to a 18-hole golf round and different walking types: a randomised cross-over study

IntroductionThe global burden of age-related cognitive decline is increasing, with the number of people aged 60 and over expected to double by 2050. This study compares the acute effects of...

Sex differences in post-exercise fatigue and function in myalgic encephalomyelitis/chronic fatigue syndrome

To assess biobehavioral sex differences in myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) utilizing a low burden exercise protocol, 22 females and 15 males with ME/CFS and 14 healthy controls underwent two six-min walk tests. Fifteen daily assessments were scheduled for fatigue and function ratings and heart monitoring. Six-min walk tests were conducted on days 8 and 9. The ME/CFS group showed high self-report fatigue and impaired physical function, whereas healthy controls did not show fatigue or function abnormalities. In patients, no significant post-exercise changes were found for heart rate variability (HRV); however, heart rate decreased in ME/CFS males from Day 14 to Day 15 (p = 0.046). Female patients showed increased fatigue (p = 0.006) after the initial walk test, but a downward slope (p = 0.008) in fatigue following the second walk test. Male patients showed a decrease in self-report work limitation in the days after exercise (p = 0.046). The healthy control group evidenced a decrease in HRV after the walk tests from Day 9–14 (p = 0.038). This pilot study did not confirm hypotheses that females as compared to males would show slower exercise recovery on autonomic or self-report (e.g. fatigue) measures. A more exertion-sensitive test may be required to document prolonged post-exertional abnormalities in ME/CFS.Trial registration: NCT NCT03331419.

Short-term heat acclimation protocols for an aging population: Systematic review.

Elderly and sedentary individuals are particularly vulnerable to heat related illness. Short-term heat acclimation (STHA) can decrease both the physical and mental stress imposed on individuals performing tasks in the heat. However, the feasibility and efficacy of STHA protocols in an older population remains unclear despite this population being particularly vulnerable to heat illness. The aim of this systematic review was to investigate the feasibility and efficacy of STHA protocols (≤twelve days, ≥four days) undertaken by participants over fifty years of age. Academic Search Premier, CINAHL Complete, MEDLINE, APA PsycInfo, and SPORTDiscus were searched for peer reviewed articles. The search terms were; (heat* or therm*) N3 (adapt* or acclimati*) AND old* or elder* or senior* or geriatric* or aging or ageing. Only studies using primary empirical data and which included participants ≥50 years of age were eligible. Extracted data includes participant demographics (sample size, gender, age, height, weight, BMI and [Formula: see text]), acclimation protocol details (acclimation activity, frequency, duration and outcome measures taken) and feasibility and efficacy outcomes. Twelve eligible studies were included in the systematic review. A total of 179 participants took part in experimentation, 96 of which were over 50 years old. Age ranged from 50 to 76. All twelve of the studies involved exercise on a cycle ergometer. Ten out of twelve protocols used a percentage of [Formula: see text] or [Formula: see text] to determine the target workload, which ranged from 30% to 70%. One study-controlled workload at 6METs and one implemented an incremental cycling protocol until Tre was reached +0.9°C. Ten studies used an environmental chamber. One study compared hot water immersion (HWI) to an environmental chamber while the remaining study used a hot water perfused suit. Eight studies reported a decrease in core temperature following STHA. Five studies demonstrated post-exercise changes in sweat rates and four studies showed decreases in mean skin temperature. The differences reported in physiological markers suggest that STHA is viable in an older population. There remains limited data on STHA in the elderly. However, the twelve studies examined suggest that STHA is feasible and efficacious in elderly individuals and may provide preventative protection to heat exposures. Current STHA protocols require specialised equipment and do not cater for individuals unable to exercise. Passive HWI may provide a pragmatic and affordable solution, however further information in this area is required.

Myocardial inefficiency is an early indicator of exercise-induced myocardial fatigue.

The effect of prolonged, high-intensity endurance exercise on myocardial function is unclear. This study aimed to determine the left ventricular (LV) response to increased exercise duration and intensity using novel echocardiographic tools to assess myocardial work and fatigue. LV function was assessed by echocardiography before, immediately, and 24 h after a cardiopulmonary exercise test (CPET) and a 91-km mountain bike leisure race. Cardiac Troponin I (cTnI) was used to assess myocyte stress. 59 healthy recreational athletes, 52 (43-59) years of age, 73% males, were included. The race was longer and of higher intensity generating higher cTnI levels compared with the CPET (p < 0.0001): Race/CPET: exercise duration: 230 (210, 245)/43 (40, 45) minutes, mean heart rate: 154 ± 10/132 ± 12 bpm, max cTnI: 77 (37, 128)/12 (7, 23) ng/L. Stroke volume and cardiac output were higher after the race than CPET (p < 0.005). The two exercises did not differ in post-exercise changes in LV ejection fraction (LVEF) or global longitudinal strain (GLS). There was an increase in global wasted work (p = 0.001) following the race and a persistent reduction in global constructive work 24 h after exercise (p = 0.003). Increased exercise intensity and duration were associated with increased myocardial wasted work post-exercise, without alterations in LVEF and GLS from baseline values. These findings suggest that markers of myocardial inefficiency may precede reduction in global LV function as markers of myocardial fatigue.

EVALUATION OF METABOLIC RESPONSE IN BONE MARROW LESIONS AFTER EXERCISE IN RELATION TO CHANGES IN ADJACENT CARTILAGE T2 VALUES

Patellofemoral pain syndrome (PFPS) is one of the most common causes of anterior knee pain in active populations. Due to its multifactorial nature, patellofemoral pain is hard to diagnose and treat. Increased stress in the subchondral bone is associated with PFPS and is correlated to elevated bone remodelling. [18F]NaF PET-MR imaging can localize regions of elevated bone remodelling and provide information about the metabolic processes involved (1, 2). Further, [18F]NaF uptake changes after exercise, thus showing that it is sensitive to changes in bone physiology resulting from acute bone loading (3, 4). For cartilage, T2 relaxation times have been used to study cartilage hydration and microstructure changes after exercise. While some studies have observed a decrease in T2 times after exercise, changes are usually transient and have largely been evaluated in the context of healthy subjects (5). An early sign of persistent abnormal mechanical stress is Bone Marrow Lesions (BMLs), which are strongly associated with pain and structural disease progression. We aimed to reproduce prior work which has shown that acute loading results in a large physiological response in bone regions with BMLs. Further, we wanted to explore if there is breakdown of the cartilage microstructure, either at baseline or in response to loading in cartilage regions adjacent to BMLs. The purpose of this study is to detect changes in the functional response of the knee joint to loading using [18F]NaF PET-MR imaging after a stair-climbing exercise in subjects with unilateral patellofemoral pain. The aims of this feasibility study are 1) to detect acute loading-induced changes in [18F]NaF uptake in bone regions with BMLs and 2) compare consequent T2 values in the cartilage adjacent to BMLs at baseline and in response to loading. 4 subjects (3 F, aged 39.5±15.0 years, BMI 26.1±5.9 kg/m2) with unilateral knee pain and BMLs (3 in patella, 1 in femur) underwent two consecutive 30-min [18F]NaF PET/MRI scans of both knees, at baseline and then repeated after a stair-climbing exercise [112 stairs, up and down]. Bone metabolic activity was quantified by calculating maximum standardized uptake values (SUVmax) in areas of BMLs in the painful leg and the corresponding region in the contralateral leg. T2 maps were calculated from quantitative DESS images [TE(1,2)=6.04, 30.44 ms] in the cartilage regions adjacent to the BMLs and in the same regions in the contralateral leg. Segmentations of cartilage were done manually in MATLAB, while SUVmax in BMLs was calculated using ROIs drawn in Horos. Pre- and post-exercise changes in SUVmax and T2 values were compared to account for loading-induced response in both metabolic and structural parameters in painful vs healthy knees. Increased [18F]NaF uptake was observed post-exercise in areas with BMLs (as compared to contralateral leg regions), confirming that PET findings correspond to structural changes observed in MRI (Fig-1). The average SUVmax values increased from 6.35±3.98 to 10.49±5.42 in the painful leg and from 1.71±1.96 to 4.04±3.21 in the contralateral leg after exercise. The average T2 relaxation times increased from 30.61±1.87 ms to 31.61±1.55 ms in the painful leg and from 27.17±2.73 ms to 27.65±2.29 ms in the contralateral leg (Fig-2). The mean change in SUVmax due to exercise was 4.15±2.42 in the BML vs 2.34±2.06 in the contralateral leg. In adjacent cartilage, a mean change in T2 values of 1.01±1.45 ms in the BML region of the painful leg and 0.47±0.48 ms in the contralateral leg was observed. In this feasibility study, [18F]NaF PET-MR showed acute loading-induced changes in BMLs, with a 2-fold increase in SUVmax in the painful leg vs the contralateral leg. While there seemed to be a higher cartilage T2 in regions adjacent to BMLs compared to the contralateral leg, the change induced by exercise was small.

The effect of prolonged interval and continuous exercise in the heat on circulatory markers of intestinal barrier integrity.

The purpose of this study was to determine the effect of prolonged high-intensity interval (INT) and moderate-intensity continuous (CONT) treadmill exercise in the heat on markers of enterocyte injury and bacterial endotoxin translocation. Nine males completed 2 h of work-matched exercise in the heat (40°C and 15% RH) as either INT (2min at 80% VO2max and 3min at 30% VO2max) or CONT (~ 50% of VO2max). Blood samples collected pre- and post-exercise were assayed for intestinal fatty acid-binding protein (I-FABP), claudin-3 (CLDN-3), and lipopolysaccharide-binding protein (LBP). I-FABP was significantly increased from pre- to post-exercise in CONT (913.96 ± 625.13 to 1477.26 ± 760.99pg•mL-1; p = 0.014, d = 0.766) and INT (714.59 ± 470.27 to 1547.93 ± 760.99pg•mL-1; p = 0.001, d = 1.160). Pre- to post-exercise changes in I-FABP were not different between CONT and INT (p = 0.088, d = 0.414). LBP was significantly increased from pre- to post-exercise in INT (15.94 ± 2.90 to 17.35 ± 3.26μg•mL-1; p = 0.028, d = 0.459) but not CONT (18.11 ± 5.35 to 16.93 ± 5.39μg•mL-1; p = 0.070, d = 0.226), and pre- to post-exercise changes in LBP were higher in the INT compared to CONT (p < 0.001, d = 1.160). No significant changes were detected from pre- to post-exercise for CLDN-3 in CONT (14.90 ± 2.21 to 15.30 ± 3.07μg•mL-1) or INT (15.55 ± 1.63 to 16.41 ± 2.11μg•mL-1) (p > 0.05). We conclude that prolonged exercise in the heat induces enterocyte injury, but interval (or intermittent) exercise may cause greater bacterial endotoxin translocation which may increase the risk for local and systemic inflammation.

Exercise Performed In Hypobaric Hypoxia Increases Markers Of Intestinal Injury And Symptoms Of Gastrointestinal Distress

Gastrointestinal (GI) complications (nausea, diarrhea, weight loss, intestinal bleeding) have been reported during high altitude ascent and their underlying cause might be related to intestinal injury. Exercise at high altitude exacerbates GI symptoms, but it is not known if markers of intestinal injury increase or are associated with GI symptoms during exercise. PURPOSE: To determine the effect of exercise in hypobaric hypoxia on markers of intestinal injury, bacterial translocation, and GI symptoms. METHODS: Using a randomized and counterbalanced design 9 males completed two experimental trials: one at simulated 4300 m of hypobaric hypoxia (HYP) and one at local altitude of 1585 m (NORM). For both trials participants performed 60-minutes of cycling at a workload that elicited 65% of their NORM VO2max. GI symptoms were assessed before and every 15-minutes during exercise. Pre- and post-exercise blood samples were assessed for markers of intestinal injury (I-FABP & CLDN-3) and bacterial translocation (LBP) using ELISA kits. Data were analyzed using two way (time x condition) repeated measures ANOVAs. Effect sizes are provided as Cohen’s d (d). Correlations were used to determine relationships between GI symptoms and pre-to post-exercise change (Δ) in I-FABP, CLDN-3, and LBP. RESULTS: All 9 participants reported at least one GI symptom in HYP compared to just 1 participant in NORM. I-FABP was significantly elevated from pre- to post-exercise in HYP (708 ± 191 to 1215 ± 518 pg/mL; p ≤ 0.05 d = 1.10) but not in NORM (759 ± 224 to 828 ± 288 pg/mL; p > 0.05 d = 0.27). CLDN-3 was significantly elevated from pre- to post-exercise in HYP (13.8 ± 0.9 to 15.3 ± 1.2 ng/mL; p ≤ 0.05 d = 1.19) but not in NORM (13.7 ± 1.8 to 14.2 ± 1.6 ng/mL; p > 0.05 d = 0.45). LBP was significantly elevated from pre- to post-exercise in HYP (10.8 ± 1.2 to 13.9 ± 2.8 μg/mL; p ≤ 0.05 d = 1.12) but not in NORM (11.3 ± 1.1 to 11.7 ± 0.9 μg/mL; p > 0.05 d = 0.32). I-FABP (d = 0.85), CLDN-3 (d = 0.95), and LBP (d = 0.69) were all significantly higher post-exercise in HYP compared to NORM (p ≤ 0.05). Overall GI discomfort was significantly correlated to ΔI-FABP (p ≤ 0.05 r = 0.50) and ΔLBP (p ≤ 0.05 r = 0.85), but not CLDN-3 (p > 0.05 r = 0.33). CONCLUSIONS: These data indicate that cycling exercise performed in HYP can damage the intestinal barrier which might explain some of the commonly reported GI symptoms.