Exhaustive Running Research Articles

Maximal Oxygen Uptake Is Achieved in Hypoxia but Not Normoxia during an Exhaustive Severe Intensity Run.

Highly aerobically trained individuals are unable to achieve maximal oxygen uptake () during exhaustive running lasting ~2 min, instead plateaus below after ~1 min. Hypoxia offers the opportunity to study the () response to an exhaustive run relative to a hypoxia induced reduction in . The aim of this study was to explore whether there is a difference in the percentage of achieved (during a 2 min exhaustive run) in normoxia and hypoxia. Fourteen competitive middle distance runners (normoxic 67.0 ± 5.2 ml.kg−1.min−1) completed exhaustive treadmill ramp tests and constant work rate (CWR) tests in normoxia and hypoxia (FiO2 0.13). The data from the CWR tests were modeled using a single exponential function. End exercise normoxic CWR was less than normoxic (86 ± 6% ramp, P < 0.001). During the hypoxic CWR test, hypoxic was achieved (102 ± 8% ramp, P = 0.490). The phase II time constant was greater in hypoxia (12.7 ± 2.8 s) relative to normoxia (10.4 ± 2.6 s) (P = 0.029). The results demonstrate that highly aerobically trained individuals cannot achieve during exhaustive severe intensity treadmill running in normoxia, but can achieve the lower in hypoxia despite a slightly slower response.

Compressed food with added functional oligopeptides improves performance during military endurance training.

Oligosaccharide or oligopeptide supplementation may have a significant impact on endurance performance. This study evaluated the effects of adding maltooligosaccharides (MO) or soy oligopeptides (SO) to compressed food (CF) on the physical response of soldiers to daily military training. Twelve soldiers were randomized to four diet groups: regular meals, CF, CFMO, and CFSO (crossover design). They participated in exercise tests including 90 minutes running at 55-65% VO2max and exhaustive running. Heart rates, rating of perceived exertion (RPE), and blood and urine samples were collected during exercise and recovery. The recovery heart rates were significantly lower with the CFMO diet compared with the other diets. Compared with all other diets, blood glucose levels were higher, post-exercise blood lactate levels were lower, and lactate clearance during recovery was higher with the CFMO diet, followed by the CFSO diet. Post-exercise levels of erythrocytes and hematocrit were significantly higher with the CFSO diet. Post-exercise urine specific gravity was lower with the CFMO diet and urine pH was decreased with the CFSO diet. Blood urea nitrogen (BUN) and uric acid (UA) were significantly higher with the CFSO diet than with the other diets. There was no significant difference in skeletal and cardiac muscle injury indices and RPE among diets. CFMO led to better heart rate recovery, improved and maintained blood glucose and increased removal of blood lactate. CFSO accelerated removal of blood lactate during recovery, maintained oxygen supply, and increased fluid retention.

Effect of thyme extract supplementation on lipid peroxidation, antioxidant capacity, PGC-1\u03b1 content and endurance exercise performance in rats

BackgroundAthletes have a large extent of oxidant agent production. In the current study, we aimed to determine the influence of thyme extract on the endurance exercise performance, mitochondrial biogenesis, and antioxidant status in rats.MethodsTwenty male Wistar rats were randomly divided into two groups receiving either normal drinking water (non-supplemented group, n = 10) or thyme extract, 400 mg/kg, (supplemented group, n = 10). Rats in both groups were subjected to endurance treadmill training (27 m/min, 10% grade, 60 min, and 5 days/week for 8 weeks). Finally, to determine the endurance capacity, time to exhaustion treadmill running at 36 m/min speed was assessed. At the end of the endurance capacity test, serum and soleus muscle samples were collected and their superoxide dismutase (SOD) and glutathione peroxidase (GPx) activity, as well as malondialdehyde (MDA) concentration were measured. Protein expression of PGC-1α, as a marker of mitochondrial biogenesis, was also determined in the soleus muscle tissue by immunoblotting assay.ResultsFindings revealed that the exhaustive running time in the treatment group was significantly (p < 0.05) prolonged. Both serum and soleus muscle MDA levels, as an index of lipid peroxidation, had a threefold increase in the thyme extract supplemented group (t18 = 8.11, p < 0.01; t18 = 4.98, p < 0.01 respectively). The activities of SOD and GPx of the soleus muscle were significantly (p < 0.05) higher in the non-supplemented group, while there was no significant difference in serum SOD, GPx activities, and total antioxidant capacity between groups. Furthermore, thyme supplementation significantly (p < 0.05) decreased PGC-1α expression.ConclusionsThyme extract supplementation increased endurance exercise tolerance in intact animals, although decrease of oxidative stress and regulation of the PGC-1α protein expression are not considered as underlying molecular mechanisms.

Cardioprotection of exercise preconditioning involving heat shock protein 70 and concurrent autophagy: a potential chaperone-assisted selective macroautophagy effect.

It has been confirmed that exercise preconditioning (EP) has a protective effect on acute cardiovascular stress. However, how Hsp70 participates in EP-induced cardioprotection is unknown. EP may involve Hsp70 to repair unfolded proteins or may also stabilize the function of the endoplasmic reticulum via Hsp70-related autophagy to work on a protective formation. Our EP protocol involves four periods of 10min running with 10min recovery intervals. We added a period of exhaustive running to test this protective effect, using histology and molecular biotechnology methods to detect related markers. EP provided cardioprotection at its early and late phases against exhaustive exercise-induced ischemic myocardial injury. Results showed that Hsp70 co-chaperone protein BAG3, ubiquitin adaptor p62 and critical autophagy protein LC3 were significantly upregulated at the early phase. Meanwhile, Hsp70, Hsp70/BAG3 co-localization extent, LC31 and LC3II were significantly upregulated at the late phase. Hsp70 mRNA levels and LC3II/I ratios were also consistent with the extent of myocardial injury following exhaustive exercise. Hsp70 increase was delayed relative to BAG3 and p62 after EP, indicating a pre-synthesized phenomenon of BAG3 and p62 for chaperone-assisted selective autophagy (CASA). The decreased Hsp70, BAG3 and p62 levels and increased Hsp70/BAG3 co-localization extent and LC3 levels induced by exhaustive exercise after EP suggest that EP-induced cardioprotection might associate with CASA. Hsp70 has a cardioprotective role and has a closer link with CASA in LEP. Additionally, EP may not cause exhaustion-dependent excessive autophagy regulation. Collectively, during early and late EP, CASA potentially plays different roles in cardioprotection.

Monument Valley, Instagram, and the Closed Circle of Representation

Monument Valley, Instagram, and the Closed Circle of Representation

Influence of Post-Exercise Carbohydrate-Protein Ingestion on Muscle Glycogen Metabolism in Recovery and Subsequent Running Exercise.

We examined whether carbohydrate-protein ingestion influences muscle glycogen metabolism during short-term recovery from exhaustive treadmill running and subsequent exercise. Six endurance-trained individuals underwent two trials in a randomized double-blind design, each involving an initial run-to-exhaustion at 70% VO2max (Run-1) followed by 4-h recovery (REC) and subsequent run-to-exhaustion at 70% VO2max (Run-2). Carbohydrate-protein (CHO-P; 0.8 g carbohydrate·kg body mass [BM-1]·h-1 plus 0.4 g protein·kg BM-1·h-1) or isocaloric carbohydrate (CHO; 1.2 g carbohydrate·kg BM-1·h-1) beverages were ingested at 30-min intervals during recovery. Muscle biopsies were taken upon cessation of Run-1, postrecovery and fatigue in Run-2. Time-to-exhaustion in Run-1 was similar with CHO and CHO-P (81 ± 17 and 84 ± 19 min, respectively). Muscle glycogen concentrations were similar between treatments after Run-1 (99 ± 3 mmol·kg dry mass [dm-1]). During REC, muscle glycogen concentrations increased to 252 ± 45 mmol·kg dm-1 in CHO and 266 ± 30 mmol·kg dm-1 in CHO-P (p = .44). Muscle glycogen degradation during Run-2 was similar between trials (3.3 ± 1.4 versus 3.5 ± 1.9 mmol·kg dm-1·min-1 in CHO and CHO-P, respectively) and no differences were observed at the respective points of exhaustion (93 ± 21 versus 100 ± 11 mmol·kg dm-1; CHO and CHO-P, respectively). Similarly, time-to-exhaustion was not different between treatments in Run-2 (51 ± 13 and 49 ± 15 min in CHO and CHO-P, respectively). Carbohydrate-protein ingestion equally accelerates muscle glycogen resynthesis during short-term recovery from exhaustive running as when 1.2 g carbohydrate·kg BM-1·h-1 are ingested. The addition of protein did not alter muscle glycogen utilization or time to fatigue during repeated exhaustive running.

Tracking Performance Changes With Running-Stride Variability When Athletes Are Functionally Overreached.

Stride-to-stride fluctuations in running-stride interval display long-range correlations that break down in the presence of fatigue accumulated during an exhaustive run. The purpose of the study was to investigate whether long-range correlations in running-stride interval were reduced by fatigue accumulated during prolonged exposure to a high training load (functional overreaching) and were associated with decrements in performance caused by functional overreaching. Ten trained male runners completed 7 d of light training (LT7), 14 d of heavy training (HT14) designed to induce a state of functional overreaching, and 10 d of light training (LT10) in a fixed order. Running-stride intervals and 5-km time-trial (5TT) performance were assessed after each training phase. The strength of long-range correlations in running-stride interval was assessed at 3 speeds (8, 10.5, and 13 km/h) using detrended fluctuation analysis. Relative to performance post-LT7, time to complete the 5TT was increased after HT14 (+18 s; P < .05) and decreased after LT10 (-20 s; P = .03), but stride-interval long-range correlations remained unchanged at HT14 and LT10 (P > .50). Changes in stride-interval long-range correlations measured at a 10.5-km/h running speed were negatively associated with changes in 5TT performance (r -.46; P = .03). Runners who were most affected by the prolonged exposure to high training load (as evidenced by greater reductions in 5TT performance) experienced the greatest reductions in stride-interval long-range correlations. Measurement of stride-interval long-range correlations may be useful for monitoring the effect of high training loads on athlete performance.

The Relationship Between Hip Kinematics and Iliotibial Band Syndrome (ITBS) in Long Distance Runners: A Critically Appraised Topic

Clinical Question:Is there evidence to suggest that runners with a history of ITBS demonstrate altered lower extremity kinematics compared with runners without a history of ITBS?Clinical Bottom Line:There is moderate evidence suggesting that hip kinematics differ between runners with a history of ITBS compared with healthy runners. Results are contradictory related to the plane of movement and direction of the kinematic change. In addition, assessing hip kinematics following an exhaustive run may be beneficial to detect change.

Foot Joint Coupling Variability in Rearfoot and Forefoot Runners After an Exhaustive Run

While most runners use a rearfoot strike (RFS), recent research suggests that midfoot or forefoot strike (FFS) running is more natural and reduces injuries. Joint coupling is believed to be an important factor in running related injuries. Further, according to the dynamical systems theory, increased joint coupling variability while running may prevent repetitive loading of tissues which may lead to overuse injury. PURPOSE: This study compared joint coupling variability of the foot in habitual RFS and FFS runners prior to and following an exhaustive run. METHODS: Fifteen FFS and 15 RFS runners performed a maximal 5 km treadmill run. Foot motion was assessed using a 7-segment foot model which identified 6 functional articulations (rearfoot, medial midfoot, lateral midfoot, medial forefoot, lateral forefoot, and 1st metatarsophalangeal). Motion capture data was collected for 10 s at the beginning and end of the run and 5 steps were processed for subsequent analysis. Vector coding methods were used to calculate 10 different joint couples. Standard deviations of the coupling angles were used to identify variability within the first 2 subphases of stance (0-20% and 21-50% stance). Mixed between-within subjects ANOVAs were used to compare differences between the foot strikes and pre and post run. RESULTS:Subphase 1: FFS group had increased variability over RFS group in 2 medial midfoot-forefoot couples (1.22° and 2.84° difference) while RFS group had increased coupling variability in 1 lateral midfoot-forefoot couple (0.94° difference). Subphase 2: RFS group had increased variability in 3 rearfoot-midfoot couplings over FFS group (3.43°, 3.66°, and 1.30° difference). Subphase 2 post run, both groups increased variability in rearfoot (0.68° difference pre to post run) and 3 rearfoot-midfoot couplings (0.77°, 0.65°, and 0.84° difference). An interaction occurred between group and pre-post run in the midfoot-forefoot where only RFS runners decreased variability over time (0.99°). CONCLUSION: FFS runners had greater variability in subphase 1, while RFS had greater variability in subphase 2 indicating that a FFS may provide better injury protection during the initial heel strike period. Increased variability post-run in subphase 2 suggests that overstressing tissues may be more critical to prevent during subphase 2.

Impact Of Exhaustive Run On The Lower Extremity Biomechanics

PURPOSE: The aim of this study was to investigate kinematic and kinetic changes occurred in stance phase during running to exhaustion. METHOD: 8 male recreational runners (age 22.5±1.6 years old, height 177.60±0.02cm and mass 80.6±8.63kg) from local community were participants in this study. They had no lower extremity injury history within-six months, and in apparent good health. AMTI three dimensional force treadmill was used to measure the ground reaction force, and the speed were set at 7.5 mile/hour with sample frequency of 1000Hz. Vicon Motion system with 8 cameras was used for capturing 3D kinematic movements of lower extremities with 40 14mm reflective markers. The sampling frequency was set at 200Hz. The participants were instructed to run on the treadmill until they cannot run, due to exhaustion, anymore. Ten seconds he data of from the start, middle and end of the run were calculated and processed by using C-Motion visual 3D software for both kinetics and kinematics parameters. RESULTS: Stride duration decreased (0.72±0.03 vs. 0.71±0.04s, at the start and end of the run, respectively), and stance phase duration increased (0.23±0.01 vs and 0.23±0.01s) as observed in this study. More ankle plantarflexion (-44.9±5.4 vs -46.4±5.5°) was noted at foot contact during run to exhaustion. No prominent adjustment of knee flexion (46.2±4.3 vs. 45.2±7.0°) was observed during foot initial contact, but an increase (12.2±4.2 vs. 10.2±3.8°) observed during toe-off. There was a decline of ankle plantarflexion moment (3.2±0.3 vs. 3.1±0.3 N-m/kg) and an increase of knee extension moment (2.8±0.4 vs. 3.0±0.7 N-m/kg) observed. CONCLUSION: There was a trend of adjustment of sagittal plane kinematics and kinetics variables observed., regarded as runners were seeking to modulate movements for protecting themselves from injury potential.

The Effect of Sweet Cassava Polysaccharides Supplementation on Oxidative Stress and Antioxidant Capacity due to Exhaustive Running

The Effect of Sweet Cassava Polysaccharides Supplementation on Oxidative Stress and Antioxidant Capacity due to Exhaustive Running

Do footfall patterns in forefoot runners change over an exhaustive run?

ABSTRACTThe purpose of this study was to investigate possible footfall pattern changes in habitual forefoot runners over a prolonged, exhaustive run. A prolonged run was performed to exhaustion in 14 habitual forefoot runners. Vertical ground reaction forces (VGRFs) and kinematics were collected at the beginning and end of the run. Ankle plantar flexor torque and triceps surae electromyographic activity were measured during pre- and post-run isometric contractions. By run’s end, there was an increase in VGRF loading rate and impact peak magnitude, greater dorsiflexion at foot contact and greater knee flexion angle throughout stance. Ankle plantar flexor torque decreased significantly from pre- to post-run tests. This was accompanied by a decrease in the integrated electromyographic activity (iEMG) output for the lateral and medial gastrocnemius. There were significant changes in landing mechanics for forefoot runners that indicate a transition towards more midfoot footfall patterns. A contributing factor may be ankle plantar flexor muscle fatigue that, at touchdown, is exposed to exaggerated eccentric loading. These findings suggest that a forefoot running pattern may become difficult to maintain in longer endurance events, and thus runners should pay attention to this in training to improve performance and mitigate potential injury.

Effect of Maximal Versus Supra-Maximal Exhausting Race on Lipid Peroxidation, Antioxidant Activity and Muscle-Damage Biomarkers in Long-Distance and Middle-Distance Runners.

BackgroundExhausting physical exercise increases lipid peroxidation and causes important muscle damages. The human body tries to mitigate these adverse effects by mobilizing its antioxidant defenses.ObjectivesThis study aims to investigate the effect of a maximal versus supra-maximal race sustained until exhaustion on lipid peroxidation, antioxidant activity and muscle-damage biomarkers in trained (i.e. long-distance and middle-distance runners) and sedentary subjects.Materials and MethodsThe study has been carried out on 8 middle-distance runners (MDR), 9 long-distance runners (LDR), and 8 sedentary subjects (SS). Each subject has undergone two exhaustive running tests, the first one is an incremental event (VAMEVAL test), the second one is a constant supra-maximal intensity test (limited-time test). Blood samples were collected at rest and immediately after each test.ResultsA significant increase in malondialdehyde (MDA) concentrations was observed in SS and MDR after the VAMEVAL test and in LDR after the Limited-Time test. A significant difference was also observed between LDR and the other two groups after the VAMEVAL test, and between LDR and MDR after the Limited-Time test. Significant modifications, notably, in myoglobin, CK, LDH, IL-6, TNF-α, and TAS were likewise noted but depending on the race-type and the sportive specialty.ConclusionsMaximal and supra-maximal races induce a significant increase in lipid peroxidation and cause non-negligible inflammation and muscle damage. These effects were relatively related to the physical exercise type and the sportive specialty.

EVALUATION OF ANTI-FATIGUE ACTIVITY OF FLAVONOIDS FROM TARTARY BUCKWHEAT IN MICE

Background: Flavonoids are the major biological activities components of tartary buckwheat which has multifunctional&#x0D; bioactivities. However, there are a limited number of studies on the effect of flavonoids from tartary buckwheat (TBF) on physical&#x0D; fatigue at present. This study aimed to investigate the anti-fatigue activity of TBF in mice.&#x0D; Materials and Methods: The mice were divided into four groups: control (C), low-dose TBF-treated (LFT), middle-dose&#x0D; TBF-treated (MFT) and high-dose TBF-treated (HFT). The treated groups received TBF (100, 200 and 400 mg/kg), while the control&#x0D; group received physiological saline. After 28 days' treatment, the mice performed exhaustive running exercise on the treadmill, along&#x0D; with the measure of exhaustive running times, blood lactic acid (BLA), serum urea nitrogen (SUN), serum creatine kinase (SCK),&#x0D; liver glycogen, superoxide dismutase (SOD), glutathione peroxidase (GPx) and catalase (CAT).&#x0D; Results: TBF prolonged the exhaustive running time of the mice. It sub-served to remove the accumulated products of metabolism&#x0D; by decreasing the levels of BLA and SUN. It ameliorated the muscle damage by decreasing the SCK levels. It improved the&#x0D; metabolic control of exercise and activated the energy metabolism by increasing the liver glycogen contents, as well as improving&#x0D; endogenous cellular antioxidant enzymes in mice by increasing the SOD, GPx and CAT activities.&#x0D; Conclusion: TBF has significant anti‑fatigue activity.

Inhibition of Glutathione Synthesis Induced by Exhaustive Running Exercise via the Decreased Influx Rate of L-Cysteine in Rat Erythrocytes

Background/Aims: The main purpose of this study was to investigate the effect of exhaustive exercise on L-cysteine uptake and its effect on erythrocyte glutathione (GSH) synthesis and metabolism. Methods: Rats were divided into three groups: sedentary control (C), exhaustive running exercise (ERE) and moderate running exercise (MRE) (n=12 rats/group). We determined the L-cysteine efflux and influx in vitro in rat erythrocytes and its relationship with GSH synthesis. Total anti-oxidant potential of plasma was measured in terms of the ferric reducing ability of plasma (FRAP) values for each exercise group. In addition, the glucose metabolism enzyme activity of erythrocytes was also measured under in vitro incubation conditions. Results: Biochemical studies confirmed that exhaustive running exercise significantly increased oxidative damage parameters in thiobarbituric acid reactive substances (TBARS) and methemoglobin levels. Pearson correlation analysis suggested that L-cysteine influx was positively correlated with erythrocyte GSH synthesis and FRAP values in both the control and exercise groups. In vitro oxidation incubation significantly decreased the level of glucose metabolism enzyme activity in the control group. Conclusion: We presented evidence of the exhaustive exercise-induced inhibition of GSH synthesis due to a dysfunction in L-cysteine transport. In addition, oxidative stress-induced changes in glucose metabolism were the driving force underlying decreased L-cysteine uptake in the exhaustive exercise group.

Sex differences in running mechanics and patellofemoral joint kinetics following an exhaustive run

Patellofemoral joint pain (PFP) is a common running-related injury that is more prevalent in females and thought to be associated with altered running mechanics. Changes in running mechanics have been observed following an exhaustive run but have not been analyzed relative to the sex bias for PFP. The purpose of this study was to test if females demonstrate unique changes in running mechanics associated with PFP following an exhaustive run. For this study, 18 females and 17 males ran to volitional exhaustion. Peak PFJ contact force and stress, PFJ contact force and stress loading rates, hip adduction excursion, and hip and knee joint frontal plane angular impulse were analyzed between females and males using separate 2 factor ANOVAs (2 (male/female)×2 (before/after exhaustion)). We observed similar changes in running mechanics among males and females over the course of the exhaustive run. Specifically, greater peak PFJ contact force loading rate (5%, P=.01), PFJ stress loading rate (5%, P<.01), hip adduction excursion (1.3°, P<.01), hip abduction angular impulse (4%, P<.01), knee abduction angular impulse (5%, P=.03), average vertical ground reaction force loading rate (10%, P<.01) and step length (2.1cm, P=.001) were observed during exhausted running. These small changes in suspected PFP pathomechanical factors may increase a runner׳s propensity for PFP. However, unique changes in female running mechanics due to exhaustion do not appear to contribute to the sex bias for PFP.

Apple Pomace Extract Improves Endurance in Exercise Performance by Increasing Strength and Weight of Skeletal Muscle.

Ursolic acid is a lipophilic pentacyclic triterpenoid found in many fruits and herbs and is used in several herbal folk medicines for diabetes. In this study, we evaluated the effects of apple pomace extract (APE; ursolic acid content, 183 mg/g) on skeletal muscle atrophy. To examine APE therapeutic potential in muscle atrophy, we investigated APE effects on the expression of biomarkers associated with muscle atrophy and hypertrophy. We found that APE inhibited atrophy, while inducing hypertrophy in C2C12 myotubes by decreasing the expression of atrophy-related genes and increasing the expression of hypertrophy-associated genes. The in vivo experiments using mice fed a diet with or without APE showed that APE intake increased skeletal muscle mass, as well as grip strength and exercise capacity. In addition, APE significantly improved endurance in the mice, as evidenced by increased exhaustive running time and muscle weight, and reduced the expression of the genes involved in the development of muscle atrophy. APE also decreased the concentration of serum lactate and lactate dehydrogenase, inorganic phosphate, and creatinine, the indicators of accumulated fatigue and exercise-induced stress. These results suggest that APE may be useful as an ergogenic functional food or dietary supplement.

Green tea extract supplementation does not hamper endurance-training adaptation but improves antioxidant capacity in sedentary men.

The purpose of this study was to investigate the effect of green tea extract (GTE) supplementation combined with endurance training on endurance capacity and performance in sedentary men. Forty untrained men (age: 20 ± 1 years) participated in this study. Subjects were assigned to 1 of 4 treatments: (i) placebo-control (CTRL), (ii) GTE, (iii) endurance training (Ex), and (iv) endurance training with GTE (ExGTE). During the 4-week intervention, exercise training was prescribed as 75% oxygen uptake reserve for three 20-min sessions per week, and either GTE (250 mg/day) or placebo was provided. Endurance capacity, malondialdehyde (MDA), total antioxidant status (TAS), and creatine kinase (CK) were examined. Ex and ExGTE but not GTE improved exhaustive-run time (Ex: +8.2%, p = 0.031; ExGTE: +14.3%, p < 0.001); in addition, Ex and ExGTE significantly increased maximal oxygen uptake by ∼14% (p = 0.041) and ∼17% (p = 0.017) above the values of the CTRL group, respectively. Both Ex and ExGTE significantly decreased the increase of CK by ∼11%-32% below that of CTRL following an exhaustive run (Ex: p = 0.007; ExGTE: p = 0.001). Moreover, TAS levels increased by ∼11% in ExGTE after training (p = 0.040), and GTE, Ex, and ExGTE markedly attenuated exercise-induced MDA production (p = 0.01, p = 0.005, p = 0.011, respectively). In conclusion, this investigation demonstrated that daily ingestion of GTE during endurance training does not impair improvements in endurance capacity. Moreover, endurance training combined with GTE not only increases antioxidant capacity without attenuating endurance training adaptations, but also further attenuates acute exercise-induced CK release.

A metabolomic study of the PPARδ agonist GW501516 for enhancing running endurance in Kunming mice.

Exercise can increase peroxisome proliferator-activated receptor-δ (PPARδ) expression in skeletal muscle. PPARδ regulates muscle metabolism and reprograms muscle fibre types to enhance running endurance. This study utilized metabolomic profiling to examine the effects of GW501516, a PPARδ agonist, on running endurance in mice. While training alone increased the exhaustive running performance, GW501516 treatment enhanced running endurance and the proportion of succinate dehydrogenase (SDH)-positive muscle fibres in both trained and untrained mice. Furthermore, increased levels of intermediate metabolites and key enzymes in fatty acid oxidation pathways were observed following training and/or treatment. Training alone increased serum inositol, glucogenic amino acids, and branch chain amino acids. However, GW501516 increased serum galactose and β-hydroxybutyrate, independent of training. Additionally, GW501516 alone raised serum unsaturated fatty acid levels, especially polyunsaturated fatty acids, but levels increased even more when combined with training. These findings suggest that mechanisms behind enhanced running capacity are not identical for GW501516 and training. Training increases energy availability by promoting catabolism of proteins, and gluconeogenesis, whereas GW501516 enhances specific consumption of fatty acids and reducing glucose utilization.

The Effect of Fatigue on the Biomechanics of Recreational Runners with Patellofemoral Pain

Patellofemoral pain syndrome (PFPS) is one of the most common injuries experienced by recreational runners. Pain is often absent at the beginning of activity, but tends to worsen with fatigue during a run. This may be due to the effect of fatigue on the magnitude of activation of muscles responsible for controlling hip and knee biomechanics, thus altering the loading environment of the patellofemoral joint and predisposing to PFPS pathology. PURPOSE: To compare the effects of fatigue on strength and muscle activation during an exhaustive run in female runners with and without PFPS. Kinematic and spatiotemporal variables were also examined as a means to understand the strength and muscle activation differences between groups. METHODS: Five females (33.5 +/-8.8 years of age) with a history of PFPS for > 2 months and five age-matched, healthy control females (32.8 +/-7.4 years of age) ran on a treadmill at a self-selected speed to a pre-determined level of fatigue (Rating of Perceived Exertion=17). Strength of the major hip muscles was measured pre- and post-run using handheld dynamometry. Surface EMG was recorded wirelessly from the following muscles: gluteus medius, tensor fascia lata, rectus femoris, and biceps femoris. EMG as well as kinematic and spatiotemporal data were collected at 3-minute intervals until termination. Comparisons were made between the 0%, 50%, and 100% intervals of the run using separate 2-way ANOVAs, with fatigue as the repeated measure for each variable of interest and post hoc Tukey HSD tests for significant main effects. RESULTS: Hip external rotation (ER) strength was significantly decreased in the PFPS group from pre- to post-run (mean difference = 0.09 Nm/kg, p = 0.045). Females with PFPS also demonstrated increased peak activation of gluteus medius. Peak hip internal rotation (IR) (mean difference = 3.44°, p = 0.291) and adduction (mean difference = 0.84°, p = 0.294) both trended toward an increase in the PFPS group from the beginning to the end of the exhaustive run. CONCLUSIONS: Females with PFPS exhibited decreased strength of hip external rotators following an exhaustive run compared to healthy, age-matched controls, which may be a factor in the increased hip IR angle in this group. EMG analysis revealed increased activation of gluteus medius. Greater activation levels may result in earlier fatigue to hip external rotators, leading to altered hip kinematics and a predisposition to PFPS.