An acute bout of unaccustomed eccentric exercise causes prolonged strength loss and delayed onset muscle soreness (DOMS) for several days. Chronic dietary supplementation with polyphenols, from pomegranates, has been shown to accelerate recovery following eccentric exercise, but the optimal dose is unknown. The purpose of this study was to determine the effect of dietary supplementation with different doses of pomegranate juice concentrate (PJC) on muscular strength, power, and soreness throughout a 96-hour time period following an acute bout of eccentric exercise. Healthy recreationally active males (n=45) were assigned to one of three treatment groups: Once-daily PJC (1x), twice-daily PJC (2x), or placebo (PLA) supplementation over a period of eight days. A 1x dose of PJC provided approximately 650 mg GAE. On day four of each treatment, subjects performed downhill running intervals (-10% grade) over a 40-minute period followed by 40 repetitions of eccentric elbow flexion at 100% of concentric 1-RM. Muscle soreness of arms and legs, maximal isometric strength of the elbow flexors (EF) and knee extensors (KE), vertical jump height (VJ[subscript height]) maximal cycling power (P[subscript max]), and 10-meter sprint velocity (V[subscript 10m]) were assessed pre-exercise and 2, 24, 48, 72, 96 hours post-exercise. Additionally, maximal instantaneous power (IP[subscript max]), maximal velocity (V[subscript max]), maximal torque (T[subscript max]), and torque at 0° (T0) were assessed on the inertial load power cycle pre-exercise and 24, 48, 72, 96 hours post-exercise. Throughout the 96-hours post-exercise, isometric EF strength was significantly higher in 1x and 2x groups as compared to PLA (main treatment effect, 83.6 ± 2.7% vs. 85.6 ± 1.9% vs. 78.4 ± 1.8%, respectively; p < 0.001). Isometric KE strength was significantly higher in 1x and 2x groups as compared to PLA (main treatment effect, 93.9 ± 1.5% vs. 91.6 ± 1.5% vs. 87.1 ± 1.8%, respectively; p < 0.001). Both VJ and V10m were significantly higher in 1x compared to PLA (main treatment effect, 99.9 ± 0.9% vs. 98.0 ± 1.0%, respectively, p = 0.037; 100.0 ± 0.8% vs. 97.8 ± 0.7%, respectively, p = 0.003). Muscle soreness and Pmax, were similar at all time points between groups. We conclude that dietary supplementation with 1x or 2x PJC results in higher isometric strength values compared to placebo for EF and KE muscles during the 96-hour period after an acute bout of eccentric exercise. / text

Introduction/purpose: Recovery from muscle damage involves a type of programmed cell death known as apoptosis. Damage Associated Molecular Patterns (DAMPs) are released after muscle damage and may cause premature apoptosis in monocytes infiltrating the damaged site. This may alter the time course of events towards recovery. Therefore, the purpose of this study was to investigate if downhill running causes a change in the susceptibility of monocytes to apoptosis. Methods: Participants (5 male, 6 female) completed a downhill running protocol consisting of 6-5 minute bouts at a speed of 6-9mph on a -15% grade treadmill. Venous blood samples were collected immediately pre-exercise (PRE), in addition to 4 -h, 24 -h and 48 -h post-exercise. Creatine kinase (CK) was measured to give an indication of muscle damage. Monocytes were analyzed by flow cytometry for expression of multicaspase and annexin v reagent was used to detect changes in the plasma membrane. A MILLIPLEX MAP human early apoptosis magnetic bead 7-plex kit (EMD Millipore, Billerica, MA) was used to assess the relative concentration of phosphorylated protein kinase B (Akt), Bcl-2 associated death promoter (BAD), B cell lymphoma-2 (Bcl-2), active caspase-8, active caspase-9, c jun N terminal kinase (JNK) and tumor protein p53 by Luminex multiplex assay. Results: CK peaked at 24- h. Monocytes showed greater expression of multicaspase at 24 –h and 48 -h than at PRE. Bcl-2, p53 and caspase-8 were all significantly greater at 24 –h than at PRE. Conclusion: Downhill running did alter the apoptotic response of monocytes and therefore may be important in the recovery process from muscle damage.

Downhill treadmill running is a commonly used method to cause exercise-induced muscle damage, especially in rodents. Previous studies have evaluated which muscles in rats are more prone to damage. However research using downhill run mice (DHR) has shown some inconsistencies in which muscle is best analyzed for damage. Purpose: The purpose of this study was to quantify the damage in various muscles in a mouse after a single bout of DHR. Methods: Male FVB mice (5 months) were injected with Evans Blue dye (EBD) and then either used as control (CON) or run downhill (-16°) at 20 meters per minute (m/min) for 30 minutes. Twenty-four hours after exercise, the gastrocnemius, soleus, plantaris, tibialis anterior (TA), quadriceps, and triceps brachii muscles were harvested (n = 6 per group per muscle). Cross-sectional slices were obtained, fixed, and mounted to analyze EBD infiltration, dystrophin (Dys), and centralized nuclei. The samples were then imaged using a fluorescent microscope. The entire sample was captured using 20x magnification, and the total number of cells, EBD+, Dys-, and centralized nuclei, were counted. A blood sample was collected to measure plasma creatine kinase (CK) activity. Results: Total number of cells was not different between groups (p > 0.05). No significant difference in any of the markers of muscle damage was found in any muscle between CON and DHR (p > 0.05). Conclusion: These data suggest that DHR does not induce muscle damage in adult (5 months) male FVB mice.

Much is known about running economy while running on level ground surfaces. However, with the dynamic of elevation changes during running, more research is needed to understand how various grades that will favor respective mechanics. PURPOSE: In this study, we focused on determining whether certain running mechanics and anatomy would predict a runner's oxygen uptake between downhill versus uphill running. METHODS: Twenty-one experienced runners completed six 5-min running trials (1 shoe x 3 grades x 2 visits) in a Saucony marathon racing shoe model (Type A) on level (3.83 m/s), uphill (+4% grade at 3.35 m/s), and downhill ( ˆ’4% grade at 4.46 m/s) conditions. These treadmill speeds at each grade were predicted as metabolic equivalents through all grades. We measured submaximal oxygen uptake and carbon dioxide production during the entire trial duration with the last 3 min of each trial being averaged. A best-fitting line was generated through oxygen uptake versus grade to classify whether runners were more economical in uphill or downhill conditions relative to other subjects. The slope of this line indicated whether runners were more economical at uphill or downhill running, where a positive slope represented a more economical uphill versus downhill runner. Various running mechanics were measured using Vicon Nexus and a Bertec treadmill. A linear regression determined any correlations between peak vertical force, stride rate, plantar velocity, and ground time against uphill/downhill running ability. RESULTS: Peak vertical force was the only factor associated with the slope of oxygen uptake versus grade (running grade ability; p < 0.01). The slope of oxygen uptake versus grade averaged 0.076 ± 0.278 ((ml/kg/min) / % grade). CONCLUSION: Runners that naturally prefer a higher peak vertical force when running on level ground led to a lower running grade ability (lower oxygen uptake during downhill versus uphill running).

Le trail running, course nature de distances, dénivelés et technicités variables, est une discipline récente à la popularité croissante. La performance en trail dépend de nombreux facteurs génétiques, énergétiques, techniques, stratégiques et motivationnels. Parmi ces facteurs, le coût énergétique de la locomotion fait débat. Les études de cette Thèse s'attachent aux corrélations plat/montée de cette variable, au calcul d'un coût en pente à partir d'un coût à plat, à l'influence de la modification forcée de la fréquence de foulée sur l'énergie consommée, et à l'impact de la fatigue générée par un ultra trail sur le coût à plat et en montée. La prise en compte des contraintes musculaires et biomécaniques en trail d'une part, des facteurs influençant l'économie de course d'autre part, ainsi que des résultats de notre principale étude de terrain, nous laissent émettre l'hypothèse que le coût énergétique et ses variations pre/post course à plat/montée, ne sont pas des indicateurs de performance de l'activité. La force, l'endurance de force et le pacing, en plus de la puissance aérobie et de l'endurance, sont les variables testées les mieux corrélées à la performance en ultra trail / Trail running is a discipline with increasing popularity over the last 2 decades. Trail performance depends on many genetic, energetic, technical, strategic and motivational factors. Among these factors, the energy cost of locomotion is debated. The studies in this Thesis focus on the level/graded correlations of this variable, on the calculation of an uphill cost from a level cost, on the influence of a forced modification of stride frequency on running economy, and on the impact of fatigue generated by an ultra trail on level and uphill costs. Taking account of the muscular and biomechanical constraints on the one hand, and the factors influencing the running economy on the other hand, as well as the results of our main field study, we hypothesize that energy cost and its pre/post fatigue variations, are not performance indicators of the activity. Force, endurance of force and pacing, in addition to aerobic power and endurance, are the tested variables best correlated to ultra trail performance

Il est bien établi chez les physiologistes, que si l’exercice de course en montée sollicite préférentiellement des contractions musculaires concentriques, l’exercice de course en descente requiert des actions musculaires frénatrices, majoritairement excentriques. L’exercice de course en descente à intensité sous-maximale génère un stimulus mécanique plus important pour un niveau de sollicitation métabolique moindre (i.e., V̇O2). Basée sur 3 études expérimentales, cette thèse de doctorat explore la physiologie spécifique de la course en déclivité, ainsi que ses prédicteurs physiologiques. Notre première étude montre une amplitude des réponses cardiorespiratoires amoindrie, une ventilation plus superficielle et une composante lente négative de consommation d’oxygène et de fréquence cardiaque en course en descente versus montée à vitesse constante et identique (8,5 km·h-1, pente de 15%). Lors de tests incrémentaux maximaux en course en descente vs montée vs plat, notre 2ème, partie A étude démontre que des coureurs bien entraînés, familiarisés avec la course en descente, peuvent atteindre FCmax, mais pas V̇O2max en descente. Lorsque les courses en descente et montée sont réalisées à même intensité métabolique (70% V̇O2max), notre 2ème (B) étude démontre que la course en descente (19 km·h-1, pente de -15%) induit des réponses cardiorespiratoires supérieures (FC et V̇E), une composante lente de V̇O2 significative et engendre une fatigue supérieure à la course en montée (6 km·h-1, pente de +15%). Enfin, une étude de terrain (étude 3) montre que les performances de 5 km de course en montée et en descente partagent quelques prédicteurs physiologiques communs (V̇O2max, force musculaire des membres inférieurs), bien que dans des proportions différentes. De plus, ces deux contre-la-montre sont également déterminés par des prédicteurs physiologiques spécifiques (i.e., raideur musculo-tendineuse en descente et indice de masse corporelle en montée). Nos résultats améliorent notre compréhension de la physiologie spécifique à la course en descente vs montée et ouvrent la voie des applications à l’entraînement des traileurs avec le but ultime d’optimiser leur performance. / It is admitted that uphill running mostly elicits concentric muscle actions whereas downhill running requires braking muscle actions inducing preferentially eccentric muscle action. Consequently, high running speed can be achieved in downhill (i.e., a high level of mechanical stress), despite low metabolic demands (i.e., low metabolic power). Using 3 experimental studies, this doctoral thesis explores the specific physiology of downhill vs uphill running as well as its physiological determinants. Our first study shows lower magnitude of the cardiorespiratory responses, a more superficial ventilation pattern and inverse V̇O2 and HR slow components in submaximal constant and same downhill vs uphill running velocity (8,5 km·h-1, 15% slope). During maximal incremental downhill vs uphill and level running, our study 2 part A demonstrates that well-trained endurance athletes, accustomed to downhill running, can reach maximal heart rate but not V̇O2max in downhill running. When downhill and uphill running are performed at similar metabolic demand (70% V̇O2max), our study 2 part B demonstrates that downhill running (19 km·h-1, -15% slope) elicits greater cardiorespiratory responses (HR and V̇E), a significant V̇O2 slow component and exacerbates muscle fatigue compared to uphill running (6 km·h-1, +15% slope). Finally, a field study (study 3) shows that 5-km downhill vs uphill running performances share some physiological predictors (V̇O2max, lower limb muscle strength) although in different proportions. In addition, this study also demonstrates that both time-trial performances are also determined by specific physiological predictors (i.e., musculotendinous stiffness for downhill and body mass index for uphill running). All in all, our results further our understanding of the specific physiology of downhill vs uphill running and open the way to training applications in trail runners with the ultimate goal to optimize trail running performance.