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At least 865 records · Page 48Linked to original sources

PubMed2005

Intermittent short-term graded running performance in middle-distance runners in hypobaric hypoxia.

This study investigated whether in trained middle-distance runners, intermittent short-term graded running performance is affected by a hypobaric hypoxic environment (simulated 2,500 m) (H). Seven male middle-distance runners performed an aerobic performance test and an intermittent short-term graded anaerobic running-performance test (MART) both in H and in a normobaric normoxic environment (N). VO(2max) and OBLA were markedly lower (by 18.1% and 8.7%, respectively) in H than in N. In MART, neither maximal running velocity (V(max)) nor exhaustion-time was different between N and H (454 (7) m min(-1) vs. 451 (6) m min(-1), respectively, and 208.7 (5.2) s vs. 205.7 (4.2) s, respectively). The blood lactate concentration at sub-maximal running speed (425 m min(-1)) was significantly greater in H than in N (paired t-test: P<0.05). These results suggest that, in trained middle-distance runners, intermittent short-term graded running performance is not affected by H, despite a considerable decrease in aerobic power in H during the aerobic performance test.

Adult↗

PubMed2007

Biomarkers of muscle and cartilage damage and inflammation during a 200 km run.

Ultra-marathon running is frequently associated with muscle fibre damage. However, ultra-marathon related information is scarce. The present study evaluated muscle and cartilage biomarkers, and cytokine secretion during a 200 km running event. Venous blood samples from 54 trained male ultra-marathon runners (mean +/- SD, 45.7 +/- 5.1 years). Plasma creatine phosphokinase (CPK), lactate dehydrogenase (LDH), aspartate aminotransferase (AST), alanine aminotransferase (ALT), lactate, glucose, high-sensitivity C-reactive protein (Hs-CRP), interleukin-6 (IL-6), TNF- proportional, variant and serum cartilage oligomeric matrix protein (COMP) content were determined before, midway and immediately after the race. CPK increased 90-fold (19-fold at 100 km) from pre-race value and LDH increased 3.7-fold (2.2-fold at 100 km). AST increased 15-fold (5-fold at 100 km) and ALT increased 3.9-fold (2-fold at 100 km). Blood lactate and glucose levels did not change significantly. Hs-CRP increased 23-fold (3-fold at 100 km) and IL-6 increased 121-fold at 100 km, and then remained stable up to 200 km, whereas TNF- proportional, variant did not change significantly. Serum COMP increased 3-fold (1.3-fold at 100 km). Post-run CPK was correlated with LDH (r = 0.62, P < 0.001), Hs-CRP (r = 0.45, P < 0.001), ALT (r = 0.89, P < 0.001), AST (r = 0.97, P < 0.001), and IL-6 (r = 0.61, P < 0.001). The present study demonstrated that blood biomarkers related to muscle and cartilage damage and inflammation were increased during a 200 km run and that this was particularly marked during the second half of the event. Ultra-marathon running clearly has a major impact on muscle and cartilage structures.

Adult↗

PubMed2000

Glucose uptake by individual skeletal muscles during running using whole-body positron emission tomography.

The purpose of this study was to examine, by positron emission tomography (PET), the distribution of [18F]fluoro-deoxy-glucose ([18F]FDG) uptake by human muscles during 35 min of running. Thirteen healthy male subjects were studied, seven of whom participated in the exercise study. Running intensity was kept constant such that the subjects' heart rates were maintained at between 140 and 150 beats per minute. [18F]FDG [62.9 (14.8) MBq, mean (SD)] was injected after 15 min of running. PET imaging was started immediately after the running ended. The ratio of [18F]FDG uptake by muscles in runners to that in control subjects (r-c ratio) varied from three to six for the muscles of the foot and leg below the knee joint. The r-c ratio of the medial head of the gastrocnemius (MG) was higher than that of its lateral head (LG). The r-c ratio of the rectus femoris (RF) was lower than that of the other three muscles of the quadriceps femoris (QF). The r-c ratio of inactive muscles located above the waist was approximately 0.7. These results suggest that, during the moderate running of this study: (1) glucose uptake by muscles of the foot and leg below the knee joint clearly increases, (2) the r-c ratio differs significantly among the skeletal muscles, which act synergistically, and (3) glucose uptake by inactive skeletal muscles decreases.

Fluorodeoxyglucose F18↗

PubMed2000

Estimation of %VO2 reserve from heart rate during arm exercise and running.

The purpose of the present investigation was to examine the relationship between the percent heart rate reserve (%HRR) in arm exercise and the corresponding percent oxygen uptake (VO2) reserve, and to compare this relationship to that occurring in running. Fourteen male physical education students took part in the study. Each subject performed a maximal running exercise test and a maximal arm cycling test. The subjects also performed three submaximal exercise bouts (in both exercise modes) at 30%, 60% and 80% of their HRR. The subjects were monitored for their heart rate (HR) at rest, maximal HR (HRmax), HR at submaximal work loads. maximal VO2 (VO2max), VO2 at rest and VO2 at submaximal loads. For each subject, load and exercise mode, %HRR and %VO2 reserve were calculated (from HRmax and VO2max as measured during running and arm cycling) and the relationship between the two was evaluated. The main finding of the present investigation is that the prediction of %VO2 reserve in arm cycling from %HRR is grossly overestimated when calculated from HRmax and VO2max measured during running. The prediction is better but still overestimated when calculated from HRmax and VO2max measured during arm cycling. The findings indicate a better prediction of %VO2 reserve from %HRR for running than for arm exercise. These findings should be taken into consideration when prescribing the target HR for arm training.

Adult↗

PubMed1998

Effect of increasing running velocity on electroencephalogram in a field test.

This study was designed to measure the electroencephalogram (EEG) after exercise with increasing intensity. In a field test with increments in running velocity a 2-min EEG was recorded, together with blood lactate concentration and heart rate, after each stage. An individual protocol was used, with up to six stages of running to ensure comparability of exercise intensity among the subjects, in each of 19 athletes (17 men, 2 women) experienced in leisure-time running. The exercise consisted initially of three running stages of aerobic exercise intensity without blood lactate accumulation followed by stages with an increase of lactate concentration. The protocol of the field test led to a progressive increase in cortical activity directly after the stages without blood lactate accumulation mainly in the delta frequency band, followed by theta and alpha-1 frequency band, and less pronounced in the alpha-2 and in the beta frequency bands. After the stages with an onset and further increase of blood lactate accumulation significant decreases in the beta-2, beta-1 and alpha-1 frequency bands occurred predominantly in temporal (T3, T4, T5, and T6) and occipital (O1, and O2) electrode positions, indicating a stage-by-stage decrease of activity. This decrease may be explained by feed-back from working muscle, via afferents to the cortex from intero- and proprio-receptors and affective processes. This could suggest that through a higher running intensity indicated by an onset of blood lactate accumulation metabolic and mechanical changes led to alterations within the afferent systems influencing the level of cortical activity.

Adult↗

PubMed1998

Influence of the oxygen uptake slow component on the aerobic energy cost of high-intensity submaximal treadmill running in humans.

During high-intensity running, the oxygen uptake (VO2) kinetics is characterised by a slow component which delays the attainment of the steady-state beyond the 3rd min of exercise. To assess if the aerobic energy cost of running measured at the 3rd min (C3) adequately reflects the variability of the true aerobic energy cost measured during the steady-state (Css), 13 highly-trained runners completed sessions of square-wave running at intensities above 80% maximal oxygen uptake (VO2max) on a level treadmill. To evaluate the time at which the steady-state VO2 was attained (tss), the VO2 responses were described using a general double-exponential equation and tss was defined as the time at which VO2 was less than 1% below the asymptotic value given by the model. All the subjects achieved a steady state for intensities equal to or greater than 92% VO2max, and 8 out of 13 achieved it at 99% VO2max. In all cases, tss was less than 13 min. For intensities greater than 85% VO2max, Css was significantly higher than C3 and was positively related to %VO2 max (r=0.44; P < 0.001) while C3 remained constant. The C3 only explained moderately the variability of Css (0.39 < r2 < 0.72, depending on the velocity or the (relative intensity at which the relationship was calculated). Moreover, the excess aerobic energy cost of running the (difference between Css and C3) was well predicted by age (0.90 < r2 < 0.93). Therefore, when the aerobic profile of runners is evaluated, it is recommended that their running efficiencies at velocities which reflect their race intensities should be determined, with VO2 data being measured at the true steady-state.

Adult↗

PubMed1999

Advantages of a smaller bodymass in humans when distance-running in warm, humid conditions.

Using a 65-kg athlete running a 2 h 10 min marathon as an example, we estimated that imbalances between approximately 1400 W of heat production and dissipation would occur in ambient temperatures of 17 degrees C at 90% relative humidity (rh) to 37 degrees C at 50% rh. Because heat production during running depends on body mass and heat loss depends on surface area, intercepts between predicted heat production and maximal heat loss with increasing speeds depend on an athlete's body mass. At 35 degrees C and 60% rh, a 45-kg athlete could maintain thermal balance by running a 2 h 13 min marathon at 19.1 km x h(-1) but a 75-kg athlete would only be able run a 3 h 28 min marathon at 12.2 km x h(-1). In both cases, the production of 970-1020 W of heat would necessitate the evaporation of at least 1.5-1.6 l of sweat per hour. A lower metabolic heat production in lighter runners at any given speed may be one reason why smallness of stature is an asset in distance running.

Adult↗

PubMed1999

Increased mRNAs for procollagens and key regulating enzymes in rat skeletal muscle following downhill running.

The purpose of the study was to investigate pre-translational regulation of collagen expression after a single bout of exercise. We analysed steady-state messenger ribonucleic acid (mRNA) levels for collagen types I, III and IV, alpha- and beta-subunits of prolyl 4-hydroxylase and lysyl oxidase (enzymes modifying procollagen chains), and enzyme activity of prolyl 4-hydroxylase from rat soleus muscle (MS) and the red parts of quadriceps femoris muscle (MQF) after 12 h and after 1, 2, 4, 7 and 14 days of downhill (-13.5 degrees ) treadmill running at a speed of 17 m.min-1 for 130 min. Histological and biochemical assays revealed exercise-induced muscle damage in MQF but not MS. Steady-state mRNA levels for the alpha- and beta-subunits of prolyl 4-hydroxylase in MQF, lysyl oxidase in MS and MQF were increased 12 h after running, whereas prolyl 4-hydroxylase activity did not increase until 2 days after exercise. The mRNA levels for the fibrillar collagens (I and III) and basement membrane type IV collagen significantly increased 1 day and 12 h after exertion, respectively. Peak mRNA levels were observed 2-4 days after running, the increases being more pronounced in MQF than in MS. No significant changes were observed in types I or III collagen at the protein level. Strenuous downhill running thus causes an increase in gene expression for collagen types I and III and their post-translational modifying enzymes in skeletal muscle in a co-ordinated manner. These changes, together with the increased gene expression of type IV collagen, may represent the regenerative response of muscle extracellular matrix to exercise-induced injury and an adaptive response to running exertion.

Animals↗

PubMed1990

Running, osteoarthritis, and bone density: initial 2-year longitudinal study.

PURPOSE: The purpose of this study was to present the 2-year follow-up results examining associations of repetitive long-term physical impact (running) with osteoarthritis and osteoporosis in 34 members of a running club now aged 52 to 74 years and 34 matched control subjects. PATIENTS AND METHODS: Roentgenograms of the hands, lateral lumbar spine, and knees were assessed in pairs (1984 and 1986) without knowledge of running status. Computerized scans of the first lumbar vertebrae were obtained to quantify bone mineral. RESULTS: A decrease in bone density over the 2-year period was statistically significant for nearly all subjects, especially for runners who decreased their running habits. At the 2-year follow-up, runners maintained greater bone density. Progression of the roentgenographic scores for osteoarthritis demonstrated a statistically significant increase in almost all groups in this normative population over the 2-year period. Female runners had more spur formation in the weight-bearing knee roentgenograms than did control subjects. CONCLUSION: With the possible exception of spur formation in women, running did not appear to influence the development of radiologic osteoarthritis in the populations studied.

Aged↗

PubMed1990

Mechanics and energetics in running with special reference to efficiency.

In running, the muscles exert forces acting internally on the body and externally on the ground to move the body's center of mass forward. The energetics of running can be studied by calculating efficiency: mechanical work done/net energy consumed. Variations in efficiency, however, can be attributed not only to the human machinery but also to methodological differences. Mechanical work has been calculated primarily by two procedures: one is from energy changes taking place on and around the body's center of mass, and the other is from segmental analysis. Using the former and assuming the energy cost to be 1 kcal kg-1 km-1, we have shown that efficiency increases with running speed from 45 to 70%, with elastic energy recoil playing a role (Cavagna and Kaneko, J. Physiol. 268, 467-481, 1977). However, the efficiency value decreases with speed if the oxygen debt is included in the calculation of the energy cost. With the same method we have also shown that the efficiency of distance runners is higher than that of sprinters if the running speed is less than 25 km h-1, and that there is a most economical step rate for maximizing the efficiency at a given constant running speed.

Biomechanical Phenomena↗

PubMed1991

Calculation of vertical ground reaction force estimates during running from positional data.

The purpose of this study was to calculate, as a function of time, segmental contributions to the vertical ground reaction force Fz from positional data for the landing phase in running. In order to evaluate the accuracy of the method, time histories of the sum of the segmental contributions were compared to Fz(t) measured directly by a force plate. The human body was modeled as a system of seven rigid segments. During running the positions of markers defining these segments were monitored using a video analysis system operating at 200 Hz. Special care was taken to minimize marker movement relative to the mass centers of segments, and low-pass cutoff frequencies of 50 Hz (markers defining leg segments) and 15-20 Hz (markers defining upper body) were used in filtering the position time histories so as to ensure that high signal frequencies were preserved. The magnitude of the high-frequency peak in Fz, also known as 'impact force peak', was estimated with errors less than 10%, while the time of occurrence of the peak was estimated with errors less than 5 ms. It would appear that the positional data were sufficiently accurate to be used for calculation of intersegmental forces and moments during the landing phase in running. Analysis of the segmental contributions to Fz(t) revealed that the first peak in Fz has its origin in the contribution of support leg segments, while its magnitude is determined primarily by the contribution of the rest of the body. These contributions could be varied independently by changing running style. It follows that if the possible relationship between 'impact force peaks' and injuries is to be investigated, or if the effects of running shoe and surface construction on these force peaks are to be evaluated, the calculation of segmental contributions to Fz(t) is a more suitable approach than measuring only Fz(t).

Acceleration↗

PubMed1993

Effects of arch height of the foot on angular motion of the lower extremities in running.

It has been suggested that a relationship exists between the height of the medial longitudinal arch of the foot and athletic injuries to the lower extremities. However, the functional significance of arch height in relation to injury is not well understood. The purpose of this study was to determine the influence of arch height on kinematic variables of the lower extremities that have been associated with the incidence of injury in running in an attempt to gain some insight into a functional relationship between arch height and injury. The three-dimensional kinematics of the lower extremities were measured during running for 30 subjects using high-speed video cameras. A joint coordinate system was used to calculate the three-dimensional orientation of the ankle joint complex for a single stance phase. Simple, linear regression analyses showed that arch height does not influence either maximal eversion movement or maximal internal leg rotation during running stance. However, assuming that knee pain in running can result from the transfer of foot eversion to internal rotation of the tibia, a functional relationship between arch height and injury may exist in that the transfer of foot eversion to internal leg rotation was found to increase significantly with increasing arch height. A substantial (27%), yet incomplete, amount of the variation in the transfer of movement between subjects was explained by arch height, indicating that there must be factors other than arch height that influence the kinematic coupling at the ankle joint complex. Additionally, the transfer of movement is only one factor of many associated with the etiology of knee pain in running.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1994

The mechanical characteristics of the human heel pad during foot strike in running: an in vivo cineradiographic study.

The compressive properties of the heel pad during the heel strike when running (barefoot and shod, two subjects, 4.5 m s-1) were studied by means of a high-speed two-dimensional cineradiographic registration (150 frames s-1) of an actual running step. Vertical ground reaction forces were measured with a force platform. In barefoot running the heel pad deforms to a maximal percentage deformation of 60.5 +/- 5.5%. In shod running the heel pad deforms only 35.5 +/- 2.5% and the nonlinear force-deformation relationship reflects an increasing stiffness when deformation rises. Although the amplitudes of the vertical ground reaction forces do not differ notably in both conditions, barefoot running implies a maximal deformation to the fatty heel tissue, reducing its functional role from shock reduction towards local protection of the heel bone. It is argued that embedding the foot in a well-fitting shoe increases the effective stiffness of the heel pad.

Adipose Tissue↗

PubMed1983

Oronasal airway choice during running.

The choice of oronasal airway was studied in 984 subjects participating in a 10 km run. Subject's age and sex was obtained from entry forms, degree of mouth opening by videotaping the subjects' upper body as they approached the camera, and average running speed from elapsed time. The degree of mouth opening was evaluated independently by three observers. Results indicated that only three (0.3%) of the 917 analyzed subjects breathed nasally during running, 96.3% breathed oronasally, 2.3% opened and closed their mouths rhythmically with breathing, and in 10 subjects it could not be determined whether the mouth was open or closed. No relationship existed between degree of mouth opening and subjects' age, sex or running speed. It was concluded that the incidence of nasal breathing during self-paced endurance running is less frequent than indicated by previous laboratory studies.

Adolescent↗

PubMed1986

Interpretation of changes in DLCO and pulmonary function after running five miles.

The purpose of this study was to evaluate changes in pulmonary function after running five miles. Of particular interest was the reaffirmation of the previously reported 'uncoupling' or dissociation of pulmonary diffusing capacity (DLCO) and cardiac output (Q) after moderate or strenuous exercise. Cardiopulmonary assessments were made on eight runners before and after completing three separate five mile runs. There were significant reductions in vital capacity (5.7%) and volume at closing with increases in residual volume (22.5%) and closing capacity post-run. Although DLCO did not change, significant change in cardiac output occurred during the DLCO 10 sec breathhold maneuver. The pre-run DLCO maneuver produced a fall in stroke volume (SV) with an increase in HR while maintaining Q. The post-run Q fell during the DLCO maneuver due to a fall in SV with HR remaining constant. The primary basis for previous speculation of the development of a transient pulmonary edema during exercise has been the failure of DLCO to increase immediately after exercise when HR and presumably Q is elevated. To avoid any misinterpretation of changes in DLCO produced by exercise, Q should be measured at the time of the DLCO determination. Our findings suggest that values for DLCO post-exercise are entirely appropriate for the pulmonary blood flow at the time of the DLCO maneuver.

Adult↗

PubMed2004

The role of selected extrinsic foot muscles during running.

OBJECTIVE: To determine the kinematic, kinetic and EMG responses to perturbations of the foot by running in varus, neutral, and valgus-wedged shoes. DESIGN: Within-subjects study comparing kinematics, kinetics and EMG while running in three different shoe conditions. BACKGROUND: Excessive pronation has been cited as a key contributor to many types of running injuries. However, the roles of the extrinsic foot muscles (those that control motion of the foot) during the stance phase of running have not been adequately identified, which is critical to determining the relationship between pronation and injury. METHODS: Ten males ran in varus, valgus, and neutral-wedged shoes while three-dimensional kinematic and kinetic data and EMG data were collected. Surface EMG data were collected from the tibialis anterior, peroneus longus, medial and lateral gastrocnemius, and soleus. Indwelling EMG was obtained from the tibialis posterior. The net joint moment, power, and total positive and negative work was calculated in the frontal plane. EMG onset, offset, and integrated values were reported. RESULTS: The maximum eversion angle, maximum inversion moment and total negative work done in the frontal plane were greatest while running in the valgus shoe and least in the varus shoe. The greater joint moment was not accompanied by changes in muscle activation patterns, although the tibialis posterior data were inconclusive in this respect. CONCLUSIONS: Greater pronation leads to greater energy absorption in the foot invertor muscles and tendons. While not conclusive, the EMG data suggest that for these muscles there was not a neuromuscular adaptation to the perturbation.

Adult↗

PubMed2005

Repeatability of lower extremity kinetics and kinematics for standardized and self-selected running speeds.

INTRODUCTION: The purpose of this study was to determine the effects of self-selected versus standardized running speeds on within-day and between-day repeatability of lower extremity kinematics and kinetics for running gait. METHODS: Subjects (six female, six male, age 18-35) were recreational athletes with no lower extremity injuries. The following study variables were analyzed using the coefficient of variation (CV): the peak angles for knee internal rotation, external rotation, varus, valgus, flexion, and extension; peak angles for ankle dorsiflexion and plantar flexion; peak impact force and propulsive force; and peak anterior, posterior, medial, and lateral ground reaction forces (GRFs). Data for the entire stance phase were analyzed using the coefficient of multiple correlation (CMC) for the following variables: anterior-posterior, medial-lateral, and vertical GRF; the angles and angular velocities for knee internal-external rotation, valgus-varus, flexion-extension, and ankle dorsiflexion-plantar flexion. Each variable was analyzed using a 2 x 2 (speed x day) repeated measures ANOVA (alpha = 0.05). RESULTS: The within-day repeatability for all of the significantly different variables was greater than the between-day repeatability. For variables with a significant difference based on speed, the standardized running speed had greater repeatability. CONCLUSIONS: Within-day repeatability is generally greater than between-day repeatability. Running speed had little effect on the repeatability of any study variable. Having subjects run at a standardized speed may not be as important as previously thought.

Adolescent↗

PubMed2005

Long range correlations in the stride interval of running.

Fluctuations in the stride interval time series of unconstrained walking are not random but exhibit long range correlations that decay as a power law [Hausdorff JM, Peng CK, Ladin Z, Wei JY, Goldberger AL. Is walking a random walk? Evidence for long range correlations in stride interval of human gait. J Appl Physiol 1995;78:349-58]. Here, we examine whether the long range correlations are present in the stride interval time series of running. Recreational female runners ran 8min trials at their preferred running speed as well as 10% and 20% slower and faster than their preferred speed. Both the average time and the amount of variability of the stride interval decreased with increasing speed. Detrended fluctuation analysis (DFA) showed that there were long range correlations present in the stride interval time series and these correlations followed a quasi U-shaped function, with the minimum at the preferred running speed. These results are consistent with the hypothesis that the preferred running speed, falling as it does between the upper and lower limits of possible running speeds, is the speed at which the most dynamical degrees of freedom are available for adaptive control of locomotion.

Adult↗