Responses of asthmatic and non-asthmatic athletes to prolonged treadmill running.

Metabolic and cardio-respiratory responses of four asthmatic and four non-asthmatic athletes to two hours of treadmill running at 70 percent of maximal oxygen uptake are compared. The asthmatic group had pre-exercise airflow obstruction, as indicated by the lower forced expiratory volume in one second (FEV1) even after medication (2.90 +/- 0.661) compared to the non-asthmatic group (4.09 +/- 1.331). Changes in blood lactate, glucose and catecholamine concentrations as a result of the two hour run were similar for the two groups. However, the pattern of breathing was different. The asthmatics had a slower breathing frequency but a similar tidal volume to the non-asthmatics. Both groups had an increase in the ventilation rate over the two hour run. For the non-asthmatic group, this increase in ventilation was achieved by an increase in the breathing frequency (p less than 0.01), whereas tidal volume was reduced (p less than 0.05). The increase in the ventilation rate over the two hour run for the asthmatic group was brought about by a small increase in breathing frequency (p less than 0.05), whereas tidal volume was not changed. This maintenance of the tidal volume by the asthmatic athletes during endurance running may compensate for the airflow obstruction, and so allow successful participation in endurance running.     

Physiologic responses to treadmill running in adult and prepubertal males

Little data are available directly comparing physiologic responses to endurance exercise in children and adults. To evaluate age related differences during maximal and submaximal treadmill exercise, physiologic parameters recorded during testing of 20 active prepubertal boys (aged 9-13 years) were compared with values obtained in nonathletic adult males aged 23-33 years. Maximum oxygen consumption (VO2 max) was 57.9 ml.kg-1.min-1 (6.9 SD) in the boys and 48.3 ml.kg-1.min-1 (4.9 SD) in the adults. Running economy examined both as VO2 at a treadmill speed of 9.6 kph and as the slope of linear regression of VO2 at four submaximal speeds was less in boys compared to men when values were expressed per kg body mass. Differences in running economy between the two groups disappeared, however, when related to body surface area. As expected, children had a higher stride frequency at a given treadmill speed, but running stride frequency was unrelated to economy with the two groups. Lower respiratory exchange ratios were observed at maximal and submaximal exercise in the children, which may reflect diminished anaerobic capacity or differences in substrate utilization. These results substantiate the high aerobic capacity previously observed in children and suggest that lower running economy in younger subjects may largely relate to a greater body surface are/mass ratio.     

Salbutamol and high-intensity treadmill running in nonasthmatic highly conditioned athletes

Salbutamol is a widely used drug among elite athletes. We wanted to provide more information on the effects of salbutamol in nonasthmatic athletes. Seventeen highly conditioned male athletes (Vo_2max > 70 ml · kg⁻¹· min⁻¹) participated in a randomized, double-blind and placebo-controlled cross-over study. Nebulized salbutamol (0.05 mg/kg) or placebo was inhaled prior to a high intensity (110% of Vo_2max) treadmill run to exhaustion. The measured variables included endurance time, oxygen uptake, ventilation, breathing rate, heart rate, and oxygen saturation. Lung function was measured as forced expiratory volume in the first second (FEV₁) before and after medication, and during the recovery from the run. The high intensity runs led to total exhaustion after 4–10 min. A close-to-significant shortening in endurance time was found when salbutamol was given. During the running (0–4 min) the oxygen uptake was slightly lower and the heart rate was slightly higher when salbutamol was given. No differences were found in peak oxygen uptake, peak heart rate, ventilation, breathing rate or oxygen saturation. FEV₁ reflected an increase in airway caliber after the inhalation of salbutamol. These changes were still present in the recovery from the test run with the exception of the measurement immediately after the exercise. Although evidence for β-adrenergic stimulation was found, it was concluded that a therapeutic dose of nebulized salbutamol does not improve performance in highly trained athletes during a high-intensity run to exhaustion.     

Thermoregulatory responses to skin wetting during prolonged treadmill running

We examined the physiological responses to skin wetting during a 120-min level treadmill run to assess whether skin wetting would reduce the dehydration and the increase in core temperature associated with prolonged exercise. Testing was conducted in an environmental chamber (T = 29.5 degrees C, wind velocity = 3 m X sec-1) under two different humidity conditions (33 or 66% relative humidity). Ten male subjects performed two runs in each humidity condition; one served as a control run. The other included spraying the body with 50 ml of water (T = 29.5 degrees C) every 10 min. Spraying had no effect on rectal temperature (Tre), heart rate, oxygen consumption, perceived exertion, sweat loss, or percent change in plasma volume in both the humid and the dry conditions. Spraying produced a significant reduction in mean skin temperature (Tsk), which increased the (Tre - Tsk) gradient. At the same time, overall skin conductance (K) was decreased, presumably as a result of cutaneous vasoconstriction due to the low Tsk. Since heat transfer from the body's core to the skin is expressed by the equation: heat transfer = K X (Tre - Tsk) the spraying had no effect on heat transfer away from the core, and Tre remained unchanged.     

Metabolic responses to prolonged work during treadmill and water immersion running

The primary aim of this study was to compare the physiological responses to prolonged treadmill (TM) and water immersion to the neck (WI) running at threshold intensity. Ten endurance runners performed TM and WI running VO2max tests. Subjects completed submaximal performance tests at ventilatory threshold (Tvent) intensities under TM and WI conditions and responses at 15 and 42 minutes examined. VO2 was lower in WI (p<0.05) at maximal effort and Tvent. The Tvent VO2 intensities interpolated from the TM and WI VO2max tests were performed in both TM (i.e., TM@TM(tvent),TM@WI(tvent), corresponding to 77.6 and 71.3% respectively of TM VO2max) and WI conditions (i.e., WI@TM(tvent), WI@WI(tvent), corresponding to 85.5% and 78.2% respectively of WI VO2max). Each of the dependent variables was analyzed using a 3-way repeated measures ANOVA (2 conditions X 2 exercise intensities X 7 time points during exercise). VO2max values were significantly lower in the WI (52.4(5.1) ml.kg(-1) min(-1)) versus TM (59.7(6.5) ml.kg(-1) min(-1)) condition. VO2 during submaximal tests were similar during the TM and WI conditions. HR and [BLa] responses to exercise at and above WI(tvent) were similar during short-term exercise, but values tended to be lower during prolonged exercise in the WI condition. There were no statistical differences in VE responses in the 2 conditions, however as with HR and [BLa] an upward trend was noted with TM exercise over the 42 minute duration of the tests. RPE at WI(tvent) was similar for TM and WI exercise sessions, however, RPE at TM(tvent) was higher during WI compared to TM running. Cardiovascular drift was observed during prolonged TM but not WI running. Results suggest differences in metabolic responses to prolonged submaximal exercise in WI, however it can be used effectively for cross training.     

Physiologic responses to maximal treadmill and deep water running in men and women.

Maximal physiologic responses to treadmill running and deep water running using a flotation device were compared in 12 trained men and 12 trained women. Although the men had significantly higher ventilation volumes, VO2max (liters of oxygen per minute and milliliters of oxygen per kilogram per minute), there were no significant differences in maximal heart rates or respiratory exchange ratios between the sexes. Significantly lower ventilation volumes, VO2max (LO2.min-1 and mlO2.kg-1.min-1), and heart rates were obtained in response to maximal water running compared to treadmill running, regardless of gender. Neither the men's nor women's maximal respiratory exchange ratios were significantly different between modes. The analysis of variance indicated that there were no significant interactions for any of the maximal responses to the tests between the sexes. The magnitude of these differences is similar to that found between treadmill running and cycling ergometry and should not preclude deep water running as a training technique. Caution, however, is advised if the training intensity is to be prescribed on the basis of land-determined heart rates.     

Fat storage in athletes: metabolic and hormonal responses to swimming and running

Despite similar rates of energy expenditure during training, it has been suggested that swimmers store greater amounts of body fat than runners. To investigate these discrepancies, eight male swimmers (S) and runners (R) were monitored during 45 min of swimming or running (75% VO2max), respectively, and six triathletes were monitored during swimming (ST) and running (RT). Each group was also monitored during two hours of recovery. Venous blood samples were obtained before exercise, immediately after exercise (0 min) and at 15, 30, 60 and 120 min of recovery. These samples were analyzed for glucose, lactate, glycerol, free fatty acids (FFA), insulin, glucagon, norepinephrine (NE) and epinephrine (E). Expired gases and heart rates (HR) were obtained during exercise and also during recovery. The caloric cost of recovery was similar, but the RER results suggested increased fat oxidation during recovery for the S and the ST. Serum glucose was greater (P less than 0.05) immediately after exercise for R (6.71 +/- 0.29 mmol/l) and RT (6.40 +/- 0.26) compared to the S (4.97 +/- 0.19) and ST (4.87 +/- 0.18), and was significantly elevated for the initial 30 min of recovery. FFA were similar throughout the recovery period; however, blood glycerol was greater immediately after exercise (0 min) for R compared to S (NS) and was significantly elevated after exercise (0 min) for RT compared to ST. Differences in blood glucose or fat release were not explained by differences in NE or E; however, the glucacon-to-insulin ratio was significantly greater after exercise in the S and ST compared to the R and RT.(ABSTRACT TRUNCATED AT 250 WORDS)     

Eryptosis and hemorheological responses to maximal exercise in athletes: Comparison between running and cycling

We compared the effects of cycling and running exercise on hemorheological and hematological properties, as well as eryptosis markers. Seven endurance‐trained subjects randomly performed a progressive and maximal exercise test on a cycle ergometer and a treadmill. Blood was sampled at rest and at the end of the exercise to analyze hematological and blood rheological parameters including hematocrit (Hct), red blood cell (RBC ) deformability, aggregation, and blood viscosity. Hemoglobin saturation (SpO2), blood lactate, and glucose levels were also monitored. Red blood cell oxidative stress, calcium content, and phosphatidylserine exposure were determined by flow cytometry to assess eryptosis level. Cycling exercise increased blood viscosity and RBC aggregation whereas it had no significant effect on RBC deformability. In contrast, blood viscosity remained unchanged and RBC deformability increased with running. The increase in Hct, lactate, and glucose concentrations and the loss of weight at the end of exercise were not different between running and cycling. Eryptosis markers were not affected by exercise. A significant drop in SpO2 was noted during running but not during cycling. Our study showed that a progressive and maximal exercise test conducted on a cycle ergometer increased blood viscosity while the same test conducted on a treadmill did not change this parameter because of different RBC rheological behavior between the 2 tests. We also demonstrated that a short maximal exercise does not alter RBC physiology in trained athletes. We suspect that exercise‐induced hypoxemia occurring during running could be at the origin of the RBC rheological behavior differences with cycling.     

Effects of shoe type on cardiorespiratory responses and rearfoot motion during treadmill running

Running kinematics and physiological responses to high intensity submaximal treadmill running in training shoes and racing flats were evaluated. Eight women (mean age = 21.9 yr) completed a peak VO2 test on the treadmill (mean peak VO2 = 49.2 ml.kg-1.min-1). In two subsequent testing sessions, subjects completed 15-min runs at a speed corresponding to 90% of peak VO2 (range = 9.9-13.4 km.hr-1) while wearing training shoes and racing flats (balanced order assignment). No significant time effect or time by shoe condition interaction was observed for the rearfoot motion variables. Maximum rearfoot angle and total rearfoot motion averaged 42% and 13.9% higher, respectively, for the racing flat (P less than 0.05). There were significant increases over time for VO2, VE, HR, and RPE, indicating an increase in cardiorespiratory response and the perception of effort over the course of the 15-min run. Thus, metabolic and perceptual indications of fatigue at the end of the run emerged but were not accompanied by rearfoot motion changes in either running shoe. These results indicate that rearfoot motion is a function of shoe design and did not change during 15 min of high intensity running.     

Salbutamol and treadmill performance in non-atopic athletes

Salbutamol and treadmill performance in non-atopic athletes. Med. Sci. Sports Exerc., Vol. 15, No. 6, pp. 520-522, 1983. Nineteen aerobic, non-atopic, athletes (10 females, 9 males) were studied in a double-blind fashion to determine the effect of a therapeutic dosage of salbutamol on pulmonary function, oxygen consumption (VO2max), heart rate (HR), and anaerobic threshold (AT). A placebo and salbutamol (in aerosol form) were administered in a dosage of two puffs four times per day. Forced vital capacity (FVC), FEV1.0, and mid-maximal expiratory flow were assessed prior to a maximal treadmill run, and at 5, 10, and 15 min of recovery. Resting and maximal HR, VO2max, AT, and VE were determined prior to and immediately after the 1-wk experimental period. Pre-test results showed no evidence of airway obstruction in any athlete. There was no significant change in any pulmonary function variable as a result of salbutamol administration. Maximal oxygen consumption showed a slight, nonsignificant (P greater than 0.05) decrease in both the salbutamol and placebo groups. There was also a similar nonsignificant decrease in pulmonary function in both groups. Resting and maximal HR and AT were unchanged. These results indicate that therapeutic administration of a selective beta-2 agonist does not affect pulmonary function or performance-related variables in non-atopic elite athletes.     

Changes in spring-mass characteristics during treadmill running to exhaustion

PURPOSE: To determine whether the stiffness characteristics of the leg change during a treadmill run to voluntary exhaustion. METHODS: Fifteen runners performed a test run at a constant speed that elicited approximately 80% of their .VO(2peak). The run was performed on a treadmill instrumented to measure vertical ground reaction forces; vertical stiffness and leg stiffness were calculated from these forces. Force data were sampled for 15 s every 5 min and immediately before the end of the test. From the force data, average stiffness characteristics were determined for each sample period. An ANOVA with repeated measures (alpha = 0.01) was performed for the group on both vertical and leg stiffness. A single-subject, case-series analysis was also performed on each subject by using ANOVA (alpha = 0.01). RESULTS: Group analysis revealed significant decreases (P < 0.01) in both vertical (23.9 to 23.1 kN.m(-1)) and leg (9.3 to 9.0 kN.m(-1)) stiffness over the run. Based on single-subject ANOVA, 14 of the 15 runners experienced significant (P < or = 0.01) changes in k(vert) over the run. A significant correlation between changes in stride rate and vertical stiffness was found (r = 0.85). Changes in the stiffness properties of the leg, as determined via the spring-mass model, resulted in changes in vertical displacement of the center of mass and leg length (distance from ankle to hip) during stance, as opposed to changes in peak force during ground contact. CONCLUSIONS: Observed changes in stride rate possibly result from changes in the stiffness characteristics of the leg during a run to fatigue.     

Acute responses to barefoot 5 km treadmill running involve changes in landing kinematics and delayed onset muscle soreness

BackgroundBarefoot running has gained popularity among physical activity practitioners, but there is a lack of information regarding the acute adaptations to this running technique without supervision. Information about acute adaptations can help to define the best way to insert barefoot running in the routine of runners willing to, and also provide orientation for those people who want to experience this technique.Research questionWhat acute adaptations can be observed among recreational runners exposed to barefoot running?MethodsSagittal 2D kinematics, plantar pressure, foot sensitivity and delayed onset muscle soreness were compared between conditions of shod and barefoot running in 13 recreational runners who performed two trials of 5 km treadmill running.ResultsWe found an acute effect of barefoot running on foot landing that changes from a rearfoot strike to a forefoot strike pattern. This change most likely contributed to the increase in neuromuscular recruitment of calf muscles (i.e. gastrocnemius and soleus) resulting in higher perception of delayed onset muscle soreness. Barefoot running also elicited higher stride cadence. Plantar pressure before and after running revealed higher pressure in the different foot regions after barefoot running. Foot sensitivity increased after running regardless of the footwear condition.ConclusionBarefoot running has acute effects on running technique including higher perception of delayed onset muscle soreness in the 48 h following the exercise.SignificanceOur results highlight the importance of following participants for days after a first session of barefoot running in order to properly manage the acute adaptation periods as well provide precise advices for those trying the barefoot technique.     

Hamstring and calf muscle activation as a function of bodyweight support during treadmill running in ACL reconstructed athletes

Rehabilitation after injury and reconstruction to the anterior cruciate ligament is thought to require a gradual reintroduction of loading, particularly during resumption of running. One strategy to achieve this is via the use of a reduced-gravity treadmill but it is unknown, if and how muscle activity varies in the reduced gravity conditions compared to regular treadmill running. Nineteen healthy participants and 18 male patients at the end of their rehabilitation (8 with a bone-patellar-bone graft, 10 with a hamstring graft) participated in this multi-muscle surface electromyography (sEMG) running study. The hamstrings and triceps surae were evaluated during a 16 km/h running while at 6 different relative bodyweight conditions from 50% (half weight-bearing) to 100% (full weight-bearing). Muscle activation was examined individually as well as normalized to a composite “entire” activation and considered across the entire gait cycle using Statistical Parametric Mapping. The healthy participants showed differences between the 50–100% BW and 60–100% conditions and in the hamstring graft group for 60–100% and 80–100% conditions. No differences were seen comparing all loading conditions in the bone-patellar-bone graft group. For the hamstrings, from 70% BW and above, there appear to be no difference in activation patterns for any of the groups.The activation patterns of the hamstrings was essentially the same from 70% indicated bodyweight through to full weight bearing when running at 16 km/h. Accordingly, when running at this relatively high speed, we do not expect any adverse effects in terms of altered motor patterns during rehabilitation of these muscles.     

Physiological responses to treadmill and cycle exercise

This study aimed to identify differences in the acute cardio-respiratory, metabolic and perceptual responses between exercise performed on the treadmill and on the cycle ergometer at several intensities. The sample comprised of 20 voluntary male participants (age=22.5 ± 1.8 years; height=177.7 ± 7.0 cm; body mass=72.6 ± 7.9 kg; fat mass=7.87 ± 1.3%) that performed 5 submaximal 8 min exercise bouts, interspersed with a 10 min period of passive recovery. Exercise intensity used on the treadmill was 10, 12, 14, 15 and 16 km/h (0% gradient), and 80, 120, 160, 180 and 200 W on the cycle ergometer (65-70 rpm). There was a significant mode effect and also mode×intensity interaction in oxygen uptake and heart rate with higher values in the treadmill protocol (F=32.0 p=0.000, η2=0.65 and F=132.0 p=0.000, η2=0.88, respectively). The respiratory exchange ratio and blood lactate concentrations were not different across modes (F1, 18=1.9 p=0.183 and F1, 17=0.1 p=0.964, respectively) and rate of perceived exertion values were higher in the cycle ergometer (F1, 12=1.2 p=0.288). Generally, results showed a larger exercise mode effect on the cardio-respiratory variables with higher response patterns on the treadmill, differing according to exercise intensity.     

Mechanical efficiency in athletes during running

The purpose of this study was to compare the external mechanical efficiency (ME) between power-trained athletes ( n = 5) and endurance-trained athletes ( n = 5). The relationships between biomechanical variables and metabolic cost were also investigated. The subjects ran at 3 different speeds (2.50 m · s⁻¹, 3.25 m · s⁻¹ and 4.00 m · s⁻¹) both on the treadmill and on the track. The external work of the subjects was determined by a kinematic arm, and energy expenditure was determined by measuring oxygen consumption and respiratory exchange ratio. Biomechanical parameters included ground reaction forces, angular displacements of the knee and ankle joints and electromyography (EMG) of the selected muscles. The mean ME (±SD) values during running on treadmill were as follows: 49.6±8.9%, 60.1±9.6% and 61.2±10.4% for the endurance group, and 47.1±3.7%, 52.0±4.3% and 57.4±5.5% for the power group. In running on the track the respective values were 57.5±11.9%, 51.5±6.1% and 62.2±9.2% for the endurance group, and 47.0±8.3%, 45.3±10.2% and 60.0±5.9% for the power group. The subject groups did not differ significantly in ME due to high interindividual variance among both subject groups. The metabolic responses such as heart rate, pulmonary ventilation and oxygen uptake differed clearly between the athletic groups but this was not the case for the most of the biomechanical variables (such as EMG, step length and vertical displacement of the centre of the gravity). In conclusion, physiological and biomechanical variables appear to affect ME in a very complex way. In other words, efficiency is related individually to the sum of many variables.     

A treadmill test of sprint running

Anaerobic power is characterized by a high degree of specificity regarding both the recruited muscles as well as the recruitment pattern. The popular Wingate Anaerobic Test (WAnT) is a cycling test that does not satisfy the need for a running-specific anaerobic test. We describe such a test, using a novel type of a commercially available treadmill (BRL 1800, Gymrol, France). The ergometer is equipped with a torque motor to neutralize the frictional resistance of the treadmill belt, and a hip-belt harness connected to a horizontal rod. Force applied to the harness is monitored by a strain gauge mounted on the rod, while vertical movement is monitored by a potentiometer at the posterior fixed end of the rod. These, in conjunction with the treadmill belt speed, enable the computation of horizontal and vertical power as well as the combined total output. Power is calculated both as 'peak' power (highest 2.5 s segment) and 'mean' power (20 s duration). Preliminary results of young athletes were generally consistent with the expected age-related changes in anaerobic power. Values obtained on the anaerobic treadmill were always higher than the corresponding WAnT values previously obtained in comparable age groups. The higher values were probably due to the larger muscle mass involved and the shorter peak and mean power durations (2.5 and 20 s versus 5 and 30 s in the WAnT, respectively). This test should enable not only running-specific anaerobic power monitoring but also the characterization of the relationship between the horizontal and vertical components of that power.     

Mechanical energy changes during treadmill running

The purpose of this study was to investigate mechanical energy changes during treadmill running, using two biomechanical models of the human body: the multi-segment model and the center of mass model. Two university distance runners ran at 3.33 and 2.67 m/s on the treadmill, while the right side was filmed by a 16-mm high-speed movie camera (100 fps). The instantaneous mechanical energies of the multi-segment model composed of 11 rigid segments (ME total) and those of the C.M. model (ME C.M.) were calculated for two strides for each trial. The following results were obtained: the trunk segment was the major contributor to the body energy variations, compared to the four limbs; internal kinetic energy, which was the difference between the energy amounts of the two models, was found to have a phase relationship directly opposite to those of the C.M. model. These findings were contrary to the previous studies on walking and were seen to be important characteristics of running energetics.     

A laboratory running test: metabolic responses of sprint and endurance trained athletes.

A laboratory-based sprint running test has been devised to examine the performance characteristics and metabolic responses of an individual to 30 seconds of maximal exercise. A non-motorised treadmill was used so that the individual was able to sprint at his own chosen speed and also to vary his speed as fatigue occurred. The treadmill was instrumented so that the chosen speeds as well as the equivalent distance travelled could be monitored by micro-computer throughout the test. The test-retest reliability of the procedure was investigated with 14 recreational runners who performed the test on different days. A good correlation (r = 0.93) was found between the values obtained for peak running speeds on the two occasions. In an attempt to establish whether or not this test could be used to identify the differences in the performance characteristics of highly trained individuals, the responses to the test of eleven sprint trained and eleven endurance trained athletes were examined. The sprint trained athletes covered a greater distance (162.2 +/- 5.95 m vis 153.51 +/- 12.32 m; p less than 0.01) and had higher blood lactate concentrations (16.52 +/- 1.23 mM vis 12.98 +/- 1.77 mM; p less than 0.01) than the endurance trained athletes. Therefore this laboratory sprint running test offers an additional way of investigating human responses to brief periods of high intensity exercise.