Nedocromil sodium and diphenhydramine HCl ameliorate exercise-induced arterial hypoxemia in highly trained athletes.

INTRODUCTION: Exercise-induced arterial hypoxemia (EIAH) has been observed in highly trained endurance athletes during near maximal exercise, which may be influenced by a histamine-mediated inflammatory response at the pulmonary capillary-alveolar membrane. In order to test this hypothesis, we examined whether the mast cell stabilizer nedocromil sodium (NS) and H1 -receptor antagonist diphenhydramine HCL (DH) would ameliorate EIAH and mitigate the drop in arterial oxyhemoglobin saturation (Sa O2 ) during intensive exercise. METHODS: Seven highly trained male cross country runners (age, 21 ± 2 years; V̇O2max , 74.7 ± 3.5 ml·kg-1 ·min-1 ) participated in the study. All subjects completed a maximal exercise treadmill test to exhaustion, followed by three 5-min constant-load exercise bouts at 70%, 80%, and 90% V̇O2max . Prior to testing, subjects received either placebo (PL), NS, or DH. RESULTS: Compared to PL, there was a significant treatment effect on Sa O2 (p < 0.001) for both NS and DH during both constant-load exercise and at V̇O2max . Post hoc tests revealed Sa O2  values, compared to PL, were significantly higher at V̇O2max and during DH trials and higher with NS at constant-load intensities except at 70% (p = 0.13). CONCLUSION: The findings provide further evidence that histamine contributes directly or indirectly to the development of EIAH during intense exercise in highly trained athletes.

Variation in Heart-Rate Profile During a Prolonged, Submaximal Swim Bout.

PURPOSE: To describe the heart-rate (HR) response during a prolonged, submaximal, multirepetition swimming bout (ie, typical early-season swimming training), as there is currently little or no literature on this topic. METHODS: A total of 12 collegiate swimmers were instructed to complete sixty 91.4-m (100-yd) freestyle repetitions at their fastest sustainable pace, allowing between 5 and 10 seconds of rest between repetitions. Each swimmer was outfitted with a cardiotachometer, which monitored HR throughout the trial. Completion time (CT) was also recorded for each repetition. Individual means of HR and CT were calculated, and linear mixed models were used to determine the trend across repetitions and between- and within-subject SD for HR and CT. RESULTS: The mean (SD) value for HR was 167.8 (10.8) beats per minute (bpm), for CT was 68.7 (4.1) seconds, and for percentage of best time was 71.2% (4.5%). There was no change (Δ rep 55-6) in HR (-0.1 bpm; 95% confidence interval, -6.8 to 6.6 bpm; P = .97), whereas CT increased (3.0 s; 95% confidence interval, 1.5-4.4 s; P = .001). The between-subjects SD (95% confidence interval) for HR was 12.6 (8.4-19.3 bpm) and for CT was 4.6 (3.1-7.0 s). The within-subject SDs for HR and CT were 4.0 (3.8-4.3 bpm) and 0.9 (0.8-0.95 s), respectively. CONCLUSIONS: The inherent individual variability between swimmers in HR during training suggests that coaches carefully consider the common practice of prescribing workout intensity using rigid HR zones.

Swimmers' Compliance to Training as a Function of Observation: A Pilot Study.

Adherence to prescribed training intensity (i.e., swim speed) has been conveyed as a key parameter regarding improvements in seasonal performance. Evidence has also suggested swimmers have difficulty complying with coach-prescribed training. How this compliance is affected by a coaching presence and oversight has yet to be examined. PURPOSE: The purpose of this study was to determine swimmers' compliance to prescribed training intensity during 3 observational conditions using activity monitors. METHOD: Individualized prediction equations were created via linear regression analyses for intensity using arm-stroke and leg-kick activity counts during a series of seven 91.4-m swim bouts in a group of 17 collegiate swimmers. Equations were used to calculate intensity performed during a standardized training session during which only the observational condition varied (e.g., a coach present on deck, no coach present on deck, and an appointed observer in addition to the coach present on deck). Compliance was calculated from the difference between prescribed training intensity and performed swim intensity. Comparisons were made between observed coaching conditions for compliance using a repeated-measures analysis of variance. RESULTS: Swimmers' compliance to prescribed training intensity during the no-coach condition was less compared with the other conditions, including (a) when a coach was present and (b) when a coach and an additional observer were present (η2 = .58). CONCLUSION: The presence of a coach or lack thereof appeared to be critical in terms of swimmers' compliance to prescribed training intensity. Additional observation by nonsupervisory individuals appeared to have no significant effect on swimmers' compliance.

Acute modulation in dietary behavior following glycogen depletion and postexercise supplementation in trained cyclists.

We investigated the influence of immediate postexercise dietary supplementation on the subsequent food consumption pattern and endurance exercise performance in physically trained individuals. On 2 occasions, trained male cyclists performed a glycogen-depleting exercise bout followed by a 2-h nutritional supplementation period, 28 h of free-living recovery, and a subsequent 40-km cycling time trial. During the 2-h postexercise supplementation, the subjects consumed equal volumes of reduced-fat chocolate milk (CM) or a sports beverage (SB) in a single-blind, randomized design. Thereafter, the cyclists maintained a food log during the free-living recovery period. Dietary and exercise performance parameters were compared between the treatment beverage visits. No differences in total caloric and macronutrient intakes were detected between the CM and SB trials over the course of the free-living recovery. However, a significant interaction (treatment × time) was detected for caloric and macronutrient intakes during the early phase of free-living recovery, such that significantly larger proportions were consumed shortly after SB as compared with CM. No difference was observed in completion time of the 40-km cycling time trial (CM: 66.9 ± 4.1 vs SB: 66.9 ± 3.7 min). Hence, the cyclists achieved similar levels of recovery during the prolonged, free-living period despite the different acute, postexercise nutrient intake rates. We suggest that given adequate time, athletes appear to subconsciously modify their food consumption in response to varied postexercise supplementation such that subsequent-day exercise performance is equivalent.

Acute hypercapnia does not alter voluntary drive to the diaphragm in healthy humans.

Although systemic hypercapnia is a common outcome of pulmonary disease, the relationship between hypercapnia and voluntary diaphragmatic activation (VAdi) is unclear. To examine whether hypercapnia independent of ventilatory work contributes to reduced central motor drive to the diaphragm in healthy humans, 14 subjects spontaneously breathed room air (NN) or a hypercapnic gas mixture (HH; 7% CO2 with air) while at rest. Thereafter, subjects volitionally hyperventilated room air (NH) matching the minute ventilation recorded during HH while maintained at eucapnic levels. Twitch interpolation with bilateral magnetic stimulation of phrenic nerves at functional residual capacity was used to assess VAdi during the three trials. Although PETCO2 was elevated during HH compared with NN and NH (52 vs 36 mmHg), VAdi was not altered across the trials (HH = 93.3 ±â€¯7.0%, NN = 94.4 ±â€¯5.0%, NH = 94.9 ±â€¯4.6%, p = 0.48). Our findings indicate that the magnitude of hypercapnia acutely imposed may not be effective in inhibiting voluntary neural drives to the diaphragm in normal resting individuals.

In-Water Resisted Swim Training for Age-Group Swimmers: An Evaluation of Training Effects.

PURPOSE: The purpose of this study is to compare the efficacy of resisted sprint swim training with that of nonresisted sprint swim training on 50-m freestyle competition time (Vmax50) in age-group swimmers. METHODS: Twenty-four age-group swimmers (age 10.6-14.9 y) were divided into resisted or nonresisted sprint swim training groups and completed a sprint swim training intervention 2 times per week for 10 weeks. Repeated 10-m sprints with progressively increasing resistance were used to determine measures of swim power. Skeletal muscle mass was estimated using B-mode ultrasound. Maturity status was estimated using predicted adult height (%Htadult) and maturity offset. RESULTS: A 2-way repeated-measures analysis of variance revealed no group × time interaction for measured variables. Vmax50 was correlated with skeletal muscle mass and swim power variables, but no significant relationship was found between relative changes in these variables. Estimated maturity status (%Htadult) appeared to be associated with initial measures of swim power and performance variables. CONCLUSIONS: Ten weeks of resisted sprint swim training was not any more effective than nonresisted sprint swim training at improving sprint swim performance in age-group swimmers.

A cross-sectional study of physical activity and arterial compliance: the effects of age and artery size.

Our study examined the relationship between habitual high levels of vigorous physical activity on large and small artery compliance via radial artery pulse wave analysis. Eighty-three healthy men (n = 44) and women (n = 39), aged 18-78 years, were recruited as habitually less active (light-to-moderate exercise ≤3 times/wk) or habitually highly active (vigorous exercise ≥5 times/wk). A multivariate analysis of variance revealed a significant interaction of age and activity level; habitual vigorous activity was associated with greater compliance in large and small arteries in older adults (40-78 years) and younger adults (18-22 years). In the large and small arteries, we observed an age-associated decrease in arterial compliance (aged ≥ 40 years), though it appears to be less pronounced in the large artery among habitually highly active subjects. This study suggests that aging may be associated with declines in large and small artery compliance that can be attenuated by habitual vigorous activity.

Prevalence of Exercise-Induced Arterial Hypoxemia in Distance Runners at Sea Level.

PURPOSE: It has been reported that ~50% of endurance-trained men demonstrate exercise-induced arterial hypoxemia (EIAH) during heavy exercise. However, this often-cited prevalence rate comes from a single study using a cohort of 25 highly trained men who completed maximal cycle ergometry. As arterial oxyhemoglobin saturation (SpO2) during maximal exercise is reported to be significantly lower during treadmill versus cycle ergometry in the same subjects, we hypothesized that the prevalence of EIAH would be greater than previously reported (and commonly referenced) in a larger cohort of highly endurance-trained men during maximal treadmill running. METHODS: Data from 124 highly trained male distance runners (V˙O2max range = 60.3-84.7 mL·kg·min) were retrospectively examined from previously published studies completed in the Indiana University Human Performance Laboratory. Subjects completed a constant speed, progressive-grade treadmill exercise test to volitional exhaustion, and arterial oxyhemoglobin saturation (SaO2ear) in all subjects was estimated using the same oximeter (Hewlett Packard 47201A). RESULTS: Using similar inclusion criteria as previously published for highly trained (V˙O2max > 68 mL·kg·min) and for EIAH (SaO2ear ≤ 91%), 55 of 79 subjects (70%) exhibited exercise-induced arterial desaturation. Across all 124 subjects, 104 (84%) demonstrated at least moderate EIAH (SaO2ear ≤ 93%) during maximal treadmill exercise. SaO2ear was significantly yet weakly correlated with V˙E/V˙O2 (P < 0.01, r = 0.28) and V˙E/V˙CO2 (P < 0.001, r = 0.33) but not with V˙O2max. CONCLUSION: These results indicate that the prevalence of EIAH in highly trained men during maximal treadmill exercise at sea level is greater compared with previously suggested data, with exercise mode perhaps playing a factor in the number of athletes who experience EIAH.

Runners maintain locomotor-respiratory coupling following isocapnic voluntary hyperpnea to task failure.

INTRODUCTION: Evidence has long suggested that mammalian ventilatory and locomotor rhythms are linked, yet determinants and implications of locomotor-respiratory coupling (LRC) continue to be investigated. Anecdotally, respiratory muscle fatigue seen at the end of heavy exercise may result in an uncoupling of movement-ventilation rhythms; however, there is no scientific evidence to substantiate this claim. PURPOSE: We sought to determine whether or not fatigue of the respiratory muscles alters locomotor-respiratory coupling patterns typically observed in highly trained individuals while running. A related query was to examine the relationship between the potential changes in LRC and measures of running economy. METHOD: Twelve male distance runners ran at four submaximal workloads (68-89 % VO2peak) on two separate days while LRC was quantified. One LRC trial served as a control (CON), while the other was performed following an isocapnic voluntary hyperpnea to task failure to induce respiratory muscle fatigue (FT+). LRC was assessed as stride-to-breathing frequency ratios (SF/fB) and degree of LRC (percentage of breaths occurring during the same decile of the step cycle). RESULT: Hyperpnea resulted in significant declines in maximal voluntary inspiratory (MIP) and expiratory (MEP) mouth pressures (ΔMIP = -10 ± 12 cm H2O; ΔMEP = -6 ± 9 cm H2O). There were no differences in minute ventilation between CON and FT+ (CON, all speeds pooled = 104 ± 25 L min(-1); FT+ pooled = 106 ± 23 L min(-1)). Stride frequency was not different between trials; however, breathing frequency was significantly greater during FT+ compared to CON at all speeds (CON pooled = 47 ± 10 br min(-1); FT+ pooled = 52 ± 9 br min(-1)), resulting in smaller corresponding SF/fB. Yet, the degree of LRC was the same during CON and FT+ (CON pooled = 63 ± 15 %; FT+ pooled = 64 ± 18 %). CONCLUSION: The results indicate that trained runners are able to continue entraining breath and step cycles, despite marked changes in exercise breathing frequency, after a fatiguing hyperpnea challenge.

Endurance exercise performance in acute hypoxia is influenced by expiratory flow limitation.

PURPOSE: We sought to determine if expiratory flow limitation influences intensive aerobic exercise performance in mild hypoxia. METHODS: Fourteen trained male cyclists were separated into flow-limited (FL, n = 7) and non-FL (n = 7) groups based on the extent of expiratory flow limitation exhibited during maximal exercise in normoxia. Participants performed two self-paced 5-km cycling time trials, one in normoxic (F IO2 = 0.21) and one in mild hypoxic (F IO2 = 0.17) conditions in a randomized, balanced order with the subjects blinded to composition of the inspirate. Percent change from normoxia to hypoxia in average power output (%ΔP TT) and time to completion (%ΔT TT) were used to assess performance. RESULTS: Hypoxia resulted in a significant decline in estimated arterial O2 saturation and decrements in performance in both groups, although FL had a significantly smaller %ΔP TT (-4.0 ± 0.5 vs. -9.0 ± 1.8 %) and %ΔT TT (1.3 ± 0.3 vs. 3.7 ± 0.9 %) compared to non-FL. At the 5th km of the time trial, minute ventilation did not change from normoxia to hypoxia in FL (3.4 ± 3.1 %) or non-FL (2.3 ± 3.7 %), but only the non-FL reported a significantly increased dyspnea rating in hypoxia compared to normoxia (~9 %). Non-FL athletes did not utilize their ventilatory reserve to defend arterial oxygen saturation in hypoxia, which may have been due to an increased measure of dyspnea in the hypoxic trial. CONCLUSION: FL athletes experience less hypoxia-related aerobic exercise performance impairment as compared to non-FL athletes, despite having less ventilatory reserve.

Large N: a strategy for improving regional sport performance.

UNLABELLED: It has been hypothesized that large differences in maximal performance can arise between various geopolitical regions solely on the basis of differing numbers of participants in the target activity. While there is evidence in support of this hypothesis for a measure of intellectual performance, the same relationship has not been examined for a measure of physical performance. PURPOSE: To determine whether the number of participants is a predictor of the best athletic performance in a region. METHODS: The 2005-2010 USA Swimming Age Group Detail reports were used to determine the number of competitive swimmers participating in each age group for the 59 local swimming communities in the United States. The USA Swimming performance database provided 50-yd-freestyle times in each community for boys and girls for each age (6-19 y). Simple linear regression was used to examine the relationship between the outcome variable (fastest time) and the predictor variable (log of the number of swimmers) for each combination of age, sex, and calendar year. RESULTS: The log of the number of swimmers in a region was a significant predictor of the best performance in that region for all 168 combinations of age, sex, and calendar year (P<.05) and explained, on average, 41%, and as much as 62%, of the variance in the fastest time. CONCLUSION: These findings have important implications for the development of regional sport strategic policy. Increasing the number of participants in the target activity appears a viable strategy for improving regional performance.

Lower-leg compression, running mechanics, and economy in trained distance runners.

The efficacy of and mechanisms behind the widespread use of lower-leg compression as an ergogenic aid to improve running performance are unknown. The purpose of this study was to examine whether wearing graduated lower-leg compression sleeves during exercise evokes changes in running economy (RE), perhaps due to altered gait mechanics. Sixteen highly trained male distance runners completed 2 separate RE tests during a single laboratory session, including a randomized-treatment trial of graduated calf-compression sleeves (CS; 15-20 mm Hg) and a control trial (CON) without compression sleeves. RE was determined by measuring oxygen consumption at 3 constant submaximal speeds of 233, 268, and 300 m/min on a treadmill. Running mechanics were measured during the last 30 s of each 4-min stage of the RE test via wireless triaxial 10-g accelerometer devices attached to the top of each shoe. Ground-contact time, swing time, step frequency, and step length were determined from accelerometric output corresponding to foot-strike and toe-off events. Gait variability was calculated as the standard deviation of a given gait variable for an individual during the last 30 s of each stage. There were no differences in VO2 or kinematic variables between CON and CS trials at any of the speeds. Wearing lower-leg compression does not alter the energetics of running at submaximal speeds through changes in running mechanics or other means. However, it appears that the individual response to wearing lower-leg compression varies greatly and warrants further examination.

Operating lung volumes are affected by exercise mode but not trunk and hip angle during maximal exercise.

INTRODUCTION: Despite VO2peak being, generally, greater while running compared to cycling, ventilation (VE) during maximal exercise is less while running compared to cycling. Differences in operating lung volumes (OLV) between maximal running and cycling could be one explanation for previously observed differences in V E and this could be due to differences in body position e.g., trunk/hip angle during exercise. PURPOSE: We asked whether OLV differed between maximal running and cycling and if this difference was due to trunk/hip angle during exercise. METHODS: Eighteen men performed three graded maximal exercise tests; one while running, one while cycling in the drop position (i.e., extreme hip flexion), and one while cycling upright (i.e., seated with thorax upright). Resting flow-volume characteristics were measured in each body position to be used during exercise. Tidal flow-volume loops were measured throughout the exercise. RESULTS: V E during maximal running (148.8 ± 18.9 L min(-1)) tended to be lower than during cycling in the drop position (158.5 ± 24.7 L min(-1); p = 0.07) and in the upright position (158.5 ± 23.7 L min(-1); p = 0.06). End-inspiratory and end-expiratory lung volumes (EILV, EELV) were significantly larger during drop cycling compared to running (87.1 ± 4.1 and 35.8 ± 6.2 vs. 83.9 ± 6.0 and 33.0 ± 5.7% FVC), but only EILV was larger during upright cycling compared to running (88.2 ± 3.5% FVC). OLV and V E did not differ between cycling positions. CONCLUSION: Since OLV are altered by exercise mode, but cycling position did not have a significant impact on OLV, we conclude that trunk/hip angle is likely not the primary factor determining OLV during maximal exercise.

Skeletal muscle mass and muscular function in master swimmers is related to training distance.

It is unknown whether or not the daily swim training distances of master swimmers (MS) affect the observed changes in skeletal muscle mass (SM) and physical function commonly associated with the aging process. Twenty-two male MS aged 52-82 years were divided into two groups based upon training distance: High MS (>3000 meters swim/session and 4.1 times/week; n=11) and moderate MS (1500-2800 meters swim/session and 3.4 times/week; n=11). Eleven age- and body mass index-matched older (aged 56-80 years) men served as controls (AMC). Subjects who performed resistance training were excluded in this study. Muscle thickness (MTH) was measured by ultrasound at nine sites on the anterior/posterior aspects of the body (forearm, upper arm, trunk, thigh, and lower leg), and from this, total and segmental SM mass values were estimated. Thigh MTH (anterior:posterior mid-thigh, A50:P50) ratio was calculated to assess the site-specific thigh muscle loss. Straight and zigzag walking performance and maximum knee extension/flexion strength were also measured. Arm SM was greater for high MS and moderate MS than for AMC. Total SM index was higher for high MS than for moderate MS and AMC. A50:P50 ratio was greater for high MS than for AMC. Absolute and relative knee extension strength, but not flexion strength, was greater in high MS than in AMC. The A50:P50 ratio inversely correlated (p<0.05) with zigzag walking time, whereas relative knee extension strength positively correlated (p<0.05) with both straight and zigzag walking performance. Training distance in older MS may be an important factor for maintaining muscle mass and function in the aging process.

Ventilatory patterns differ between maximal running and cycling.

To determine the effect of exercise mode on ventilatory patterns, 22 trained men performed two maximal graded exercise tests; one running on a treadmill and one cycling on an ergometer. Tidal flow-volume (FV) loops were recorded during each minute of exercise with maximal loops measured pre and post exercise. Running resulted in a greater VO2peak than cycling (62.7±7.6 vs. 58.1±7.2mLkg(-1)min(-1)). Although maximal ventilation (VE) did not differ between modes, ventilatory equivalents for O2 and CO2 were significantly larger during maximal cycling. Arterial oxygen saturation (estimated via ear oximeter) was also greater during maximal cycling, as were end-expiratory (EELV; 3.40±0.54 vs. 3.21±0.55L) and end-inspiratory lung volumes, (EILV; 6.24±0.88 vs. 5.90±0.74L). Based on these results we conclude that ventilatory patterns differ as a function of exercise mode and these observed differences are likely due to the differences in posture adopted during exercise in these modes.

Possibility of leg muscle hypertrophy by ambulation in older adults: a brief review.

It is known that ambulatory exercises such as brisk walking and jogging are potent stimuli for improving aerobic capacity, but it is less understood whether ambulatory exercise can increase leg muscle size and function. The purpose of this brief review is to discuss whether or not ambulatory exercise elicits leg muscle hypertrophy in older adults. Daily ambulatory activity with moderate (>3 metabolic equivalents [METs], which is defined as the ratio of the work metabolic rate to the resting metabolic rate) intensity estimated by accelerometer is positively correlated with lower body muscle size and function in older adults. Although there is conflicting data on the effects of short-term training, it is possible that relatively long periods of walking, jogging, or intermittent running for over half a year can increase leg muscle size among older adults. In addition, slow-walk training with a combination of leg muscle blood flow restriction elicits muscle hypertrophy only in the blood flow restricted leg muscles. Competitive marathon running and regular high intensity distance running in young and middle-aged adults may not produce leg muscle hypertrophy due to insufficient recovery from the damaging running bout, although there have been no studies that have investigated the effects of running on leg muscle morphology in older subjects. It is clear that skeletal muscle hypertrophy can occur independently of exercise mode and load.

Inspiratory loading and limb locomotor and respiratory muscle deoxygenation during cycling exercise.

The aim of this study was to determine the effect of inspiratory loading on limb locomotor (LM) and respiratory muscle (RM) deoxygenation ([deoxy (Hb+Mb)]) using NIRS during constant-power cycling exercise. Sixteen, male cyclists completed three, 6-min trials. The intensity of the first 3-min of each trial was equivalent to ~80% V(O(2max)) (EX(80%)); during the final 3-min, subjects received an intervention consisting of either moderate inspiratory loading (Load(mod)), heavy inspiratory loading (Load(heavy)), or maximal exercise (Load(EX)). Load(heavy) significantly increased LM [deoxy(Hb+Mb)] from 12.2±9.0 µm during EX(80%) to 15.3±11.7 µm, and RM [deoxy(Hb+Mb)] from 5.9±3.6 µm to 9.5±6.6 µm. LM and RM [deoxy(Hb+Mb)] were significantly increased from EX(80%) to Load(EX); 12.8±9.1 µm to 16.4±10.3 µm and 5.9±2.9 µm to 11.0±6.4 µm, respectively. These data suggest an increase in respiratory muscle load increases muscle deoxy(Hb+Mb) and thus may indicate a reduction in oxygen delivery and/or increased oxygen extraction by the active muscles.

Multi-age-grouping paradigm for young swimmers.

The purpose of this study was to examine the adequacy of "multi-age" classification systems in youth sports with a specific focus on the unisex multi-age-groupings used by USA Swimming. In addition, we offer an analytical rationale for the multi-age-groupings and potential alternatives. We examined the top 100 US swim performances for three years (2005, 2006, and 2007) for girls and boys in 15 age-groups (7 to 20 years and a singular group of 21 years and older). Data for each age and sex were pooled over the three years and means were calculated for each of seven competitive swim events. Swim times differed among each age up to the 14-year age-group in girls (F (14,30885) = 183.9, P < 0.01, Cohen's d = 1.19-3.72, large effect) and 16-year age-group in boys (F (14,30885) = 308.7, P < 0.01, Cohen's d = 0.81-3.64, large effect) for all events. Age-related differences in swim times continued later in boys than girls likely due to differences between the sexes in timing of growth and maturation. Because of the differences in swim performance in contemporary multi-age-groups, stratifying swimmers by a single age is the best means to ensure competitive fairness and equality, although there is no rationale for swimmers under the age of 8 years to compete in separate unisex competitive groups.

Ground contact time as an indicator of metabolic cost in elite distance runners.

UNLABELLED: Differences in running economy at common speeds have been demonstrated between male and female distance runners, as well as between middle-distance (MD) and long-distance (LD) specialists. Whether measures of foot ground contact time (tc), known to be proportional to the mass-specific cost of locomotion, follows the same running economy relationships in these groups is unknown. PURPOSE: This study examined if differences in tc and selected gait kinematic variables exist between elite male and female distance runners, as well as between elite MD and LD specialists, as running speed increases. METHODS: Twelve male and six female elite distance runners completed multiple 30-s trials on a treadmill at common competitive racing velocities. Wireless triaxial 10-g accelerometers, sampling at 1024 Hz, were securely attached to the laces of each shoe. Values of tc, swing time, stride length, and stride frequency were determined from accelerometric output corresponding to foot strike and toe-off events obtained from a minimum of 20 consecutive steps of each foot. A proportional estimate of metabolic cost was obtained by using 1/tc. RESULTS: Women displayed shorter tc, swing time, and stride length with greater stride frequency compared with men at common speeds; however, these differences were largely negated by normalizing to standing height. At common speeds, women demonstrated smaller measures of tc compared with men, suggesting an increased metabolic cost, paralleling published oxygen uptake data. MD specialists displayed smaller increases in 1/tc as speed increased, compared with LD specialists. CONCLUSIONS: Elite distance runners demonstrate ground contact measures that suggest that known differences in running economy between sexes and event specialties may be a result of differences in running gait.

Inspiratory muscle training lowers the oxygen cost of voluntary hyperpnea.

The purpose of this study was to determine if inspiratory muscle training (IMT) alters the oxygen cost of breathing (Vo(2RM)) during voluntary hyperpnea. Sixteen male cyclists completed 6 wk of IMT using an inspiratory load of 50% (IMT) or 15% placebo (CON) of maximal inspiratory pressure (Pi(max)). Prior to training, a maximal incremental cycle ergometer test was performed to determine Vo(2) and ventilation (V(E)) at multiple workloads. Pre- and post-training, subjects performed three separate 4-min bouts of voluntary eucapnic hyperpnea (mimic), matching V(E) that occurred at 50, 75, and 100% of Vo(2 max). Pi(max) was significantly increased (P < 0.05) by 22.5 ± 8.7% from pre- to post-IMT and remained unchanged in the CON group. The Vo(2RM) required during the mimic trial corresponded to 5.1 ± 2.5, 5.7 ± 1.4, and 11.7% ± 2.5% of the total Vo(2) (Vo(2T)) at ventilatory workloads equivalent to 50, 75, and 100% of Vo(2 max), respectively. Following IMT, the Vo(2RM) requirement significantly decreased (P < 0.05) by 1.5% (4.2 ± 1.4% of Vo(2T)) at 75% Vo(2 max) and 3.4% (8.1 ± 3.5% of Vo(2T)) at 100% Vo(2 max). No significant changes were shown in the CON group. IMT significantly reduced the O(2) cost of voluntary hyperpnea, which suggests that a reduction in the O(2) requirement of the respiratory muscles following a period of IMT may facilitate increased O(2) availability to the active muscles during exercise. These data suggest that IMT may reduce the O(2) cost of ventilation during exercise, providing an insight into mechanism(s) underpinning the reported improvements in whole body endurance performance; however, this awaits further investigation.