Distance Running Performance Research Articles

Effects of compression garments on surface EMG and physiological responses during and after distance running

BackgroundThe few previous studies that focused on the effects of compression garments (CG) on distance running performance have simultaneously measured electromyogram, physiological, and perceptual parameters. Therefore, this study investigated the effects of CG on muscle activation and median frequency during and after distance running, as well as blood-lactate concentration and rating of perceived exertion (RPE) during distance running. MethodsEight healthy male recreational runners were recruited to randomly perform two 40 min treadmill running trials, one with CG, and the other with control garment made of normal cloth. The RPE and the surface electromyography (EMG) of 5 lower extremity muscles including gluteus maximus (GM), rectus femoris (RF), semitendinosus (ST), tibialis anterior (TA), and gastrocnemius (GAS) were measured during the running trial. The blood-lactate levels before and after the running trial were measured. ResultsWearing CG led to significant lower muscle activation (p < 0.05) in the GM (decreased 7.40%–14.31%), RF (decreased 4.39%–4.76%), and ST (decreased 3.42%–7.20%) muscles; moreover, significant higher median frequency (p< 0.05) in the GM (increased 5.57%) and ST (increased 10.58%) muscles. Wearing CG did not alter the RPE values or the blood-lactate levels (p > 0.05). ConclusionWearing CG was associated with significantly lower muscle activation and higher median frequency in the running-related key muscles during distance running. This finding suggested that wearing CG may improve muscle function, which might enhance running performance and prevent muscle fatigue.

Altered Running Economy Directly Translates to Altered Distance-Running Performance.

Our goal was to quantify if small (1%-3%) changes in running economy quantitatively affect distance-running performance. Based on the linear relationship between metabolic rate and running velocity and on earlier observations that added shoe mass increases metabolic rate by ~1% per 100 g per shoe, we hypothesized that adding 100 and 300 g per shoe would slow 3000-m time-trial performance by 1% and 3%, respectively. Eighteen male sub-20-min 5-km runners completed treadmill testing, and three 3000-m time trials wearing control shoes and identical shoes with 100 and 300 g of discreetly added mass. We measured rates of oxygen consumption and carbon dioxide production and calculated metabolic rates for the treadmill tests, and we recorded overall running time for the time trials. Adding mass to the shoes significantly increased metabolic rate at 3.5 m·s by 1.11% per 100 g per shoe (95% confidence interval = 0.88%-1.35%). While wearing the control shoes, participants ran the 3000-m time trial in 626.1 ± 55.6 s. Times averaged 0.65% ± 1.36% and 2.37% ± 2.09% slower for the +100-g and +300-g shoes, respectively (P < 0.001). On the basis of a linear fit of all the data, 3000-m time increased 0.78% per added 100 g per shoe (95% confidence interval = 0.52%-1.04%). Adding shoe mass predictably degrades running economy and slows 3000-m time-trial performance proportionally. Our data demonstrate that laboratory-based running economy measurements can accurately predict changes in distance-running race performance due to shoe modifications.

Echinacea Supplementation: Does it Really Improve Aerobic Fitness?

[Purpose]Echinacea is an herbal supplement used by endurance athletes for its performance boosting properties. It is thought that Echinacea improves the blood’s oxygen carrying capacity by increasing production of erythropoietin (EPO), a glycoprotein that regulates red blood cell formation. Subsequently, these changes would lead to an overall improvement in maximal oxygen uptake (VO2max) and running economy (RE), two markers of aerobic fitness. The purpose of this review is to briefly discuss the physiological variables associated with distance running performance and how these variables are influenced by Echinacea supplementation.[Methods]To determine Echinacea’s ergogenic potential, human studies that used Echinacea in conjunction to analyzing the blood’s oxygen carrying capacity and/or aerobic fitness were assessed.[Results]Taken together, the majority of the published literature does not support the claim that Echinacea is a beneficial ergogenic aid. With the exception of one study, several independent groups have reported Echinacea supplementation does not increase EPO production, blood markers of oxygen transport, VO2max or RE in healthy untrained or trained subjects.[Conclusion]To date, the published literature does not support the use of Echinacea as an ergogenic aid to improve aerobic fitness in healthy untrained or trained subjects.

Incline Treadmill Interval Training: Short vs. Long Bouts and the Effects on Distance Running Performance

This study compared 6 weeks of incline treadmill interval training (INC) performed on a 10% treadmill grade using either sprint-like efforts or slower, longer bouts. 24 individuals were randomly assigned between 2 groups that each completed 2 INC and one 30-min level-grade sessions∙wk-1. Training intensities, bout durations and the number of intervals per INC session were the velocity associated with VO2max (Vmax), 30 s and 10-14 (INCShort n=12), and 68%Vmax, ~3 min and 4-6 (INCLong n=12), respectively. All 30-min sessions were at 65%Vmax. Pre- and post-testing assessed VO2max; lactate threshold (VLT); running economy; and time-to-exhaustion at various conditions including 80%Vmax and 20% grade (CFMod). Both groups improved significantly in all tests; additionally, INCShort improved significantly more so in VLT and CFMod despite INCLong performing more than 2 times the running each INC session (P<0.05). Mean effect size (ES) of the relative improvement in a majority of tests revealed a trivial to very large ES of INCShort vs. INCLong training (ES range: 0.05-4.05). We conclude sprint-like INC better than slower, longer INC at improving a key determinant of distance running performance (VLT), and better at preparing individuals for running on courses with a variety of grades.

Barefoot Running Reduces the Submaximal Oxygen Cost in Female Distance Runners.

Berrones, AJ, Kurti, SP, Kilsdonk, KM, Cortez, DJ, Melo, FF, and Whitehurst, M. Barefoot running reduces the submaximal oxygen cost in female distance runners. J Strength Cond Res 30(8): 2348-2353, 2016-Being a competitive distance runner is, in part, attributable to a high V[Combining Dot Above]O2max. However, running economy (RE) is a more robust indicator of distance running performance among endurance athletes of similar V[Combining Dot Above]O2max levels. The purpose of this study was to examine the influence of unshod (barefoot) vs. shod (wearing shoes) running on RE (expressed as ml·kg·min) during three 5-minute submaximal running trials representing 65, 75, and 85% of V[Combining Dot Above]O2max. Other physiologic and perceptual variables such as respiratory exchange ratio, lactate, heart rate, and ratings of perceived exertion were also chosen as dependent variables. We measured V[Combining Dot Above]O2max in 14 recreationally active trained distance female runners (age = 27.6 ± 1.6 years; height = 163.3 ± 1.7 cm; weight = 57.8 ± 1.9 kg) who were completely inexperienced with unshod running. After initial testing, each subject was randomized to either unshod or shod for days 2 and 3. We analyzed the data with a 2-way (condition by intensity) repeated-measures analysis of variance. Submaximal oxygen consumption was significantly reduced at 85% of V[Combining Dot Above]O2max (p = 0.018), indicating an improvement in RE, but not during the 65% or 75% trials (p > 0.05, both). No other dependent measure was different between unshod and shod conditions. Our results indicate that the immediate improvement to RE while barefoot occurs at a relatively high fraction of maximal oxygen consumption. For the recreational or competitive distance runner, training or competing while barefoot may be a useful strategy to improve endurance performance.

Synchronizing Foot Strike and Cardiac Cycle Phase Affects Heart Rate and Metabolic Responses to Running

The interplay between physiological factors such as muscle perfusion and venous return to the heart has a major role in cardiovascular and peripheral responses during running. Timing cardiac contraction (i.e. systole) to occur in synchrony with skeletal muscle relaxation (swing phase of the gait cycle) may reduce cardiac afterload and promote coronary and skeletal muscle perfusion. In turn, this should manifest in a reduced HR response at a constant running velocity, secondary to an increased stroke volume. PURPOSE: To assess HR and metabolic responses associated with running when foot strikes are timed to occur during 1) the systolic phase of the cardiac cycle, or 2) the diastolic phase. METHODS: Ten elite male distance runners performed a testing session on the treadmill at 4.72 m/s (5:40 min/mile) pace while matching their steps to an auditory tone and wearing a chest strap that generated accelerometer and ECG signals. Testing began with a 3-min control stage (no tone), immediately followed by 2 or 3 pairs of “toned” stepping phases (pair = 2 x 3-min), where the signal to step was given either at 100% of the subject’s R-R interval (systolic stepping; SS) or 45% of R-R (diastolic stepping; DS). The order of DS and SS within each pair was randomized and double blinded. VO2, VE and RER were measured continuously. RESULTS: Twenty-eight pairs of DS + SS were used for HR, step rate (SR) and length (SL) comparisons and 24 pairs were included in metabolic data analyses. All subjects accurately timed their steps with the auditory tones (DS: 45.0 ± 4.3 %; SS: 100.1 ± 5.0 % of R-R interval). While VO2 was similar, HR, SR, VE and RER were significantly (p < 0.001) lower during DS compared to SS (HR: 172 ± 6 vs 175 ± 7 beats·min-1; SR: 172 ± 6 vs 175 ± 7 steps·min-1; VE: 100.0 ± 10.8 vs 103.7 ± 11.8 l·min-1; RER: 0.93 ± 0.03 vs 0.95 ± 0.03, for DS & SS, respectively) despite subjects having to lengthen their steps more during DS compared to SS (p < 0.001; 2.5 ± 3.1 vs 0.9 ± 3.2 % of control SL, respectively) to match HR. CONCLUSION: Synchronizing foot strike to occur during diastole, as opposed to systole, reduces HR during running, presumably as a result of an increase in stroke volume and/or enhanced muscle perfusion. The cardiac advantage with DS may be beneficial to distance running performance. Supported by a grant from Pulson Inc.

Anaerobic and aerobic contributions to 800 m and 8 km season bests

Objective: Both anaerobic and aerobic factors contribute to distance running performance. How these factors relate to middle and long distance running performance in National Association of Intercollegiate Athletics (NAIA) runners has not been previously determined. The purpose of this study was to examine relationships between anaerobic and aerobic assessments and two season best race times (800 m and 8 km) in NAIA runners participating in track and cross-country at a small Midwestern American college. Design: This study employed a cross-sectional design. Data was collected from a lab visit as well as from season best running times. Methods: 11 subjects (f = 4) completed a graded exercise test for VO2max and ventilatory threshold assessment, a 40 m sprint, a standing long jump, and a vertical jump. Correlations were performed between 800 m and 8 km season bests and the afore mentioned tests. Results: 800 m run time correlated only with VO2max (r = -.600; p = .044). 8 km run time correlated most strongly with vertical jump height (r = -.823; p = .011) but also with 40 m sprint (r = .704; p = .039) and VO2max (r = -.670; p = .047). Conclusions: Anaerobic and aerobic contributions to season best race times in NAIA runners were slightly different than expected based on previous work in different populations. This information may be useful for NAIA track and cross-country coaches interested in determining tests that best relate to running performance in their athletes.

The Effect of Energy Status on Distance Running Performance Across a Competitive Season in Female Cross-country Runners

Female cross-country runners are at a higher risk for chronic energy deficiency (ED). Cross-sectional evidence demonstrates the negative effects of ED on surrogate markers of performance. The association between chronic ED and distance running performance in female cross-country runners across a season is unclear. PURPOSE: To examine competitive 5km time trial performance across a season in female cross-country runners categorized by energy status. METHODS: 18 female cross-country runners (19.5 ± 0.3 yrs, 54.6 ± 1.4 kg, 61.2 ± 1.7 mL/kg/min) participated in this prospective observational study across a 10-12 week competitive season. Outcome measures were assessed pre and post-season. Resting energy expenditure (REE) was measured using indirect calorimetry and compared to the Harris Benedict predicted REE (REE/pREE) as a marker of ED. Performance was assessed during an outdoor 5km time trial. Fasting blood samples were assayed for total triiodothyronine (TT3). Repeated measures ANOVA were performed to compare log TT3 and 5km time trial outcomes across the season among participants grouped by tertiles (n=6 each group) of pre-season REE/pREE (severe ED (SED; REE/pREE<0.84), moderate ED (MED; 0.84≤REE/pREE<0.90), and energy replete (ER; REE/pREE≥0.90)). RESULTS: There was a significant group effect (p=0.004), however no time or interaction effects (p>0.49) were observed for the 5km time trial. Pre-season the SED group was 4.1s (p=0.005) slower vs the MED group, while no differences were observed between the ER and the SED or MED groups (p>0.1). Post-season the SED group was 3.7s (p=0.002) and 2.6s (p=0.023) slower vs the MED and ER groups, respectively. For log TT3 there were no significant time or group effects (p>0.15), however a trend toward a significant interaction effect (p=0.097) was observed. Pre-season log TT3 was lower (p=0.043) in the SED vs MED groups, a trend to significance (p=0.067) was observed between the SED and ER groups, with no difference between the ER and MED groups. Log TT3 was not different between groups post-season (p=0.36). CONCLUSIONS: We provide evidence of decrements in 5km time trial performance in severely ED female cross-country runners. Early detection of severe ED utilizing REE may be a strategy for preventing suboptimal distance running performance across a competitive season.

Effects of a 4-week inspiratory muscle training program on the performance in distance runners: a randomized controlled trial

Effects of a 4-week inspiratory muscle training program on the performance in distance runners: a randomized controlled trial

Skinfold Thickness As A Predictor Of 5k Performance For Trained, Female Runners

Greater levels of adipocity have traditionally been linked to a decrease in distance running performance, as excess amounts of body fat have been seen to increase energy expenditure necessary to perform weight bearing movements. PURPOSE: The purpose of the current investigation was to determine the predictive power of specific skinfold sites, including thigh, suprailiac and triceps on both 5k performance and Vo2max levels for trained, female distance runners. METHODS: Thirty-five trained female subjects volunteered to participate in the study. All subjects were required to have a 5k performance of 22:00 or less within the past 12 months. Body composition was estimated using skinfold calipers at the thigh, suprailiac and triceps. Subjects completed an incremental treadmill test to exhaustion to determine Vo2max. Each subject reported their fastest three 5k race times completed within the last 12 months. The median of these three times was recorded as 5k performance. RESULTS: Thigh skinfold and suprailiac skinfold were significantly (p < .05) correlated with 5k performance (r = -.49, r = -.43, respectively) while triceps skinfold was not significantly (p > .05) correlated with 5k performance (r = -.10). Thigh skinfold and suprailiac skinfold were used to create a multiple regression equation. The overall regression model was statistically significant F(2, 31) = 5.43, p < .05. The regression equation revealed 25.9% of the variance in 5k performance could be predicted by thigh skinfold and suprailiac skinfold (p < .05). There was no significant relationship between thigh skinfold, suprailiac skinfold, and triceps skinfold with Vo2max (r = -.22, r = -.26, r = .06, respectively, p > .05). CONCLUSION: Skinfold thickness in the thigh, suprailiac and triceps was not correlated with Vo2max, however thigh and suprailiac skinfold thickness were significantly correlated with 5k performance. Adiposity may not directly affect maximal oxygen uptake, but may effect biomechanical efficiency of movement, hence directly effecting the velocity at which a 5k race may be completed. Skinfold thickness in the thigh and thoracic region may be a useful predictor of 5k performance for female distance runners, while adiposity in the triceps is not an important factor in determining endurance performance.

Acute Weighted Vest Running Effect on Middle Distance Running Performance

Acute Weighted Vest Running Effect on Middle Distance Running Performance

Competitive Marathon Runners Exhibit Greater Running Economy than Recreational Runners

INTRODUCTION: Running economy (RE) has been identified as a predictor of distance running performance. More experienced runners are generally more economical than novice or recreational runners, requiring less oxygen to cover the same distance. Given the metabolic cost of marathon running, it was hypothesized that competitive runners (COMP) would be more economical than recreational runners (REC), and that RE at sub-maximal paces would be associated with marathon performance (MP) in both groups. PURPOSE: To compare RE in COMP versus REC runners, and to determine whether it is associated with MP in each group. METHODS: Twenty-nine runners (ages 18-47, 15 male and 14 female) completed a time trial or road race (from 2-miles to 10-km), a 30-minute sub-maximal treadmill run progressing through 6 stages of 5-min from 75 to 100% of 10-km race velocity, and a 26.2 mile road marathon. If necessary, velocities for the 30-min run were set by converting race times to a 10-km equivalent. Oxygen use was assessed continuously during the 30-min run via metabolic cart. Projected marathon finish times were determined using published race time equivalency charts. Marathon performance was reported as percent difference from predicted finish time, with a positive value indicating a slower than expected marathon. Twelve runners (30 ± 8 years, 3 female) had projected marathon finish times of 3:10 or faster (2:58 ± 13 min) and were categorized as COMP, with the other nineteen runners (20 ± 1 years, 11 female) categorized as REC (4:18 ± 41 min). RESULTS: Average O2 use over the 30-min run was 194.7 ± 9.8 ml/kg/km for COMP and 211.6 ± 17.3 ml/kg/km for REC (p=0.005). Both groups ran slower than predicted for the marathon. The percent off expected MP for COMP was 1.7 ± 3.2% and for REC was 15.7 ± 5.8% (p≤0.001). For all runners, O2 use was associated with MP (p≤0.001). By group, there was a trend toward an association between RE and MP. The correlations for REC and COMP runners were 0.419 (p=0.094) and 0.386 (p=0.215). CONCLUSIONS: Competitive runners are more economical than recreational runners and run closer to the marathon finish times predicted by shorter races. Within each category, runners with better RE tend to run closer to their predicted times in the marathon. Running economy may be a more important predictor of performance in the marathon than in races of shorter distances.

Effects of Explosive Type Strength Training on Selected Physical and Technical Performance Characteristics in Middle Distance Running - a Case Report

Abstract Introduction . Distance running performance is a simple function of developing high speeds and maintaining this speed as long as possible. Thus a correct running technique becomes an important component of performance. Technique is effective if the competitor can reach a better performance result with the same or lower energy consumption. The purpose of this investigation was to examine a six weeks application explosive type strength training on lower extremities power and maximum speed performance improvement in order to facilitate running technique in sub-elite male middle-distance runner. Material and methods . A sub-elite runner performed twice a week special exercises and running drills. He completed a pre and post-training jumping (SJ, CMJ, standing long jump, standing five jump) and speed (20 m from standing and flying start) field tests. For kinematical analysis, a video (SIMI Motion System) of a 10 m sprint from a 20 m flying start was collected. Results . Improvement occurred in all measurements but strong changes were evident in the 10 m from 20 flying start and in stride frequency from 3.90 to 4.01 Hz, due to decreasing of ground contact time from 160 to 156 ms. No strong evidence in the participant's running technique changes. Conclusion . This proved that six weeks of dynamic type strength program seems to improve neuromuscular characteristics of running speed and explosive power and no changes in running technique.

Mean platelet volume (MPV) predicts middle distance running performance.

BackgroundRunning economy and performance in middle distance running depend on several physiological factors, which include anthropometric variables, functional characteristics, training volume and intensity. Since little information is available about hematological predictors of middle distance running time, we investigated whether some hematological parameters may be associated with middle distance running performance in a large sample of recreational runners.MethodsThe study population consisted in 43 amateur runners (15 females, 28 males; median age 47 years), who successfully concluded a 21.1 km half-marathon at 75–85% of their maximal aerobic power (VO2max). Whole blood was collected 10 min before the run started and immediately thereafter, and hematological testing was completed within 2 hours after sample collection.ResultsThe values of lymphocytes and eosinophils exhibited a significant decrease compared to pre-run values, whereas those of mean corpuscular volume (MCV), platelets, mean platelet volume (MPV), white blood cells (WBCs), neutrophils and monocytes were significantly increased after the run. In univariate analysis, significant associations with running time were found for pre-run values of hematocrit, hemoglobin, mean corpuscular hemoglobin (MCH), red blood cell distribution width (RDW), MPV, reticulocyte hemoglobin concentration (RetCHR), and post-run values of MCH, RDW, MPV, monocytes and RetCHR. In multivariate analysis, in which running time was entered as dependent variable whereas age, sex, blood lactate, body mass index, VO2max, mean training regimen and the hematological parameters significantly associated with running performance in univariate analysis were entered as independent variables, only MPV values before and after the trial remained significantly associated with running time. After adjustment for platelet count, the MPV value before the run (p = 0.042), but not thereafter (p = 0.247), remained significantly associated with running performance.ConclusionThe significant association between baseline MPV and running time suggest that hyperactive platelets may exert some pleiotropic effects on endurance performance.

Echinacea Purpurea Supplementation Does Not Enhance V[Combining Dot Above]O2max in Distance Runners

Baumann, CW, Bond, KL, Rupp, JC, Ingalls, CP, and Doyle, JA. Echinacea purpurea supplementation does not enhance V[Combining Dot Above]O2max in distance runners. J Strength Cond Res 28(5): 1367–1372, 2014—Oral supplementation of Echinacea purpurea (ECH) has been reported to increase levels of serum erythropoietin and as a result improve endurance performance in untrained subjects. The purpose of this study was to determine if ECH supplementation alters maximal oxygen uptake (V[Combining Dot Above]O2max) in trained endurance runners. Using a double-blind design, 16 trained endurance runners (9 ECH and 7 placebo [PLA]) supplemented with either 8,000 mg·d−1 of ECH or wheat flour (PLA) for 6 weeks. Maximal aerobic treadmill tests and blood samples were measured before and after supplementation to determine V[Combining Dot Above]O2max, hematocrit (Hct), and hemoglobin (Hb). V[Combining Dot Above]O2max, Hct, and Hb did not differ between the ECH and PLA groups before or after supplementation. Furthermore, supplementation of ECH failed to improve V[Combining Dot Above]O2max (67.37 ± 4.62 vs. 67.23 ± 5.82 ml·kg−1·min−1), Hct (43.57 ± 2.38 vs. 42.85 ± 1.46%), or Hb (14.93 ± 1.27 vs. 15.55 ± 0.80 g·dL−1) from baseline measurements. Echinacea purpurea supplementation of 8,000 mg·d−1 for 6 weeks failed to increase V[Combining Dot Above]O2max, Hct, or Hb in trained endurance runners and thus does not seem to influence physiological variables that affect distance running performance.

Effects of Resistance Training on Running Economy and Cross-country Performance

Heavy-resistance training and plyometric training offer distinct physiological and neuromuscular adaptations that could enhance running economy and, consequently, distance-running performance. To date, no studies have examined the effect of combining the two modes of training on running economy or performance. Fifty collegiate male and female cross-country runners performed a 5-km time trial and a series of laboratory-based tests to determine aerobic, anthropometric, biomechanical, and neuromuscular characteristics. Thereafter, each athlete participated in a season of six to eight collegiate cross-country races for 13 wk. After the first 4 wk, athletes were randomly assigned to either heavy-resistance or plyometric plus heavy-resistance training. Five days after completing their final competition, runners repeated the same set of laboratory tests. We also estimated the effects of the intervention on competition performance throughout the season using athletes of other teams as controls. Heavy-resistance training produced small-moderate improvements in peak speed, running economy, and neuromuscular characteristics relative to plyometric resistance training, whereas changes in biomechanical measures favored plyometric resistance training. Men made less gains than women in most tests. Both treatments had possibly harmful effects on competition times in men (mean = 0.5%; 90% confidence interval = ±1.2%), but there may have been benefit for some individuals. Both treatments were likely beneficial for all women (-1.2%; ±1.3%), but heavy-resistance training was possibly better than plyometric resistance training. The changes in laboratory-based parameters related to distance-running performance were consistent with the changes in competition times for women but only partly for men. Our data indicate that women should include heavy-resistance training in their programs, but men should be cautious about using it in season until more research establishes whether certain men are positive or negative responders.

Energy cost of running and Achilles tendon stiffness in man and woman trained runners.

The energy cost of running (Erun), a key determinant of distance running performance, is influenced by several factors. Although it is important to express Erun as energy cost, no study has used this approach to compare similarly trained men and women. Furthermore, the relationship between Achilles tendon (AT) stiffness and Erun has not been compared between men and women. Therefore, our purpose was to determine if sex‐specific differences in Erun and/or AT stiffness existed. Erun (kcal kg−1 km−1) was determined by indirect calorimetry at 75%, 85%, and 95% of the speed at lactate threshold (sLT) on 11 man (mean ± SEM, 35 ± 1 years, 177 ± 1 cm, 78 ± 1 kg, 1 = 56 ± 1 mL kg−1 min−1) and 18 woman (33 ± 1 years, 165 ± 1 cm, 58 ± 1 kg, 2 = 50 ± 0.3 mL kg−1 min−1) runners. AT stiffness was measured using ultrasound with dynamometry. Man Erun was 1.01 ± 0.06, 1.04 ± 0.07, and 1.07 ± 0.07 kcal kg−1 km−1. Woman Erun was 1.05 ± 0.10, 1.07 ± 0.09, and 1.09 ± 0.10 kcal kg−1 km−1. There was no significant sex effect for Erun or RER, but both increased with speed (P < 0.01) expressed relative to sLT. High‐range AT stiffness was 191 ± 5.1 N mm−1 for men and 125 ± 5.5 N mm−1, for women (P < 0.001). The relationship between low‐range AT stiffness and Erun was significant at all measured speeds for women (r2 = 0.198, P < 0.05), but not for the men. These results indicate that when Erun is measured at the same relative intensity, there are no sex‐specific differences in Erun or substrate use. Furthermore, differences in Erun cannot be explained solely by differences in AT stiffness.

A Study on Improving Middle-and-Long Distance Running Performance of College Students with Segmented Intensity Indicator Training Method

The track and field teams in colleges and universities are made up of the specially recruited athletes and normally recruited athletes, which are established in order to take part in the matches on and off campus or home and abroad. Extracurricular track and field training is the essential part of the physical education in colleges and universities, indicating the level of physical education on campus. To improve specific endurance, intensity timed running shorter than specific distance is adopted. Super intensity running shorter than specific distance is important in improving middle-distance performance. When using speed agility run, repeated run and regular standard-speed run in exercise, if the specific temporal requirement were not calculated before, it is easy to cause unreasonable physical power distribution. In unplanned run, the speed of each segment can not reach personal specific level. The effect of exercise is bad when your strength is consumed blindly, thus the performance will not improve. Therefore, reasonable time of each segment should be calculated before run and in every exercise, which is important for athletes to create the best performance. The purpose of the study is to explore the use and application of segmented intensity indicator middle and long distance training in colleges. By studying middle and long distance athletes in 6 colleges using segmented intensity indicator training method and comparing the performance before and after the training, the author concludes that this method could effectively improve college middle- and -long distance running performance. On the basis of the training directed by the method of segmented intensity indicator, the extent of the performing improvement before and after the training, and the statistic analysis of this difference of the extent, it is concluded that this study is of great benefit to the training of middle-and-long distance running and achieves good performance.

Effects of Lean Beef Supplementation on Iron Status, Body Composition and Performance of Collegiate Distance Runners

Iron deficiency is prevalent among endurance athletes, particularly females. Low iron may compromise oxygen delivery and physical performance. Vegetarianism, desire for convenience, and perceived health risks associated with red meat contribute to low bioavailable iron intakes. The purpose of this study was to examine if lean beef supplementation would maintain iron status, improve body composition and increase performance of distance runners after 8 weeks. Twenty-eight (14 female) Division-I cross-country runners were stratified by iron status, use of iron supplements, and gender, and randomized into a control (n = 14) and intervention group. All participants maintained their typical diet and consumed a daily multivitamin, while the intervention group consumed 9 ounces of lean beef weekly. Dietary intake (total iron, heme-iron, protein, zinc), body composition, VO2max, and iron status (hemoglobin, hematocrit, serum iron, serum ferritin, total iron binding capacity [TIBC]) were measured at baseline and post-intervention. The intervention group had greater intakes of total and heme-iron. There were no group differences in amino acids, protein, or calories. Both groups had a significant body fat increase and lean mass decease over time. There was a significant VO2max increase over time in both groups. There were no group differences due to the intervention in serum ferritin, hemoglobin, serum iron, and TIBC. There was a significant difference in hematocrit between groups as a result of the intervention. In conclusion, increasing bioavailable iron from red meat may have effects on body composition and maintenance of blood iron markers; however, its direct impact on performance among endurance athletes is unclear.

RESPONSE

Dear Editor-in-Chief: Thank you for the opportunity to respond. Although we welcome a critical analysis of our work, it appears that Lamberts and Noakes have misinterpreted what we wrote. We actually concluded, "Among well-trained subjects heterogeneous in V˙O2max and running performance, velocity at V˙O2max (vV˙O2max) is the best predictor of running performance because it integrates both maximal aerobic power and economy of running" (6). This is different than concluding that "the cardiovascular model (CVM) explains endurance performance better than the central governor model (CGM)," as they have claimed we did. Lamberts and Noakes label the classic model of physiological factors that determine endurance running performance "the cardiovascular model." We do not agree with this terminology because a number of factors (V˙O2max, running economy, and fractional utilization of V˙O2max) are involved (1,4,5). Lamberts and Noakes contend that "by recruiting the largest possible number of skeletal muscle fibers with the greatest contractile capacity, superior athletes will have the shortest foot contact times and the longest flight time, resulting in superior performance." However, sprinters should be able to recruit a larger number of muscle fibers with the greatest contractile ability because they possess the highest percentage type II muscle fibers. Sprinters also have shorter foot contact times and longer flight times than distance runners (2,3). If Lambert and Noakes were correct, then sprinters would be able to achieve higher peak treadmill velocities and would have faster 16-km run times than distance runners. Because this is not the case, it appears that something is wrong with their theory. We agree that cross-sectional studies cannot prove causation. However, alterations in O2 delivery (through blood doping, erythropoietin, beta blockade, induced anemia, and breathing hypoxic gas mixtures) will impact V˙O2max and endurance performance in predictable ways (1). These findings lend credibility to the claim that V˙O2max is a determinant of distance running performance. In addition, there are logical reasons why V˙O2max, running economy, and fractional utilization of V˙O2max are causally linked to distance running performance. Regarding the claim that we have not proven or disproven the central governor model (CGM), this is true. But the burden of proof for providing evidence to back up the CGM falls on Noakes et al. because they are the leading proponents of this model. Our study was not designed to test Dr. Noakes' CGM, which proposes that a central governor in the brain limits exercise performance to protect the heart and other organ systems from damage. Our study demonstrates that the same variables (V˙O2max and running economy) that are highly correlated with the 16-km run performance are also highly correlated with peak treadmill velocity. Lamberts and Noakes state, "Nor does [our] model predict that exercise performance is limited by oxygen delivery to the muscle…." This highlights the primary difference between the classic model for explaining distance running performance and the CGM. In our view, any model that does not acknowledge O2 delivery as a determinant of endurance exercise performance is severely flawed. James E. McLaughlin Exercise Physiology Department Lynchburg College Lynchburg, VA Edward T. Howley David R. Bassett, Jr. Department of Exercise, Sport, and Leisure Studies University of Tennessee Knoxville, TN