Trained Middle-distance Runners Research Articles

Free Achilles tendon strain during selected rehabilitation, locomotor, jumping, and landing tasks

A better understanding of the strains experienced by the Achilles tendon during commonly prescribed exercises and locomotor tasks is needed to improve efficacy of Achilles tendon training and rehabilitation programs. The aim of this study was to estimate in vivo free Achilles tendon strain during selected rehabilitation, locomotor, jumping, and landing tasks. Sixteen trained runners with no symptoms of Achilles tendinopathy participated in this study. Personalised free Achilles tendon moment arm and force-strain curve were obtained from imaging data and used in conjunction with motion capture and surface electromyography to estimate free Achilles tendon strain using electromyogram-informed neuromusculoskeletal modelling. There was a strong correspondence between Achilles tendon force estimates from the present study and experimental data reported in the literature (R2 > 0.85). The average tendon strain was highest for maximal hop landing (8.8±1.6%), lowest for walking at 1.4 m/s (3.1±0.8%) and increased with locomotor speed during running (run 3.0 m/s: 6.5±1.6%; run 5.0 m/s: 7.9±1.7%) and during heel rise exercise with added mass (BW: 5.8±1.3%; 1.2 BW: 6.9±1.7%). The peak tendon strain was highest during running (5 m/s: 13.7±2.5%) and lowest during walking (1.4 m/s: 7±1.8%). Overall findings provide a preliminary evidence base for exercise selection to maximise anabolic tendon remodelling during training and rehabilitation of the Achilles tendon.

Sex differences in adaptation to intermittent post-exercise sauna bathing in trained middle-distance runners

BackgroundThe purpose of this study was to investigate the effect of sex on the efficacy of intermittent post-exercise sauna bathing to induce heat acclimation and improve markers of temperate exercise performance in trained athletes.MethodsTwenty-six trained runners (16 female; mean ± SD, age 19 ± 1 years, V̇O2max F: 52.6 ± 6.9 mL⋅kg−1⋅min−1, M: 64.6 ± 2.4 mL⋅kg−1⋅min−1) performed a running heat tolerance test (30 min, 9 km⋅h−1/2% gradient, 40 °C/40%RH; HTT) and temperate (18 °C) exercise tests (maximal aerobic capacity [V̇O2max] and lactate profile) pre and post 3 weeks of normal exercise training plus 29 ± 1 min post-exercise sauna bathing (101–108 °C) 3 ± 1 times per week.ResultsFemales and males exhibited similar reductions (interactions p > 0.05) in peak rectal temperature (− 0.3 °C; p < 0.001), skin temperature (− 0.9 °C; p < 0.001) and heart rate (− 9 beats·min−1; p = 0.001) during the HTT at post- vs pre-intervention. Only females exhibited an increase in active sweat glands on the forearm (measured via modified iodine technique; F: + 57%, p < 0.001; M: + 1%, p = 0.47). Conversely, only males increased forearm blood flow (measured via venous occlusion plethysmography; F: + 31%, p = 0.61; M: + 123%; p < 0.001). Females and males showed similar (interactions p > 0.05) improvements in V̇O2max (+ 5%; p = 0.02) and running speed at 4 mmol·L−1 blood lactate concentration (+ 0.4 km·h−1; p = 0.001).ConclusionsThree weeks of post-exercise sauna bathing effectively induces heat acclimation in females and males, though possibly amid different thermoeffector adaptations. Post-exercise sauna bathing is also an effective ergogenic aid for both sexes.

Lower volume throughout the taper and higher intensity in the last interval session prior to a 1500m time trial improves performance.

Eight highly trained middle-distance runners (1500m personal best 4:01.4± 0:09.2min) completed two 7-day tapers, separated by at least 3 weeks of regular training: (i) prescribed using prediction models from elite middle-distance runners, where continuous running volume was reduced by 30% and interval intensity was equal to 1500m race pace (RP); and (ii) continuous running volume was reduced by 60% and intensity of the final interval session was completed at 110% of 1500m race pace (HI). Performance was assessed using 1500m time trials on an indoor 200m track 1 day before, and 1 day after each taper. Performance time was improved after HI by 5.2± 3.7s (mean± 90% confidence limits, p= 0.03) and by 3.2± 3.8s after RP (p= 0.15). The first and second 300m segments of the 1500m time trial were faster post-taper in RP (p= 0.012 and p= 0.017, respectively) and HI (both p= 0.012). Running faster than race pace late in a low-volume taper is recommended to improve 1500m track performance. A positive pacing strategy is adopted after tapering, although care should be taken to avoid an over-fast start. Novelty: A large reduction in volume during tapering and an increase in final interval session intensity improves running performance. Athletes adopt a negative pacing strategy before tapering and a positive-pacing strategy after tapering.

Intermittent post-exercise sauna bathing improves markers of exercise capacity in hot and temperate conditions in trained middle-distance runners

PurposeThis study investigated whether intermittent post-exercise sauna bathing across three-weeks endurance training improves exercise heat tolerance and exercise performance markers in temperate conditions, compared to endurance training alone. The subsidiary aim was to determine whether exercise-heat tolerance would further improve following 7-Weeks post-exercise sauna bathing.MethodsTwenty middle-distance runners (13 female; mean ± SD, age 20 ± 2 years, VO2max 56.1 ± 8.7 ml kg−1 min−1) performed a running heat tolerance test (30-min, 9 km h−1/2% gradient, 40 °C/40%RH; HTT) and temperate (18 °C) exercise tests (maximal aerobic capacity [VO2max], speed at 4 mmol L−1 blood lactate concentration ([La−]) before (Pre) and following three-weeks (3-Weeks) normal training (CON; n = 8) or normal training with 28 ± 2 min post-exercise sauna bathing (101–108 °C, 5–10%RH) 3 ± 1 times per week (SAUNA; n = 12). Changes from Pre to 3-Weeks were compared between-groups using an analysis of co-variance. Six SAUNA participants continued the intervention for 7 weeks, completing an additional HTT (7-Weeks; data compared using a one-way repeated-measures analysis of variance).ResultsDuring the HTT, SAUNA reduced peak rectal temperature (Trec; − 0.2 °C), skin temperature (− 0.8 °C), and heart rate (− 11 beats min−1) more than CON at 3-Weeks compared to Pre (all p < 0.05). SAUNA also improved VO2max (+ 0.27 L−1 min−1; p = 0.02) and speed at 4 mmol L−1 [La−] (+ 0.6 km h−1; p = 0.01) more than CON at 3-Weeks compared to Pre. Only peak Trec (− 0.1 °C; p = 0.03 decreased further from 3-Weeks to 7-Weeks in SAUNA (other physiological variables p > 0.05).ConclusionsThree-weeks post-exercise sauna bathing is an effective and pragmatic method of heat acclimation, and an effective ergogenic aid. Extending the intervention to seven weeks only marginally improved Trec.

Determinants of last lap speed in paced and maximal 1500-m time trials.

The present study identified the physiological and performance characteristics that are deterministic during a maximal 1500-m time trial and in paced 1500-m time trials, with an all-out last lap. Thirty-two trained middle-distance runners (n = 21 male, VO2peak: 72.1 ± 3.2; n = 11, female, VO2peak: 61.2 ± 3.7mL kg-1 min-1) completed a 1500-m time trial in the fastest time possible (1500FAST) as well as a 1500MOD and 1500SLOW trial whereby mean speed was reduced during the 0-1100m by 5% and 10%, respectively. Anaerobic speed reserve (ASR), running economy (RE), the velocity corresponding with VO2peak (VVO2peak), maximal sprint speed (MSS) and maximal accumulated oxygen deficit (MAOD) were determined during additional testing. Carnosine content was quantified by proton magnetic resonance spectroscopy in the gastrocnemius and expressed as a Z-score to estimate muscle fibre typology. 1500FAST time was best explained by RE and VVO2peak in female runners (adjusted r2 = 0.80, P < 0.001), in addition to the 0-1100-m speed relative to VVO2peak in male runners (adjusted r2 = 0.72, P < 0.001). Runners with a higher gastrocnemius carnosine Z-score (i.e., higher estimated percentage of type II fibres) and greater MAOD, reduced their last lap time to a greater extent in the paced 1500-m trials. Neither ASR nor MSS was associated with last lap time in the paced trials. These findings suggest that VVO2 peak and RE are key determinants of 1500-m running performance with a sustained pace from the start, while a higher carnosine Z-score and MAOD are more important for last lap speed in tactical 1500-m races.

The Free Achilles Tendon Is Shorter, Stiffer, Has Larger Cross-Sectional Area and Longer T2* Relaxation Time in Trained Middle-Distance Runners Compared to Healthy Controls

Tendon geometry and tissue properties are important determinants of tendon function and injury risk and are altered in response to ageing, disease, and physical activity levels. The purpose of this study was to compare free Achilles tendon geometry and mechanical properties between trained elite/sub-elite middle-distance runners and a healthy control group. Magnetic resonance imaging (MRI) was used to measure free Achilles tendon volume, length, average cross-sectional area (CSA), regional CSA, moment arm, and T2* relaxation time at rest, while freehand three-dimensional ultrasound (3DUS) was used to quantify free Achilles tendon mechanical stiffness, Young’s modulus, and length normalised mechanical stiffness. The free Achilles tendon in trained runners was significantly shorter and the average and regional CSA (distal end) were significantly larger compared to the control group. Mechanical stiffness of the free Achilles tendon was also significantly higher in trained runners compared to controls, which was explained by the group differences in tendon CSA and length. T2* relaxation time was significantly longer in trained middle-distance runners when compared to healthy controls. There was no relationship between T2* relaxation time and Young’s modulus. The longer T2* relaxation time in trained runners may be indicative of accumulated damage, disorganised collagen, and increased water content in the free Achilles tendon. A short free Achilles tendon with large CSA and higher mechanical stiffness may enable trained runners to rapidly transfer high muscle forces and possibly reduce the risk of tendon damage from mechanical fatigue.

Quantifying the Training-Intensity Distribution in Middle-Distance Runners: The Influence of Different Methods of Training-Intensity Quantification.

To compare the training-intensity distribution (TID) across an 8-week training period in a group of highly trained middle-distance runners employing 3 different methods of training-intensity quantification. A total of 14 highly trained middle-distance runners performed an incremental treadmill test to exhaustion to determine the heart rate (HR) and running speed corresponding to the ventilatory thresholds (gas-exchange threshold and respiratory-compensation threshold), as well as fixed rating of perceived exertion (RPE) values, which were used to demarcate 3 training-intensity zones. During the following 8weeks, the TID (total and percentage of time spent in each training zone) of all running training sessions (N = 695) was quantified using continuous running speed, HR monitoring, and RPE. Compared with the running-speed-derived TID (zone 1, 79.9% [7.3%]; zone 2, 5.3% [4.9%]; and zone 3, 14.7% [7.3%]), HR-demarcated TID (zone 1, 79.6% [7.2%]; zone 2, 17.0% [6.3%]; and zone 3, 3.4% [2.0%]) resulted in a substantially higher training time in zone 2 (effect size ± 95% confidence interval: -1.64 ± 0.53; P < .001) and lower training time in zone 3 (-1.59 ± 0.51; P < .001). RPE-derived TID (zone 1, 39.6% [8.4%]; zone 2, 31.9% [8.7%]; and zone 3, 28.5% [11.6%]) reduced time in zone 1 compared with both HR (-5.64 ± 1.40; P < .001) and running speed (-5.69 ± 1.9; P < .001), whereas time in RPE training zones 2 and 3 was substantially higher than both HR- and running-speed-derived zones. The results show that the method of training-intensity quantification substantially affects computation of TID.

The relationship between performance and biomechanics in middle-distance runners

ABSTRACT The present study aimed to identify movement patterns most related to running performance among highly trained middle-distance runners. Eleven male runners performed overground running trials on an indoor running track, and three-dimensional analyses techniques were used to measure running kinematics and kinetics. Performance was measured as season and personal best time over 1500 m. The average velocity during the running trials was 7.2 ± 0.3 m/s. The average season and personal best 1500 m race times were 3:49.7 ± 0:05.8 and 3:46.0 ± 0:08.3 minutes, respectively. Regression analysis revealed that a smaller range of sagittal-plane hip motion during swing, less thorax flexion at toe-off and a smaller ankle plantarflexion angle at contact accounted for 95.7% (p < 0.001) of the variation in season best running performance. Less sagittal-plane hip motion during swing and a smaller ankle plantarflexion angle at contact also explained 79% of the variance in personal best time. Slower middle-distance runners make initial ground contact with a more plantarflexed ankle and greater forward lean of the trunk. We recommend that coaches and runners pay attention to ankle, shank and thorax angles during technical development and training to identify opportunities to optimise middle-distance running mechanics and performance.

Overreaching Attenuates Training-induced Improvements in Muscle Oxidative Capacity.

The aim of this study was to determine whether muscle oxidative capacity is influenced by alterations in training volume in middle-distance runners. Twenty-four highly trained middle-distance runners (n = 16 males; V˙O2peak = 73.3(4.3) mL·kg·min; n = 8 females, V˙O2peak = 63.2(3.4) mL·kg·min) completed 3 wk of normal training (NormTr), 3 wk of high-volume training (HVTr; a 10%, 20%, and 30% increase in training volume during each successive week from NormTr), and a 1-wk taper (TapTr; 55% exponential reduction in training volume from HVTr week 3). Before and immediately after each training period, the rate of recovery of muscle oxygen consumption (mV˙O2) of the gastrocnemius medialis was measured using near-infrared spectroscopy, with the rate constant indicating muscle oxidative capacity. Time to exhaustion (TTE) and V˙O2peak were determined during a maximal incremental treadmill test. Twelve subjects were classified as being functionally overreached (FOR) after HVTr (decreased running TTE and high perceived fatigue), whereas the other 12 subjects were classified as acutely fatigued (AF; no decrease in running TTE). The AF group demonstrated a significant increase in muscle oxidative capacity after HVTr (rate constant: 15.1% ± 9.7% min; P = 0.009), with no further improvement after TapTr, whereas there was no change in muscle oxidative capacity for FOR at any time point (P > 0.05). Compared with the FOR group, the AF group had substantially larger improvements in TTE from pre-HVTr to post-TapTr (FOR, 8.8% ± 3.7%; AF, 3.2% ± 3.0%; P = 0.04). The present study was able to demonstrate that muscle oxidative capacity was increased in response to a period of HVTr, but only in runners who did not develop FOR. Furthermore, runners who did not develop FOR had substantially larger performance improvements after a taper period.

Impact of 8weeks of repeated ischemic preconditioning on running performance.

To examine if repeated exposure to IPC treatment prior to training sessions improves oxygen uptake and 1-km running performance in highly trained middle-distance runners. Fourteen highly trained endurance runners (11 male/3 female, 19 ± 2years, 64 ± 5mlkg-1min-1) completed a baseline maximal oxygen consumption ([Formula: see text]) test and 1-km running performance test before random assignment to an IPC or control group. Both groups were prescribed identical endurance training over an 8-week varsity season; however, the IPC group performed an IPC protocol (5min ischemia, repeated 3 times, each separated by 5min reperfusion) before every training session. After 8weeks of training, participants completed a follow-up [Formula: see text] test and 1-km time trial. [Formula: see text] did not increase from baseline in either group following the 8-week training bout (P = 0.2), and neither group varied more than the other ([Formula: see text] = IPC 0.6 ± 2mlkg-1min-1; control 1.5 ± 2mlkg-1min-1, P = 0.6) or beyond typical measurement error. The IPC decreased 1-km time trial time by 0.4% (0.5 ± 2s), while the control group decreased by 1% (1.5 ± 3s), but neither change was significant compared to baseline (P = 0.2). There was also no difference in time trial improvement between IPC and control (P = 0.6). However, there was a trend towards IPC significantly improving running economy at low intensity (P = 0.057). Our data suggest that over a normal 8-week season in a population of highly trained middle-distance runners there is no benefit of undergoing chronic, repeated IPC treatments before training for augmenting maximal aerobic power or 1-km performance time.

Four Weeks of Classical Altitude Training Increases Resting Metabolic Rate in Highly Trained Middle-Distance Runners.

High altitude exposure can increase resting metabolic rate (RMR) and induce weight loss in obese populations, but there is a lack of research regarding RMR in athletes at moderate elevations common to endurance training camps. The present study aimed to determine whether 4 weeks of classical altitude training affects RMR in middle-distance runners. Ten highly trained athletes were recruited for 4 weeks of endurance training undertaking identical programs at either 2200m in Flagstaff, Arizona (ALT, n = 5) or 600m in Canberra, Australia (CON, n = 5). RMR, anthropometry, energy intake, and hemoglobin mass (Hbmass) were assessed pre- and posttraining. Weekly run distance during the training block was: ALT 96.8 ± 18.3km; CON 103.1 ± 5.6km. A significant interaction for Time*Group was observed for absolute (kJ.day-1) (F-statistic, p-value: F(1,8)=13.890, p = .01) and relative RMR (F(1,8)=653.453, p = .003) POST-training. No significant changes in anthropometry were observed in either group. Energy intake was unchanged (mean ± SD of difference, ALT: 195 ± 3921kJ, p = .25; CON: 836 ± 7535kJ, p = .75). A significant main effect for time was demonstrated for total Hbmass (g) (F(1,8)=13.380, p = .01), but no significant interactions were observed for either variable [Total Hbmass (g): F(1,8)=1.706, p = .23; Relative Hbmass (g.kg-1): F(1,8)=0.609, p = .46]. These novel findings have important practical application to endurance athletes routinely training at moderate altitude, and those seeking to optimize energy management without compromising training adaptation. Altitude exposure may increase RMR and enhance training adaptation,. During training camps at moderate altitude, an increased energy intake is likely required to support an increased RMR and provide sufficient energy for training and performance.

Effect of a Single Finnish Sauna Session on White Blood Cell Profile and Cortisol Levels in Athletes and Non-Athletes

The aim of the present study was to investigate the effect of Finnish sauna bathing on a white blood cell profile, cortisol levels and selected physiological indices in athletes and non-athletes. The study evaluated 9 trained middle-distance runners and 9 male non-athletes. The subjects from both groups participated in 15-minute sauna sessions until their core temperature rose by 1.2°C (mean temperature in the sauna room was 96° ± 2°C; relative humidity was 15 ± 3%) with a 2 minute cool down with water at a temperature of 19–20°C. Body mass was measured before and after the session and blood samples were taken for tests. Rectal temperature was monitored at five-minute intervals during the whole session. Serum total protein, haematological indices and cortisol levels were determined. Sauna bathing caused higher body mass loss and plasma volume in the athletes compared to the group of non-athletes. After the sauna session, an increased number of white blood cells, lymphocyte, neutrophil and basophil counts was reported in the white blood cell profile. Higher increments in leukocyte and monocyte after the sauna bathing session were recorded in the group of athletes compared to untrained subjects. The obtained results indicated that sauna bathing stimulated the immune system to a higher degree in the group of athletes compared to the untrained subjects.

The effect of acute taurine ingestion on 3-km running performance in trained middle-distance runners

Limited research examining the effect of taurine (TA) ingestion on human exercise performance exists. The aim of this study was to investigate the effect of acute ingestion of 1,000 mg of TA on maximal 3-km time trial (3KTT) performance in trained middle-distance runners (MDR). Eight male MDR (mean ± SD: age 19.9 ± 1.2 years, body mass 69.4 ± 6.6 kg, height 180.5 ± 7.5 cm, 800 m personal best time 121.0 ± 5.3 s) completed TA and placebo (PL) trials 1 week apart in a double-blind, randomised, crossover designed study. Participants consumed TA or PL in capsule form on arrival at the laboratory followed by a 2-h ingestion period. At the end of the ingestion period, participants commenced a maximal simulated 3KTT on a treadmill. Capillary blood lactate was measured pre- and post-3KTT. Expired gas, heart rate (HR), ratings of perceived exertion (RPE), and split times were measured at 500-m intervals during the 3KTT. Ingestion of TA significantly improved 3KTT performance (TA 646.6 ± 52.8 s and PL 658.5 ± 58.2 s) (p = 0.013) equating to a 1.7 % improvement (range 0.34-4.24 %). Relative oxygen uptake, HR, RPE and blood lactate did not differ between conditions (p = 0.803, 0.364, 0.760 and 0.302, respectively). Magnitude-based inference results assessing the likeliness of a beneficial influence of TA were 99.3 %. However, the mechanism responsible for this improved performance is unclear. TA's potential influence on exercise metabolism may involve interaction with the muscle membrane, the coordination or the force production capability of involved muscles. Further research employing more invasive techniques may elucidate TA's role in improving maximal endurance performance.

Improvement of 800-m Running Performance With Prior High-Intensity Exercise

Prior high-intensity exercise increases the oxidative energy contribution to subsequent exercise and may enhance exercise tolerance. The potential impact of a high-intensity warm-up on competitive performance, however, has not been investigated. To test the hypothesis that a high-intensity warm-up would speed VO2 kinetics and enhance 800-m running performance in well-trained athletes. Eleven highly trained middle-distance runners completed two 800-m time trials on separate days on an indoor track, preceded by 2 different warm-up procedures. The 800-m time trials were preceded by a 10-min self-paced jog and standardized mobility drills, followed by either 6 × 50-m strides (control [CON]) or 2 × 50-m strides and a continuous high-intensity 200-m run (HWU) at race pace. Blood [La] was measured before the time trials, and VO2 was measured breath by breath throughout exercise. 800-m time-trial performance was significantly faster after HWU (124.5 ± 8.3 vs CON, 125.7 ± 8.7 s, P < .05). Blood [La] was greater after HWU (3.6 ± 1.9 vs CON, 1.7 ± 0.8 mM; P < .01). The mean response time for VO2 was not different between conditions (HWU, 27 ± 6 vs CON, 28 ± 7 s), but total O2 consumed (HWU, 119 ± 18 vs CON, 109 ± 28 ml/kg, P = .05) and peak VO2 attained (HWU, 4.21 ± 0.85 vs CON, 3.91 ± 0.63 L/min; P = .08) tended to be greater after HWU. These data indicate that a sustained high-intensity warm-up enhances 800-m time-trial performance in trained athletes.

Influence of Training Loads on Patterns of Illness in Elite Distance Runners

To investigate relationships between training mileage and intensity, and the type, incidence, severity, and duration of respiratory illness in distance runners, and the impact of illness on submaximal and maximal running performance. A longitudinal observational study of distance runners with serial monitoring of training loads and clinical patterns of illness. A 4-month winter training period in the Southern Hemisphere. A total of 20 highly trained (elite) male middle-distance and distance runners competing at the national and international levels. Training was quantified by mileage (km), intensity (scale, 1-5), and load (volume x intensity). Symptoms and signs of respiratory illness (type, duration, and severity) were verified by a physician at a weekly review. Performance was monitored by measuring submaximal and maximal oxygen uptake and time to exhaustion on a incremental treadmill test. A majority of subjects (15/20) experienced 1 or more episodes of respiratory illness (mean, 2.5 episodes; range, 1-5), with 79% of symptoms classified as upper respiratory in origin. There were no significant differences in mean weekly mileage (P = 0.43), training intensity (P = 0.85), or training load (P = 0.45) between healthy runners and those affected by illness. Mean weekly (88 +/- 46 km) and mean monthly (373 +/- 163 km) mileages prior to each episode of illness were similar to the overall study means (95.5 +/- 36.4 km and 382 +/- 146 km). There were no substantial relationships between mean weekly training mileage, intensity, or training load and the number of illnesses reported (all r < 0.20). Neither submaximal nor maximal running performance was significantly affected by the presence of illness. Differences in training mileage, intensity, and load were not associated with the incidence of respiratory illness in highly trained middle-distance and distance runners. Runners with mild illness can be reassured that symptoms will not necessarily impair submaximal and maximal performance.

Re-assessing accumulated oxygen deficit in middle-distance runners

The purpose of this study was to re-assess the accumulated oxygen deficit (AOD), incorporating recent methodological improvements i.e., 4 min submaximal tests spread above and below the lactate threshold (LT). We Investigated the Influence of the VO2 -speed regression, on the precision of the estimated total energy demand and AOD. utilising different numbers of regression points and including measurement errors. Seven trained middle-distance runners (mean +/- SD age: 25.3 +/- 5.4y, mass: 73.7 +/- 4.3kg. VO2max 64.4 +/- 6.1 mL x kg(-1) x min(-1)) completed a VO2max, LT, 10 x 4 min exercise tests (above and below LT) and high-intensity exhaustive tests. The VO2 -speed regression was developed using 10 submaximal points and a forced y-intercept value. The average precision (measured as the width of 95% confidence Interval) for the estimated total energy demand using this regression was 7.8mL O2 Eq x kg(-1) x min(-1). There was a two-fold decrease in precision of estimated total energy demand with the Inclusion of measurement errors from the metabolic system. The mean AOD value was 43.3 mL O2 Eq x kg(-1) (upper and lower 95% CI 32.1 and 54.5mL o2 Eq x kg(-1) respectively). Converting the 95% CI for estimated total energy demand to AOD or including maximum possible measurement errors amplified the error associated with the estimated total energy demand. No significant difference in AOD variables were found, using 10,4 or 2 regression points with a forced y-intercept. For practical purposes we recommend the use of 4 submaximal values with a y-intercept. Using 95% CIs and calculating error highlighted possible error in estimating AOD. Without accurate data collection, increased variability could decrease the accuracy of the AOD as shown by a 95% CI of the AOD.

Immune function in Swedish élite orienteers

During 1979-1992 an increased frequency of sudden unexpected cardiac death (SUD) occurred among young male Swedish élite orienteers. Subacute-to-chronic myocarditis was found in 12/16 (75%) at autopsy and Chlamydia pneumoniae, or a cross-reacting agent, was suspected on the basis of diagnostic tests performed. Because myocarditis is an infrequent cause of SUD and clusters of SUD are rare, whereas Chlamydia pneumoniae infections are ubiquitous and seldom cause severe myocarditis, 119 top ranked élite orienteers (67 males and 52 females) and 36 highly trained male middle-distance runners and cross-country skiers, serving as controls, underwent immunologic screening in an effort to reveal possible immune dysfunction. Except for two orienteers and one runner/skier who showed genetic C3-deficiency or IgA-deficiency, the results showed no significant differences between the orienteers and controls with respect to immunoglobulin levels, complement activation, lymphocyte subsets, including activated T lymphocytes, and sIL-2r-alpha. IL-1 beta, IL-6, TNF-alpha, and sCD8, tested in the orienteers only, were normal. However, IFN-gamma was significantly higher in controls than in orienteers, who showed normal levels, whereas the orienteers had increased sELAM-1 and sICAM-1 levels. Finally, sIL-2 receptor-alpha was similarly elevated in orienteers and controls. We conclude that, with the tests employed, no immunologic disturbance could be revealed in the orienteers that may potentially have increased their susceptibility to myocarditis and SUD.

Influence of physical exercise on simple reaction time: effect of physical fitness.

The influence of physical fitness and energy expenditure on a simple reaction time task performed during exercise was investigated. Two groups of 10 subjects were used, one was composed of trained middle-distance runners and one of students who had no regular physical training. The subjects performed a simple reaction time task while pedalling on a cycloergometer at different relative power output corresponding to 20, 40, 60, and 80% of their own maximal aerobic power and immediately after exercise. During exercise, the results showed a decrease in cognitive performance for both groups whereas no significant effect was found after exercise. A significant effect of physical fitness on simple reaction time was noted during exercise. The data are interpreted in terms of optimization of performance focusing particularly on the relations between energy cost of the physical task and attentional demand.

Longitudinal associations between anaerobic threshold and distance running performance.

Longitudinal alterations in anaerobic threshold (AT) and distance running performance were assessed three times within a 4-month period of intensive training, using 20 male, trained middle-distance runners (19-23 yr). A major effect of the high intensity regular intensive training together with 60- to 90-min AT level running training (2 d X wk-1) was a significant increase in the amount of O2 uptake corresponding to AT (VO2 AT; ml O2 X min-1 X kg-1) and in maximal oxygen uptake (VO2max; ml O2 X min-1 X kg-1). Both VO2 AT and VO2max showed significant correlations (r = -0.69 to -0.92 and r = -0.60 to -0.85, respectively) with the 10,000 m run time in every test. However, further analyses of the data indicate that increasing VO2 AT (r = -0.63, P less than 0.05) rather than VO2max (r = -0.15) could result in improving the 10,000 m race performance to a larger extent, and that the absolute amount of change (delta) in the 10,000 m run time is best accounted for by a combination of delta VO2 AT and delta 5,000 m run time. Our data suggest that, among runners not previously trained over long distances, training-induced alterations in AT in response to regular intensive training together with AT level running training may contribute significantly to the enhancement of AT and endurance running performance, probably together with an increase in muscle respiratory capacity.

Effect of acute induced metabolic alkalosis on 800-m racing time.

Six trained middle-distance runners wer studied under alkalotic (NaHCO3 ingestion), placebo (CaCO3 ingestion), and control conditions to determine the effect of an acute induced metabolic alkalosis on time to run an 800-m race. Pre-exercise, following NaHCO3 ingestion, pH and standard [HCO3-] were significantly higher. In the alkalotic condition, subjects ran faster (2.9 s) and the corresponding post-exercise values for blood [lactate] and extracellular H+ were higher than in the control and placebo conditions, suggesting an increased anaerobic energy contribution. These results support the speculation that the increase in extracellular buffering following NaHCO3 ingestion facilitated H+ efflux from the cells of working muscle, thereby delaying the decrease in intracellular pH and postponing fatigue. It is concluded that the ingestion of NaHCO3 by trained middle-distance runners prior to an 800-m race has an ergogenic benefit.