Laboratory Treadmill Test Research Articles

The Relationship between Aerobic Capacity, Anthropometric Characteristics, and Performance in the Yo-Yo Intermittent Recovery Test among Elite Young Football Players: Differences between Playing Positions

The objectives of this study were to investigate (a) the relationship between the Yo-Yo intermittent recovery test level 1 (YYIR1) and a laboratory test for measuring maximal oxygen uptake (VO2max), (b) the relationships between anthropometric characteristics and variables of the two aerobic tests (field and laboratory), and (c) differences in performance and anthropometric characteristics among five different playing positions. The study involved 27 U17 young soccer players (16.0 ± 0.6 years). They randomly underwent a maximal laboratory treadmill test to measure VO2max and the YYIR1 test. Pearson correlation was used to find potential correlations, and a one-way ANOVA was used to find differences between playing positions. Statistical significance was set at p < 0.05. The results showed that height was moderately negatively correlated (r = −0.455, p = 0.017) as well as body mass (r = −0.395, p = 0.042). Significant positive correlation was observed between vVO2max and the distance covered in YYIR1 (r = 0.393, p = 0.042). Finally, no differences were observed between playing positions in any anthropometric characteristic or in any variable of the two aerobic tests (laboratory or field) (p > 0.05). In conclusion, the YYIR1 test is not suitable for estimating VO2max. Additionally, the lack of differences between playing positions may be due to the limited specialization of the training load received by the players until this age.

Augmented Cooper test: Biomechanical contributions to endurance performance.

Running mechanics are modifiable with training and adopting an economical running technique can improve running economy and hence performance. While field measurement of running economy is cumbersome, running mechanics can be assessed accurately and conveniently using wearable inertial measurement units (IMUs). In this work, we extended this wearables-based approach to the Cooper test, by assessing the relative contribution of running biomechanics to the endurance performance. Furthermore, we explored different methods of estimating the distance covered in the Cooper test using a wearable global navigation satellite system (GNSS) receiver. Thirty-three runners (18 highly trained and 15 recreational) performed an incremental laboratory treadmill test to measure their maximum aerobic speed (MAS) and speed at the second ventilatory threshold (sVT2). They completed a 12-minute Cooper running test with foot-worm IMUs and a chest-worn GNSS-IMU on a running track 1–2 weeks later. Using the GNSS receiver, an accurate estimation of the 12-minute distance was obtained (accuracy of 16.5 m and precision of 1.1%). Using this distance, we showed a reliable estimation [R2 > 0.9, RMSE ϵ (0.07, 0.25) km/h] of the MAS and sVT2. Biomechanical metrics were extracted using validated algorithm and their association with endurance performance was estimated. Additionally, the high-/low-performance runners were compared using pairwise statistical testing. All performance variables, MAS, sVT2, and average speed during Cooper test, were predicted with an acceptable error (R2 ≥ 0.65, RMSE ≤ 1.80 kmh−1) using only the biomechanical metrics. The most relevant metrics were used to develop a biomechanical profile representing the running technique and its temporal evolution with acute fatigue, identifying different profiles for runners with highest and lowest endurance performance. This profile could potentially be used in standardized functional capacity measurements to improve personalization of training and rehabilitation programs.

Novel track field test to determine Vpeak, relationship with treadmill test and 10-km running performance in trained endurance runners.

ObjectivesThe aim of this study was to determine the peak running velocity on the track field (Vpeak_TF) based on the laboratory treadmill test (Vpeak_T), and relate the Vpeak values as well as their correlation with the 10-km running performance in trained endurance runners.MethodTwenty male trained endurance runners (age: 29.5 ± 5.3 years; V̇O2max: 67.5±17.6 ml · kg-1·min-1) performed three maximum incremental tests to determine the Vpeak: one for Vpeak_T determination and two to obtain Vpeak_TF on the official track field (400 m), and a 10-km running performance. During the incremental tests, maximum heart rate (HRmax), maximal rating of perceived exertion (RPEmax), and peak lactate concentration (LApeak) were determined.ResultsThe results showed significant difference between the Vpeak_TF and Vpeak_T (18.1 ± 1.2 vs. 19.2 ± 1.5 km·h-1, respectively), as well as the total time of the tests, the distance traveled and the RPEmax determined during the tests. A high correlation was observed between the Vpeak values (r = 0.94), and between Vpeak_TF and Vpeak_T with 10-km running performance (r = -0.95 vs. r = -0.89, respectively).ConclusionsThe good agreement and association with Vpeak_T and high correlation with 10-km running performance demonstrate that the novel track field test is efficient for Vpeak_TF determination.

Validity of the 20 Meter Multi-Stage Shuttle Run Test (MSSRT) In Predicting VO2 Max

The purpose of this study was to investigate the validity of the 20 meter multi-stage shuttle run test (MST) in predicting VO2max compared to the directly measured reading from the laboratory. 4 male participants, who were diverse in terms of their ages and who were active physically, performed the MST and an incremental treadmill tests. Predicted VO2max values were obtained for the MST based on their stages and shuttles and actual VO2max values were obtained from the laboratory treadmill test. Results showed that all predicted VO2max values for the MST over-predicted that of the actual VO2max values from the laboratory test. This study seems to suggest that there is no validity in the MST in predicting VO2max of an individual as compared to the actual VO2max values from the laboratory.

Validity and Reliability of an On-Court Fitness Test for Assessing and Monitoring Aerobic Fitness in Squash.

James, C, Tenllado Vallejo, F, Kantebeen, M, and Farra, S. Validity and reliability of an on-court fitness test for assessing and monitoring aerobic fitness in squash. J Strength Cond Res 33(5): 1400-1407, 2019-Current on-court assessments of aerobic fitness in squash are not designed to yield a wealth of physiological data. Moreover, tests may require complex computer equipment or involve simulated racket strokes, which are difficult to standardize at high intensities. This study investigated the validity and reliability of a squash-specific fitness test which can yield both a standalone performance score, as well as pertinent physiological markers such as V[Combining Dot Above]O2max, the lactate turnpoint and oxygen cost, in a sport-specific environment. Eight national squash players completed 3 tests in a counterbalanced order: an incremental laboratory treadmill test (LAB) and 2 on-court fitness tests (STs) that involved repeated shuttle runs at increasing speeds. V[Combining Dot Above]O2max during ST was agreeable with LAB (typical error [TE] = 3.3 ml·kg·min, r = 0.79). The mean bias between LAB and ST was 2.5 ml·kg·min. There were no differences in maximum heart rate, postexercise blood lactate concentration, or end of test rating of perceived exertion between LAB and ST (p > 0.05). The ST was highly reliable, with 74 (10) laps completed in ST1 and 75 (12) laps in ST2 (mean bias = 1 lap, TE = 3 laps, r = 0.97). Physiological markers were also reliable, including V[Combining Dot Above]O2max, (TE = 1.5 ml·kg·min, r = 0.95), the lap number at 4 mMol (TE = 4 laps, r = 0.77), and average V[Combining Dot Above]O2 across the first 4 stages (TE = 0.94 ml·kg·min, r = 0.95). We observed good agreement between LAB and ST for assessing V[Combining Dot Above]O2max and between both on-court trials for assessing test performance and selected physiological markers. Consequently, we recommend this test for monitoring training adaptations and prescribing individualized training in elite squash players.

Effect of 3-week high-intensity interval training on VO2max, total haemoglobin mass, plasma and blood volume in well-trained athletes.

This study examined the haematological adaptations to high-intensity interval training (HIT), i.e. total haemoglobin mass (tHb-mass), blood volume (BV), and plasma volume (PV), and its effects on VO2max in well-trained athletes. Twenty-seven male and eight female well-trained (VO2max 63.7±7.7ml/min/kg) athletes were randomly assigned to the HIT (HITG, N=19) or the control group (CG, N=16). Over a 3-week period, the HITG performed 11 HIT sessions, consisting of four 4-min interval bouts at an exercise intensity of 90-95% of the individual maximal heart rate (HRmax), separated by 4-min active recovery periods. Before and 5±2days after the intervention, tHb-mass, BV and PV were determined by the CO-rebreathing method. VO2max was assessed in a laboratory treadmill test. tHb-mass (from 753±124 to 760±121g), BV (from 5.6±0.8 to 5.6±0.9l) and PV (from 3.2±0.5 to 3.2±0.5l) remained unchanged after HIT and did not show an interaction (group×time). Within the HITG, VO2max improved from baseline by +3.5% (p=0.011), but remained unchanged in the CG. No interaction (group×time) was seen for VO2max. The HITG showed a significant reduction in HRmax compared to the baseline measurement (-2.3%, p≤0.001), but HRmax remained unchanged in the CG. There was a significant interaction (group×time) for HRmax (p=0.006). Also, oxygen pulse significantly increased only in HITG from 22.9±4.4 to 23.9±4.2ml/beat, with no interaction (p=0.150). Eleven HIT sessions added to usual training did neither improve VO2max nor haematological parameters compared to the CG.

Validity of the Yo-Yo Intermittent Recovery Test Level 1 for Direct Measurement or Indirect Estimation of Maximal Oxygen Uptake in Female Soccer Players

To evaluate the validity of the Yo-Yo Intermittent Recovery Test Level 1 (YYIR1) for the direct assessment and the indirect estimation of maximal oxygen consumption (VO2max) in female soccer players compared with a maximal laboratory treadmill test (LTT). Eighteen female soccer players (21.5 ± 3.4 y, 165.6 ± 7.5 cm, 63.3 ± 7.4 kg; mean ± SD) completed an LTT and a YYIR1 in random order (1 wk apart). Their VO2max was directly measured via portable spirometry during both tests and indirectly estimated from a published non-gender-specific formula (YYIR1-F1). The measured VO2max values in LTT and YYIR1 were 55.0 ± 5.3 and 49.9 ± 4.9 mL · kg-1 · min-1, respectively, while the estimated VO2max values from YYIR1-F1 corresponded to 45.2 ± 3.4 mL · kg-1 · min-1. Large positive correlations between the VO2max values from YYIR1 and LTT (r = .83, P < .001, 90% confidence interval = .64-.92) and YYIR1-F1 and LTT (r = .67, P = .002, .37-.84) were found. However, the YYIR1 significantly underestimated players' VO2max by 9.4% compared with LTT (P < .001) with Bland-Altman 95% limits of agreement ranging from -20.0% to 1.4%. A significant underestimation from the YYIR1-F1 (P < .001) was also identified (17.8% with Bland-Altman 95% limits of agreement ranging from -31.8% to -3.8%). The YYIR1 and YYIR1-F1 are not accurate methods for the direct assessment or indirect estimation of VO2max in female soccer players. The YYIR1-F1 lacks gender specificity, which might have been the reason for its larger error.

Physical match performance of youth football players in relation to physical capacity

The aims of the study were to (1) analyse the activity profile of youth football players during competitive matches, and (2) examine the relationship between physical match performance and intermittent exercise performance as well as . Thirty youth male football players, aged 14–17 years, carried out a laboratory treadmill test for determination of as well as the Yo-Yo intermittent recovery level 1 (Yo-Yo IR1) and Yo-Yo intermittent endurance level 2 (Yo-Yo IE2) tests. Time–motion analysis and heart rate (HR) recordings were performed during two competitive matches per player. Distance covered during the match was 6311±948 (range: 4435–8098) m, of which 12% were high-intensity activities (HIA; 759±437 [374–2062] m), and 5% was backwards running (309±205 [12–776] m). Mean match HR was 168±12 (140–187) bpm, corresponding to 85% (69–91) of maximum HR. The total distance covered in the last 13.3-min period of the match was 40%, 26% and 17% lower than in the first, second and fourth 13.3-min periods of the match, respectively (P<0.05). The distance covered in backwards running decreased by 31% and 37% from the first to the last 13.3-min periods of the first and second half, respectively (P<0.05). The Yo-Yo IR1 was significantly associated with the time spent with sprinting during the match (r=0.63; P=0.002) and during the last 13.3-min period (r=0.63; P=0.022). Both Yo-Yo IR1 and Yo-Yo IE2 were correlated with the time spent with match HIA (r=0.56 and r=0.57, respectively; P<0.05). No significant relationship was observed between and match time–motion variables (r=−0.13–0.25; P>0.05) or Yo-Yo test performances (r=0.09–0.26; P>0.05). In conclusion, youth football players have a high heart-rate loading during match play and a decreased running performance towards the end of the game. The intermittent exercise capacity, as determined in the Yo-Yo IR1 test, appears to be a valid indicator of high-intensity exercise performance in youth matches.

Differences in Physiological Characterization between Yo-Yo Intermittent Recovery Test Level 1 and Level 2 in Japanese College Soccer Players

We aim to investigate the differences in physiological characterization between Yo-Yo intermittent recovery test level 1 (Yo-Yo IR1) and level 2 (Yo-Yo IR2) in Japanese college soccer players. Eighty-two Japanese college soccer players (elite, n=40; non-elite, n=42) participated in the study. All subjects took part in three tests Yo-Yo IR1, Yo-Yo IR2, and laboratory treadmill tests. The order of the three tests was randomized across subjects. The Yo-Yo IR1 test was not significantly different between elite (2369.0±319.2 m) and non-elite (2315.2±346.3 m) players. In contrast, the Yo-Yo IR2 test was significantly different between elite (1035.0±147.5 m) and non-elite (919.0±119.3 m) players. Anaerobic threshold (AT) was significantly correlated with both Yo-Yo IR1 and Yo-Yo IR2, although the correlation was stronger for Yo-Yo IR2. Our findings suggest that the Yo-Yo IR2 test will probably be a better tool than Yo-Yo IR1 in measuring endurance capacity in Japanese college soccer players.

Prediction of [formula omitted] from a new field test based on portable indirect calorimetry

We assessed the validity and reliability of the new 15 m square shuttle run test (SST) for predicting laboratory treadmill test (TT) maximal oxygen uptake ( V ˙ O 2 max ) compared to the 20 m multistage shuttle run test (MST) in 45 adult males. Thirty participants performed a TT and a SST once to develop a V ˙ O 2 max prediction model. The remaining 15 participants performed the TT and MST once and the SST twice for cross-validation purposes. Throughout testing V ˙ O 2 max was determined via portable indirect calorimetry while blood lactate concentration was assessed at the fifth recovery minute. Comparisons of TT V ˙ O 2 max (51.3 ± 3.1 ml kg −1 min −1) with SST measured (51.2 ± 3.2 ml kg −1 min −1) and predicted (50.9 ± 3.3 ml kg −1 min −1) V ˙ O 2 max showed no differences while TT blood lactate was higher compared to SST (10.3 ± 1.7 mmol vs. 9.7 ± 1.7 mmol, respectively). In contrast, MST measured (53.4 ± 3.5 ml kg −1 min −1) and predicted (57.0 ± 4.5 ml kg −1 min −1) V ˙ O 2 max and blood lactate (11.2 ± 2.0 mmol) were significantly higher compared to TT. No test–retest differences were detected for SST measured and predicted V ˙ O 2 max and blood lactate. It is concluded that the SST is a highly valid and reliable predictive test for V ˙ O 2 max .

Validity of The ʼBeep-Testʼ in Estimating VO2max Among Female College Soccer Players

Soccer performance is highly dependent on players' maximal aerobic power, which can be measured directly in the laboratory (i.e. VO2 max) or indirectly using time efficient field tests (i.e. Leger and Lambert's 'Beep-Test'). PURPOSE: To determine the validity of the 'Beep-Test' in estimating VO2max among female college soccer players. METHODS: Ten NCAA Division I female college soccer players performed a VO2max laboratory treadmill test and the 'Beep-Test' within a 2 week period during their off-season. The 'Beep-Test' (Leger and Lambert, 1982) is a timed test performed to fatigue using multistage 20-meter shuttle runs for the prediction of VO2 max. A series of beeps from a pre-recorded audio cassette indicates the running velocity with which players complete the 20-meter shuttle runs. The starting velocity is 8 km/h and it increases by 0.5 km/h every 2 minutes. The test ends when a player either fails to complete the 20-meter distance two consecutive times within the allotted time or cannot complete the stage due to exhaustion. RESULTS: A correlation coefficient of r = 0.783 (P < 0.01 level) and SEE = 4.32 ml/kg/min were found between the VO max laboratory treadmill test (47.8 ±3.5 ml/km/min) and the 'Beep-Test' (50.9 ± 4.9 ml/km/min). CONCLUSION: The 'Beep-Test' provides a reasonably valid prediction of VO max among female collegiate soccer players. However, it overestimates VO2max by about 3 ±3(t= −3.227, df=9, P < 0.05).

Physical Demands during an Elite Female Soccer Game: Importance of Training Status

To examine the activity profile and physical loading of elite female soccer players during match play and to study the relationship between training status and physical match performance. Time-motion analysis and HR recordings were performed on 14 elite female soccer players during competitive matches. In addition, the players carried out a laboratory treadmill test and the Yo-Yo intermittent recovery test. The total distance covered during a game was 10.3 km (range: 9.7-11.3) with high-intensity running (HIR) accounting for 1.31 km (0.71-1.70). HIR was performed 125 times (72-159) for 2.3 s (2.0-2.4) on average. The average and peak HR in a game were 167 beats per minute (bpm) (152-186) and 186 (171-205), respectively, corresponding to 87% (81-93) and 97% (96-100) of HR(max). Maximal pulmonary oxygen uptake (VO2max) was 49.4 mL.min(-1).kg(-1) (43.4-56.8), and incremental treadmill test (ITT) performance was 4.49 min (3.38-5.17). The Yo-Yo test performance was 1379 m (600-1960). The total distance covered during match play did not correlate with VO2max or ITT performance but correlated with the Yo-Yo test result (r = 0.56, P < 0.05). Significant positive correlations were observed between HIR and VO2max (r = 0.81, P < 0.05), ITT (r = 0.82, P < 0.05), and Yo-Yo test performance (r = 0.76, P < 0.05). No relationship was observed between HR(max) during match play and any of the performance measures. The present study demonstrated that 1) HIR during games varies markedly between elite female soccer players, 2) all players have high HR throughout a competitive game with periods of near-maximal values, 3) the distance covered by HIR during match play is closely related to the physical capacity, and 4) the Yo-Yo intermittent recovery test can be used as an indicator of the physical match performance of elite female players.

ACTIVITY PROFILE AND PHYSIOLOGICAL DEMANDS OF TOP CLASS ASSISTANT REFEREEING IN SOCCER

To examine the movement pattern and physiological demands of top-class assistant refereeing in soccer, computerized time motion analyses were performed on 12 assistant referees in 18 competitive top-level matches. Heart rates (HR) were recorded continuously and blood lactates were measured in blood samples taken immediately after each half. In addition, 10 of the assistant referees (41 (range: 35–47) yrs, 181 (175–189) cm, 79.7 (69.1–90.2) kg, 44.7 (40.9–49.8) mlO2/min/kg) carried out a laboratory treadmill test. To study sprint performance during the game 12 assistant referees performed a repeated sprint protocol (3x30-m sprints separated by 25s) immediately before and after additional 6 competitive games. Total distance covered by the top class assistant referees was 7.18 (5.78–8.16) km of which 1.10 (0.86–1.43) km was high intensity running and 1.03 (0.12–2.09) km was sideways running. The total number of match activities recorded was 943 (807–1115) corresponding to a change in activity every 6 s on average. The mean distance of the 76 (55–103) high intensity runs recorded was 14 m and 89% of those were shorter than 25 m. Mean HR was 137 (117–159) beats/min corresponding to 74 (65–88)% of HRmax or, estimated from treadmill HR-VO2 relationships, 66 (56–80)% of VO2max. Blood lactate was 4.7 (1.6–11.0) and 4.8 (1.1–13.7) mmol/l after first and second half, respectively. The peak distance to the off-side line was higher (p < 0.05) in the second than in first half (mean ± SEM 7 ± 1 vs. 4 ± 0 m), whereas the mean distance to the off-side line was 2 ± 0 m in both halves. Sprinting performance was lower (p < 0.05) in the first and second 30-m sprint after compared to before the game (0.13 ± 0.04 and 0.07 ± 0.03 s slower, respectively). The present study demonstrates that 1) top-class assistant soccer refereeing is characterized by brief intense bouts of forward and sideways running interspersed with long low activity periods; 2) a top-class assistant referee has a moderate aerobic energy production during the game and episodes of very high anaerobic energy turnover; 3) sprint performance decreases towards the end of a top-level game and this seems to affect the assistant referees' ability to keep up with play.

Activity profile and physiological demands of top-class soccer assistant refereeing in relation to training status

To determine the movement patterns and physiological demands of top-class soccer assistant referees, we performed computerized time-motion analysis and measured heart rate and blood lactate concentration in 15 assistant referees during 22 competitive matches in the top Danish league. To relate match performance to the physical capability of the assistant referees, they performed a 3 2 30 m sprint protocol before and after matches and a laboratory treadmill test within 3 weeks of the games. The mean total distance covered by the top-class assistant referees was 7.28 (range 5.78-8.16) km, of which 1.15 (0.86-1.44) km was high-intensity running and 1.16 (0.12-2.34) km was sideways running. The amount of high-intensity running during a game was correlated with performance of repeated sprints (r = 0.80, P ≪ 0.05). Mean heart rate was 137 (117-159) beats · min-1 , corresponding to 73% (60-88%) of maximal heart rate and 65% (53-80%) of maximal oxygen uptake. Blood lactate concentration was 4.7 (1.6-11.0) and 4.8 (1.1-13.7) mmol · l -1 after the first and second half, respectively. Sprinting performance was poorer (P ≪ 0.05) after than before the games. The peak distance to the offside line was greater (P ≪ 0.05) in the second than the first half (7 - 1 vs 5 - 0 m). Our results show that: (1) top-class assistant soccer refereeing is characterized by brief intense bouts of forward and sideways running interspersed with long periods of low activity; (2) top-class soccer assistant referees have moderate aerobic energy production during games with episodes of high aerobic and anaerobic energy turnover; (3) assistant referees' performance of repeated sprints correlates with the amount of high-intensity running performed in a game; and (4) sprint performance decreases towards the end of a game, which appears to affect assistant referees' ability to keep up with play.

A statistical model for estimating oxides of nitrogen emissions from light duty motor vehicles

Motor vehicle emission rate models for predicting oxides of nitrogen (NO x) emissions are insensitive to vehicle modes of operation such as cruise, acceleration, deceleration, and idle, because they are based on average trip speed. Research has shown that NO x emissions are sensitive to engine load; hence, load-based variables need to be included in emissions models. Ongoing studies attempting to incorporate these `modal' variables have experienced difficulties with: (1) incomplete and/or non-representative data sets of emissions test data vis-a-vis the modal operating profiles of the tested vehicles; (2) lack of information for predicting on-road operating parameters of vehicles; and (3) non-representative vehicles recruited for emissions tests. The objective of this research was to develop a statistical model for predicting NO x emissions from light-duty gasoline motor vehicles. The primary end use of this model is forecasting, rather than explanation of the factors that affect NO x emissions, which brings to bear different requirements from the statistical model. The three challenges noted above are addressed by: (1) analyzing a data set of more than 13 000 hot-stabilized laboratory treadmill tests on 19 driving cycles (specific speed versus time testing conditions), and 114 variables describing vehicle, engine and test cycle characteristics; (2) making the models compatible with empirical data on how vehicles are being operated in-use; and (3) developing statistical weights to account for the differences in model year distributions between the emissions testing database and the current national on-road fleets. The NO x emissions model is estimated using ordinary least-squares regression techniques, with transformed response variable and regression weights. Tree regression is employed as a tool for mining relationships among variables in the data, with particular focus on identifying useful interactions among discrete variables. Details of the model development process are presented, as well as results for the final model showing the predicted emissions algorithm for the current motor vehicle fleet in Atlanta, GA metropolitan region.

Beta-Endorphin and adrenocorticotrophin after incremental exercise and marathon running--female responses.

Investigations of exercise-induced increases in beta-endorphin, adrenocorticotropic hormone (ACTH) and cortisol concentration have been carried out mainly in men. Data concerning the female reaction are sparse and less clear. In a comparison between incremental exercise and marathon running 14 experienced female marathon runners volunteered to run to exhaustion according to an incremental treadmill protocol. They ran a marathon 4 weeks later. Blood was analysed for beta-endorphin, ACTH and cortisol concentration immediately prior to the laboratory treadmill test, 3, 30 and 60 min later, as well as prior to the marathon, after 60 min and 120 min of running and 3, 30 min, and 24 h after completion of the run. At each blood collection, lactate concentration, heart frequency and perceived exertion were determined. The mean marathon running time was 3.22 h. Baseline concentrations for beta-endorphin of 22 pmol.l-1 before the marathon and 19 pmol.l-1 before the treadmill exercise increased 1.4-fold 30 min after the marathon and 1.9-fold after the treadmill exercise; for ACTH the baseline of 4.7 and 4.0 pmol.l-1 was increased by 8.3- and 10.3-fold, respectively. Cortisol concentration rose exponentially from a baseline 17 micrograms.dl-1 and peaked at 2.2-fold 30 min after the run, when the maximal concentration also had been reached after the treadmill test, increasing 1.3-fold from a baseline of 21 micrograms.dl-1. The maximal values for cortisol concentration after both exercises differed from each other, while the maxima of ACTH and beta-endorphin concentrations were similar. The ACTH and beta-endorphin concentration declined more slowly during the recovery after the marathon than after the treadmill. Cortisol concentration was below baseline 24 h later. In comparison with men studied earlier, female marathon runners showed higher baseline concentrations and lesser increases in beta-endorphin and lower baseline concentrations and larger increases in ACTH concentration after both types of exercise. The delayed decrease in concentration of the hormones after the marathon was similar in male and female runners.

The Reliability and Validity of the 20-Meter Shuttle Test as a Predictor of Peak Oxygen Uptake in Edinburgh School Children, Age 13 to 14 Years

This study examined the reliability and validity of the 20-meter shuttle test as a predictor of peak VO2 in Edinburgh school children. Thirty-three children (15 boys, 18 girls) performed three shuttle tests and three laboratory treadmill tests of peak VO2. Multiple regression analysis revealed that the prediction of peak VO2 (ml·kg−1·min−1) from shuttle run performance was improved by including skinfold thickness measurements in the prediction models, particularly with the female group. Predictive power was greatest for females when using maximal shuttle speed (kmhr−1) best of three repeat tests and triceps skinfold thickness (mm) (R2 = .85, SEE = 2.4), and for males when using maximal shuttle speed (km·hr−1) best of three repeat tests and the sum of the triceps and subscapular skinfolds (R2 = .68, SEE = 3.23). When using shuttle run performance to predict peak VO2 (ml·kg−1·min−1) in children of this age group, body composition measures must be included in the equation.

Relationship between plasma ammonia and blood lactate concentrations after maximal treadmill exercise in circumpubertal girls and boys.

The purpose of the study was to define a relationship between plasma ammonia [NH3]pl and blood lactate concentrations [la-]b after exercise in children and to find out whether the [NH3]pl, determined during laboratory treadmill tests, may be useful as a predictor of the children's sprint running ability. A group of 20 girls and 14 boys trained in athletics or swimming and 8 untrained boys, aged 13.2 to 13.7 years, participated in the study. Their [NH3]pl and [la-]b were measured before and after incremental maximal treadmill exercise. In addition, the subjects' running performance was tested in 30-, 60- and 600- or 1000-m runs under field conditions. The [NH3]pl during the treadmill runs increased by 20.1 (SD 17.3), 24 (SD 16.7) and 10 (SD 4.3) mumol.l-1 in the girls, the trained boys and the untrained boys, respectively. The postexercise [NH3]pl correlated positively with [la-]b (r = 0.565 in the girls and 0.812 in the boys) and treadmill speed attained during the test (r = 0.489 in the girls and 0.490 in the boys). Significant correlations were also found between [NH3]pl obtained during the treadmill test and the times of 30- and 60-m runs (r = -0.676 and -0.648, respectively) in the boys but not in the girls. A comparison of the present data with those reported previously in adults showed that increases in [NH3]pl during maximal exercise in children would seem to be lower than in adult subjects both in absolute values and in relation to [la-]b.(ABSTRACT TRUNCATED AT 250 WORDS)

20-MST and PWC170 validity in non-Caucasian children in the UK.

The validity was investigated of 20-MST (20 Metre Endurance Shuttle Run Test) and PWC170 (Physical Working Capacity) field tests with laboratory-measured peak oxygen uptake (VO2peak) in a multiracial UK population of 12-year olds: 103 subjects completed the 20-MST and 96 of these completed the PWC170. To assess validity, a laboratory treadmill test was completed by ten boys and ten girls who had performed both field tests. VO2peak was 43.8 ml kg-1 min-1 for boys and 38.5 ml kg-1 min-1 for girls. Pearson product-moment correlation showed 20-MST to be a reliable measure of cardiorespiratory fitness (r = 0.83, boys; r = 0.76, girls, P less than 0.03), while correlations with PWC170 were lower (r = 0.64, boys; r = 0.54, girls) and not significant. The 20-MST was consistent in retest (n = 20) - reliability coefficients r = 0.73, boys; r = 0.88, girls; P less than 0.01. The results suggest 20-MST is a valid, measure of fitness in this population when compared with VO2peak. PWC170 is less valid, possibly due to cultural and social backgrounds. The cycle test was inappropriate in this population, especially for girls unaccustomed to exercise and cycling. The 20-MST test is recommended for large groups of children when facilities are limited. It requires limited skill or habituation and is relatively non-invasive.