Laboratory Treadmill Research Articles

A replicate crossover trial on the inter-individual variability of sleep indices in response to acute exercise undertaken by healthy men.

Using the necessary replicate-crossover design, we investigated whether there is inter-individual variability in home-assessed sleep in response to acute exercise. Eighteen healthy men (mean(SD): 26(6) years) completed two identical control (8-h laboratory rest, 08:45-16:45) and two identical exercise (7-h laboratory rest; 1-h laboratory treadmill run [62(7)% peak oxygen uptake], 15:15-16:15) trials in randomised sequences. Wrist-worn actigraphy (MotionWatch 8) measured home-based sleep (total sleep time, actual wake time, sleep latency, sleep efficiency) two nights before (nights 1-2) and three nights after (nights 3-5) the exercise/control day. Pearson's correlation coefficients quantified the consistency of individual differences between the replicates of control-adjusted exercise responses to explore: (1) immediate (night 3 minus night 2); (2) delayed (night 5 minus night 2); and (3) overall (average post-intervention minus average pre-intervention) exercise-related effects. Within-participant linear mixed models and a random-effects between-participant meta-analysis estimated participant-by-trial response heterogeneity. For all comparisons and sleep outcomes, the between-replicate correlations were non-significant, ranging from trivial-to-moderate (r range = -0.44 to 0.41, P≥0.065). Participant-by-trial interactions were trivial. Individual differences SDs were small, prone to uncertainty around the estimates indicated by wide 95% confidence intervals and did not provide support for true individual response heterogeneity. Meta-analyses of the between-participant, replicate-averaged condition effect revealed that, again, heterogeneity (τ) was negligible for most sleep outcomes. Control-adjusted sleep in response to acute exercise was inconsistent when measured on repeated occasions. Inter-individual differences in sleep in response to exercise were small compared to the natural (trial-to-trial) within-subject variability in sleep outcomes.

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.

Variability in Running Economy of Kenyan World-Class and European Amateur Male Runners with Advanced Footwear Running Technology: Experimental and Meta-analysis Results

BackgroundAdvanced footwear technology improves average running economy compared with racing flats in sub-elite athletes. However, not all athletes benefit as performance changes vary from a 10% drawback to a 14% improvement. The main beneficiaries from such technologies, world-class athletes, have only been analyzed using race times.ObjectiveThe aim of this study was to measure running economy on a laboratory treadmill in advanced footwear technology compared to a traditional racing flat in world-class Kenyan (mean half-marathon time: 59:30 min:s) versus European amateur runners.MethodsSeven world-class Kenyan and seven amateur European male runners completed a maximal oxygen uptake assessment and submaximal steady-state running economy trials in three different models of advanced footwear technology and a racing flat. To confirm our results and better understand the overall effect of new technology in running shoes, we conducted a systematic search and meta-analysis.ResultsLaboratory results revealed large variability in both world-class Kenyan road runners, which ranged from a 11.3% drawback to a 11.4% benefit, and amateur Europeans, which ranged from a 9.7% benefit to a 1.1% drawback in running economy of advanced footwear technology compared to a flat. The post-hoc meta-analysis revealed an overall significant medium benefit of advanced footwear technology on running economy compared with traditional flats.ConclusionsVariability of advanced footwear technology performance appears in both world-class and amateur runners, suggesting further testing should examine such variability to ensure validity of results and explain the cause as a more personalized approach to shoe selection might be necessary for optimal benefit.

Neglected problem: Influence of school bag on lumbar segment in children.

School bag (SB) load causes significant changes in the height and symmetry of the intervertebral discs at each level of the spine from T12-L1 to L5-S1. This study aims to determine the change in the size of the lumbar segment angle at a particularly critical point L3-L4 of the spine in relation to the load of the average weight of SB in healthy male children (students) at standing and after 2-minute gait. 47 boys, aged 12.2 ± 0.92 years, underwent photogrammetric measurements in the sagittal plane in statics and dynamics, walking on a laboratory treadmill. Measurements were repeated with the weight of SB with a constant load of 6,251 kg, which represents 13.78% of the average body weight of our sample. The lumbar angle (LA) connecting the point of the big toe, the lumbar point L3-L4 and the processus spinosus C7 was measured. In gait, LA was measured in the phases of the middle support and the initial contact of the heel. T-test of paired samples was used to estimate the change in LA at standing from 4.953° and walking phases from 6.295° to 7.332° in relation to the unloaded state, and the value of the effect size (ES) indicates that the impact of SB load is significant. Cumulatively, microtraumas caused by SB load significantly affect the increase in intervertebral pressure at the L3-L4 point, which is susceptible to degenerative processes and which can be the cause of lumbar syndrome (LS). Preventive measures are needed in order to lighten SB in this population and introduce up to 10% of students' body weight into the safe zone.

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.

Comparison of the Field-Based Intermittent Running Fitness Test 30-15 and the Treadmill Multistage Incremental Test for the Assessment of Cardiorespiratory Fitness in Elite Handball Players.

The aim of the present study was to investigate whether the physiological parameters indicative of cardiorespiratory fitness obtained during the 30-15 intermittent fitness (30-15IFT) test and the multistage laboratory treadmill endurance (TR) test differ. Nineteen elite handball players were recruited for the current study and assigned in a cross-over manner to one of two tests to be performed 48 h apart at each visit to the testing facility. The results showed that VO2max (percentage difference [PC] = 6.1%; p = 0.004) and maximal running velocity (V) (PC = 19.4%; p < 0.001) were significantly higher for the 30-15IFT test than that obtained during the TR test. Furthermore, the onset of blood lactate accumulation was shown to be significantly higher for all measures considered to predict it during 30-15IFT compared to TR as follows: VO2max (PC = 12.6%; p = 0.001), running speed (PC = 33.9%; p < 0.001), and maximal heart rate (PC = 7.5%; p < 0.001). The current study highlights the importance of sport-specific testing, particularly for measuring individual cardiorespiratory fitness in elite handball players, as TR may underestimate crucial variables used for both diagnostics and training prescription.

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.

Study of exercise treadmill test in type 2 diabetes mellitus patients

Background: The aim of this study was to assess the prevalence and clinical predictors of silent myocardial ischemia in patients with type 2 diabetes mellitus, and the early diagnosis of coronary artery disease.Methods: A cross sectional prospective study was conducted including all confirmed diabetic patients in the age group between 40-60 in Bharati medical college hospital Pune in western Maharashtra. A detailed clinical examination and history was taken and relevant laboratory investigations, Electrocardiogram and Treadmill Stress test was done using Bruce protocol. The quantitative data was represented as their mean ± SD. Categorical and nominal data was expressed in percentage. All analysis was carried out by using SPSS software version 21.Results: Male preponderance was seen in the study with 64% of the study subjects. The mean age of the study subjects was 50.67±5.51 years. A p&lt;0.001 was obtained showing positive correlation between BMI and TMT positivity. TMT positivity steadily increased with the duration of diabetes mellitus. Obtained p&lt;0.001. The correlation between dyslipidemia and TMT positivity was significant, with a p=0.007. Correlation of Fasting as well as Post-prandial blood glucose levels with TMT positivity proved to be statistically significant, with a p&lt;0.001.Conclusions: Exercise Treadmill test in diabetic patients has a significant role in screening diabetic individuals for coronary ischemia. The results obtained clearly indicate that an exercise treadmill test may be proposed as the first test for screening for coronary ischemia in diabetic population as it is safer, cheaper and non-invasive.

Physiological and Perceptual Responses to Self-Selected Exercise Pace on A Track Versus Treadmill

Objective: To investigate differences between a controlled and non-controlled exercise modality when walking and running at self-selected pace. Methods: Male and female participants (N=30, 21.07±0.88 years of age) engaged in four sessions testing V̇O2max, one-mile walk and run on an indoor track, and one-mile walk and run on a laboratory treadmill. With a significance level set at p&lt;0.05, the following results were found. Results: Walking and running heart rate and rating of perceived exertion were significantly higher on the treadmill compared to the track (p&lt;0.05). However, energy expenditure showed no significant difference between exercise modality (p=0.611). Treadmill exercise resulted in higher V̇O2 values for males during both walk and run pace (p=0.041 and p=0.002, respectively). Conclusions: Exercise programming is an individualized process which should consider differences among modalities, settings, and affective responses. We observed an increased perceived effort during treadmill exercise while maintaining similar energy expenditure. The provisions of autonomy and individuality may decrease perceived effort while maintaining energy expenditure, thus providing positive affective responses promoting adherence. With these differences between modalities in mind, exercise professionals should consider appropriate adjustments to intensity when targeting specific adaptations. These adjustments may also influence adherence to a prescribed program.

Birds keep their balance underfoot

Every day is a balancing act for two-legged, land-dwelling animals traversing tree roots, rocks or any other obstacles they may encounter. The balance system of one nimble two-legged animal, the guinea fowl, is remarkably robust, allowing them to remain stable even when encountering the most extreme trips and slips: their leg muscles rapidly counteract a bad step in response to signals sent from nerve sensors embedded in the muscles. A team of researchers led by Monica Daley, now at the University of California, Irvine, USA, had previously conducted a series of experiments to learn how the guinea fowls’ muscles pull off this feat, but the role of the nerve sensors had eluded them. So, they decided to study how guinea fowl take obstacles in their stride when a critical sensory nerve is knocked out.They first trained the animals to run on a laboratory treadmill set to speeds ranging from 1.3 to 2.0 m s−1 – the equivalent to a brisk walk in humans. Then, to challenge the birds’ stability, they introduced 5 cm high hurdles on the treadmill at every 10th step taken by the animal. Once the birds were used to hurdling, the team severed the sensory nerve in the ankle muscle that, under normal circumstances, corrects the muscle length back to normal and maintains balance during running. In addition, the team implanted mechanical and electrical sensors in the ankle muscle to measure its force production and to gauge when nerve and brain signals activated the muscle. Finally, to find out how the birds fared when their nerve signals were cut, the team compared the birds’ responses with those of another group of birds with intact nerves.When the researchers looked at how the birds cleared the hurdles, they found that those with a severed nerve were still able to retain their stability, which underscores their remarkable agility. However, the birds that lacked sensory signals from the ankle muscle relied on generating a large burst of muscle force when stepping over the hurdle. This suggests that the birds compensated for the loss of the sensory feedback from the ankle nerve by using an alternative strategy to activate their muscles and maintain stability.To learn more about this substitute strategy, the team turned their attention to the muscle activations and found that the birds that lacked sensory nerve signals from the ankle activated their ankle muscles about 23 ms sooner and over a longer duration than the birds with an intact nerve. The shift in muscle activation timing suggests that the brain compensated for the loss of nerve signals by ramping up its signal to the ankle muscle. The compensation shows that the signal from the ankle muscle sensory nerve plays a role in maintaining balance – without the nerve signal, the brain must step in to compensate for the loss.Daley and her colleagues have shown that nerve sensors that monitor ankle muscle length contribute to maintaining balance in guinea fowl. The current results add to the understanding of how balance is maintained across two- and four-legged vertebrates and may even have implications for understanding how human balance problems arise from nerve injury or neurodegenerative disorders – because we, like guinea fowls, are only as stable as our next foothold.

The effectiveness of real-time haptic feedback gait retraining for reducing resultant tibial acceleration with runners

ObjectivesTo examine the effectiveness of real-time haptic feedback gait retraining for reducing resultant tibial acceleration (TA-R) with runners, the retention of changes over four weeks, and the transfer of learning to overground running. DesignCase control. SettingBiomechanical laboratory treadmill, and track-based overground, running. Participants18 experienced uninjured high tibial acceleration runners. Main outcome measuresTA-R measured while treadmill and overground running assessed at pre-, post- and 4-weeks post-intervention. ResultsAcross the group, a 50% reduction in TA-R was measured post-intervention (ES: 0.9, z = −18.2, p < .001), and 41% reduction at 4-weeks (ES: 0.8, z = −12.9, p < .001) with treadmill running. A 28% reduction (ES: 0.7, z = −13.2, p < .001), and a 17% reduction in TA-R were measured at these same time points when runners ran overground (ES: 0.7, z = −11.2, p < .001). All but two runners responded positively to the intervention at the post-intervention assessment. Eleven runners were categorised as positive responders to the intervention at the 4-week post-intervention. ConclusionsHaptic feedback based on TA-R appears to be as effective, but less invasive and expensive, compared to other more established modalities, such as visual feedback. This new approach to movement retraining has the potential to revolutionise the way runners engage in gait retraining.

Low-cost, open-source, variable speed and incline treadmill for studying impacts of neonatal locomotion.

There is a need for a small-scale, laboratory treadmill to investigate impacts of neonatal locomotion on neuromuscular and musculoskeletal development in small animal models. Adult mice and rats are routinely assessed using commercially available treadmills, but these treadmills can be relatively expensive and they may lack features needed to evaluate developing animals. Therefore, to overcome these limitations, a new treadmill was designed, built and calibrated. This open-source treadmill was designed specifically for neonatal and postnatal mice and rats, and it fits within a neonatal incubator. By using predominantly off-the-shelf and 3D printed components, and a microcontroller, this treadmill was low cost and easy to reproduce. The design also included variable incline, and a transparent belt and enclosures for video and gait analysis. A touchscreen interface provided user-friendly control over belt speed and run time. Moreover, validation experiments showed high accuracy in belt speed control, allowing for tightly regulated experimental conditions. Overall, this new low-cost, open-source, variable speed and incline treadmill can be used to advance understanding of neonatal locomotion, and neuromuscular and musculoskeletal development.

Terrestrial locomotion of the Svalbard rock ptarmigan: comparing field and laboratory treadmill studies

Research into the terrestrial locomotion of birds is often based upon laboratory treadmill experiments. However, it is unclear how transposable these results are for birds moving in the wild. Here, using video recordings, we compared the kinematics of locomotion (stride frequency, stride length, stance phase, swing phase, duty factor) and speed range of Svalbard rock ptarmigan (Lagopus muta hyperborea) under field and laboratory treadmill conditions. Our findings indicate that the kinematics of walking and aerial running are conserved when moving on the treadmill and in the field. Differences, however, were found when grounded running under the two conditions, linked to substrate. Substrate effects were confirmed by analysing trials only moving over very hard snow. In line with laboratory treadmill energetic predictions, wild ptarmigan have a preferred speed during walking and to a lesser extent when aerial running but not when moving with a grounded running gait. The birds were also capable of a higher top speed in the field than that observed during treadmill studies. Our findings demonstrate that laboratory treadmill research provides meaningful information relevant to wild birds while highlighting the importance of understanding the substrate the animals are moving over.

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.

A "Wearable" Test for Maximum Aerobic Power: Real-Time Analysis of a 60-m Sprint Performance and Heart Rate Off-Kinetics.

Maximum aerobic power () as an indicator of body fitness is today a very well-known concept not just for athletes but also for the layman. Unfortunately, the accurate measurement of that variable has remained a complex and exhaustive laboratory procedure, which makes it inaccessible to many active people. In this paper we propose a quick estimate of it, mainly based on the heart rate off-kinetics immediately after an all-out 60-m sprint run. The design of this test took into account the recent availability of wrist wearable, heart band free, multi-sensor smart devices, which could also inertially detect the different phases of the sprint and check the distance run. 25 subjects undertook the 60-m test outdoor and a test on the laboratory treadmill. Running average speed, HR excursion during the sprint and the time constant (τ) of HR exponential decay in the off-kinetics were fed into a multiple regression, with measured as the dependent variable. Statistics revealed that within the investigated range (25–55 ml O2/(kg min)), despite a tendency to overestimate low values and underestimate high values, the three predictors confidently estimate individual (R2 = 0.65, p < 0.001). The same analysis has been performed on a 5-s averaged time course of the same measured HR off-kinetics, as these are the most time resolved data for HR provided by many modern smart watches. Results indicate that despite of the substantial reduction in sample size, predicted still explain 59% of the variability of the measured .

Does Preferred Running Velocity Vary with Variations in Running Condition?

Running form is often studied within the laboratory. During these studies, researchers must make the difficult decision to capture runners at a set velocity, which allows for straight forward comparisons between participants, or at their preferred velocity (PRV). Although theoretically we are capturing natural movement when we ask runners to move at a PRV, it is unknown how a laboratory PRV over-ground or on a treadmill may differ from each other or from running on a longer course outdoors. PURPOSE: The purpose of this study was to determine a PRV for two groups of runners (recreational and competitive) over-ground in the laboratory, on a laboratory treadmill, and outside on a track. METHODS: Healthy competitive (n=10) and recreational (n=9) runners completed running trials in each of three conditions: (1) over-ground, where PRV was determined as the average of five trials; (2) on the treadmill, where PRV was determined over five trials where participants were blinded to the velocity but asked to alter the velocity until they were comfortable; and (3) around a track where the split times of two laps were taken as two separate trials. RESULTS: There was not a significant interaction between group and condition (p=0.468) but there were significant main effects for both group (p<0.001) and condition (p<0.001). The competitive runners had a faster PRV (3.1 m/s) than recreational runners (2.7 m/s). Treadmill PRV was significantly slower (2.5 m/s) than over-ground PRV (3.1 m/s; p<0.001) and track PRV (3.1 m/s; p<0.001), which were similar to each other (p=0.618). CONCLUSIONS: Environment can change a runner’s perception of preferred velocity, which was demonstrated in this study with a significantly slower preferred velocity while running on a treadmill. Therefore, one should take caution when interpreting or collecting running data that utilizes a preferred running velocity, and the environment in which the data were collected should be considered.

Treadmill exercise-induced E/e' elevation as a predictor of cardiovascular event in end-stage renal disease on peritoneal dialysis.

Diastolic dysfunction is associated with cardiovascular (CV) events in end-stage renal disease (ESRD) on continuous ambulatory peritoneal dialysis (CAPD). However, conventional measurement of LA volume and E/e' using Doppler echocardiography has been limited to predict CV events in patients with ESRD on CAPD. From September 2007 to September 2008, 30 consecutive patients with exertional dyspnea in ESRD on CAPD and normal systolic function was prospectively enrolled and underwent laboratory testing, coronary angiography, and treadmill exercise stress echocardiography (TESE). We divided the patients according to the presence of exercise-induced change of E/e' tissue Doppler and investigated whether this factor predicted CV events in ESRD on CAPD. Mean CAPD duration of all patients (70% male; mean age, 49 years) was 12 months. Patients with exercise-induced elevated E/e' (n = 12, 40%) and non-elevated E/e' (n = 18, 60%) demonstrated similar baseline characteristics. Exercise-induced elevated E/e' was predictable (cut-off value 14%, sensitivity 63%, and specificity 95%), with a hazard ratio of 1.13 (confidence interval, 1.03 to 1.24; p = 0.005), and significantly associated with CV events compared to the non-elevated E/e' group (log-rank, p = 0.007). Exercise-induced elevated E/e' determined using TESE might be feasible to predict CV events in patients with ESRD on CAPD.

Blood lactate thresholds and walking/running economy are determinants of backpack-running performance in trained soldiers

We developed a standardized laboratory treadmill protocol for assessing physiological responses to a simulated backpack load-carriage task in trained soldiers, and assessed the efficacy of blood lactate thresholds (LTs) and economy in predicting future backpack running success over an 8-mile course in field conditions. LTs and corresponding physiological responses were determined in 17 elite British soldiers who completed an incremental treadmill walk/run protocol to exhaustion carrying 20 kg backpack load. Treadmill velocity at the breakpoint (r = −0.85) and Δ 1 mmol l−1 (r = −0.80) LTs, and relative V˙O2 at 4 mmol l−1 (r = 0.76) and treadmill walk/run velocities of 6.4 (r = 0.76), 7.4 (r = 0.80), 11.4 (r = 0.66) and 12.4 (r = 0.65) km h−1 were significantly associated with field test completion time. We report for the first time that LTs and backpack walk/run economy are major determinants of backpack load-carriage performance in trained soldiers.

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.