Reliability and validity of a continuous incremental treadmill protocol for the determination of lactate threshold, fixed blood lactate concentrations, and VO2max

The Effect of Specific Treadmill Protocol on Aerobic Performance Parameters in Flat-Terrain-Trained Athletes

This study examined the differences in physiological, metabolic and running dynamics responses between level and inclined treadmill protocols and their implications for accurately determining training intensities. Twenty-three healthy, active adults (18 male and 5 female) from 25 to 59 years old (age: 42.7 years, height: 1.77 m, body mass: 71.9 kg, VO2max: 54.3 mL·kg-1·min-1) completed both protocols. Physiological markers (gas exchange threshold (GET), respiratory compensation point (RCP), VO2max), metabolic variables (HR, VO2, VCO2, RER, VE, speed) and running dynamic variables (running economy (RE), stride length (SL), ground contact time (GCT), cadence) were measured and matched for the external work rate at each stage. The data were analyzed using one-way repeated measures ANOVA with Tukey's post hoc procedure. No significant differences were observed in the physiological markers for the inclined and flat protocols across all the intensities. However, the metabolic variables showed significant differences (p = 0.0333 to <0.0001) between the inclined and flat protocols at higher intensities. The RE was consistently improved in the flat protocol compared with the inclined protocol, with significant differences observed at the high-intensity stages (p = 0.0232 to <0.0001). While the physiological markers remained unaffected, metabolic responses and running kinematics differed significantly between the protocols. These results highlight that training intensity zones derived from inclined protocols may not be appropriate for flat terrain training, underlining the importance of testing specificity in athlete preparation.

Physiological Demands of Competitive Collegiate Dance

ABSTRACT

Seifert Gonzales, AM and Stenson, MC. Physiological demands of competitive collegiate dance. J Strength Cond Res 38(9): e503-e509, 2024-Competitive collegiate dance combines elements of gymnastics and acrobatics with more traditional styles, such as ballet, jazz, and modern dance. Assessing the physiological demands and identifying clear measures of intensity and duration of such dance provide a framework for planning the competitive season and developing strength and conditioning programs. This study examined the blood lactate (BL), heart rate (HR), and ratings of perceived exertion (RPE) of 14 well-trained female dancers on a competitive collegiate dance team. Subjects completed a treadmill test to determine their lactate threshold (LT) and then performed a 120-second choreographed jazz dance routine in cumulative 30-second segments, during which physiological markers were measured. All subjects exceeded their individually determined LT values by 90 seconds into the dance routine. A moderate (rs = 0.53; p < 0.001) positive correlation was observed between HR and RPE, as was a strong (rs = 0.70; p < 0.001) positive correlation between BL and RPE. Subjects worked at or above LT for much of the 120-second jazz dance routine, indicating that competitive collegiate dance is physiologically demanding and highly anaerobic. Understanding the physiological demands of competitive collegiate dance allows strength and conditioning professionals to develop, monitor, and adjust training parameters, which will aid in minimizing injury and maximizing competitive performance in collegiate dancers.

Reassembling the Field-based Applicability of the Lactate Threshold for Old Age

This study aimed to investigate the applicability of the Lactate Threshold (LT) to predict maximal oxygen uptake (˙VO2max) and demarcate the boundary between the moderate- to heavy-intensity domain (HRm-h) in old age in comparison to the most utilized methods. A cross-sectional validation study was conducted. Participants aged 61 to 77 performed a familiarization procedure, an incremental maximal exercise treadmill test (CPX) for ˙VO2max determination, the Six-minute Walk Test (6MWT), and a discontinuous incremental field test for LT determination. Lower (P<0.01) internal effort was required for LT testing (76±8%HRmax) compared to 6MWT (92±9%HRmax). The application of the 6MWT reference equations overestimated ˙VO2max by 10-23%. LTs better estimated the ˙VO2max (r ≈0.90, SEE: ≈3.0] compared to the 6MWT (r=0.68, SEE=5.5). HRm-h determined by the CPX differed (20%; P=0.001) from that obtained by LT. HRm-h stratification indicated participants fall into the very light to the vigorous intensity domains. LT testing is more submaximal than the 6MWT, and is a valuable tool to estimate the ˙VO2max in older male adults. Implementation of LT testing in physical activity programs might help improving the quality of aerobic exercise training in older men.

Cardiopulmonary and metabolic responses during a 2-day CPET in myalgic encephalomyelitis/chronic fatigue syndrome: translating reduced oxygen consumption to impairment status to treatment considerations

BACKGROUND

Post-exertional malaise (PEM), the hallmark symptom of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), represents a constellation of abnormal responses to physical, cognitive, and/or emotional exertion including profound fatigue, cognitive dysfunction, and exertion intolerance, among numerous other maladies. Two sequential cardiopulmonary exercise tests (2-d CPET) provide objective evidence of abnormal responses to exertion in ME/CFS but validated only in studies with small sample sizes. Further, translation of results to impairment status and approaches to symptom reduction are lacking.

METHODS

Participants with ME/CFS (Canadian Criteria; n = 84) and sedentary controls (CTL; n = 71) completed two CPETs on a cycle ergometer separated by 24 h. Two-way repeated measures ANOVA compared CPET measures at rest, ventilatory/anaerobic threshold (VAT), and peak effort between phenotypes and CPETs. Intraclass correlations described stability of CPET measures across tests, and relevant objective CPET data indicated impairment status. A subset of case-control pairs (n = 55) matched for aerobic capacity, age, and sex, were also analyzed.

RESULTS

Unlike CTL, ME/CFS failed to reproduce CPET-1 measures during CPET-2 with significant declines at peak exertion in work, exercise time, V ˙ e, V ˙ O2, V ˙ CO2, V ˙ T, HR, O2pulse, DBP, and RPP. Likewise, CPET-2 declines were observed at VAT for V ˙ e/ V ˙ CO2, PetCO2, O2pulse, work, V ˙ O2 and SBP. Perception of effort (RPE) exceeded maximum effort criteria for ME/CFS and CTL on both CPETs. Results were similar in matched pairs. Intraclass correlations revealed greater stability in CPET variables across test days in CTL compared to ME/CFS owing to CPET-2 declines in ME/CFS. Lastly, CPET-2 data signaled more severe impairment status for ME/CFS compared to CPET-1.

CONCLUSIONS

Presently, this is the largest 2-d CPET study of ME/CFS to substantiate impaired recovery in ME/CFS following an exertional stressor. Abnormal post-exertional CPET responses persisted compared to CTL matched for aerobic capacity, indicating that fitness level does not predispose to exertion intolerance in ME/CFS. Moreover, contributions to exertion intolerance in ME/CFS by disrupted cardiac, pulmonary, and metabolic factors implicates autonomic nervous system dysregulation of blood flow and oxygen delivery for energy metabolism. The observable declines in post-exertional energy metabolism translate notably to a worsening of impairment status. Treatment considerations to address tangible reductions in physiological function are proffered.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov, retrospectively registered, ID# NCT04026425, date of registration: 2019-07-17.

Physical performance testing in climbing-A systematic review

Due to the increasing popularity of climbing, the corresponding diagnostics are gaining in importance for both science and practice. This review aims to give an overview of the quality of different diagnostic testing- and measurement methods for performance, strength, endurance, and flexibility in climbing. A systematic literature search for studies including quantitative methods and tests for measuring different forms of strength, endurance, flexibility, or performance in climbing and bouldering was conducted on PubMed and SPORT Discus. Studies and abstracts were included if they a) worked with a representative sample of human boulderers and/or climbers, b) included detailed information on at least one test, and c) were randomized-controlled-, cohort-, cross-over-, intervention-, or case studies. 156 studies were included into the review. Data regarding subject characteristics, as well as the implementation and quality of all relevant tests were extracted from the studies. Tests with similar exercises were grouped and the information on a) measured value, b) unit, c) subject characteristics (sex and ability level), and d) quality criteria (objectivity, reliability, validity) were bundled and displayed in standardized tables. In total, 63 different tests were identified, of which some comprised different ways of implementation. This clearly shows that there are no uniform or standard procedures in climbing diagnostics, for tests on strength, endurance or flexibility. Furthermore, only few studies report data on test quality and detailed information on sample characteristics. This not only makes it difficult to compare test results, but at the same time makes it impossible to give precise test recommendations. Nevertheless, this overview of the current state of research contributes to the creation of more uniform test batteries in the future.

The Relationship between Ergometric Treadmill or Bicycle Performance and Isokinetic Trunk Strength - a Retrospective Analysis

The relationship between trunk strength and athletic performance is well known. In the past, trunk strength and athletic performance were measured in field tests. Previous studies encouraged sport-specific analyses. The goal of this study was to investigate whether there is a relation between ergometrically measured treadmill or bicycle endurance and isokinetic trunk strength. This retrospective analysis included 1334 bicycle and 1838 treadmill ergometry examinations in 1149 subjects. Bicycle and treadmill ergometer performance were analysed in relation to isokinetic trunk strength. Statistics were performed by Pearson correlation and mixed or generalised linear models. Higher treadmill and bicycle power correlated with higher isokinetic trunk strength, with highest absolute trunk strength in the treadmill group. For both running and cycling endurance, a positive correlation with trunk strength could be quantified in regression models. Increased ergometry endurance and lower flexion/extension ratios are connected weakly. Ergometry performance had the strongest correlation with extension trunk strength (r=0.312-0.398 for bicycle ergometry and r=0.168-0.229 for treadmill ergometry, p<0.001). We encourage prospective studies using both kinds of ergometry to evaluate the effect of trunk strengthening to enhance sport-specific endurance performance. Weight-adapted trunk strength values showed overall greater correlation to trunk strength and we recommend the use of weight-adapted values.

Is the maximal lactate steady state concept really relevant to predict endurance performance?

PURPOSE

There is no convincing evidence for the idea that a high power output at the maximal lactate steady state (PO_{_MLSS}) and a high fraction of [Formula: see text]O_2max at MLSS (%[Formula: see text]O_{2_MLSS}) are decisive for endurance performance. We tested the hypotheses that (1) %[Formula: see text]O_{2_MLSS} is positively correlated with the ability to sustain a high fraction of [Formula: see text]O_2max for a given competition duration (%[Formula: see text]O_{2_TT}); (2) %[Formula: see text]O_{2_MLSS} improves the prediction of the average power output of a time trial (PO_{_TT}) in addition to [Formula: see text]O_2max and gross efficiency (GE); (3) PO_{_MLSS} improves the prediction of PO_{_TT} in addition to [Formula: see text]O_2max and GE.

METHODS

Twenty-one recreationally active participants performed stepwise incremental tests on the first and final testing day to measure GE and check for potential test-related training effects in terms of changes in the minimal lactate equivalent power output (∆PO_LEmin), 30-min constant load tests to determine MLSS, a ramp test and verification bout for [Formula: see text]O_2max, and 20-min time trials for %[Formula: see text]O_{2_TT} and PO_{_TT}. Hypothesis 1 was tested via bivariate and partial correlations between %[Formula: see text]O_{2_MLSS} and %[Formula: see text]O_{2_TT}. Multiple regression models with [Formula: see text]O_2max, GE, ∆PO_LEmin, and %[Formula: see text]O_{2_MLSS} (Hypothesis 2) or PO_{_MLSS} instead of %[Formula: see text]O_{2_MLSS} (Hypothesis 3), respectively, as predictors, and PO_{_TT} as the dependent variable were used to test the hypotheses.

RESULTS

%[Formula: see text]O_{2_MLSS} was not correlated with %[Formula: see text]O_{2_TT} (r = 0.17, p = 0.583). Neither %[Formula: see text]O_{2_MLSS} (p = 0.424) nor PO_{_MLSS} (p = 0.208) did improve the prediction of PO_{_TT} in addition to [Formula: see text]O_2max and GE.

CONCLUSION

These results challenge the assumption that PO_{_MLSS} or %[Formula: see text]O_{2_MLSS} are independent predictors of supra-MLSS PO_{_TT} and %[Formula: see text]O_{2_TT}.

Short-term High-Intensity Interval Training Improves Fitness Before Surgery: A Randomised Clinical Trial

PURPOSE

Improving cardiopulmonary reserve, or peak oxygen consumption( V ˙ O_2peak ), may reduce postoperative complications, however this may be difficult to achieve between diagnosis and surgery. Our primary aim was to assess the efficacy of an approximate 14-session, preoperative High Intensity Interval Training(HIIT) program to increase V ˙ O_2peak by a clinically-relevant 2 mL·kg^-1 ·min^-1 . Our secondary aim was to document clinical outcomes.

METHODOLOGY

In this prospective study, participants aged 45-85 undergoing major abdominal surgery were randomised to standard care or 14 sessions of HIIT over 4 weeks. HIIT sessions involved approximately thirty minutes of stationary cycling. Interval training alternated one minute of high (with the goal of reaching 90% max heart rate at least once during the session) and low/moderate intensity cycling. Cardiopulmonary exercise testing(CPET) measured the change in V ˙ O_2peak from baseline to surgery. Clinical outcomes included postoperative complications, length of stay(LOS) and Short Form-36 quality of life questionnaire(SF-36).

RESULTS

Of 63 participants, 46 completed both CPETs and 50 completed clinical follow-up. There was a significant improvement in the HIIT group's mean ± SD V ˙ O_2peak (HIIT 2.87 ± 1.94 mL·kg¹ ·min^-1 vs standard care 0.15 ± 1.93, with an overall difference of 2.73 mL·kg¹ ·min^-1 95%CI [1.53, 3.93] p<0.001). There were no statistically significant differences between groups for clinical outcomes, although the observed differences consistently favoured the exercise group. This was most notable for total number of complications (0.64 v 1.16 per patient, p=0.07), SF-36 physical component score (p=0.06), and LOS (mean 5.5 v 7.4 days, p=0.07).

CONCLUSIONS

There was a significant improvement in V ˙ O_2peak with a four-week preoperative HIIT program. Further appropriately-powered work is required to explore the impact of preoperative HIIT on postoperative clinical outcomes.

A Comparison of the Validity of Three Exercise Tests for Estimating Maximal Oxygen Uptake in Korean Adults Aged 19–64 Years

The purpose of this study was to compare the validity of three submaximal exercise tests (SMETs) and develop practical predictive models for the VO2max in Korean adults. A total of 541 (287 males and 254 females) adults participated in this study. Their ages ranged from 19 to 64. The VO2max was measured using the maximal-graded exercise treadmill test. The SMETs were performed by a treadmill test, the YMCA step test, and the PACER test. Regression analysis was conducted to compare the validity of the VO2max predictive equations using SMETs. The validity of the predictive models was evaluated using explanatory power, standard error of estimate (SEE), and Bland-Altman analysis. The explanatory power between the measured VO2max and the predicted VO2max was 58.0% (<0.001), 59.2% (<0.001), and 71.7% (<0.001), respectively. The SEEs were 4.545, 4.478, and 3.732 (mL/kg/min). The models were significant predictors of VO2max and had acceptable validity in a large sample of Korean adults. Especially, among the predictive models, PACER had the highest acceptable effectiveness. Therefore, the equations developed in this study are recommended to better evaluate the cardiovascular endurance of Korean adults.

Predicting Cardiorespiratory Fitness in Female Soccer Players: The Basque Female Football Cohort Study

PURPOSE

To develop gender-specific operational equations for prediction of cardiorespiratory fitness in female footballers.

METHOD

Forty-eight semiprofessional female footballers performed an intermittent progressive maximal running test for determination of fixed blood lactate concentration (FBLC) thresholds. Relationships between FBLC thresholds and the physiological responses to submaximal running were examined. Developed equations (n = 48) were compared with equations previously obtained in another investigation performed in males (n = 100).

RESULTS

Submaximal velocity associated with 90% maximal heart rate was related to FBLC thresholds (r = .76 to .79; P < .001). Predictive power (R2 = .82 to .94) of a single blood lactate concentration (BLC) sample measured at 10 or 11.5 km·h-1 was very high. A single BLC sample taken after a 5-minute running bout at 8.5 km·h-1 was related to FBLC thresholds (r = -.71; P < .001). No difference (P = .15) in the regression lines predicting FBLC thresholds from velocity associated with 90% maximal heart rate was observed between the female and male cohorts. However, regressions estimating FBLC thresholds by a single BLC sample were different (P = .002).

CONCLUSIONS

Velocity associated with 90% maximal heart rate was robustly related to FBLC thresholds and might serve for mass field testing independently of sex. BLC equations accurately predicted FBLC thresholds. However, these equations are gender-specific. This is the first study reporting operational equations to estimate the FBLC thresholds in female footballers. The use of these equations reduces the burden associated with cardiorespiratory testing. Further cross-validation studies are warranted to validate the proposed equations and establish them for mass field testing.

The Maximal Lactate Steady State Workload Determines Individual Swimming Performance

The lactate threshold (LT) and the strongly related maximal lactate steady state workload (MLSS_W) are critical for physical endurance capacity and therefore of major interest in numerous sports. However, their relevance to individual swimming performance is not well understood. We used a custom-made visual light pacer for real-time speed modulation during front crawl to determine the LT and MLSS_W in a single-exercise test. When approaching the LT, we found that minute variations in swimming speed had considerable effects on blood lactate concentration ([La^-]). The LT was characterized by a sudden increase in [La^-], while the MLSS_W occurred after a subsequent workload reduction, as indicated by a rapid cessation of blood lactate accumulation. Determination of the MLSS_W by this so-called "individual lactate threshold" (ILT)-test was highly reproducible and valid in a constant speed test. Mean swimming speed in 800 and 1,500 m competition (S-Comp) was 3.4% above MLSS_W level and S-Comp, and the difference between S-Comp and the MLSS_W (Δ S-Comp/MLSS_W) were higher for long-distance swimmers (800-1,500 m) than for short- and middle-distance swimmers (50-400 m). Moreover, Δ S-Comp/MLSS_W varied significantly between subjects and had a strong influence on overall swimming performance. Our results demonstrate that the MLSS_W determines individual swimming performance, reflects endurance capacity in the sub- to supra-threshold range, and is therefore appropriate to adjust training intensity in moderate to severe domains of exercise.

Mild Physical Activity Does Not Improve Spatial Learning in a Virtual Environment

It is well-established that physical exercise in humans improves cognitive functions, such as executive functions, pattern separation, and working memory. It is yet unknown, however, whether spatial learning, long known to be affected by exercise in rodents, is also affected in humans. In order to address this question, we recruited 20 healthy young male adults (18-30 years old) divided into exercise and control groups (n = 10 in each group). The exercise group performed three sessions per week of mild-intensity aerobic exercise for 12 weeks, while the control group was instructed not to engage in any physical activity. Both groups performed maximal oxygen uptake (VO_2max) tests to assess their cardiovascular fitness at baseline and every 4 weeks through the 12 weeks of the training program. The effects of mild aerobic exercise were tested on performance in two different virtual reality (VR)-based spatial learning tasks: (1) virtual Morris water maze (VMWM) and (2) virtual Radial arm water maze (VRAWM). Subjects were tested in both tasks at baseline prior to the training program and at the end of 12 weeks training program. While the mild-intensity aerobic exercise did not affect subjects' VO_2max parameters, mean time to anaerobic threshold increased for the exercise group compared with control. No effect was observed, however, on performance in the VMWM or VRAWM between the two groups. Based on these results, we suggest that mild-intensity aerobic exercise does not improve spatial learning and memory in young, healthy adults.

Comparison of Lactate and Electromyographical Thresholds After an Exercise Bout

Snarr, RL, Esco, MR, Tolusso, DV, Hallmark, AV, Earley, RL, Higginbotham, JC, Fedewa, MV, and Bishop, P. Comparison of lactate and electromyographical thresholds after an exercise bout. J Strength Cond Res 33(12): 3322-3331, 2019-The electromyographical threshold (EMGT) has been previously validated as a means to predict the work rate at which lactate threshold (LT) occurs. The reliability of these measures has yet to be examined after a bout of exercise. The purpose was to determine the agreement between electromyography (EMG) and LT after a 30-minute bout of steady-state aerobic exercise. Participants completed 2 graded exercise tests (GXT) on a cycle ergometer separated by 30 minutes of steady-state exercise. Blood lactate was measured the last 45 seconds of each stage during both GXTs, whereas EMG of the vastus lateralis was monitored continuously. Individual agreement demonstrated that pre-exercise and post-exercise LT occurred at the same work rate in 2 of 10 participants, whereas EMGT occurred at the same work rate in 6 of 10 participants. Results showed no mean difference between work rates for LT or EMG threshold for the pre-exercise GXT, but LT was significantly lower (p < 0.01) than EMGT during the post-exercise GXT. Post-GXT LT work rates were also determined to be significantly lower than pre-GXT LT (p = 0.034), whereas no differences existed in EMG thresholds. Although both LT and EMGT testing may display similar properties, they are not interchangeable. The physiological responses to increasing exercise intensity between La and EMG signaling seem to be associated, and their interaction may not be cause-effect. Because of poor individual agreement, caution should be used when determining LT through the use of EMG. Further research is needed to determine the ability of these 2 metrics to prescribe training intensities.

The influence of protocol design on the identification of ventilatory thresholds and the attainment of peak physiological responses during synchronous arm crank ergometry in able-bodied participants

Purpose

To examine the effects of stage duration on power output (PO), oxygen uptake (VO₂), and heart rate (HR) at peak level and ventilatory thresholds during synchronous arm crank ergometry.

Methods

Nineteen healthy participants completed a ramp, 1-min stepwise, and 3-min stepwise graded arm crank exercise test. PO, VO_2, and HR at the first and second ventilatory threshold (VT1, VT2) and peak level were compared among the protocols: a repeated measures analysis of variance was performed to test for systematic differences, while intraclass correlation coefficients (ICC) and Bland–Altman plots were calculated to determine relative and absolute agreement.

Results

Systematic differences among the protocols were found for PO at VT1, VT2, and peak level. At peak level, PO differed significantly among all protocols (ramp: 115 ± 37 W; 1-min stepwise: 108 ± 34 W; 3-min stepwise: 94 ± 31 W, p ≤ 0.01). No systematic differences for HR or VO₂ were found among the protocols. VT1 and VT2 were identified at 52% and 74% of VO₂peak, respectively. The relative agreement among protocols varied (ICC 0.02–0.97), while absolute agreement was low with small-to-large systematic error and large random error.

Conclusions

PO at VTs and peak level was significantly higher in short-stage protocols compared with the 3-min stepwise protocol, whereas HR and VO₂ showed no differences. Therefore, training zones based on PO determined in short-stage protocols might give an overestimation. Moreover, due to large random error in HR at VTs between the protocols, it is recommended that different protocols should not be used interchangeably within individuals.

Ventilatory efficiency during constant-load test at lactate threshold intensity: Endurance versus resistance exercises

There is a lack of evidence about the ventilatory efficiency in resistance exercises despite the key role played in endurance exercises. This study aimed to compare the cardiorespiratory, metabolic responses and ventilatory efficiency between half-squat (HS) and cycle ergometer exercises during a constant-load test at the lactate threshold (LT) intensity. Eighteen healthy male participants were randomly assigned in a crossover design to carry out HS or cycle ergometer tests. For the three HS tests, a one repetition maximum (1RM) test was performed first to determine the load (kg) corresponding to the 1RM percentages. In the second test, the incremental HS exercise was carried out to establish the load (kg) at the LT intensity. Finally, a constant-load HS test was performed at the LT intensity. The first cycle ergometer test was incremental loading to determine the intensity in watts corresponding to the LT, followed by a constant-load test at the LT intensity. A recovery time of 48 hours between each test was established. During both constant-load test, cardiorespiratory and metabolic responses were monitored. A significant exercise mode x time interaction effect was only detected in oxygen uptake (VO2), heart rate, and blood lactate (p < 0.001). No differences were found between the two types of exercise in ventilatory efficiency (p >0.05). Ventilation (VE) and carbon dioxide were highly correlated (p <0.001) in the cycle ergometer (r = 0.892) and HS (r = 0.915) exercises. In the VO2 efficiency slope (OUES), similarly significant and high correlations (p <0.001) were found between VO2 and log10 VE in the cycle ergometer (r = 0.875) and in the HS (r = 0.853) exercise. Although the cardioventilatory responses were greater in the cycle ergometer test as compared to HS exercise, ventilatory efficiency was very similar between the two exercise modalities in a predominantly aerobic metabolism.

The Effect of Vitamin D Supplementation on Skeletal Muscle in the mdx Mouse Model of Duchenne Muscular Dystrophy

Vitamin D (VitD) has shown to be beneficial in reversing muscle weakness and atrophy associated with VitD deficiency. Duchenne muscular dystrophy is characterized by worsening muscle weakness and muscle atrophy, with VitD deficiency commonly observed. This study aimed to investigate the effect of VitD supplementation on dystrophic skeletal muscle. Eight-week old female control (C57BL/10; n = 29) and dystrophic (C57BL/mdx; n = 23) mice were randomly supplemented with one of three VitD enriched diets (1000, 8000 & 20,000 IU/kg chow). Following a four-week feeding period, the extensor digitorum longus (EDL) and soleus muscles contractile and fatigue properties were tested ex vivo, followed by histological analysis. As expected, mdx muscles displayed higher mass yet lower specific forces and a rightward shift in their force frequency relationship consistent with dystrophic pathology. There was a trend for mdx muscle mass to be larger following the 20,000 IU/kg diet, but this did not result in improved force production. Fiber area in the EDL was larger in mdx compared to controls, and there were higher amounts of damage in both muscles, with VitD supplementation having no effect. Four weeks of VitD supplementation did not appear to have any impact upon dystrophic skeletal muscle pathology at this age.

Effect of heart rate on shooting performance in elite archers

Aim

The aim of the present study was to examine the effect of heart rate on shooting performance in elite archers.

Methods

Regularly trained 13 (7 female, 6 male) international level elite archers performed a (specific) protocol twice with 3 days interval in an indoor area. In order to raise the heart rate (HR) and related physiological stress the archers performed 4 sets of steady pace shuttle runs (males 10 km h^-1; females 8 km h^-1) for 3 minutes in a 20 m course following with 1 minute stop during which they performed 3 shots to 18 meter distance indoor target, and followed by 1 minute rest, where blood sample was collected from ear lobe for blood lactate (BL) analysis. Heart rate monitors were used for heart rate (HR) recordings with 5 seconds intervals for resting, running, shooting, and recovery periods. The score of the shots were recorded as in the normal archery indoor competition. Average (overall) results were taken into account for statistical analysis.

Results

Mean HR and BL during resting shoot in 1^st and 2^nd tests were 119.0 and 112.2 bpm (range 1^st test: 101–142 bpm, 2^nd test: 96–135 bpm) and 1.72 and 1.65 mmol.L⁻¹ (range 1^st test: 0.9–2.6 mmol.L⁻¹, 2^nd test: 0.8–2.3 mmol.L⁻¹) respectively. Mean HR and BL during post exercise shooting in 1^st and 2^nd tests were 168 and 166 bpm (range 1^st test: 152–191 bpm, 2^nd test: 147–188 bpm) and 4.21 and 3.44 mmol.L⁻¹ (range 1^st test: 1.3–7.0 mmol.L⁻¹, 2^nd test: 1.3–5.7 mmol.L⁻¹) respectively. There was not any statistically difference between shooting scores (27.50–27.23 points) after running exercise and resting (p > 0.05).

Conclusion

It was concluded that, under simulated indoor competition environment, high HR values do not influence short distance shooting scores.

The Slow Component of Oxygen Uptake and Efficiency in Resistance Exercises: A Comparison With Endurance Exercises

Introduction

There is a lack of information regarding the slow component of oxygen uptake (VO₂sc) and efficiency/economy in resistance exercises despite the crucial role played in endurance performance.

Purpose

this study aimed to compare the VO₂sc, efficiency/economy, metabolic, cardiorespiratory responses, rating of perceived effort and mechanical fatigue between cycling and half-squat (HS) exercises during a constant-load test at lactate threshold (LT₁) intensity.

Methods

Twenty-one healthy men were randomly assigned in a crossover design to perform cycle-ergometer or HS tests. The order of the two cycle ergometer tests was an incremental test for determining load-intensity in watts (W) at LT₁, followed by a constant-load test at the LT₁ intensity. For the three HS tests, the order was a 1RM test to determine the load (kg) corresponding to the 1RM percentages to be used during the second test, incremental HS exercise to establish the load (kg) at the LT₁ intensity, and finally, a constant-load HS test at the LT₁ intensity. A rest period of 48 h between each test was established. During the HS and cycle-ergometer constant-load tests, cardiorespiratory and metabolic responses were recorded. Lower limbs fatigue was determined by a jump test before and after the constant-load tests.

Results

A significant exercise mode × time interaction effect was detected in VO₂, heart rate, energy expenditure (EE), gross efficiency (GE), and economy (p < 0.05). A significant and sustained VO₂ raise was confirmed in HS exercise (p < 0.05) and a steady-state VO₂ was revealed in cycle-ergometer. A higher GE and economy were obtained in HS test than in cycle-ergometer exercise (p < 0.001). In both exercises, a non-significant decrease was observed in GE and economy (p > 0.05). Lower limbs fatigue was only detected after constant-load HS test.

Conclusion

Although the VO₂, heart rate and EE responses were higher in cycling exercise, the constant-load HS test induced a greater VO₂sc and EE raise than the cycling test in a predominantly aerobic metabolism. These results could explain a decrease observed in jump performance only after HS test. GE and economy could benefit from the eccentric phase of the HS exercise.

Efficacy of Hot Yoga as a Heat Stress Technique for Enhancing Plasma Volume and Cardiovascular Performance in Elite Female Field Hockey Players

Perrotta, AS, White, MD, Koehle, MS, Taunton, JE, and Warburton, DER. Efficacy of hot yoga as a heat stress technique for enhancing plasma volume and cardiovascular performance in elite female field hockey players. J Strength Cond Res 32(10): 2878-2887, 2018-This investigation examined the efficacy of hot yoga as an alternative heat stress technique for enhancing plasma volume percentage (PV%) and cardiovascular performance. Ten international caliber female field hockey players completed six 60-minute hot yoga sessions using permissive dehydration over 6 days, followed by a 6-day national team camp. Changes in PV% were examined throughout the intervention and postintervention period. A graded maximal exercise test was performed in a thermoneutral environment (23.2 ± 1.0° C) 24 hours before and 24 hours after intervention. Six days of hot yoga initiated a moderate state of hypovolemia (PV% = -3.5%, 90% confidence limit [CL] [-6.9 to -0.13]), trivial improvements in maximal aerobic power (V[Combining Dot Above]O2max) (effect size [ES] = 0.06, 90% CL [-0.16 to 0.28]), and run time to exhaustion (ES = 0.11, 90% CL [-0.07 to 0.29]). Small meaningful improvements were observed in running speed (km·h) at ventilatory threshold (VT1) (ES = 0.34, 90% CL [-0.08 to 0.76]), VT2 (ES = 0.53, 90% CL [-0.05 to 1.1]), along with adaptations in the respiratory exchange ratio during high-intensity exercise (ES = -0.25, 90% CL [-0.62 to 0.12]). A large plasma volume expansion transpired 72 hours after intervention (PV% = 5.0%, 90% CL [1.3-8.7]) that contracted to a small expansion after 6 days (PV% = 1.6%, 90% CL [-1.0 to 4.2]). This investigation provides practitioners an alternative heat stress technique conducive for team sport, involving minimal exercise stress that can preserve maximal cardiovascular performance over periodized rest weeks within the yearly training plan. Furthermore, improvements in submaximal performance and a delayed hypervolemic response may provide a performance-enhancing effect when entering a 6-day competition period.

Repeatability and predictive value of lactate threshold concepts in endurance sports

Introduction

Blood lactate concentration rises exponentially during graded exercise when muscles produce more lactate than the body can remove, and the blood lactate-related thresholds are parameters based on this curve used to evaluate performance level and help athletes optimize training. Many different concepts of describing such a threshold have been published. This study aims to compare concepts for their repeatability and predictive properties of endurance performance.

Methods

Forty-eight well-trained male cyclists aged 18–50 performed 5 maximal graded exercise tests each separated by two weeks. Blood lactate-related thresholds were calculated using eight different representative concepts. Repeatability of each concept was assessed using Cronbach’s alpha and intra-subject CV and predictive value with 45 minute time trial tests and a road race to the top of Mont Ventoux was evaluated using Pearson correlations.

Results

Repeatability of all concepts was good to excellent (Cronbach’s alpha of 0.89–0.96), intra-subject CVs were low with 3.4–8.1%. Predictive value for performance in the time trial tests and road race showed significant correlations ranging from 0.65–0.94 and 0.53–0.76, respectively.

Conclusion

All evaluated concepts performed adequate, but there were differences between concepts. One concept had both the highest repeatability and the highest predictability of cycling performance, and is therefore recommended to be used: the Dmax modified method. As an easier to apply alternative, the lactate threshold with a fixed value of 4 mmol/L could be used as it performed almost as well.

Trial registration

Dutch Trial Registry NTR5643

The Relationship Between Lactate and Ventilatory Thresholds in Runners: Validity and Reliability of Exercise Test Performance Parameters

The aims of this study were (1) to establish the best fit between ventilatory and lactate exercise performance parameters in running and (2) to explore novel alternatives to estimate the maximal aerobic speed (MAS) in well-trained runners. Twenty-two trained male athletes ( V ˙ O_2max 60.2 ± 4.3 ml·kg·min^-1) completed three maximal graded exercise tests (GXT): (1) a preliminary GXT to determine individuals' MAS; (2) two experimental GXT individually adjusted by MAS to record the speed associated to the main aerobic-anaerobic transition events measured by indirect calorimetry and capillary blood lactate (CBL). Athletes also performed several 30 min constant running tests to determine the maximal lactate steady state (MLSS). Reliability analysis revealed low CV (<3.1%), low bias (<0.5 km·h^-1), and high correlation (ICC > 0.91) for all determinations except V-Slope (ICC = 0.84). Validity analysis showed that LT, LT+1.0, and LT+3.0 mMol·L^-1 were solid predictors of VT₁ (-0.3 km·h^-1; bias = 1.2; ICC = 0.90; p = 0.57), MLSS (-0.2 km·h^-1; bias = 1.2; ICC = 0.84; p = 0.74), and VT₂ (<0.1 km·h^-1; bias = 1.3; ICC = 0.82; p = 0.9l9), respectively. MLSS was identified as a different physiological event and a midpoint between VT₁ (bias = -2.0 km·h^-1) and VT₂ (bias = 2.3 km·h^-1). MAS was accurately estimated (SEM ± 0.3 km·h^-1) from peak velocity (V_peak) attained during GXT with the equation: MAS_EST (km·h^-1) = V_peak (km·h^-1) ^* 0.8348 + 2.308. Current individualized GXT protocol based on individuals' MAS was solid to determine both maximal and submaximal physiological parameters. Lactate threshold tests can be a valid and reliable alternative to VT and MLSS to identify the workloads at the transition from aerobic to anaerobic metabolism in well-trained runners. In contrast with traditional assumption, the MLSS constituted a midpoint physiological event between VT₁ and VT₂ in runners. The V_peak stands out as a powerful predictor of MAS.

Effect of ramp slope on different methods to determine lactate threshold in semi-professional soccer players

The present study aimed to investigate the effect of stage duration in incremental protocols on lactate threshold (LT), determined by different methods. Sixteen semi-professional soccer-players performed a 4-min stage incremental discontinuous (DP) and two maximal incremental running continuous (1 km h^-1· min^-1, CP1; and 1 km h^-1·2 min^-1 CP2) protocols. Blood-lactate concentration [La^-] was measured at baseline and during the protocols. LT was determined using D_MAX, D_MAX-MOD, 4-mM⋅L^-1, Δ1-mM⋅L^-1 and Log-Log methods. Log-Log showed no difference in LT between CP1, CP2 and DP. Conversely, LT was determined at higher velocity in CP1 than CP2 for D_MAX (15.2 ± 0.5 vs 14.4 ± 1.2 km⋅h^-1, P = 0.002), D_MAX-MOD (16.0 ± 0.5 vs 14.7 ± 1.3 km⋅h^-1, P < 0.001), 4-mM⋅L^-1 (15.5 ± 1.4 vs 14.4 ± 1.2 km⋅h^-1, P < 0.001), Δ1-mM⋅L^-1 (15.5 ± 1.3 vs 14.4 ± 1.2 km⋅h^-1, P < 0.001). Higher LT in CP1 than DP for D_MAX (15.2 ± 0.5 vs 13.0 ± 1.0 km⋅h^-1, P < 0.001) and D_MAX-MOD (16.0 ± 0.5 vs 13.6 ± 1.6 km⋅h^-1, P < 0.001) was found (P < 0.001). Log-Log resulted in shorter but accurate protocols to determine LT.

A "Blood Relationship" Between the Overlooked Minimum Lactate Equivalent and Maximal Lactate Steady State in Trained Runners. Back to the Old Days?

Maximal Lactate Steady State (MLSS) and Lactate Threshold (LT) are physiologically-related and fundamental concepts within the sports and exercise sciences. Literature supporting their relationship, however, is scarce. Among the recognized LTs, we were particularly interested in the disused “Minimum Lactate Equivalent” (LE_min), first described in the early 1980s. We hypothesized that velocity at LT, conceptually comprehended as in the old days (LE_min), could predict velocity at MLSS (_VMLSS) more accurate than some other blood lactate-related thresholds (BL_RTs) routinely used nowadays by many sport science practitioners. Thirteen male endurance-trained [_VMLSS 15.0 ± 1.1 km·h⁻¹; maximal oxygen uptake (V.O2max) 67.6 ± 4.1 ml·kg⁻¹·min⁻¹] homogeneous (coefficient of variation: ≈7%) runners conducted 1) a submaximal discontinuous incremental running test to determine several BL_RTs followed by a maximal ramp incremental running test for V.O2max determination, and 2) several (4–5) constant velocity running tests to determine _VMLSS with a precision of 0.20 km·h⁻¹. Determined BL_RTs include LE_min and LE_min-related LE_min plus 1 (LE_min+1mM) and 1.5 mmol·L⁻¹ (LE_min+1.5mM), along with well-established BL_RTs such as conventionally-calculated LT, D_max and fixed blood lactate concentration thresholds. LE_min did not differ from LT (P = 0.71; ES: 0.08) and was 27% lower than MLSS (P < 0.001; ES: 3.54). LE_min+1mM was not different from MLSS (P = 0.47; ES: 0.09). LE_min was the best predictor of _VMLSS (r = 0.91; P < 0.001; SEE = 0.47 km·h⁻¹), followed by LE_min+1mM (r = 0.86; P < 0.001; SEE = 0.58 km·h⁻¹) and LE_min+1.5mM (r = 0.84; P < 0.001; SEE = 0.86 km·h⁻¹). There was no statistical difference between MLSS and estimated MLSS using LE_min prediction formula (P = 0.99; ES: 0.001). Mean bias and limits of agreement were 0.00 ± 0.45 km·h⁻¹ and ±0.89 km·h⁻¹. Additionally, LE_min, LE_min+1mM and LE_min+1.5mM were the best predictors of V.O2max (r = 0.72–0.79; P < 0.001). These results support LE_min, an objective submaximal overlooked and underused BL_RT, to be one of the best single MLSS predictors in endurance trained runners. Our study advocates factors controlling LE_min to be shared, at least partly, with those controlling MLSS.

Protocol, and practical challenges, for a randomised controlled trial comparing the impact of high intensity interval training against standard care before major abdominal surgery: study protocol for a randomised controlled trial

BACKGROUND

Risk factors, such as the number of pre-existing co-morbidities, the extent of the underlying pathology and the magnitude of the required operation, cannot be changed before surgery. It may, however, be possible to improve the cardiopulmonary fitness of the patient with an individualised exercise program. We are performing a randomised controlled trial (RCT) assessing the impact of High Intensity Interval Training (HIIT) on preoperative cardiopulmonary fitness and postoperative outcomes in patients undergoing major abdominal surgery.

METHODS

Consecutive eligible patients undergoing elective abdominal surgery are being randomised to HIIT or standard care in a 1:1 ratio. Participants allocated to HIIT will perform 14 exercise sessions on a stationary cycle ergometer, over a period of 4-6 weeks before surgery. The sessions, which are individualised, aim to start with ten repeated 1-min blocks of intense exercise with a target of reaching a heart rate exceeding 90% of the age predicted maximum, followed by 1 min of lower intensity cycling. As endurance improves, the duration of exercise is increased to achieve five 2-min intervals of high intensity exercise followed by 2 min of lower intensity cycling. Each training session lasts approximately 30 min. The primary endpoint, change in peak oxygen consumption (Peak VO2) measured during cardiopulmonary exercise testing, is assessed at baseline and before surgery. Secondary endpoints include postoperative complications, length of hospital stay and three clinically validated scores: the surgical recovery scale; the postoperative morbidity survey; and the SF-36 quality of life score. The standard deviation for changes in Peak VO2 will be assessed after the first 30 patients and will be used to calculate the required sample size.

DISCUSSION

We want to assess if 14 sessions of HIIT is sufficient to improve Peak VO2 by 2 mL/kg/min in patients undergoing major abdominal surgery and to explore the best clinical endpoint for a subsequent RCT designed to assess if improving Peak VO2 will translate into improving clinical outcomes after surgery.

TRIAL REGISTRATION

Australian New Zealand Clinical Trials Registry, ACTRN12617000587303 . Registered on 26 April 2017.

A Lactate Kinetics Method for Assessing the Maximal Lactate Steady State Workload

During a continuously increasing exercise workload (WL) a point will be reached at which arterial lactate accumulates rapidly. This so-called lactate threshold (LT) is associated with the maximal lactate steady state workload (MLSS_W), the highest WL, at which arterial lactate concentration [LA] does not change. However, the physiological range in which the LT and the MLSS_W occur has not been demonstrated directly. We used minor WL variations in the MLSS_W range to assess arterial lactate kinetics in 278 treadmill and 148 bicycle ergometer exercise tests. At a certain workload, minimal further increment of running speed (0.1-0.15 m/s) or cycling power (7-10 W) caused a steep elevation of [LA] (0.9 ± 0.43 mM, maximum increase 2.4 mM), indicating LT achievement. This sharp [LA] increase was more pronounced when higher WL increments were used (0.1 vs. 0.30 m/s, P = 0.02; 0.15 vs. 0.30 m/s, P < 0.001; 7 vs. 15 W, P = 0.002; 10 vs. 15 W, P = 0.001). A subsequent workload reduction (0.1 m/s/7 W) stopped the [LA] increase indicating MLSS_W realization. LT based determination of running speed (MLSS_W) was highly reproducible on a day-to-day basis (r = 0.996, P < 0.001), valid in a 10 km constant velocity setting (r = 0.981, P < 0.001) and a half marathon race (r = 0.969, P < 0.001). These results demonstrate a fine-tuned regulation of exercise-related lactate metabolism, which can be reliably captured by assessing lactate kinetics at the MLSS_W.

Cardiopulmonary Exercise Test Methodology for Assessing Exertion Intolerance in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome

Background: Concise methodological directions for administration of serial cardiopulmonary exercise testing (CPET) are needed for testing of patients with Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS). Maximal CPET is used to evaluate the coordinated metabolic, muscular, respiratory and cardiac contributions to energy production in patients with ME/CFS. In this patient population, CPET also elicits a robust post-exertional symptom flare (termed, post-exertional malaise); a cardinal symptom of the disease. CPET measures are highly reliable and reproducible in both healthy and diseased populations. However, evidence to date indicates that ME/CFS patients are uniquely unable to reproduce CPET measures during a second test, despite giving maximal effort during both tests, due to the effects of PEM on energy production. Methodology: To document and assess functional impairment due to the effects of post-exertional malaise in ME/CFS, a 2-day CPET procedure (2-day CPET) has been used to first measure baseline functional capacity (CPET1) and provoke post-exertional malaise, then assess changes in CPET variables 24 h later with a second CPET to assess the effects of post-exertional malaise on functional capacity. The second CPET measures changes in energy production and physiological function, objectively documenting the effects of post-exertional malaise. Use of CPET as a standardized stressor to induce post-exertional malaise and quantify impairment associated with post-exertional malaise has been employed to examine ME/CFS pathology in several studies. This article discusses the results of those studies, as well as the standardized techniques and procedures for use of the 2-day CPET in ME/CFS patients, and potentially other fatiguing illnesses. Conclusions: Basic concepts of CPET are summarized, and special considerations for performing CPET on ME/CFS patients are detailed to ensure a valid outcome. The 2-day CPET methodology is outlined, and the utility of the procedure is discussed for assessment of functional capacity and exertion intolerance in ME/CFS.

Physiological responses during intermittent running exercise differ between outdoor and treadmill running

The aim of this study was to compare the physiological responses during 15 min of intermittent running consisting of 30 s of high-intensity running exercise at maximal aerobic velocity (MAV) interspersed with 30 s of passive recovery (30–30) performed outdoor versus on a motorized treadmill. Fifteen collegiate physically active males (age, 22 ± 1 years old; body mass, 66 ± 7 kg; stature, 176 ± 06 cm; weekly training volume, 5 ± 2 h·week−1), performed the Fitness Intermittent Test 45–15 to determine maximal oxygen uptake (V̇O2max) and MAV and then completed in random order 3 different training sessions consisting of a 30-s run/30-s rest on an outdoor athletic track (30–30 Track) at MAV; a 30-s run/30-s rest on a treadmill (30–30 Treadmill) at MAV; a 30-s run/30-s rest at MAV+15% (30–30 + 15% MAV Treadmill). Oxygen uptake (V̇O2), time above 90%V̇O2max (t90%V̇O2max), and rating of perceived exertion (RPE) were measured during each training session. We observed a statistical significant underestimation of V̇O2 (53.1 ± 5.4 mL·kg−1·min−1 vs 49.8 ± 6.7 mL·kg−1·min−1, –6.3%, P = 0.012), t90%V̇O2max (8.6% ± 11.5% vs 38.7% ± 32.5%, –77.8%, P = 0.008), RPE (11.4 ± 1.4 vs 16.5 ± 1.7, –31%, P < 0.0001) during the 30–30 Treadmill compared with the same training session performed on track. No statistical differences between 30–30 +15 % MAV Treadmill and 30–30 Track were observed. The present study demonstrates that a 15% increase in running velocity during a high-intensity intermittent treadmill training session is the optimal solution to reach the same physiological responses than an outdoor training session.

Test-retest reliability of physiological parameters in elite junior distance runners following allometric scaling

This study aimed to quantify the intra-individual reliability of a number of physiological variables in a group of national and international young distance runners. Sixteen (8 male, 8 female) participants (16.7 ± 1.4 years) performed a submaximal incremental running assessment followed by a maximal running test, on two occasions separated by no more than seven days. Maximal oxygen uptake (V̇O_2max), speed at V̇O_2max (km h^-1), running economy and speed and heart rate (HR) at fixed blood lactate concentrations were determined. V̇O_2max and running economy were scaled for differences in body mass using a power exponent derived from a larger cohort of young runners (n = 42). Running economy was expressed as oxygen cost and energy cost at the speed associated with lactate turnpoint (LTP) and the two speeds prior to LTP. Results of analysis of variance revealed an absence of systematic bias between trials. Reliability indices showed a high level of reproducibility across all parameters (typical error [TE] ≤2%; intra-class correlation coefficient >0.8; effect size <0.6). Expressing running economy as energy cost appears to provide superior reliability than using oxygen cost (TE ∼1.5% vs. ∼2%). Blood lactate and HR were liable to daily fluctuations of 0.14-0.22 mmol L^-1 and 4-5 beats min^-1 respectively. The minimum detectable change values (95% confidence) for each parameter are also reported. Exercise physiologists can be confident that measurement of important physiological determinants of distance running performance are highly reproducible in elite junior runners.

On-field prediction vs monitoring of aerobic capacity markers using submaximal lactate and heart rate measures

This study aimed to validate the use of a single blood lactate concentration measurement taken following a 5-minute running bout at 10 km·h^-1 (BLC₁₀ ) and the speed associated with 90% of maximal heart rate (S₉₀ ) to predict and monitor fixed blood lactate concentration (FBLC) thresholds in athletes. Three complementary studies were undertaken. Study I: A cross-sectional study examining the associations of BLC₁₀ and S₉₀ with running speeds at FBLC of 3 (S3mM) and 4 mmol·L^-1 (S4mM) in 100 athletes. Study II: A cross-validation study assessing the predictive capacity of BLC₁₀ and S₉₀ to estimate FBLC thresholds in real practice. Study III: A longitudinal study examining whether training-induced changes in FBLC thresholds could be monitored using BLC₁₀ and S₉₀ in 80 athletes tested before and after an intensified training period. Study I: BLC₁₀ (r=-.87 to -.89) and S₉₀ (r=.73-.79) were very largely (P<.001) related to FBLC thresholds. Study II: Predictive models yielded robust correlations between estimated and measured FBLC thresholds (r=.75-.91; P<.001). The limits of agreements, however, revealed that prediction of FBLC thresholds could be biased up to 9%-15%. Study III: BLC₁₀ was very largely related to training-induced changes in FBLC thresholds (r=-.72 to -.76; P<.001). Increases in S₉₀ were associated with improvements in FBLC thresholds, but decreases in S₉₀ led to unclear changes in FBLC thresholds. This study supports the use of BLC₁₀ as a simple, low-cost, non-fatiguing, and time-efficient functional variable to monitor, but not predict, FBLC thresholds in athletes. The present results also question the use of S₉₀ to detect declines in endurance performance.

Omni Scale Rating of Perceived Exertion at Ventilatory Breakpoint by Direct Observation of Children's Kinematics

Direct kinematic observation was used to measure ratings of perceived exertion at the ventilatory breakpoint (RPE-Vpt) in 10- to 14-yr.-old girls ( n = 22) and boys ( n = 22). RPE for the overall body, legs, and chest were simultaneously estimated by a trained observer and self-rated by a subject during treadmill exercise using the Children's OMNI-Walk/Run Scale. Subjects' heart rate and oxygen consumption were measured during each minute of exercise. Vpt for the girls and boys, respectively, were 64.2 and 66.5% VO2 max. RPE-Vpt ranged from 6.0 to 6.5 Overall, 7.1 to 7.6 Legs, and 5.0 to 5.5 Chest for both the observation and self-rating procedures. Responses indicated (a) RPE-Vpt (Overall, Legs, Chest) did not differ ( p>.05) between the observer and self-rating procedures and (b) Observer RPE-Vpt-Legs was greater ( p<.05) than RPE-Vpt-Chest. Findings validated direct kinematic observation to code group-normalized RPE-Vpt for girls and boys performing treadmill exercise.

Validity and Reliability of Ventilatory and Blood Lactate Thresholds in Well-Trained Cyclists

PURPOSE

The purpose of this study was to determine, i) the reliability of blood lactate and ventilatory-based thresholds, ii) the lactate threshold that corresponds with each ventilatory threshold (VT1 and VT2) and with maximal lactate steady state test (MLSS) as a proxy of cycling performance.

METHODS

Fourteen aerobically-trained male cyclists ([Formula: see text] 62.1±4.6 ml·kg-1·min-1) performed two graded exercise tests (50 W warm-up followed by 25 W·min-1) to exhaustion. Blood lactate, [Formula: see text] and [Formula: see text] data were collected at every stage. Workloads at VT1 (rise in [Formula: see text];) and VT2 (rise in [Formula: see text]) were compared with workloads at lactate thresholds. Several continuous tests were needed to detect the MLSS workload. Agreement and differences among tests were assessed with ANOVA, ICC and Bland-Altman. Reliability of each test was evaluated using ICC, CV and Bland-Altman plots.

RESULTS

Workloads at lactate threshold (LT) and LT+2.0 mMol·L-1 matched the ones for VT1 and VT2, respectively (p = 0.147 and 0.539; r = 0.72 and 0.80; Bias = -13.6 and 2.8, respectively). Furthermore, workload at LT+0.5 mMol·L-1 coincided with MLSS workload (p = 0.449; r = 0.78; Bias = -4.5). Lactate threshold tests had high reliability (CV = 3.4-3.7%; r = 0.85-0.89; Bias = -2.1-3.0) except for DMAX method (CV = 10.3%; r = 0.57; Bias = 15.4). Ventilatory thresholds show high reliability (CV = 1.6%-3.5%; r = 0.90-0.96; Bias = -1.8-2.9) except for RER = 1 and V-Slope (CV = 5.0-6.4%; r = 0.79; Bias = -5.6-12.4).

CONCLUSIONS

Lactate threshold tests can be a valid and reliable alternative to ventilatory thresholds to identify the workloads at the transition from aerobic to anaerobic metabolism.

The influence of the regression model and final speed criteria on the reliability of lactate threshold determined by the Dmax method in endurance-trained runners

Few studies verified the reliability of the lactate threshold determined by Dmax method (LT_Dmax) in runners and it remains unclear the effect of the regression model and the final speed on the reliability of LT_Dmax. This study aimed to examine the test-retest reliability of the speed at LT_Dmax in runners, considering the effects of the regression models (exponential-plus-constant vs third-order polynomial) and final speed criteria (complete vs proportional). Seventeen male, recreational runners performed 2 identical incremental exercise tests, with increments of 1 km·h^-1 each for 3 min on treadmill to determine peak treadmill speed (V_peak) and lactate threshold. Earlobe capillary blood samples were collected during rest between the stages. The V_peak was defined as the speed of the last complete stage (complete final speed criterion) and as the speed of the last complete stage added to the fraction of the incomplete stage (proportional final speed criterion). Lactate threshold was determined from exponential-plus-constant and from third-order polynomial regression models with both complete and proportional final speed criteria and from fixed blood lactate level of 3.5 mmol·L^-1 (LT_3.5mM). The LT_Dmax obtained from the exponential-plus-constant regression model presented higher reliability (coefficient of variation (CV) ≤ 3.7%) than the LT_Dmax calculated from the third-order polynomial regression model (CV ≤ 5.8%) and LT_3.5mM (CV = 5.4%). The proportional final speed criterion is more appropriate when using the exponential-plus-constant regression model, but less appropriate when using the third-order polynomial regression model. In conclusion, exponential-plus-constant using the proportional final speed criterion is preferred over LT_3.5mM and over third-order polynomial regression model to determine a reliable LT_Dmax.

Acute Physiological and Mechanical Responses During Resistance Exercise at the Lactate Threshold Intensity

The purpose of this study was to examine acute metabolic, mechanical, and cardiac responses to half-squat (HS) resistance exercise performed at a workload corresponding to the lactate threshold (LT). Thirteen healthy subjects completed 3 HS exercise tests separated by 48-hour rest periods: a maximal strength or 1 repetition maximum (1RM) test, an incremental load test to establish the % 1RM at which the LT was reached, and a constant load test at the LT intensity. During the last test, metabolic, mechanical, and cardiac responses were monitored respectively through blood lactate concentrations, height (H), average power (AP) and peak power (PP) recorded in a countermovement jump test, and heart rate (HR). During the constant load test, lactate concentrations and HR remained stable whereas significant reductions were detected in H, AP, and PP (p ≤ 0.05). Only low correlation was observed between lactate concentrations and the H (r = 0.028), AP (r = 0.072), and PP (r = 0.359) losses produced. Half-squat exercise at the LT elicits stable HR and blood lactate responses within a predominantly aerobic metabolism, although this exercise modality induces significant mechanical fatigue.

Validity of arm-leg elliptical ergometer for VO2max analysis

Maximal oxygen consumption ((Equation is included in full-text article.)) can be determined through multiple exercise modalities intended to elicit an individual's maximal aerobic exertion. Uphill treadmill running is considered the best modality for measuring (Equation is included in full-text article.). Previous studies have examined correlations between treadmill and elliptical ergometer tests as well as the cycle ergometer, but none of the studies use an arm-leg elliptical ergometer (ALE). The purpose of this study was to develop an ALE (Equation is included in full-text article.)testing protocol and determine whether ALE produces valid (Equation is included in full-text article.)values as compared with the treadmill. Twelve undergraduate students (mean age: 20.8 years) completed 2 (Equation is included in full-text article.)tests, 1 on a treadmill and 1 on ALE. (Equation is included in full-text article.)correlation between ALE and treadmill was examined, and paired t-tests were run for (Equation is included in full-text article.)and maximum heart rate (HRmax). A strong positive correlation was found between ALE and treadmill (Equation is included in full-text article.)values (r = 0.84; p < 0.001). There were no differences between (Equation is included in full-text article.)values; however, HRmax values were higher on the treadmill than ALE (p = 0.003). Although future research is needed to examine the observed differences in HRmax between the 2 testing modalities and gender differences in muscle recruitment patterns, the results of this study suggest that ALE is a valid modality for (Equation is included in full-text article.)testing. This will be particularly valuable as a clinical tool to assess (Equation is included in full-text article.)in populations requiring low-impact exercise.

Which is more important for reducing the odds of metabolic syndrome in men: Cardiorespiratory or muscular fitness?

OBJECTIVE

To examine combined associations of cardiorespiratory fitness (CRF) and muscular fitness (MF) with metabolic syndrome (MetSy) in a sample of young men.

METHODS

Participants were 557 men aged 19-47 years. CRF was quantified as peak oxygen uptake measured during an incremental treadmill test by a metabolic cart, while a composite MF score was calculated as the sum of z-scores from a push-ups and sit-ups test. The presence of MetSy was defined according to the updated NCEP-ATP III criteria.

RESULTS

We found a graded inverse relationship between CRF and MetSy presence. The most aerobically fit individuals had 90% lower odds of having MetSy compared to their least fit counterparts, independent of MF (odds ratio [OR] = 0.10, 95% CI = 0.04-0.21). Conversely, an increment in MF across the first three quartiles was not associated with lower odds of MetSy; only the most muscularly fit men were 2.5 times less likely to have MetSy (OR = 0.41, 95% CI = 0.21-0.78). Finally, participants with high CRF but low MF exhibited a 50% decrease in odds of having MetSy (OR = 0.49, 95% CI = 0.26-0.91), while no protective effect was found for having high MF but low CRF (OR = 0.95, 95% CI = 0.55-1.62).

CONCLUSIONS

CRF exhibited a strong protective effect against having MetSy, while the effect of MF was less pronounced.

Phase I safety study of ranolazine in pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) causes right ventricular ischemia, dysfunction, and failure. PAH patients may benefit from antianginal agents based on a shared pathophysiology with left ventricular ischemia. A single-center, randomized, placebo-controlled trial (1∶1) to assess the acute vasoreactivity and safety of ranolazine in PAH was conducted. Plasma samples for pharmacokinetic (PK) studies were drawn during hemodynamic measurements at 0, 60, 90, 120, 240, and 360 minutes from a Swan-Ganz catheter. All patients received 500-mg doses, uptitrated to 1,000 mg at week 4, monthly evaluations, and a complete objective assessment after 12 weeks, followed by an open-label extension. Thirteen patients were randomized and 12 enrolled (6 ranolazine, 6 placebo). All patients completed the acute phase; 10 completed the 12-week study. There were no acute changes in invasive hemodynamics. At 12 weeks ranolazine was well tolerated. Only 1 of the 5 patients on ranolazine had a serum concentration considered to be in the therapeutic range. Two serious adverse events required early withdrawal (both in the ranolazine group); gastrointestinal complaints were the most common adverse event. Efficacy measures did not demonstrate any differences between treatment groups. During the open-label trial, 2 additional patients reached a therapeutic concentration. Ranolazine in PAH appears safe, without acute hemodynamic effects after a 500-mg dose. Ranolazine administrated to PAH patients receiving background PAH therapies did not consistently reach therapeutic levels. Future studies should first perform PK analysis in PAH patients receiving PAH therapies and explore the safety and tolerability of the higher doses perhaps necessary to achieve therapeutic levels in PAH patients. (

TRIAL REGISTRATION

Clinicaltrials.gov identifier NCT01757808.).

Heart Rate-Based Prediction of Fixed Blood Lactate Thresholds in Professional Team-Sport Players

The aim of this study was to investigate whether the speed associated with 90% of maximal heart rate (S90%HRmax) could predict speeds at fixed blood lactate concentrations of 3 mmol·L(-1) (S3mM) and 4 mmol·L(-1) (S4mM). Professional team-sport players of futsal (n = 10), handball (n = 16), and basketball (n = 10) performed a 4-stage discontinuous progressive running test followed, if exhaustion was not previously achieved, by an additional maximal continuous incremental running test to attain maximal heart rate (HRmax). The individual S3mM, S4mM, and S90%HRmax were determined by linear interpolation. S3mM (11.6 ± 1.5 km·h(-1)) and S4mM (12.5 ± 1.4 km·h(-1)) did not differ (p > 0.05) from S90%HRmax (12.0 ± 1.2 km·h(-1)). Very large significant (p < 0.001) relationships were found between S90%HRmax and S3mM (r = 0.82; standard error of the estimates [SEE] = 0.87 km·h(-1)), as well as between S90%HRmax and S4mM (r = 0.82; SEE = 0.87 km·h(-1)). S3mM and S4mM inversely correlated with %HRmax associated with running speeds of 10 and 12 km·h(-1) (r = 0.78-0.81; p < 0.001; SEE = 0.94-0.87 km·h(-1)). In conclusion, S3mM and S4mM can be accurately predicted by S90%HRmax in professional team-sport players.

Detection of the Lactate Threshold in Runners: What is the Ideal Speed to Start an Incremental Test?

Incremental tests on a treadmill are used to evaluate endurance athletes; however, no criterion exists to determine the intensity at which to start the test, potentially causing the loss of the first lactate threshold. This study aimed to determine the ideal speed for runners to start incremental treadmill tests. The study consisted of 94 runners who self-reported the average speed from their last competitive race (10–42.195 km) and performed an incremental test on a treadmill. The speeds used during the first three test stages were normalised in percentages of average competition speed and blood lactate concentration was analysed at the end of each stage. The relationship between speed in each stage and blood lactate concentration was analysed. In the first stage, at an intensity corresponding to 70% of the reported average race speed, only one volunteer had blood lactate concentration equal to 2 mmol·L⁻¹, and in the third stage (90% of the average race speed) the majority of the volunteers had blood lactate concentration ≥2 mmol·L⁻¹. Our results demonstrated that 70% of the average speed from the subject’s last competitive race – from 10 to 42.195 km – was the best option for obtaining blood lactate concentration <2 mmol·L⁻¹ in the first stage, however, 80% of the average speed in marathons may be a possibility. Evaluators can use 70% of the average speed in competitive races as a strategy to ensure that the aerobic threshold intensity is not achieved during the first stage of incremental treadmill tests.

Different endurance characteristics of female and male german soccer players

The aims of the present study were to assess gender differences regarding lactate threshold and intermittent shuttle run performance in female and male soccer players as well as to investigate the relationships between both endurance characteristics in both genders. Fourteen female (1(st) division) and thirteen male (4(th) division) soccer players completed an incremental test (IT) to determine running velocities at 2 and 4 mmol · l(-1) blood lactate (v2 and v4) and maximum velocity (vmax) as well as an interval shuttle run test (ISRT) to determine running distance. Based on v2 and v4 and their percentages in relation to vmax, three intensity zones were calculated: a low lactate zone (<v2), a lactate accommodation zone (v2 to v4), and a lactate accumulation zone (>v4). Female soccer players have a lower v4 (8.2%), vmax (11.3%) and ISRT distance (31.6%). No gender difference was found in v2. In contrast to males, ISRT distance correlates with vmax as well as with v2 and v4 in female soccer players. The intensity zones <v2 and >v4 differ between genders. The present study revealed that gender differences increase when the running performance is intermittent including change of directions. In both genders, different relationships between lactate threshold and intermittent shuttle run performance exist. During incremental testing, the running performances of female and male players reflect different distributions of aerobic and anaerobic metabolic pathways. The revealed gender differences should be considered for soccer endurance training.

Test-retest reliability of second lactate turnpoint using two different criteria in competitive cyclists

The aim of this study was to determine the relative and absolute reliability of second lactate turnpoint using fixed and individual blood lactate method in competitive cyclists. Twenty-eight male, well-trained cyclists (30.2 ± 10.1 years, 72.0 ± 7.4 kg, 177.3 ± 4.7 cm) were recruited to participate in this study. Cyclists completed two incremental cycling tests to exhaustion over a period of 7 days to determine their peak power output, maximal oxygen uptake, maximal heart rate, maximal blood lactate concentration and two lactate turnpoint criteria. The fixed blood concentration criterion (3.5 mM) and an individual criterion were assessed by a lactate-power curve, considering power output, heart rate and oxygen uptake. The main finding of this study was that both lactate turnpoint criteria showed identical low within-subject variation for power output (2.8% coefficient of variation). High values for test-retest correlations ranging from r = 0.70 to r = 0.94 were found for all variables in both threshold criteria. In conclusion, the individual and fixed method to determine the second lactate turnpoint showed similar high absolute and relative reliability in competitive cyclists.

Comparison of calculated and experimental power in maximal lactate-steady state during cycling

BACKGROUND

The purpose of this study was the comparison of the calculated (MLSSC) and experimental power (MLSSE) in maximal lactate steady-state (MLSS) during cycling.

METHODS

13 male subjects (24.2 ± 4.76 years, 72.9 ± 6.9 kg, 178.5 ± 5.9 cm, V˙O2max: 60.4 ± 8.6 ml min-1 kg-1, V˙Lamax: 0.9 ± 0.19 mmol l-1 s-1) performed a ramp-test for determining the V˙O2max and a 15 s sprint-test for measuring the maximal glycolytic rate (V˙Lamax). All tests were performed on a Lode-Cycle-Ergometer. V˙O2max and V˙Lamax were used to calculate MLSSC. For the determination of MLSSE several 30 min constant load tests were performed. MLSSE was defined as the highest workload that can be maintained without an increase of blood-lactate-concentration (BLC) of more than 0.05 mmol l-1 min-1 during the last 20 min. Power in following constant-load test was set higher or lower depending on BLC.

RESULTS

MLSSE and MLSSC were measured respectively at 217 ± 51 W and 229 ± 47 W, while mean difference was -12 ± 20 W. Orthogonal regression was calculated with r = 0.92 (p < 0.001).

CONCLUSIONS

The difference of 12 W can be explained by the biological variability of V˙O2max and V˙Lamax. The knowledge of both parameters, as well as their individual influence on MLSS, could be important for establishing training recommendations, which could lead to either an improvement in V˙O2max or V˙Lamax by performing high intensity or low intensity exercise training, respectively. Furthermore the validity of V˙Lamax -test should be focused in further studies.

Inability of myalgic encephalomyelitis/chronic fatigue syndrome patients to reproduce VO₂peak indicates functional impairment

BACKGROUND

Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) is a multi-system illness characterized, in part, by increased fatigue following minimal exertion, cognitive impairment, poor recovery to physical and other stressors, in addition to other symptoms. Unlike healthy subjects and other diseased populations who reproduce objective physiological measures during repeat cardiopulmonary exercise tests (CPETs), ME/CFS patients have been reported to fail to reproduce results in a second CPET performed one day after an initial CPET. If confirmed, a disparity between a first and second CPET could serve to identify individuals with ME/CFS, would be able to document their extent of disability, and could also provide a physiological basis for prescribing physical activity as well as a metric of functional impairment.

METHODS

22 subjects diagnosed with ME/CFS completed two repeat CPETs separated by 24 h. Measures of oxygen consumption (VO₂), heart rate (HR), minute ventilation (Ve), workload (Work), and respiratory exchange ratio (RER) were made at maximal (peak) and ventilatory threshold (VT) intensities. Data were analyzed using ANOVA and Wilcoxon's Signed-Rank Test (for RER).

RESULTS

ME/CFS patients showed significant decreases from CPET1 to CPET2 in VO₂peak (13.8%), HRpeak (9 bpm), Ve peak (14.7%), and Work@peak (12.5%). Decreases in VT measures included VO₂@VT (15.8%), Ve@VT (7.4%), and Work@VT (21.3%). Peak RER was high (≥1.1) and did not differ between tests, indicating maximum effort by participants during both CPETs. If data from only a single CPET test is used, a standard classification of functional impairment based on VO₂peak or VO₂@VT results in over-estimation of functional ability for 50% of ME/CFS participants in this study.

CONCLUSION

ME/CFS participants were unable to reproduce most physiological measures at both maximal and ventilatory threshold intensities during a CPET performed 24 hours after a prior maximal exercise test. Our work confirms that repeated CPETs warrant consideration as a clinical indicator for diagnosing ME/CFS. Furthermore, if based on only one CPET, functional impairment classification will be mis-identified in many ME/CFS participants.

Swimming Stroke Mechanical Efficiency and Physiological Responses of 100-m Backstroke with and without the use of paddles

The use of swimming aids during training contributes to greater swimming efficiency by the improvement of the swimming specific power of the athlete. The purpose of this study was to compare the swimming stroke technical characteristics and the physiological responses of swimming 100-m backstroke, with and without the use of paddles at maximum and sub-maximum intensities at the same swimming speed. Eight swimmers competing at the national level participated in this study. The measurements took place at 4 different sessions. At every session, each participant swam individually one 100-m backstroke swimming trial with or without paddles at the same speed and two levels of intensity (100% and 85% of maximum speed). The results revealed lower stroke length, greater stroke number and gliding length without the use of swimming paddles at both intensities. Blood lactate concentration (10.03±2.96 vs. 5.85±2.23 mmol/l) and Rating of Perceived Exertion (17.43±2.07 vs. 12±2.82) were greater without the use of swimming paddles only at 100% of maximum speed. Thus, swimming backstroke with paddles compared to unaided swimming, at a similar speed, showed a greater efficiency at maximal but not at sub-maximal intensity.

A Comparison of Laboratory-Based Kayak Testing Protocols

Purpose:

To compare the differences in peak oxygen uptake (VO2peak) and lactate threshold (LT2) between the 7 × 4-min incremental step test (7-ST) and the maximal accumulated oxygen deficit (MAOD) test protocols in sprint kayak athletes.

Methods:

Nine highly trained kayak athletes performed the 2 laboratory test protocols. The 7-ST involved six 4-min submaximal incremental stages, each separated by a 1-min recovery, before a 4-min all-out effort. The MAOD test involved four 4-min submaximal incremental stages (also with each stage separated by a 1-min recovery), followed by 20-min recovery and a 4-min all-out effort.

Results:

No statistically significant differences in VO2peak were recorded between the 2 protocols (P > .05). However, distance covered, power output, stroke rate, and speed were almost certainly greater in the MAOD test (magnitude-based inference: 99–100% positive), while blood lactate (BLa), heart rate (HR), and rating of perceived exertion (RPE) were likely lower (magnitude-based inference: 78–92% negative). The derived measures of LT2 (excluding HR) were not different between the 2 protocols.

Conclusion:

The results of this study suggest that both the 7-ST and MAOD test protocols are comparable with regard to the measurement of VO2peak and LT2 in highly trained sprint kayak athletes. However, since differences in the measures of distance traveled, power, stroke rate, HR, BLa, and RPE were reported in the maximal stage of the these 2 test protocols, their interchangeable use in a laboratory setting is not ideal if the data output is to be compared and contrasted over time.

Combining internal- and external-training-load measures in professional rugby league

PURPOSE

This study investigated the effect of training mode on the relationships between measures of training load in professional rugby league players.

METHODS

Five measures of training load (internal: individualized training impulse, session rating of perceived exertion; external-body load, high-speed distance, total impacts) were collected from 17 professional male rugby league players over the course of two 12-wk preseason periods. Training was categorized by mode (small-sided games, conditioning, skills, speed, strongman, and wrestle) and subsequently subjected to a principal-component analysis. Extraction criteria were set at an eigenvalue of greater than 1. Modes that extracted more than 1 principal component were subjected to a varimax rotation.

RESULTS

Small-sided games and conditioning extracted 1 principal component, explaining 68% and 52% of the variance, respectively. Skills, wrestle, strongman, and speed extracted 2 principal components each explaining 68%, 71%, 72%, and 67% of the variance, respectively.

CONCLUSIONS

In certain training modes the inclusion of both internal and external training-load measures explained a greater proportion of the variance than any 1 individual measure. This would suggest that in training modes where 2 principal components were identified, the use of only a single internal or external training-load measure could potentially lead to an underestimation of the training dose. Consequently, a combination of internal- and external-load measures is required during certain training modes.

The effect of exercise intensity on endothelial function in physically inactive lean and obese adults

Purpose

To examine the effects of exercise intensity on acute changes in endothelial function in lean and obese adults.

Methods

Sixteen lean (BMI <25, age 23±3 yr) and 10 obese (BMI >30, age 26±6 yr) physically inactive adults were studied during 3 randomized admissions [control (C, no exercise), moderate-intensity exercise (M, @ lactate threshold (LT)) and high-intensity exercise (H, midway between LT and VO₂peak) (30 min)]. Endothelial function was assessed by flow-mediated dilation (FMD) at baseline and 1, 2, and 4 h post-exercise.

Results

RM ANCOVA revealed significant main effects for group, time, and group x condition interaction (p<0.05). A diurnal increase in FMD was observed in lean but not obese subjects. Lean subjects exhibited greater increases in FMD than obese subjects (p = 0.0005). In the obese group a trend was observed for increases in FMD at 2- and 4-hr after M (p = 0.08). For lean subjects, FMD was significantly elevated at all time points after H. The increase in FMD after H in lean subjects (3.2±0.5%) was greater than after both C (1.7±0.4%, p = 0.015) and M (1.4±0.4%, p = 0.002). FMD responses of lean and obese subjects significantly differed after C and H, but not after M.

Conclusion

In lean young adults, high-intensity exercise acutely enhances endothelial function, while moderate-intensity exercise has no significant effect above that seen in the absence of exercise. The FMD response of obese adults is blunted compared to lean adults. Diurnal variation should be considered when examining the effects of acute exercise on FMD.