Use of blood lactate measurements for prediction of exercise performance and for control of training. Recommendations for long-distance running

Attenuation of the increase of heart rate and oxygen consumption during progressive exercise in professional rugby players

BACKGROUND

The response of oxygen uptake (VO2) and heart rate (HR) to continuous progressive large muscle mass exercise is not always linear. This study aimed to compare the patterns of the Speed/VO2 (S/VO2) and speed/HR (S/HR) relationships during an incremental treadmill-running test in professional rugby players.

METHODS

Fourteen professional rugby athletes performed a maximal incremental treadmill-running test, following the Conconi test protocol. Speed, heart rate, and gas exchange parameters were recorded. The slope of the S/VO2 and S/HR relationships were mathematically determined.

RESULTS

The S/VO2 and S/HR relationships were linear up to a submaximal speed and curvilinear thereafter. The speed of locomotion at which the slope of the S/VO2 and S/HR relationships start to attenuate (VO2att and HRatt) were coincident (12.3±1.0 and 12.4±0.9 km/h), strongly correlated and in good agreement. VO2 values at VO2att (44.9±8.7 mL/kg/min) were significantly correlated with VO2 values at the ventilatory threshold (43.3±6.0 mL/kg/min) (R2=0.83, P=0.001) and in good agreement. The running speed/VO2 ratio (ΔS/ΔVO2) up to VO2att was significantly lower than that beyond VO2att (2.98±1.1 vs. 5.16±2.31); P<0,001).

CONCLUSIONS

The speed/oxygen uptake and S/HR relationships during progressive exercise start to attenuate at a coincident exercise intensity, and at oxygen uptake values strongly correlated with the ventilatory threshold. These findings further support the usefulness of the attenuation of the S/HR relationship as a practical tool for exercise testing and training purposes in professional rugby players.

Intensity Distribution of Collegiate Cross-Country Competitions

The primary purpose of the current investigation was to perform an intensity distribution analysis of a collegiate cross-country (CC) competition, with a secondary purpose to compare race times (RT) with modeled performance times (MPT). Participants completed an incremental treadmill test to determine gas exchange threshold (GET), while the three-minute all-out test was conducted on a 400 m outdoor track to determine critical velocity (CV) and D prime (D'). GET and CV were used as physiological markers for the intensity zones based on heart rate (HR) and running velocity (RV), while CV and D' were used to determine modeled performance times. Participants wore a Global Positioning System (GPS) watch and heart rate (HR) monitor during competition races. Statistically, less time was spent in HR Zone 1 (12.1% ± 13.7%) compared to Zones 2 (37.6% ± 30.2%) and 3 (50.3% ± 33.7%), while a statically greater amount of time was spent in RV Zone 2 (75.0% ± 20.7%) compared to Zones 1 (8.4% ± 14.0%) and 3 (16.7% ± 19.1%). RTs (1499.5 ± 248.5 seconds (s)) were statistically slower compared to MPTs (1359.6 ± 192.7 s). The observed differences in time spent in each zone are speculated to be related to the influence of environmental conditions on internal metrics and difference in the kinetics of HR and running velocity. Differences in RTs and MPTs are likely due to the MPT equation modeling all-out performance and not considering race strategies.

Psychophysiological Responses in Soldiers during Close Combat: Implications for Occupational Health and Fitness in Tactical Populations

This study explores the psychophysiological responses and subjective exertion experiences of soldiers in simulated hand-to-hand combat, aligning these findings with established physiological benchmarks. Active military personnel were monitored for heart rate, blood lactate levels, subjective exertion, cortical arousal, and muscle strength during combat scenarios. The results showed significant increases in heart rate and blood lactate, indicating intense cardiovascular demands and a reliance on anaerobic energy systems. Contrary to these physiological changes, soldiers reported lower levels of exertion, suggesting a possible underestimation of physical effort or individual differences in perception and mental resilience to stress. Notably, a decrease in cortical arousal post-combat was observed, potentially signaling cognitive function deficits in decision-making and information processing in high-stress environments. This decline was more pronounced than typically seen in other high-stress situations, highlighting the unique cognitive demands of hand-to-hand combat. Additionally, an increase in muscle strength was noted, underscoring the physiological adaptations arising from intensive combat training. These findings provide valuable insights into the psychophysiological effects of hand-to-hand combat, emphasizing the complex interplay between physical exertion, cognitive function, and stress response in military contexts. The study underscores the need for comprehensive training strategies that address both physical and psychological aspects to enhance combat readiness and decision-making under stress.

Exercise evaluation with metabolic and ventilatory responses and blood lactate concentration in mice

This study aimed to clarify the differential exercise capacity between 2-month-old and 10-month-old mice using an incremental running test. Metabolic and ventilatory responses and blood lactate concentration were measured to evaluate exercise capacity. We examined whether incremental running test results reflected metabolic and ventilatory responses and blood lactate concentration observed during the steady-state running test. Metabolic response significantly declined with age, whereas ventilatory response was similar between the groups. A low-intensity/moderate exercise load of 10/min in an incremental running test was performed on both mice for 30 min. They showed a characteristic pattern in ventilatory response in 10-month mice. The results of incremental running tests didn't necessarily reflect the steady-state metabolic and ventilatory responses because some parameters showed an approximation and others did not in incremental and steady-state tests, which changed with age. Our study suggests metabolic and ventilatory responses depending on age and provides basic knowledge regarding the objective and quantitative assessment of treadmill running in an animal model.

From Incremental Test to Continuous Running at Fixed Lactate Thresholds: Individual Responses on %VO2max, %HRmax, Lactate Accumulation, and RPE

With Norway's successes in middle and long-distance running, lactate-guided threshold training has regained importance in recent years. Therefore, the aim of the present study was to investigate the individual responses on common monitoring parameters based on a lactate-guided conventional training method. In total, 15 trained runners (10 males, 5 females; 18.6 ± 3.3 years; VO2max: 59.3 ± 5.9 mL kg-1 min-1) completed a 40-min continuous running session at a fixed lactate threshold load of 2 mmol L-1. Lactate (La), oxygen uptake (VO2), heart rate (HR), and rating of perceived exertion (RPE) were recorded. The chosen workload led to lactate values of 2.85 ± 0.56 mmol L-1 (range: 1.90-3.80), a percentage of VO2max utilization (%VO2max) of 79.2 ± 2.5% (range: 74.9-83.8), a percentage of HRmax utilization (%HRmax) of 92.2 ± 2.5% (range: 88.1-95.3), and an RPE of 6.1 ± 1.9 (range: 3-10) at the end of the running session. Thereby, the individual responses differed considerably. These results indicate that a conventional continuous training method based on a fixed lactate threshold can lead to different individual responses, potentially resulting in various physiological impacts. Moreover, correlation analyses suggest that athletes with higher lactate threshold performance levels must choose their intensity in continuous training methods more conservatively (lower percentage intensity based on a fixed threshold) to avoid eliciting excessively strong metabolic responses.

A systematic review of exercise protocols applied to athymic mice in tumor-related experiments

Athymic mice are unable to produce T-cells and are then characterized as immunodeficient. This characteristic makes these animals ideal for tumor biology and xenograft research. New non-pharmacological therapeutics are required owing to the exponential increase in global oncology costs over the last 10 years and the high cancer mortality rate. In this sense, physical exercise is regarded as a relevant component of cancer treatment. However, the scientific community lacks information regarding the effect of manipulating training variables on cancer in humans, and experiments with athymic mice. Therefore, this systematic review aimed to address the exercise protocols used in tumor-related experiments using athymic mice. The PubMed, Web of Science, and Scopus databases were searched without restrictions on published data. A combination of key terms such as athymic mice, nude mice, physical activity, physical exercise, and training was used. The database search retrieved 852 studies (PubMed, 245; Web of Science, 390; and Scopus, 217). After title, abstract, and full-text screening, 10 articles were eligible. Based on the included studies, this report highlights the considerable divergences in the training variables adopted for this animal model. No studies have reported the determination of a physiological marker for intensity individualization. Future studies are recommended to explore whether invasive procedures can result in pathogenic infections in athymic mice. Moreover, time-consuming tests cannot be applied to experiments with specific characteristics such as tumor implantation. In summary, non-invasive, low-cost, and time-saving approaches can suppress these limitations and improve the welfare of these animals during experiments.

Six-minute rowing test: a practical tool for training prescription, from ventilatory thresholds and power outputs, in amateur male rowers

Background

The 6-minute rowing ergometer test (6-minRT) is valid and reliable for establishing maximal aerobic power (MAP) in amateur male rowers. However, ventilatory thresholds (VTs) have not yet been established with their mechanical correspondence in this test.

Objective

The primary objective was to determine the VTs in the 6-minRT achieved by amateur male rowers, while the secondary objective was to determine the correspondence between ventilatory, mechanical, and heart rate (HR) outcomes of the 6-minRT.

Methods

Sixteen amateur male rowers were part of the study. All participants were instructed to perform an incremental test (IT) and a 6-minRT. Determination of the ventilatory parameters for the first ventilatory threshold (VT1), the second ventilatory threshold (VT2), and 6minRTVO2max were performed by correlating the outcomes of VT1, VT2, and VO2max obtained in the IT, with the outcomes of 6-minRT. For these purposes, Pearson's test was used, with the following criteria: trivial, <0.1; small, 0.1-0.3; moderate, 0.3-0.5; high, 0.5-0.7; very high, 0.7-0.9; or practically perfect, >0.9. The significance level was p < 0.05.

Results

The IT analysis determined that VT1 and VT2 correspond to 55 and 80% of VO2max, respectively. A high correlation was observed between IT outcomes in VT1, VT2, and VO2max, with the outcomes of 6-minRT (r > 0.6).

Conclusion

Based on IT ventilatory parameters and concordance analysis, VT1 and VT2 of 6-minRT are determined at 55 and 80%, respectively, of both ventilatory parameters and their corresponding mechanical outcomes and HR.

Mental, physical, and phychophysiological responses to FFP2/N95 face mask during HIIT in active women

Training systems based on high-intensity interval training (HIIT) have experienced great influence in recent years within the context of exercise and sport. This study aims to provide insight on whether the immediate outcomes (e.g., central and peripheral acute responses) may be intensified or attenuated when a HIIT protocol is performed using a FFP2/N95 face mask in active healthy adult women. In other words, it strives to provide new findings relative to the use of face masks as a potential performance enhancing tool. In the current study, the same training session was carried out on two occasions under different conditions (i.e., with FFP2/N95 and without FFP2/N95) in a cross-over experimental design. The following study variables were assessed before and after the HIIT in both sessions: Lactate, cortisol, alpha-amylase, selective attention, countermovement jump (CMJ), and power output. Additionally, central and peripheral Rates of Perceived Exertion (RPE) were assessed before and during the HIIT. This study makes novel contributions to prior research, showing that the use of FFP2/N95 face mask (vs. no mask) yielded higher alpha-amylase, selective attention, and peripheral RPE scores. No significant differences were found for lactate, cortisol, CMJ, and power output. Interestingly, central RPE scores were significantly lower under FFP2/N95 face mask (vs. no mask) condition. The main suggestion in light of these results is that researchers and practitioners should consider potential peripheral and central responses to training stimuli when using FFP2/N95 face masks.

An Examination of Subjective and Objective Measures of Stress in Tactical Populations: A Scoping Review

Persons working in tactical occupations are often exposed to high-stress situations. If this stress is to be measured, an understanding of the stress outcomes used in these occupations is needed. The aim of this review was to capture and critically appraise research investigating subjective and objective outcome measures of physiological stress in tactical occupations. Several literature databases (PubMed, EMBASE, EBsco) were searched using key search words and terms. Studies meeting inclusion criteria were critically evaluated and scored by two authors using the Joanne Briggs Institute (JBI) critical appraisal tool. Of 17,171 articles, 42 studies were retained. The Cohen's Kappa agreement between authors was 0.829 with a mean JBI Score of included studies of 8.1/9 ± 0.37 points. Multiple subjective and objective measures were assessed during a variety of high-stress tasks and environments across different occupations, including police officers, emergency service personnel, firefighters, and soldiers in the military. Common objective outcomes measures were heart rate, cortisol, and body temperature, and subjective measures were ratings of perceived exertion, and the Self Trait Anxiety Inventory. Often used in combination (i.e., subjective and objective), these outcome measures can be used to monitor stressors faced by tactical personnel undergoing on-the-job training.

Comparative analysis of cardiorespiratory fitness, bio-motor abilities, and body composition indicators among sprint kayakers of different age groups and expertise levels

This study compared cardiorespiratory fitness, bio-motor abilities, and body composition indexes of sprint kayakers categorized into three different age groups and two expertise levels of international- and club-level athletes. Seventy-three male juniors (n = 14, age = 16.2 ± 0.8), under 23 [U23 (n = 15, age = 20.2 ± 1.6)], professionals (n = 16, age = 27.1 ± 4.8), club-level (n = 15, age = 26.9 ± 6.6), and international-level (n = 13, age = 27.3 ± 3.2) sprint kayakers were studied. Cardiorespiratory fitness (assessed using incremental exercise test), 500 and 1,000-m paddling performance (assessed using kayak ergometer), upper-body power (assessed using 30 s all-out Wingate test) and strength (assessed through one repetition tests for bench press, cable row, and prone bench pull exercises), as well as body composition indexes (measured using dual-energy X-ray absorptiometry) were evaluated on four occasions separated by 48 h recovery. U23 and, especially, professionals indicated significantly (p < 0.05) greater outcomes for the majority of the cardiorespiratory fitness parameters [maximal oxygen uptake (VO2max), velocity corresponding to VO2max, Oxygen pulse, maximal ventilation, and second ventilatory threshold] and 500 and 1,000-m performance. U23 and professional sprint kayakers significantly (p < 0.05) differed in the first ventilatory threshold and 500, and 1,000-m performance but not in VO2max or the second ventilatory threshold. Professionals also showed a lower fat mass, higher muscle mass, and higher strength (bench press, prone bench pull, and seated cable row) and power than U23 and junior kayakers. Strength and power indicators had significantly greater values in U23 athletes compared to juniors. International-level athletes also showed superior VO2max, velocity corresponding to VO2max, middle (500-m), and long-distance (1,000-m) time trial performance, strength and power, lower fat, and higher muscle mass than club-level sprint kayakers. Cardiorespiratory fitness (particularly ventilatory threshold), body composition, and muscle strength/power are the best differentiating factors for sprint kayakers of different ages and expertise levels. These findings could aid coaches in prescribing training programs focusing on improving determining factors in paddling performance, as well as in predicting performance and identifying talent.

An Energy-Efficient Flexible Multi-Modal Wireless Sweat Sensing System Based on Laser Induced Graphene

Real-time sweat monitoring is vital for athletes in order to reflect their physical conditions, quantify their exercise loads, and evaluate their training results. Therefore, a multi-modal sweat sensing system with a patch-relay-host topology was developed, which consisted of a wireless sensor patch, a wireless data relay, and a host controller. The wireless sensor patch can monitor the lactate, glucose, K⁺, and Na⁺ concentrations in real-time. The data is forwarded via a wireless data relay through Near Field Communication (NFC) and Bluetooth Low Energy (BLE) technology and it is finally available on the host controller. Meanwhile, existing enzyme sensors in sweat-based wearable sports monitoring systems have limited sensitivities. To improve their sensitivities, this paper proposes a dual enzyme sensing optimization strategy and demonstrates Laser-Induced Graphene (LIG)-based sweat sensors decorated with Single-Walled Carbon Nanotubes (SWCNT). Manufacturing an entire LIG array takes less than one minute and costs about 0.11 yuan in materials, making it suitable for mass production. The in vitro test result showed sensitivities of 0.53 μA/mM and 3.9 μA/mM for lactate and glucose sensing, and 32.5 mV/decade and 33.2 mV/decade for K⁺ and Na⁺ sensing, respectively. To demonstrate the ability to characterize personal physical fitness, an ex vivo sweat analysis test was also performed. Overall, the high-sensitivity lactate enzyme sensor based on SWCNT/LIG can meet the requirements of sweat-based wearable sports monitoring systems.

Maximum Heart Rate- and Lactate Threshold-Based Low-Volume High-Intensity Interval Training Prescriptions Provide Similar Health Benefits in Metabolic Syndrome Patients

Exercise is an integral part of metabolic syndrome (MetS) treatment. Recently, low-volume high-intensity interval training (LOW-HIIT) has emerged as a time-efficient approach to improving cardiometabolic health. Intensity prescriptions for LOW-HIIT are typically based on maximum heart rate (HR_max) percentages. However, HR_max determination requires maximal effort during exercise testing, which may not always be feasible/safe for MetS patients. This trial compared the effects of a 12-week LOW-HIIT program based on: (a) HR_max (HIIT-HR), or (b) submaximal lactate threshold (HIIT-LT), on cardiometabolic health and quality of life (QoL) in MetS patients. Seventy-five patients were randomized to HIIT-HR (5 × 1 min at 80-95% HR_max), HIIT-LT (5 × 1 min at 95-105% LT) groups, both performed twice weekly on cycle ergometers, or a control group (CON). All patients received nutritional weight loss consultation. All groups reduced their body weight (HIIT-HR: -3.9 kg, p < 0.001; HTT-LT: -5.6 kg, p < 0.001; CON: -2.6 kg, p = 0.003). The HIIT-HR and HIIT-LT groups similarly, improved their maximal oxygen uptake (+3.6 and +3.7 mL/kg/min, p < 0.001), glycohemoglobin (-0.2%, p = 0.005, and -0.3%, p < 0.001), homeostasis model assessment index (-1.3 units, p = 0.005, and -1.0 units, p = 0.014), MetS z-score (-1.9 and -2.5 units, p < 0.001) and QoL (+10 points, p = 0.029, and +11 points, p = 0.002), while the CON did not experience changes in these variables. We conclude that HIIT-LT is a viable alternative to HIIT-HR for patients who are not able/willing to undergo maximal exercise testing.

Does Lactate-Guided Threshold Interval Training within a High-Volume Low-Intensity Approach Represent the "Next Step" in the Evolution of Distance Running Training?

The aim of the present study was to describe a novel training model based on lactate-guided threshold interval training (LGTIT) within a high-volume, low-intensity approach, which characterizes the training pattern in some world-class middle- and long-distance runners and to review the potential physiological mechanisms explaining its effectiveness. This training model consists of performing three to four LGTIT sessions and one VO_2max intensity session weekly. In addition, low intensity running is performed up to an overall volume of 150-180 km/week. During LGTIT sessions, the training pace is dictated by a blood lactate concentration target (i.e., internal rather than external training load), typically ranging from 2 to 4.5 mmol·L^-1, measured every one to three repetitions. That intensity may allow for a more rapid recovery through a lower central and peripheral fatigue between high-intensity sessions compared with that of greater intensities and, therefore, a greater weekly volume of these specific workouts. The interval character of LGTIT allows for the achievement of high absolute training speeds and, thus, maximizing the number of motor units recruited, despite a relatively low metabolic intensity (i.e., threshold zone). This model may increase the mitochondrial proliferation through the optimization of both calcium and adenosine monophosphate activated protein kinase (AMPK) signaling pathways.

Physical Demands during Official Competitions in Elite Handball: A Systematic Review

An understanding of physical demands during official competitions is essential to achieving the highest performance in handball. The aim of this systematic review was to summarise the available scientific evidence associated with physical demands during official competitions in elite handball according to playing positions, competition level and gender. Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, 17 studies were selected after a systematic search and selection process of three digital databases: PubMed, Web of Science and Sport Discus. The quality of the selected studies was evaluated using the Strengthening the Reporting of Observational Studies in Epidemiology checklist; the average score was 18.47 points. The sample consisted of 1175 handball players, of whom 1042 were men (88.68%) and 133 were women (11.32%). The results show that an elite handball player covered on average 3664.4 ± 1121.6 m during a match. The average running pace was 84.8 ± 17.2 m∙min-1. The total distance covered was largely greater in national competitions (4506.7 ± 647.9 m) compared with international competitions (2190.3 ± 1950.5 m) (effect size (ES) = 1.2); however, the running pace did not present any significant difference between the international or national level (ES = 0.06). In regard to gender, the total distance covered was moderately greater in female competitions (4549.1 ± 758.6 m) compared with male competitions (3332.6 ± 1257.7 m) (ES = 0.9), and the running pace was largely greater in female competitions (110.5 ± 7.2 m∙min-1) compared with male competitions (78.4 ± 19.7 m∙min-1) (ES = 1.6). In relation to playing position, backs and wings covered a moderately greater total distance (ES = 0.7 and 0.6) and slightly more meters per minute (ES = 0.4 and 0.2) than pivots. Moreover, the technical activity profile differed between playing positions. Backs performed moderately more throws than pivots and wings (ES = 1.2 and 0.9), pivots exhibited largely more body contact than backs and wings, and wings performed moderately more fast breaks (6.7 ± 3.0) than backs (2.2 ± 2.3) (ES = 1.8). Therefore, this research study provides practical applications for handball coaches and strength and conditioning professionals with respect to designing and implementing more individualised training programmes to maximise performance and reduce injury risk.

Can salivary lactate be used as an anaerobic biomarker?

Background

Salivary lactate has been suggested as a non-invasive anaerobic biomarker in sports medicine for decades, yet has not been widely applied until now. This study aimed to explore possible issues related to its application and suggest directions for future method improvement.

Methods

A liquid chromatography-mass spectrometry (LC-MS) method for the determination of salivary lactate was developed, validated and applied on saliva samples collected from a group of professional sprinters (n = 20). The samples were collected via chewing a cotton ball for one minute and centrifuging it afterwards. The evaluation included variation with mouth rinse times, consistency at different sampling times, change after treadmill or cycle ergometer trainings, and association with blood lactate. Sample sizes were calculated prior to the study. One-way analysis of variance (ANOVA), intra-class correlation coefficients (ICC) and relative standard deviation (RSD) were used to evaluate data variances. Pearson correlation was applied to show correlation between salivary and blood lactate. Effect sizes and power were calculated following ANOVA and correlation analyses.

Results

The RSD of the LC-MS method was 19.70%. Salivary lactate concentration was affected by mouth rinse times before sampling (ANOVA p = 0.025, η ² = 0.40, 1 - β = 0.99, ICC = 0.23, mean RSD of four sampling = 55.30%), and stabilized after mouth rinsing for three times. The concentrations at resting state across three weeks were consistent at group level (ANOVA p = 0.57, η ² = 0.03, 1 - β = 0.20), but varied greatly individually (ICC = 0.22, mean RSD = 56.16%). Salivary lactate level significantly increased after treadmill and cycle ergometer trainings (ANOVA p = 0.0002, η ² = 0.46, 1 - β = 0.9999 and ANOVA p = 0.0019, η ² = 0.40, 1 - β = 0.9993, respectively), and displayed positive correlation with blood lactate concentration (r = 0.61, p = 0.0004, 1 - β = 0.9596). Significant difference between male and female participants was observed in none of the tests conducted in this study.

Discussion

Salivary lactate was found to be a potential anaerobic biomarker. However, reproducible methods for sample collection and analysis, as well as more knowledge on the secretion mechanism and pattern of salivary lactate are required to make it a practical anaerobic biomarker.

The potential of Curcuma extract to alleviate muscle damage in amateur soccer players

Compounds with high bioactive are commonly used as a nutritional approach for accelerating muscle damage recovery after strenuous exercise. There are still inconsistent results of post-exercise antioxidant supplementation on the circulating muscle damage biomarker. This study aimed to examine the effect of post-exercise Curcuma extract supplementation in ice cream on muscle damage and inflammatory markers in amateur soccer players. Male amateur soccer athletes (aged 14 – 18 years) participated in a randomized double-blind placebo-controlled study under two conditions: control group (n = 10) and treatment group (n = 10). The treatment group was treated with Curcuma extract ice cream (250 mg/100 g) for 21 days. Blood samples were drawn before training, considered baseline, and 3 h after training on day 21. The level of creatine kinase, IL-6, haemoglobin (Hb), and lactic acid were quantified. There was a significant decrease in creatine kinase change in the treatment group compared to the control group (p <0.05). No change in IL-6 and Hb levels in the treatment group. Lactic acid decreased by 16.3% from baseline in the treatment group (p <0.05). Curcuma extract ice cream potentiates to ameliorate exercise-induced muscle damage.

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}.

Effects of Maximal and Submaximal Anaerobic and Aerobic Running on Subsequent Change-of-Direction Speed Performance among Police Students

Simple Summary

Change-of-direction maneuvers are frequently performed by police officers and athletes. These maneuvers are typically performed with the intention of being maximally fast. Often, an officer or an athlete will run at a certain pace before commencing a change-of-direction speed maneuver. Depending on the duration and intensity of this running activity, their performance of the change-of-direction speed maneuver may be reduced. This study determined the degree to which the preceding maximal and submaximal anaerobic and aerobic activity affect the subsequent performance of the change-of-direction speed maneuver. We found that both anaerobic and aerobic running activities decreased the speed of the subsequent performance on the Illinois Agility Test. We also found that anaerobic running at 85% and 90% had a greater impact on change-of-direction speed performance than did aerobic running at these intensities. Above 90% intensity, anaerobic and aerobic performance similarly impacted the change-of-direction speed. As such, given the requirement for tactical personnel and intermittent, multidirectional sports athletes to perform a change-of-direction speed maneuver following a period of submaximal anaerobic or aerobic activity, increasing fitness may be a means of reducing the negative impacts of preceding submaximal impacts on change-of-direction speed performance.

Abstract

Change-of-direction speed (CODS) directly impacts success in sports, police, and military performance. Movements requiring CODS are often preceded by aerobic or anaerobic running. Therefore, this study investigated the effects of maximal and submaximal anaerobic and aerobic running on subsequent CODS performance. A sample of 50 police students (42% female and 58% male) performed a maximal 300-yard shuttle run test (SR300y) and a 2.4-km Cooper test (CT2.4km) at maximal effort and also at 95, 90, 85, 80, and 75% of maximal effort. CODS was assessed using the Illinois Agility Test (IAT) immediately following each intensity level of each test at 12 separate testing sessions. To avoid fatigue, the period between each consecutive session was a minimum of 3 days. Paired samples t-tests were used to determine the differences between the two conditions (anaerobic lactic and aerobic) and for the IAT. A repeated measure analysis of variance with a Bonferroni post hoc test was used to analyze partial effects of different running intensities on the IAT. A significant reduction in speed was observed between the initial IATmax time and the IATmax time after performing the SR300y at intensities of 95, 90, 85, and 80% of maximal speed on this test. IAT performance was significantly slower when performed after the CT2.4km at 95 and 90% of maximal aerobic speed. The effects of the SR300y on the IAT were significantly greater than the effects of the CT2.4km. No significant differences were found by sex. Building up to 90% intensity, anaerobic running has a greater negative impact on subsequent CODS performance than does aerobic running.

Training Periodization, Methods, Intensity Distribution, and Volume in Highly Trained and Elite Distance Runners: A Systematic Review

PURPOSE

This review aimed to determine (1) performance and training characteristics such as training intensity distribution (TID), volume, periodization, and methods in highly trained/elite distance runners and (2) differences in training volume and TID between event distances in highly trained/elite distance runners.

METHODS

A systematic review of the literature was carried out using the PubMed/MEDLINE, Scopus, and Web of Science databases.

RESULTS

Ten articles met the inclusion criteria. Highly trained/elite distance runners typically follow a pyramidal TID approach, characterized by a decreasing training volume from zone 1 (at or below speed at first ventilatory/lactate threshold [LT]) to zone 2 (between speeds associated with either both ventilatory thresholds or 2 and 4 mmol·L-1 LTs [vLT1 and vLT2, respectively]) and zone 3 (speed above vVT2/vLT2). Continuous-tempo runs or interval training sessions at vLT2 in zone 2 (ie, medium and long aerobic intervals) and those in zone 3 (ie, anaerobic or short-interval training) were both used at least once per week each in elite runners, and they were used to increase the number of either vLT2 or z3 sessions to adopt either a pyramidal or a polarized approach, respectively. More pyramidal- and polarized-oriented approaches were used by marathoners and 1500-m runners, respectively.

CONCLUSIONS

Highly trained and elite middle- and long-distance runners are encouraged to adopt a traditional periodization pattern with a hard day-easy day basis, consisting in a shift from a pyramidal TID used during the preparatory and precompetitive periods toward a polarized TID during the competitive period.

Assessing the usefulness of submaximal exercise heart rates for monitoring cardiorespiratory fitness changes in elite youth soccer players

AIM

This study aimed to assess the value of monitoring fitness in elite youth soccer players (U15 to U19 age groups) by analyzing the concomitant changes in heart rate at submaximal intensity (HR12km/h) and the velocity at a lactate concentration of 4 mmol/l (v4mmol/l).

METHODS

Players were tested by means of an incremental treadmill test on two occasions during the summer pre-season in two consecutive seasons. Based on data from a total of 170 test comparisons from the U15 (n = 48 test comparisons), U16 (n = 40 test comparisons), U17 (n = 46 test comparisons), and U19 (n = 36 test comparisons) age groups, the agreement between substantial changes in HR12km/h and v4mmol/l was analyzed using the threshold combination of HR12km/h = 4.5% and v4mmol/l = 6.0%.

RESULTS

Results revealed 2% full mismatches, 36% partial agreements, and 62% full agreements for the whole sample in terms of fitness change interpretation between both variables. The respective values for the U15 to U19 age groups ranged between 0% and 5% full mismatches, 28-44% partial agreements, and 56-68% full agreements with no meaningful differences between age groups.

CONCLUSION

In conclusion, our findings confirm the practical value of using HR12km/h to monitor fitness changes in elite youth soccer players when lactate sampling during incremental tests is not possible.

Determination of second lactate threshold using near-infrared spectroscopy in elite cyclists

The use of near-infrared spectroscopy could be an interesting alternative to other invasive or expensive methods to estimate the second lactate threshold. Our objective was to compare the intensities of the muscle oxygen saturation breakpoint obtained with the Humon Hex and the second lactate threshold in elite cyclists. Ninety cyclists performed a maximal graded exercise test. Blood capillary lactate was obtained at the end of steps and muscle oxygenation was continuously monitored. There were no differences (p>0.05) between muscle oxygen oxygenation breakpoint and second lactate threshold neither in power nor in heart rate, nor when these values were relativized as a percentage of maximal aerobic power or maximum heart rate. There were also no differences when men and women were studied separately. Both methods showed a highly correlation in power (r=0.914), percentage of maximal aerobic power (r=0.752), heart rate (r=0.955), and percentage of maximum heart rate (r=0.903). Bland-Altman resulted in a mean difference of 0.05±0.27 W·kg-1, 0.91±4.93%, 0.63±3.25 bpm, and 0.32±1.69% for power, percentage of maximal aerobic power, heart rate and percentage of maximum heart rate respectively. These findings suggest that Humon may be a non-invasive and low-cost alternative to estimate the second lactate threshold intensity in elite cyclists.

Comparison and Performance Validation of Calculated and Established Anaerobic Lactate Thresholds in Running

Background and Objectives: This study aimed to compare the calculated running velocity at the anaerobic lactate threshold (cLT_An), determined by a mathematical model for metabolic simulation, with two established threshold concepts (onset of blood lactate accumulation (OBLA; 4 mmol∙L⁻¹) and modified maximal deviation method (mDmax)). Additionally, all threshold concepts were correlated with performance in different endurance running events. Materials and Methods: Ten sub-elite runners performed a 30 s sprint test on a cycle ergometer adjusted to an isokinetic mode set to a cadence of 120 rpm to determine maximal lactate production rate (VLa_max), and a graded exercise test on a treadmill to determine maximal oxygen uptake (VO_2max). Running velocities at OBLA, mDmax, and cLT_An were then compared with each other, and further correlated with running performance over various distances (3000 m, 5000 m, and 10,000 m). Results: The mean difference in cLT_An was −0.13 ± 0.43 m∙s⁻¹ and −0.32 ± 0.39 m∙s⁻¹ compared to mDmax (p = 0.49) and OBLA (p < 0.01), respectively. cLT_An indicated moderate to good concordance with the established threshold concepts (mDmax: ICC = 0.87, OBLA: ICC = 0.74). In comparison with other threshold concepts, cLT_An exhibited comparable correlations with the assessed running performances (cLT_An: r = 0.61–0.76, mDmax: r = 0.69–0.79, OBLA: r = 0.56–0.69). Conclusion: Our data show that cLT_An can be applied for determining endurance performance during running. Due to the consideration of individual physiological profiles, cLT_An offers a physiologically justified approach to assess an athlete’s endurance performance.

Using Submaximal Exercise Heart Rate for Monitoring Cardiorespiratory Fitness Changes in Professional Soccer Players: A Replication Study

PURPOSE

To assess the value of monitoring changes in fitness in professional soccer players, using changes in heart rate at submaximal intensity (HR12km/h) over the velocity at a lactate concentration of 4 mmol/L (v4mmol/L). The authors reexamined (1) a range of threshold magnitudes, which may improve detecting substantial individual changes and (2) the agreement between changes in these 2 variables.

METHODS

On at least 2 occasions during different moments of the season, 97 professional soccer players from Germany (first, second, and fourth division) completed an incremental test to determine HR12km/h and v4mmol/L. Optimal thresholds for changes in HR12km/h and v4mmol/L were assessed, using various methods (eg, smallest worthwhile change + typical error [TE], successive reiterations approach). Agreement between both variable changes was examined for the whole sample (225 comparisons), 4 different subgroups (depending on the moment of the season), and in an individual over 6 years (n = 23 tests).

RESULTS

Changes of 4.5% and 6.0% for HR12km/h and v4mmol/L, respectively, were rated as optimal to indicate substantial changes in fitness. Depending on the (sub)groups analyzed, these thresholds yielded 0% to 2% full mismatches, 22% to 38% partial agreements, and 60% to 78% full agreements in terms of fitness change interpretation between both variables.

CONCLUSIONS

When lactate sampling during incremental tests is not possible, practitioners willing to monitor adult professional soccer players' (Germany; first, second, and fourth division) training status can confidently implement short, 3-minute submaximal runs, with 4.5% changes in HR12km/h being indicative of true substantial fitness changes, with 60% to 78% accuracy. Future studies should investigate the potential role of confounding factors of HR12km/h to improve changes in fitness prediction.

[Musculoskeletal laboratory diagnostics in competitive sport]

Hintergrund

Die labordiagnostische Untersuchung stellt eine wichtige Möglichkeit zur Beurteilung und Optimierung der Leistungs- und Regenerationsfähigkeit professioneller Athleten dar. Ferner ist sie für die Prävention, Diagnostik und Rehabilitation von Verletzungen und Überbelastungen von Bedeutung.

Fragestellung

Ziel dieser Arbeit ist die Darstellung muskuloskelettaler laborchemischer Parameter, die relevante Erkenntnisse für die medizinische Betreuung von Leistungssportlern liefern.

Material und Methoden

Literaturrecherche und narratives Review.

Ergebnisse

Die Bestimmung des Vitamin-D-, Calcium- und Knochenstoffwechsels stellt die laborchemische Basisdiagnostik im Rahmen der Beurteilung des Skelettstatus mit zusätzlichem präventivem Nutzen bezüglich muskuloskelettaler Verletzungen dar. Ferner können muskuläre Serummarker, z. B. Laktatdehydrogenase (LDH), Kreatinkinase (CK), Myoglobin und Aspartat-Aminotransferase (ASAT), helfen, eine metabolische Adaptation an das physische Training festzustellen und Aussagen über die muskuläre Arbeitslast und mögliche Schädigungen zu gewinnen. Die Energieverfügbarkeit kann durch eine entsprechende Bilanzierung sowie die laborchemische Bestimmung der Makro- und Mikronährstoffe eingeschätzt und optimiert werden.

Schlussfolgerungen

Die labordiagnostische Untersuchung besitzt in der Betreuung von Athleten eine sportartenübergreifende klinische Relevanz. Sie dient der Erreichung einer höchstmöglichen Leistungsfähigkeit sowie optimalen Prävention von Knochen- und Muskelverletzungen, wobei sämtliche Mangelzustände (z. B. Vitamin D) ausgeglichen werden sollten. Durch eine Periodisierung der laborchemischen Untersuchungen, mit zumindest zwei Labordiagnostiken im Jahr, und Aufstellung individueller Variabilitäts- und Referenzbereiche kann ferner eine bessere Beurteilbarkeit erreicht werden.

Using a Portable Near-infrared Spectroscopy Device to Estimate The Second Ventilatory Threshold

A breakpoint in a portable near-infrared spectroscopy (NIRS) derived deoxygenated haemoglobin (deoxy[Hb]) signal during an incremental VO2max running test has been associated with the second ventilatory threshold (VT2) in healthy participants. Thus, the aim was to examine the association between this breakpoint (NIRS) and VT₂ in well-trained runners. Gas exchange and NIRS data were collected during an incremental VO_2max running test for 10 well-trained runners. The breakpoint calculated in oxygen saturation (StO₂) and the VT₂ were determined and compared in terms relative to %VO_2max, absolute speed, VO₂, and maximum heart rate (HRmax). There were no significant differences (p>0.05) between the breakpoint in StO₂ and VT₂ relative to %VO_2max (87.00±6.14 and 88.28 ± 3.98 %), absolute speed (15.70±1.42 and 16.10±1.66 km·h^-1), VO₂ (53.71±15.17 and 54.66±15.57 ml·kg^-1·min^-1), and%HRmax (90.90±4.17 and 91.84±3.70%). There were large and significant correlations between instruments relative to%VO_2max (r=0.68, p<0.05), absolute speed (r=0.86, p<0.001), VO₂ (r=0.86, p<0.001), and %HR_max (r=0.69; p<0.05). A Bland and Altman analysis of agreement between instruments resulted in a mean difference of - 1.27±4.49%, -0.40±0.84 km·h^-1,-0.90±3.07 ml·kg^-1·min^-1, and - 0.94±3.14 for %VO_2max, absolute speed, VO_2, and %HR_max, respectively. We conclude that a portable NIRS determination of the StO₂ breakpoint is comparable with VT₂ using gas exchange and therefore appropriate for use in determining exercise training above VT₂ intensity. This is the first study to analyze the validity with the running mode using a NIRS portable device.

Predicting Maximal Oxygen Uptake Using the 3-Minute All-Out Test in High-Intensity Functional Training Athletes

Maximal oxygen uptake (VO2max) and critical speed (CS) are key fatigue-related measurements that demonstrate a relationship to one another and are indicative of athletic endurance performance. This is especially true for those that participate in competitive fitness events. However, the accessibility to a metabolic analyzer to accurately measure VO2max is expensive and time intensive, whereas CS may be measured in the field using a 3 min all-out test (3MT). Therefore, the purpose of this study was to examine the relationship between VO2max and CS in high-intensity functional training (HIFT) athletes. Twenty-five male and female (age: 27.6 ± 4.5 years; height: 174.5 ± 18.3 cm; weight: 77.4 ± 14.8 kg; body fat: 15.7 ± 6.5%) HIFT athletes performed a 3MT as well as a graded exercise test with 48 h between measurements. True VO2max was determined using a square-wave supramaximal verification phase and CS was measured as the average speed of the last 30 s of the 3MT. A statistically significant and positive correlation was observed between relative VO2max and CS values (r = 0.819, p < 0.001). Based on the significant correlation, a linear regression analysis was completed, including sex, in order to develop a VO2max prediction equation (VO2max (mL/kg/min) = 8.449(CS) + 4.387(F = 0, M = 1) + 14.683; standard error of the estimate = 3.34 mL/kg/min). Observed (47.71 ± 6.54 mL/kg/min) and predicted (47.71 ± 5.7 mL/kg/min) VO2max values were compared using a dependent t-test and no significant difference was displayed between the observed and predicted values (p = 1.000). The typical error, coefficient of variation, and intraclass correlation coefficient were 2.26 mL/kg/min, 4.90%, and 0.864, respectively. The positive and significant relationship between VO2max and CS suggests that the 3MT may be a practical alternative to predicting maximal oxygen uptake when time and access to a metabolic analyzer is limited.

Monitoring the swimmer's training load: A narrative review of monitoring strategies applied in research

The high incidence of injury during swim training and the increasing demands of the sports make monitoring of the swimmer's training load a key concept requiring further investigation. Research has previously introduced numerous methods for the purposes of monitoring the swimmer's training load, but a narrative review discussing the strengths and limitations of each method is lacking. Consequently, this narrative review aims to summarize the monitoring strategies that have been applied in research on competitive swimmers. This knowledge can assist professionals in the field in choosing which method is appropriate in their particular setting. The results from this study showed that external training load was predominantly obtained through real-life observation of the swimmers' training volume. However, research has investigated a number of internal load monitoring tools, including blood lactate, training heart rate, and perceived effort of training. To date, blood lactate markers are still considered most accurate and especially recommended at higher levels of competitive swimming or for those at greater risk of injury. Further, mood state profiling has been suggested as an early indicator of overtraining and may be applied at the lower competitive levels of swimming. Professionals in the field should consider the individual, the aim of the current training phase, and additional logistical issues when determining the appropriate monitoring strategy in their setting.

Metabolomics of Endurance Capacity in World Tour Professional Cyclists

The study of elite athletes provides a unique opportunity to define the upper limits of human physiology and performance. Across a variety of sports, these individuals have trained to optimize the physiological parameters of their bodies in order to compete on the world stage. To characterize endurance capacity, techniques such as heart rate monitoring, indirect calorimetry, and whole blood lactate measurement have provided insight into oxygen utilization, and substrate utilization and preference, as well as total metabolic capacity. However, while these techniques enable the measurement of individual, representative variables critical for sports performance, they lack the molecular resolution that is needed to understand which metabolic adaptations are necessary to influence these metrics. Recent advancements in mass spectrometry-based analytical approaches have enabled the measurement of hundreds to thousands of metabolites in a single analysis. Here we employed targeted and untargeted metabolomics approaches to investigate whole blood responses to exercise in elite World Tour (including Tour de France) professional cyclists before and after a graded maximal physiological test. As cyclists within this group demonstrated varying blood lactate accumulation as a function of power output, which is an indicator of performance, we compared metabolic profiles with respect to lactate production to identify adaptations associated with physiological performance. We report that numerous metabolic adaptations occur within this physically elite population (n = 21 males, 28.2 ± 4.7 years old) in association with the rate of lactate accumulation during cycling. Correlation of metabolite values with lactate accumulation has revealed metabolic adaptations that occur in conjunction with improved endurance capacity. In this population, cycling induced increases in tricarboxylic acid (TCA) cycle metabolites and Coenzyme A precursors. These responses occurred proportionally to lactate accumulation, suggesting a link between enhanced mitochondrial networks and the ability to sustain higher workloads. In association with lactate accumulation, altered levels of amino acids before and after exercise point to adaptations that confer unique substrate preference for energy production or to promote more rapid recovery. Cyclists with slower lactate accumulation also have higher levels of basal oxidative stress markers, suggesting long term physiological adaptations in these individuals that support their premier competitive status in worldwide competitions.

Salivary Metabolomics: From Diagnostic Biomarker Discovery to Investigating Biological Function

Metabolomic profiling of biofluids, e.g., urine, plasma, has generated vast and ever-increasing amounts of knowledge over the last few decades. Paradoxically, metabolomic analysis of saliva, the most readily-available human biofluid, has lagged. This review explores the history of saliva-based metabolomics and summarizes current knowledge of salivary metabolomics. Current applications of salivary metabolomics have largely focused on diagnostic biomarker discovery and the diagnostic value of the current literature base is explored. There is also a small, albeit promising, literature base concerning the use of salivary metabolomics in monitoring athletic performance. Functional roles of salivary metabolites remain largely unexplored. Areas of emerging knowledge include the role of oral host-microbiome interactions in shaping the salivary metabolite profile and the potential roles of salivary metabolites in oral physiology, e.g., in taste perception. Discussion of future research directions describes the need to begin acquiring a greater knowledge of the function of salivary metabolites, a current research direction in the field of the gut metabolome. The role of saliva as an easily obtainable, information-rich fluid that could complement other gastrointestinal fluids in the exploration of the gut metabolome is emphasized.

Maturation, morphological, motor and technical characteristics of under 16 female track and field athletes

Abstract There is growing interest in identifying morphological, motor, maturation characteristics, as well as their changes, of children and adolescents in systematized training in various sports. Knowledge of these characteristics is important for coaches and researchers because they provide parameters for assessing youth development during training. For track and field, studies on the category under 16 are scarce. Thus, the objectives of this study are to describe the profile and to design a percentile table of morphological, motor, maturation and event-specific variables of under 16 athletes. 105 young athletes were evaluated on two consecutive days. On the first day, an anamnesis of athletes and coaches was performed. Anthropometric and anaerobic measurements were analyzed in shot put, long jump, 800 m run. On the second day, flexibility, vertical impulse, upper limb strength, speed and maximal aerobic speed were evaluated. The biological maturation was evaluated by the percentage of the predicted height. A table with percentiles was prepared with the data of all athletes. Another table with the results of the whole group plus mean and standard deviation was prepared. A last table was prepared containing data divided by group of sports events. The morphological variables presented differences between the groups as to body mass, BMI and sum of skinfolds. Significant differences were observed only for the motor variable VMA. No significant differences were observed only for long jump. When divided by groups, it was evident that throwers are different from the other athletes in some morphologic variables and in specific sports events.

Rational engineering of Aerococcus viridansl-lactate oxidase for the mediator modification to achieve quasi-direct electron transfer type lactate sensor

The l-lactate oxidase (LOx) based lactate sensors are widely used for clinical diagnostics, sports medicine, and food quality control. However, dissolved oxygen interference and electroactive interferent effects are inherent issues of current lactate sensors. In this paper, a quasi-direct electron transfer (quasi-DET) type lactate sensor was developed using rationally engineered Aerococcus viridans LOx (AvLOx) modified with amine-reactive phenazine ethosulfate (PES). Since the modification of wild type AvLOx by PES did not result quasi-DET, engineered AvLOx with additional Lys residue was designed. The additional Lys residue was introduced by substituting residue locating on the surface of AvLOx, and within 20 Å of the isoalloxazine ring of FMN. Among several constructed mutants, Ala96Leu/Asn212Lys double mutant showed the highest dye-mediated dehydrogenase activity with negligible oxidase activity, showing quasi-DET properties after PES modification, when the enzyme was immobilized on screen printed carbon electrode. The constructed electrode did not show oxygen interference in cyclic voltammetric analysis and distinct catalytic current with 20 mM l-lactate. The sensor performance of a chronoamperometric l-lactate sensor employing PES modified Ala96Leu/Asn212Lys AvLOx, marked with linear range between 0 and 1 mM, with sensitivity of 13 μA/mM∙cm², and a limit of detection of 25 μM for l-lactate. By applying -200 mV vs. Ag/AgCl, l-lactate could be monitored with negligible interference from 170 μM ascorbic acid, 1.3 mM acetaminophen, 1.4 mM uric acid or 20 mM glucose. These results indicated that a quasi-DET type lactate sensor was developed that did not suffer from the interference of oxygen and representative electroactive ingredient compounds.

Enhanced Performance of Reagent-Less Carbon Nanodots Based Enzyme Electrochemical Biosensors

This work reports on the advantages of using carbon nanodots (CNDs) in the development of reagent-less oxidoreductase-based biosensors. Biosensor responses are based on the detection of H2O2, generated in the enzymatic reaction, at 0.4 V. A simple and fast method, consisting of direct adsorption of the bioconjugate, formed by mixing lactate oxidase, glucose oxidase, or uricase with CNDs, is employed to develop the nanostructured biosensors. Peripherical amide groups enriched CNDs are prepared from ethyleneglycol bis-(2-aminoethyl ether)-N,N,N',N'-tetraacetic acid and tris(hydroxymethyl)aminomethane, and used as precursors. The bioconjugate formed between lactate oxidase and CNDs was chosen as a case study to determine the analytical parameters of the resulting L-lactate biosensor. A linear concentration range of 3.0 to 500 µM, a sensitivity of 4.98 × 10-3 µA·µM-1, and a detection limit of 0.9 µM were obtained for the L-lactate biosensing platform. The reproducibility of the biosensor was found to be 8.6%. The biosensor was applied to the L-lactate quantification in a commercial human serum sample. The standard addition method was employed. L-lactate concentration in the serum extract of 0.9 ± 0.3 mM (n = 3) was calculated. The result agrees well with the one obtained in 0.9 ± 0.2 mM, using a commercial spectrophotometric enzymatic kit.

High intensity interval training and molecular adaptive response of skeletal muscle

Increased cardiovascular fitness, V˙O_2max, is associated with enhanced endurance capacity and a decreased rate of mortality. High intensity interval training (HIIT) is one of the best methods to increase V˙O_2max and endurance capacity for top athletes and for the general public as well. Because of the high intensity of this type of training, the adaptive response is not restricted to Type I fibers, as found for moderate intensity exercise of long duration. Even with a short exercise duration, HIIT can induce activation of AMPK, PGC-1α, SIRT1 and ROS pathway as well as by the modulation of Ca²⁺ homeostasis, leading to enhanced mitochondrial biogenesis, and angiogenesis. The present review summarizes the current knowledge of the adaptive response of HIIT.

Modifications of the Dmax method in comparison to the maximal lactate steady state in young male athletes

OBJECTIVE

To investigate the influence of different approaches for first-rise determination on the accuracy of Dmax as an estimate of the maximal lactate steady state (MLSS).

METHODS

Seventeen male cyclists and 18 male runners with different levels of endurance performance completed graded exercise tests either on a cycle ergometer or treadmill to determine Dmax, calculated by the final data point and five modifications of the first rise in blood lactate concentration. Two or more constant load tests over 30 min were performed to determine MLSS. Differences between the modifications of the first rise in blood lactate concentration as well as the corresponding Dmax variants and MLSS were tested, using one-way repeated measure ANOVA with Bonferroni post-hoc tests, and illustrated, using the Bland-Altman method. The absolute agreement was observed, using intra-class correlation coefficients, based on a single measure, absolute agreement, 2-way mixed effects model.

RESULTS

The peak power output/running velocity of the groups averaged 275 ± 43 W and 4.3 ± 0.4 m · s^-1, respectively. The mean power output/running velocity at MLSS was 229 ± 38 W and 3.77 ± 0.38 m · s^-1. For both running and cycling the original Dmax described by Cheng et al. was significantly lower than MLSS (p < 0.01). All modifications showed good agreement with MLSS (ICC ≥0.75). According to the Bland-Altman method the mean differences of the modifications compared to MLSS in cycling ranged from -7 (43) to 2 (41) W. In running the mean differences ranged from -0.12 (0.34) to -0.08 (0.35) m· s^-1.

CONCLUSION

We suggest using the first rise in blood lactate concentration for calculating Dmax instead of the first data point of a lactate curve as originally described. The approach of first rise determination has no substantial influence on the accuracy of Dmax compared to MLSS in cycling and running.

Photobiomodulation Therapy on Physiological and Performance Parameters During Running Tests: Dose-Response Effects

Dellagrana, RA, Rossato, M, Sakugawa, RL, Baroni, BM, and Diefenthaeler, F. Photobiomodulation therapy on physiological and performance parameters during running tests: Dose-response effects. J Strength Cond Res 32(10): 2807-2815, 2018-This study was aimed at verifying effects of photobiomodulation therapy (PBMT) with different energy doses (15, 30, and 60 J per site) on physiological and performance parameters during running tests. Fifteen male recreational runners participated in a crossover, randomized, double-blind, and placebo-controlled trial. They performed testing protocol in 5 sessions with different treatments: control, placebo, and PBMT with 15, 30, or 60 J per site (14 sites in each lower limb). Physiological and performance variables were assessed during submaximal (at 8 and 9 km·h) and maximal running tests. Photobiomodulation therapy with 30 J significantly improved running economy (RE) at 8 and 9 km·h (3.01%, p=0.008 and 3.03%, p=0.009, respectively), rate of perceived exertion (RPE) at 8 km/h21 (7.86%, p=0.033), velocity at V[Combining Dot Above]O2max (3.07%, p= 0.029), peak of velocity (PV) (1.49%, p=0.035), and total time to exhaustion (TTE) (3.41%, p=0.036) compared with placebo. Photobiomodulation therapy with 15 J improved running economy at 9 km/h21 (2.98%, p=0.025), rate of perceived exertion at 8 km/h21 (4.80%, p=0.010), PV (1.33%, p=0.008), total time to exhaustion (3.06%, p=0.008), and total distance (4.01%, p=0.011) compared with the placebo; whereas PBMT with 60 J only increased RE at 9 km/h21 (3.87%, p=0.024) compared with placebo. All PBMT doses positively affected physiological and/or performance parameters; however, magnitude-based inference reported that PBMT applied with 30 J led to more beneficial effects than 15 and 60 J.

Blood Biomarkers in Sports Medicine and Performance and the Future of Metabolomics

The field of sports medicine and performance has undergone an important transformation in the past years where the scientific approach is becoming increasingly more important for teams and athletes. Physical and physiological fitness, nutrition, fatigue and recovery, as well as injury prevention are key elements of the scientific monitoring of athletes nowadays. Many different methods are used nowadays as part of the scientific monitoring and testing of the competitive athlete. Among them, physiological and metabolic testing, biomechanical and movement assessments, GPS-based tracking systems, heart rate monitors, power meters, and training software are an integrative part of the scientific monitor program of many teams and athletes.Blood biomarkers through traditional blood analysis have been used for over three decades (mainly in Europe) to monitor athletic performance. In the same manner that different cells in the body respond to the stress of an infection or a disease, cells in athletes respond to the stress of competition and training. Nowadays, the area of blood biomarkers is an emerging field in the US offering important level of possibilities to monitor athletes. The field of metabolomics can offer a significantly higher level of blood biomarkers for sports medicine and performance monitoring.

Sex-Related Differences in the Maximal Lactate Steady State

The maximal lactate steady state (MLSS) is one of the factors that differentiates performance in aerobic events. The purpose of this study was to investigate the sex differences in oxygen consumption (VO₂), heart rate (HR), and the respiratory exchange ratio (RER) at the MLSS in well-trained distance runners. Twenty-two (12 female, 10 male) well-trained distance runners (23 ± 5.0 years) performed multiple 30-min steady-state runs to determine their MLSS, during which blood lactate and respiratory gas exchange measures were taken. To interpret the MLSS intensity as a training tool, runners completed a time-to-exhaustion (TTE) run at their MLSS. The relative intensity at which the MLSS occurred was identical between males and females according to both oxygen consumption (83 ± 5 %O₂max) and heart rate (89 ± 7 %HRmax). However, female runners displayed a significantly lower RER at MLSS compared to male runners (p < 0.0001; 0.84 ± 0.02 vs. 0.88 ± 0.04, respectively). There was not a significant difference in TTE at MLSS between males (79 ± 17 min) and females (80 ± 25 min). Due to the observed difference in the RER at the MLSS, it is suggested that RER derived estimates of MLSS be sex-specific. While the RER data suggest that the MLSS represents different metabolic intensities for males and females, the relative training load of MLSS appears to be similar in males and female runners.

Association of Lower Limb Compression Garments During High-Intensity Exercise with Performance and Physiological Responses: A Systematic Review and Meta-analysis

BACKGROUND

Although compression garments are used to improve sports performance, methodological approaches and the direction of evidence regarding garments for use in high-intensity exercise settings are diverse.

OBJECTIVES

Our primary aim was to summarize the association between lower-limb compression garments (LLCGs) and changes in sports performance during high-intensity exercise. We also aimed to summarize evidence about the following physiological parameters related to sports performance: vertical jump height (VJ), maximal oxygen uptake (VO₂max), submaximal oxygen uptake (VO₂submax), blood lactate concentrations ([La]), and ratings of perceived exertion (RPE, 6-20 Borg scale).

METHODS

We searched electronic databases (PubMed, EMBASE, Cochrane Library, and ClinicalTrials.gov) and reference lists for previous reviews. Eligible studies included randomized controlled trials with athletes or physically active subjects (≥ 18 years) using any type of LLCG during high-intensity exercise. The results were described as weighted mean difference (WMD) with a 95% confidence interval (95% CI).

RESULTS

The 23 included studies showed low statistical heterogeneity for the pooled outcomes. We found that LLCGs yielded similar running performance to controls (50-400 m: WMD 0.06 s [95% CI - 1.99 to 2.11]; 800-3000 m: WMD 6.10 s [95% CI - 7.23 to 19.43]; > 5000 m: WMD 1.01 s [95% CI - 84.80 to 86.82]). Likewise, we found no evidence that LLCGs were superior in secondary outcomes (VJ: WMD 2.25 cm [95% CI - 2.51 to 7.02]; VO₂max: WMD 0.24 mL.kg^-1.min^-1 [95% CI - 1.48 to 1.95]; VO₂submax: WMD - 0.26 mL.kg^-1.min^-1 [95% CI - 2.66 to 2.14]; [La]: WMD 0.19 mmol/L [95% CI - 0.22 to 0.60]; RPE: WMD - 0.20 points [95% CI - 0.48 to 0.08]).

CONCLUSIONS

LLCGs were not associated with improved performance in VJ, VO₂max, VO₂submax, [La], or RPE during high-intensity exercise. Such evidence should be taken into account when considering using LLCGs to enhance running performance.

Practical Model of Low-Volume Paddling-Based Sprint Interval Training Improves Aerobic and Anaerobic Performances in Professional Female Canoe Polo Athletes

Sheykhlouvand, M, Khalili, E, Gharaat, M, Arazi, H, Khalafi, M, and Tarverdizadeh, B. Practical model of low-volume paddling-based sprint interval training improves aerobic and anaerobic performances in professional female canoe polo athletes. J Strength Cond Res 32(8): 2375-2382, 2018-Brief, intense exercise training using running and cycling as exercise interventions may induce aerobic and anaerobic adaptations in athletes from a wide range of sports. However, this has not been studied extensively for those sports in which the upper body is predominantly involved. Our purpose was to examine the effects of kayak paddling-based sprint interval training (SIT) on cardiorespiratory fitness and anaerobic performance. Sixteen professional female canoe polo athletes (age = 27.6 ± 1.9 years; height = 165.7 ± 5.2 cm; body mass = 62.6 ± 8.5 kg; body mass index = 22.8 kg·m; body fat = 23.8 ± 4.9%) were randomized to either an intense exercise training consisting of sets of 5 × 5-second maximum sprint efforts interspersed by a 10-second recovery between each sprint (3, 4, 5, and 6 sets/session from first to fourth week, respectively, with 3 minutes of rest between each set), performed 3 times per week for 4 weeks (n = 8), or a usual training control group (n = 8). Before and after the training period, aerobic and anaerobic measurements were assessed using a kayak specific test and Wingate protocol, respectively. Training increased V[Combining Dot Above]O2peak, O2 pulse, anaerobic threshold, peak, and mean power output in the SIT group compared with the control group (p ≤ 0.05) who showed no changes in these variables when tested 4 weeks apart without SIT. Paddling-based SIT was a potent stimulus and time-efficient strategy to induce rapid adaptations in aerobic and anaerobic performances in professional female canoe polo athletes who can use this training method to achieve fitness in a short period.

Nutrition, hydration and ergogenic aids strategies in ultraendurance mountain events

BACKGROUND

The purpose of the present research was to analyze nutrition, hydration and ergogenic aids strategies in ultraendurance mountain events.

METHODS

A total of 386 ultraendurance mountain races finishers were analyzed. They were divided into three groups according to their race distance: G1, distance less than 45 km (N.=250); G2, distances between 45 and 90 km (N.=71); G3, distances longer than 90 km (N.=65). The ergogenic, nutritional and hydration strategies were quantified after each race by a questionnaire.

RESULTS

We found a higher ingestion of (0.56±0.95), caffeine (G3 203.8±211.5 mg), water (G3 7.1±3.7 l) and portion of sandwich (nutrition 5.3±7.4) nonsteroidal anti-inflammatory drug (NSAID) in longer distance probes. Higher performance runners in low and medium distances consumed a significantly (P>0.05) lower quantity of gels (higher 0.76±0.98 vs. lower 1.38±1.38), and muesli bar (higher 1.09±1.13 vs. lower 2.04±1.94), and in long distances higher performance consumed more water (M±SD; higher 8.23±3.92 vs. lower 6.12±3.28) than lower performance ones. They also could maintain a higher rated of perceived exertion than lower performance (G3 M±SD; higher 16.7±2.28 vs. lower 18.2±1.71).

CONCLUSIONS

Higher distance presented higher nutritional, caffeine and NSAIDs ingestion than lower distances, also, higher performance athletes of higher distance presenter higher water and nutritional ingestion than lower performance ones. In lower distance probes, higher performance athletes presented lower hydration and nutritional ingestion than lower performance athletes.

Differences within Elite Female Tennis Players during an Incremental Field Test

PURPOSE

To compare technical and physiological responses between junior and professional female players during an incremental field test to exhaustion specific to tennis.

METHODS

Twenty-seven female players (n = 14 and 13 for juniors and professionals, respectively) completed an incremental field test to exhaustion specific to tennis, which consisted of hitting alternatively forehand and backhand strokes at increasing ball frequency (ball machine) every minute. Ball accuracy and ball velocity were determined by radar and video analysis for each stroke, in addition to cardiorespiratory responses (portable gas analyzer).

RESULTS

The stage corresponding to the second ventilatory threshold (+20.0%, P = 0.027), time to exhaustion (+18.9%, P = 0.002) and maximum oxygen uptake (+12.4%, P = 0.007) were higher in professionals than in juniors. The relative percentage of maximal HR was lower at both the first (-4.7%, P = 0.014) and the second (-1.3%, P = 0.018) ventilatory thresholds in professionals. Backhand ball velocity was the only technical parameter that displayed larger (+7.1%, P = 0.016) values in professionals.

CONCLUSIONS

Compared with juniors, female professional tennis players possess higher exercise capacity, maximal and submaximal aerobic attributes along with faster backhand stroke velocities during an incremental field test specific to tennis.

Psychophysiological response to acute-high-stress combat situations in professional soldiers

The study of psychophysiological responses of soldiers in combat situations remains a challenge, especially in melee combat-a close proximity unarmed fight-defined by high unpredictability. Gaining knowledge about psychophysiological changes in high-stress situations is required to optimise training. This study aimed to analyse modifications in autonomic modulation, cortical arousal, heart rate, muscle strength, blood lactate concentration, and rating of perceived exertion of veteran soldiers in a melee combat simulation. Twenty veteran soldiers were analysed before and after a melee combat simulation in accordance with realistic situations that occur in actual operations areas. The simulation consisted of actions performed by a binomial unit in a security and protection mission in an operations area. The melee combat caused an increase in sympathetic modulation, blood lactate concentration, heart rate, muscle strength, a decreased tendency in cortical arousal, and a lower rating of perceived exertion than the organic response measured. An intense fight-flight response was observed in soldiers by the limbic system activation, causing a misinterpretation of perceived exertion. Finally, implications for the design of simulation environments for tactics training in high-stress professions are discussed.

Validity and reliability of a novel metabolic flexibility test in children with obesity

Existing methods for diagnosing diabetes and for identifying risk of diabetes development are completed under resting conditions and based on adult data. Studying additional methods to identify metabolic risk in children is warranted. Our objective was to examine the validity and reliability of a metabolic flexibility (MetFlex) test for screening glycemia and insulin resistance (IR) in children. We hypothesized higher MetFlex during exercise would be correlated with lower fasting glucose and homeostasis model assessment of insulin resistance (HOMA-IR) and higher whole body insulin sensitivity index (WBISI) and insulin secretion-sensitivity index-2 (ISSI-2). Thirty-four children with obesity (14 boys, 20 girls) attended two visits. At visit 1, an oral glucose tolerance test (OGTT) was followed by anthropometric and aerobic fitness (V̇o_2max) assessments. Insulin and glucose during the OGTT were used to calculate HOMA-IR, WBISI, and ISSI-2. At visit 2, a ¹³C-enriched carbohydrate drink was ingested before 60 min of exercise at 45% V̇o_2max. Breath measurements were collected to calculate area under the curve exogenous carbohydrate to measure MetFlex. Pearson's r correlation showed no significant association between MetFlex during exercise with fasting glucose ( r = -0.288, P = 0.110). MetFlex was associated with log-HOMA-IR ( r = -0.597, P = 0.024), log-WBISI ( r = 0.575, P = 0.051), and log-ISSI-2 ( r = 0.605, P = 0.037) in boys but not girls. When repeated ( n = 18), MetFlex was deemed a reliable test (intraclass correlation coefficient = 0.692). MetFlex during exercise was negatively associated with IR and β-cell function in boys. Further research is required to explore clinical utility of the MetFlex test and explain the lack of association in girls. NEW & NOTEWORTHY This study is the first to investigate the validity and reliability of a novel noninvasive metabolic flexibility (MetFlex) test for identifying insulin resistance in children with obesity. MetFlex was measured during exercise using [¹³C]glucose stable isotope methodology. Findings showed that MetFlex was negatively associated with insulin resistance in boys but not in girls with obesity. Future work is required to investigate these sex differences. MetFlex test results were deemed reliable when repeated on a separate day.