Is Perceived Exertion a Useful Indicator of the Metabolic and Cardiovascular Responses to a Metabolic Conditioning Session of Functional Fitness?

Moderate-Duration Dynamic Stretching During Warm-up Improves Running Economy and Running Performance in Recreational Distance Runners

PURPOSE

The purpose of this study was to investigate, in distance runners, the acute effects of moderate durations (60 s per leg) of static (SS) and dynamic stretching (DS) on running economy (RE) and performance.

METHODS

Twelve recreational runners completed a randomized crossover design. Initially, the second ventilatory threshold (VT2) and the speed associated with the maximal oxygen uptake (VO2max) (vVO2max) were determined through an incremental test. Then, participants completed submaximal continuous-running (75%VT2 and 85%VT2) and running-until-exhaustion (vVO2max) tests preceded by 3 warm-ups: running plus SS or DS (SS or DS conditions) and running without stretching (NS condition). The SS and DS conditions consisted of 5 minutes of running plus 10 minutes of SS or DS, respectively, and the NS condition consisted of 15 minutes of running without stretching. RE at 75%VT2 and 85%VT2, time to exhaustion, and total running distance were evaluated. Rating of perceived exertion was also assessed.

RESULTS

Running economy at 75%VT2 resulted significantly better in the DS than in the NS (P < .001) and in the SS (P < .05). Time to exhaustion and total running distance were significantly improved in DS compared with NS (P < .001) and SS (P < .01). No differences in rating of perceived exertion among conditions were found.

CONCLUSIONS

Our results showed that, in recreational distance runners, a preexercise moderate-duration bout of DS improved RE and enhanced total running distance and time to exhaustion, whereas 60 seconds of SS did not induce significant improvements. Overall, our study demonstrates the effectiveness of moderate DS durations in optimizing RE and performance parameters, showing that such effects depend on the stretching modality used.

The physical demands and physiological responses to CrossFit®: a scoping review with evidence gap map and meta-correlation

BACKGROUND

CrossFit® combines different types of activities (weightlifting, gymnastics, and cardiovascular training) that challenge aerobic and anaerobic pathways. Over the last few years, the scientific interest in CrossFit® has increased considerably. However, there have been no published reviews characterizing the physical demands and physiological responses to CrossFit®. The present study synthesizes current evidence on the physical demands and physiological responses to CrossFit®.

METHODS

The search was performed in three electronic databases (PubMed, Scopus, and Web of Science). Manuscripts related to the physical and physiological performance of adult CrossFit® participants written in English, Portuguese, and Spanish were retrieved for the analysis.

RESULTS

In addition, a meta-correlation was conducted to examine the predictors of CrossFit® performance. A total of 68 papers were included in the review. Physical and physiological markers differed between the different workouts analyzed. In addition, 48 to 72 h are needed to recover from a CrossFit® challenge. Specific tests that involve CrossFit® movements were more related to CrossFit® performance than non-specific.

CONCLUSION

Although the characterization of CrossFit® is dependent on the workout examined, the benefits of muscle hypertrophy are aligned with the recent findings of concurrent training. The characterization of CrossFit® entire sessions and appropriate recovery strategies should be considered in future studies to help coaches manipulate and adjust the training load.

Exploring the relationship between Total Athleticism score and CrossFit® Open Performance in amateur athletes: single measure involving body fat percentage, aerobic capacity, muscle power and local muscle endurance

There has been an increasing interest among CrossFit® coaches and practitioners in identifying indicators of sport performance. This study aimed to examine the correlation between anthropometric measures, cardiorespiratory capacity, power, local muscle endurance, and total athleticism score, with performance in the CrossFit® Open 2021. Fourteen male volunteers (aged 30.3 ± 5.8 years) participated in the study and underwent a series of tests on separate weeks. These tests included assessments of body fat percentage (subcutaneous adipose thickness measured at seven sites), maximal oxygen consumption (2 km test in rowing ergometer), muscle power (one repetition maximum in power clean), and muscle endurance (Tibana test, which included the conclusion of four distinct rounds of work). These results were used to calculate the total score of athleticism, which was then compared to the participants performance during the CrossFit® Open 2021. The athletes presented an average of body fat (8.6 ± 2.0%), maximal oxygen consumption (53.3 ± 2.4 mL. (kg.min)-1), 2km row time (07:00 ± 00:21 mm:ss), 1-Repetition maximum in power clean (125.2 ± 21.2 kg) and Tibana test performance (281.0 ± 35.9 repetitions). Interestingly, the top five athletes with the highest scores also achieved the highest z-scores in the CrossFit® Open 2021. Conversely, the four athletes with the lowest TSA score had the lowest z-scores in the CrossFit® Open. Moreover, almost perfect correlation (r = 0.91; p<0.01) was found between the total athleticism score and z-scores in the CrossFit® Open 2021. The total score may be a single measure and holistic indication of athleticism level in CrossFit®. Furthermore, coaches can potentially apply this useful tool for monitoring athletic performance and designing training sessions that address specific areas of CrossFit® performance.

The relationship between prescribed ratings of perceived exertion and force production in repeated isometric contractions

Ratings of perceived exertion (RPE) are frequently used to monitor and prescribe exercise intensity. However, studies examining the shape and robustness of how feelings of effort map onto objective outputs are limited and report inconsistent results. To address this, we investigated whether (1) producing isometric forces according to RPE levels reliably leads to differences in force output, (2) if feelings of effort map linearly or non-linearly onto force output, and (3) if this mapping is robust when visual feedback and social facilitation are present. In a counterbalanced repeated measures design, N = 26 participants performed isometric handgrip contractions prescribed by ten levels of the Borg CR-10 scale. They did so either with or without the availability of concurrent visual feedback regarding their force production, and in the presence or absence of another person performing the same task simultaneously. We found that subjects reliably produced different force outputs that corresponded to each RPE level. Furthermore, concurrent visual feedback led to a linearization of force output, while in the absence of feedback, the produced forces could also be described by quadratic and cubic functions. Exploratory post-hoc analyses revealed that participants perceived moderate RPE levels to be more challenging to produce. By shedding light on the dynamic nature of the mapping between RPE and objective performance, our findings provide helpful insights regarding the utility of RPE scales.

The Feasibility of Whole-Body Vibration Training as an Approach to Improve Health in Autistic Adults

Background: Individuals with autism spectrum disorder (ASD) often lead sedentary lives, contributing to cardiovascular disease and muscular atrophy, requiring innovative therapeutic exercise approaches. Whole-body vibration (WBV) exercise training offers a unique option for those with limited motor control. This six-week pilot study aimed to assess the feasibility and effectiveness of WBV training in individuals with ASD. Methods: Six participants (age: 22.17 ± 2.14 years) underwent twice-weekly WBV sessions (10–24 min, 5–25 Hz). Cardiovascular biomarkers, including body composition, leg strength, blood pressure, waist/hip ratio, and body mass index (BMI), were measured. Qualitative outcomes on exercise tolerance, protocol completion, and perceived exertion were collected at each session. Data analyses, including measures of central tendencies and the Wilcoxon Signed Rank Test, evaluated the intervention’s effectiveness. Results: WBV training was safe and well-tolerated in adults with ASD. Despite no statistically significant improvements in cardiovascular and muscular strength indices, participants showed good adherence and tolerance to the protocol. Conclusion: Although WBV training had no significant impact on measured outcomes, it emerged as a feasible and well-tolerated exercise for individuals with ASD. It shows promise for addressing cardiovascular risk factors and reducing sedentary behaviors, suggesting the need for longer interventions to fully uncover its therapeutic potential.

Short intermittent taekwondo test to assess athlete's physiological and metabolic profile

BACKGROUND

The aim of this study was to assess the effectiveness of a new Short Intermittent Taekwondo Test (SITT) in 17 black belt athletes.

METHODS

Maximal oxygen uptake (V̇O2max), carbon dioxide production (V̇CO2), respiratory exchange ratio (RER), heart rate (HR), and blood lactate concentration [La]+ during treadmill cardiopulmonary exercise test (CPET) and SITT were compared. SITT started with 10 sec of all-out kicks, alternating legs, and progressively increasing 5 s on each stage until the 4th stage. After the 4th stage the participants performed 25 s of turning kicks (Dolleo chagi), on each stage until the last (10th stage). The passive recovery phase after the 4th and the 7th stage lasted 30 s.

RESULTS

V̇O2max and maximal HRmax were not significantly different (P=0.85 vs. P=0.76) between tests, while RER and [La]+ were significantly higher in SITT than in CPET (P=0.002 vs. P=0.001). No difference in RPE (P=0.84) was found. A significant positive correlation between two tests for V̇O2max and HRmax was found.

CONCLUSIONS

Our findings showed that SITT induces physiological responses like CPET suggesting that it can be used to assess aerobic power in national taekwondo athletes, thus helping coaches to select correctly training intensities and monitor athletes' aerobic performance along the training phases.

Acute Effects of Stretching Exercises on Posterior Chain: Analysis of Shear Modulus by Elastography SSI

The posterior chain muscles of the lower limb include the hamstrings and triceps surae, along with the Achilles tendon. This study aimed to investigate the acute effects of static stretching exercises commonly used in clinical and training settings on the shear modulus (µ) of these muscles and tendon using Supersonic Shear-Wave Imaging (SSI) elastography. Fifteen healthy adults participated in the study, performing stretching exercises for hamstrings and triceps surae. Shear modulus and joint range of motion (ROM) were measured before and after the stretching protocols. The hip and ankle mean ROM significantly increased by 19.27% and 24.10%, respectively. However, the stretching protocol did not significantly alter in µ of the hamstrings, the gastrocnemius muscles, and the Achilles tendon. K-means clustering analysis identified a group where the subjects with lower initial ROM showed higher amplitude gains and a significant decrease in the semimembranosus stiffness after stretching. These findings suggest that the stretching protocol was effective in improving joint mobility but not sufficient to elicit immediate mechanical changes in muscle and tendon stiffness. Neural adaptations and nonmuscular structures might contribute to increased ROM. The study highlights the importance of considering individual initial ROM and subsequent responses when evaluating the effects of stretching exercises on muscle and tendon properties.

Movement Velocity as an Indicator of Mechanical Fatigue and Resistance Exercise Intensity in Cross Modalities

Purpose: This study analyzed the acute mechanical response to three workouts of the day (WOD) protocols in as many repetitions as possible (AMRAP), every minute on the minute (EMOM), and for time (FT) models by quantifying the degree of mechanical fatigue induced by popular resistance exercises in the Cross modalities, front squat (FS), and shoulder press (SP). We also analyzed whether the exercises' fastest velocity (Vfastest) could be an objective indicator of relative intensity (%1RM). Methods: Nine trained men performed three FS and SP exercises protocols. The degree of fatigue was quantified by the velocity loss (VL) achieved in both exercises and the velocity loss achieved in the WOD (VLWOD). Results: The VLWOD in the AMRAP, EMOM, and FT protocols was 73.2 ± 10.9%, 61.6 ± 15.1%, and 76.1 ± 8.8%, respectively. In the AMRAP and FT protocol, the Vfastest showed very strong relationships with the %1RM for FS and SP (r = -0.83, -0.75, respectively, p < .01); while in the EMOM protocol, there was a strong relationship between these variables, only for the SP (r = -0.61, p < .05). In the FT protocol, we observed an extremely strong relationship for FS (r = -0.91, p < .001) and very strong (r = -0.71, p < .05) for SP between these variables. Conclusion: Therefore, the AMRAP and FT training models induce the highest degrees of mechanical fatigue in the FS and SP exercises, and the Vfastest is a reliable tool for estimating relative intensity in resistance exercises of Cross modalities.

Effects of acute beta-alanine supplementation on post-exertion rating of per-ceived exertion, heart rate, blood lactate, and physical performance on the 6-minute race test in middle-distance runners

Introduction

Background: the use of beta-alanine (BA) to increase physical performance in the heavy-intensity domain zone (HIDZ) is widely documented. However, the effect of this amino acid on the post-exertion rating of perceived exertion (RPE), heart rate (HR), and blood lactate (BL) is still uncertain. Objectives: a) to determine the effect of acute BA supplementation on post-exertion RPE, HR, and BL in middle-distance athletes; and b) to determine the effect of acute BA supplementation on physical performance on the 6-minute race test (6-MRT). Material and methods: the study included 12 male middle-distance athletes. The de-sign was quasi-experimental, intrasubject, double-blind & crossover. It had two treat-ments (low-dose BA [30 mg·kg-1] and high-dose BA [45 mg·kg-1]) and a placebo, 72 hours apart. The effect of BA was evaluated at the end of the 6-MRT and post-exertion. The variables were RPE, HR and BL, and 6-MRT (m) distance. The statistical analysis included a repeated-measures ANOVA (p < 0.05). Results: the analysis evidenced no significant differences at the end of 6-MRT for all variables (p ˃ 0.05). However, both doses of BA generated a lower post-exertion RPE. The high dose of BA caused significant increases in post-exertion BL (p ˂ 0.05). Conclusion: acute supplementation with BA generated a lower post-exertion RPE. This decrease in RPE and the post-exertion BL increase could be related to an increase in physical performance in HIDZ.

Effects of High-Intensity Warm-Up on 5000-Meter Performance Time in Trained Long-Distance Runners

Warm-up protocols with high intensities before continuous running provide potential benefits for middle-distance runners. Nevertheless, the effect of high-intensity warm-ups on long-distance runners remains unclear. The purpose of this study was to verify the effect of a high-intensity warm-up protocol on 5000 m performance in trained runners. Thirteen male runners (34 ± 10 years, 62 ± 6 kg, 62.7 ± 5.5 ml/kg/min) performed two 5000 m time trials, preceded by two different warm-ups. One high-intensity warm up (HIWU: 1x 500 m (70% of the running intensity) + 3x 250 m (100% of the running intensity) and one low-intensity warm up (LIWU: 1x 500 m (70% of the running intensity) + 3x 250 m (70% of the running intensity)), where the running intensities were calculated using the results obtained in the Cooper test. Physiological and metabolic responses, and endurance running performance parameters, were evaluated by the Counter Movement Jump (CMJ), running rating of perceived exertion (RPE), blood lactate concentration (BLa), and performance running. Total time for the 5000 m was lower using HIWU when compared to LIWU (1141.4 ± 110.4 s vs. 1147.8 ± 111.0 s; p = 0.03; Hedges' g = 0.66). The HIWU warm-up led to an improvement in pacing strategy during the time trial. After warm-up protocols, the performance on the CMJ was improved only when applying HIWU (p = 0.008). Post warm-up BLa was significantly higher for HIWU vs. LIWU (3.5 ± 1.0 mmol·L-1 vs. 2.3 ± 1.0 mmol·L-1; p = 0.02), with similar behavior for the RPE (p = 0.002), internal load of the session (p = 0.03). The study showed that a high-intensity warm-up protocol can improve performance in the 5000 m in trained endurance runners.

Effects of Different Recovery Modalities on Delayed Onset Muscle Soreness, Recovery Perceptions, and Performance Following a Bout of High-Intensity Functional Training

The purpose of this study was to investigate the effects of the foam rolling technique and static stretching on perceptual and neuromuscular parameters following a bout of high-intensity functional training (HIFT), which consisted of 100 pull-ups, 100 push-ups, 100 sit-ups, and 100 air squats (Angie benchmark) in recreationally trained men (n = 39). Following baseline measurements (Feeling Scale, Visual Analogue Scale, Total Quality Recovery, Sit-and-Reach, Countermovement Jump, and Change-of-Direction t-test), the volunteers performed a single bout of HIFT. At the end of the session, participants were randomly assigned to one of three distinct groups: control (CONT), foam rolling (FR), or static stretching (SS). At the 24 h time-point, a second experimental session was conducted to obtain the post-test values. The level of significance was set at p < 0.05. Regarding power performance, none of the three groups reached pretest levels at 24 h point of the intervention. However, the CONT group still showed a greater magnitude of effect at the 24 h time-point (ES = 0.51, p ≥ 0.05). Flexibility presented the same recovery pattern as power performance (post × 24 h CONT = ES = 0.28, FR = ES = 0.21, SS = ES = 0.19). At 24 h, all groups presented an impaired performance in the COD t-test (CONT = ES = 0.24, FR = ES = 0.65, SS = ES = 0.56 p ≥ 0.05). The FR protocol resulted in superior recovery perceptions (pre × 24 h TQR = ES = 0.32 p ≥ 0.05). The results of the present study indicate that the use of FR and SS exercises may not be indicated when aiming to restore neuromuscular performance following a single bout of HIFT. The use of the FR technique during the cooldown phase of a HIFT session may be helpful in improving an individual's perception of recovery.

Acute physiological outcomes of high-intensity functional training: a scoping review

Background

Systematic reviews and meta-analyses related to high-intensity functional training (HIFT) have been conducted. However, due to a restricted pool of available research, these investigations are often limited in scope. As such, a scoping review investigating the present literature surrounding the acute physiological response to HIFT-based exercise was chosen as a more appropriate structured review.

Methodology

A scoping review was conducted following Arksey and O'Malley's framework. Three large scale databases were searched to reveal any article pertaining to HIFT and related exercise terminology.

Results

A total of 2,241 articles were found during the initial search. Following this, titles, then abstracts, and full-texts were reviewed to determine inclusion eligibility. A total of 60 articles which investigated a combined total of 35 unique HIFT workouts were included within this review.

Conclusions

A variety of physiological parameters and HIFT workouts have been examined. Markers of intensity (e.g., blood lactate concentrations, heart rate) have been most consistently assessed across all studies, and these support the idea that HIFT workouts are typically performed at high-intensity. In contrast, the inclusion of most other measures (e.g., hormonal, markers of inflammation and damage, energy expenditure, performance) has been inconsistent and has thus, limited the possibility for making generalized conclusions. Differences in study methodologies have further impacted conclusions, as different studies have varied in sample population characteristics, workouts assessed, and time points. Though it may be impossible to comprehensively research all possible HIFT workouts, consistent adoption of population definitions and workload quantification may overcome this challenge and assist with future comparisons.

Shuttle Running Within a Small-Sided Game: Effects on Internal and External Workloads, in Young Elite Soccer Players

PURPOSE

To compare the effects of 2 small-sided games (SSGs), shuttle running within the bout (SSG-S) versus possession play only (SSG-P) on acute physiological and metabolic responses, perception of effort, and performance.

METHODS

Ten young elite male soccer players (age 18.6 [1.9] y) performed two 5vs5 SSG formats (SSG-S and SSG-P) consisting of 4 × 4 minutes with 1 minute of passive recovery between bouts, 2 times each, once a week, and in a randomized order. Heart rate, blood lactate concentration, and rating of perceived exertion were assessed as indices of internal workload. Total and relative distances, distance at moderate and high speed, distances traveled in accelerations (≥2 m·s-2) and decelerations (≤-2 m·s-2; DDEC), and average metabolic power were chosen as indices of external workload and collected with a 10-Hz portable global positioning system device.

RESULTS

Total distance, distances traveled in acceleration, distances traveled in deceleration, average metabolic power (always P < .01 and g > 1.62-large effect), and distance at moderate speed (P = .03 and g = 0.84-large effect) were significantly higher in SSG-S than in SSG-P. Moreover, the SSG-S showed higher blood lactate concentration (P = .0001, g = 12.58-large effect) and rating of perceived exertion (P = .03, g = 1.14-large effect) values than SSG-P. No significant differences in peak heart rate, relative distance, and distance at high speed were found.

CONCLUSIONS

Our study showed, in young competitive male soccer players, the effectiveness of an SSG format that includes shuttle running within each bout in the development of more relevant internal and external workloads. These experimental data should encourage coaches to use this new SSG regimen within the traditional weekly training program.

The Impacts of Combined Blood Flow Restriction Training and Betaine Supplementation on One-Leg Press Muscular Endurance, Exercise-Associated Lactate Concentrations, Serum Metabolic Biomarkers, and Hypoxia-Inducible Factor-1α Gene Expression

The purpose of this investigation was to compare the impacts of a potential blood flow restriction (BFR)-betaine synergy on one-leg press performance, lactate concentrations, and exercise-associated biomarkers. Eighteen recreationally trained males (25 ± 5 y) were randomized to supplement 6 g/day of either betaine anhydrous (BET) or cellulose placebo (PLA) for 14 days. Subsequently, subjects performed four standardized sets of one-leg press and two additional sets to muscular failure on both legs (BFR [LL-BFR; 20% 1RM at 80% arterial occlusion pressure] and high-load [HL; 70% 1RM]). Toe-tip lactate concentrations were sampled before (PRE), as well as immediately (POST0), 30 min (POST30M), and 3 h (POST3H) post-exercise. Serum homocysteine (HCY), growth hormone (GH) and insulin-like growth factor-1 concentrations were additionally assessed at PRE and POST30M. Analysis failed to detect any significant between-supplement differences for total repetitions completed. Baseline lactate changes (∆) were significantly elevated from POST0 to POST30 and from POST30 to POST3H (p < 0.05), whereby HL additionally demonstrated significantly higher ∆Lactate versus LL-BFR (p < 0.001) at POST3H. Although serum ∆GH was not significantly impacted by supplement or condition, serum ∆IGF-1 was significantly (p = 0.042) higher in BET versus PLA and serum ∆HCY was greater in HL relative to LL-BFR (p = 0.044). Although these data fail to support a BFR-betaine synergy, they otherwise support betaine’s anabolic potential.

Quantifying CrossFit®: Potential solutions for monitoring multimodal workloads and identifying training targets

The design of high-intensity functional training (HIFT; e. g., CrossFit^®) workouts and targeted physiological trait(s) vary on any given training day, week, or cycle. Daily workouts are typically comprised of different modality and exercise combinations that are prescribed across a wide range of intensities and durations. The only consistent aspect appears to be the common instruction to maximize effort and workout density by either completing "as many repetitions as possible" within a time limit (e.g., AMRAP, Tabata) or a list of exercises as quickly as possible. However, because effort can vary within and across workouts, the impact on an athlete's physiology may also vary daily. Programming that fails to account for this variation or consider how targeted physiological systems interrelate may lead to overuse, maladaptation, or injury. Athletes may proactively monitor for negative training responses, but any observed response must be tied to a quantifiable workload before meaningful changes (to programming) are possible. Though traditional methods exist for quantifying the resistance training loads, gymnastic movements, and cardiorespiratory modalities (e.g., cycling running) that might appear in a typical HIFT workout, those methods are not uniform, and their meaning will vary based on a specific exercise's placement within a HIFT workout. To objectively quantify HIFT workloads, the calculation must overcome differences in measurement standards used for each modality, be able to account for a component's placement within the workout and be useful regardless of how a workout is commonly scored (e.g., repetitions completed vs. time-to-completion) so that comparisons between workouts are possible. This review paper discusses necessary considerations for quantifying various HIFT workout components and structures, and then details the advantages and shortcomings of different methods used in practice and the scientific literature. Methods typically used in practice range from being excessively tedious and not conducive for making comparisons within or across workouts, to being overly simplistic, based on faulty assumptions, and inaccurate. Meanwhile, only a few HIFT-related studies have attempted to report relevant workloads and have predominantly relied on converting component and workout performance into a rate (i.e., repetitions per minute or second). Repetition completion rate may be easily and accurately tracked and allows for intra- and inter-workout comparisons. Athletes, coaches, and sports scientists are encouraged to adopt this method and potentially pair it with technology (e.g., linear position transducers) to quantify HIFT workloads. Consistent adoption of such methods would enable more precise programming alterations, and it would allow fair comparisons to be made between existing and future research.

Time Course of Recovery Following CrossFit® Karen Benchmark Workout in Trained Men

The establishment of fatigue following the acute exercise stimulus is a complex and multi-factorial process, that might arise due to a range of distinct physiological mechanisms. However, a practical method of assessing CrossFit^® athletes’ recovery status has been neglected entirely in real-world sporting practice. The study describes the acute and delayed time course of recovery following the CrossFit^® Benchmark Workout Karen. Eight trained men (28.4 ± 6.4 years; 1RM back squat 139.1 ± 26.0 kg) undertook the Karen protocol. The protocol consists of 150 Wall Balls (9 kg), aiming to hit a target 3 m high. Countermovement jump height (CMJ), creatine kinase (CK), and perceived recovery status scale (PRS) (general, lower and upper limbs) were assessed pre, post-0h, 24, 48 and 72 h after the session. The creatine kinase concentration 24 h after was higher than pre-exercise (338.4 U/L vs. 143.3 U/L; p = 0.040). At 48h and 72 h following exercise, CK concentration had returned to baseline levels (p > 0.05). The general, lower and upper limbs PRS scores were lower in the 24-h post-exercise compared to pre-exercise (general PRS: 4.7 ± 1.5 and 7.7 ± 1.7; p = 0.013; upper limbs PRS: 6.6 ± 1.3 and 7.5 ± 1.3; p = 0.037; lower limbs PRS: 3.9 ± 2.5 and 7.3 ± 0.1; p = 0.046). Our findings provide insights into the fatigue profile and recovery in acute CrossFit^® and can be useful to coaches and practitioners when planning training programs. Moreover, recovery status can be useful to optimize training monitoring and to minimize the potential detrimental effects associated with the performance of repeated high-intensity sessions of CrossFit^®.

TRAINING LOAD THROUGH HEART RATE AND PERCEIVED EXERTION DURING CROSSFIT®

ABSTRACT Introduction: Monitoring of CrossFit® training load should be considered to facilitate training outcomes and avoid overtraining. Objective: The purpose of the present study was to examine the heart rate (HR), rating of perceived exertion (RPE), and internal load responses to each segment of a CrossFit® training session. Methods: An observational, cross-sectional design was used in this study. Fifteen healthy male recreational athletes with at least six months experience in CrossFit® training participated in this study. Seven non-consecutive CrossFit® training sessions consisting of mobility, warm-up, skill, and workout segments were performed with a minimum of 48 hours between sessions. Exercise modalities within sessions were constantly varied according to the CrossFit® training programming template. HR was measured every two minutes throughout each session. Peak HR, average HR, RPE after each segment, and session RPE were recorded. Results: HR significantly increased during each segment of the training sessions (p < 0.01), except between the warm-up and skill segments (p = 0.180). Mean total session HR was 65.1 ± 5.4% HRmax and peak HR was 95.3 ± 4.1% HRmax. RPE and internal load increased significantly in each segment (p < 0.05). While intensity measurements increased during CrossFit® training, the HR responses differed from the RPE and internal load. Conclusion: When switching from one segment to another, HR fell below the HRpeak of the previous segment, which shows that the time spent switching between the training segments influenced the average HR of the entire session. Level of evidence III; Case control study; Investigating the results of treatment.

High-Intensity Interval Training for Rowing: Acute Responses in National-Level Adolescent Males

Background: This study investigated the acute effects of two high-intensity interval training (HIIT) programs on physiological responses and internal workload. Methods: Ten national-level adolescent male rowers (age: 15.7 ± 0.2 years; maximal oxygen uptake (VO2max): 60.11 ± 1.91 mL∙kg−1∙min−1) performed two HIIT testing sessions: short (S-HIIT) and long (L-HIIT). In S-HIIT, the rowers performed 25 reps of 30 s at 100% power at VO2max (Pmax) interspersed with 30 s at P@20% Pmax; whereas in L-HIIT, the rowers executed 4 × 4 min at P@90% Pmax interspersed with 3 min of active recovery (P@30% Pmax). Results: The acute physiological responses and internal workload were evaluated. The significance level was set at p < 0.05. Oxygen uptake (VO2) (p < 0.05), time spent per session at ~90% VO2max (p < 0.01), total VO2 consumed (p < 0.01), total distance (p < 0.001), the rating of perceived exertion, blood lactate concentration and heart rate (always p < 0.0001) were significantly higher in L-HIIT than in S-HIIT. However, peak power output was significantly lower in L-HIIT compared to S-HIIT (p < 0.0001). Conclusion: In adolescent rowers, both HIIT tests stimulated aerobic and anaerobic systems. The L-HIIT test was associated with acute cardiorespiratory and metabolic responses, as well as higher perceptions of effort than the S-HIIT test. In adolescent rowers, HIIT emerges as an asset and could be introduced into a traditional in-season, moderate-intensity and endurance-based rowing program once a week.

Effects of Training Loads on Stress Tolerance and Mucosal Immunity in High-Intensity Functional Fitness Athletes

Purpose: This study aimed to analyze the effects of training load on stress tolerance (ST) and secretory immunoglobulin A (SIgA) in male and female high-intensity functional fitness (HIFF) athletes during two different 10 and consecutive weekly training volume loads [higher (week 1) and lower volume (week 2)]. Methods: 14 athletes [7 males: 29.3 (±5.8) years; 86.3 (±8.2) kg and 176.8 (±3.8) cm and 7 females: 32.7 (±4.4) years; 60.0 (±6.7) kg and 162.5 (±5.9) cm] participated. The ST, assessed by Daily Analysis of Life Demand in Athletes questionnaire (DALDA) and Saliva sampling were performed in four time-points (pre (T1) and post (T2) week 1; pre (T3) and post (T4) week 2). Results: Female athletes showed a decrease in ST (symptoms of stress) from 15 T1 to T3 [F_(3,36) = 7.184, p˂ 0.001, ηp² = 0.374], without difference in male athletes (p > .05). There is a significant difference of SIgA concentration [F_(3.36) = 3.551; p = .024; ηp² = 0.228], with a significant decrease in female athletes group in T2 compared to T1 (p = .013) and T4 (p = .023). In addition, the different training volume loads did not impact mucosal immunity in male athletes (p > .05). Conclusion: The current findings suggest that higher HIFF volume results in decreased ST and SIgA concentration in female 20 athletes and a subsequent decrease in training volume loads contributed to restoring these variables.

Time-course effects of functional fitness sessions performed at different intensities on the metabolic, hormonal, and BDNF responses in trained men

Background

To investigate the time-course effects of a self-regulated training session (performed at an rating perceived exertion of 6/10), all-out session, and a control session on the metabolic, hormonal, and brain derived neurotrophic factor (BDNF) responses in Functional-Fitness (FFT) participants.

Methods

In a randomized, crossover fashion, eight healthy males (age 28.1 ± 5.4 years old; body mass 77.2 ± 4.4 kg; VO_2max: 52.6 ± 4.6 mL.(kg.min)⁻¹; 2000 m rowing test 7.35 ± 0.18 min; 1RM back squat 135.6 ± 21.9 kg) performed a FFT session under two different conditions: all-out, or with the intensity controlled to elicit an rating perceived exertion (RPE) of 6 in the Borg 10-point scale (RPE6). A control session (no exercise) was also completed. Metabolic (lactate and creatine kinase), hormonal (testosterone and cortisol), and BDNF responses were assessed pre, post-0 h, 1 h, 2 h and 24 h after the sessions.

Results

Creatine kinase concentrations were significantly higher (p ≤ 0.05) after 24 h for both training sessions. Total and free testosterone concentrations were lower post-2 h for all-out when compared to the RPE6 session (p ≤ 0.05). Serum cortisol concentration increased post-0 h (p = 0.011) for RPE6 and post-0 h (p = 0.003) and post-1 h (p = 0.030) for all-out session when comparing to baseline concentrations. BDNF was significantly higher (p = 0.002) post-0 h only for the all-out session when compared to baseline. A positive correlation between blood lactate concentrations and BDNF (r = 0.51; p = 0.01) was found for both effort interventions.

Conclusions

A single FFT session when performed in all-out format acutely increases the concentrations of serum BDNF. However, physiological stress markers show that the all-out session requires a longer recovery period when compared to the RPE6 protocol. These findings can be helpful to coaches and practitioners design FFT session.

Locus coeruleus neurons encode the subjective difficulty of triggering and executing actions

The brain stem noradrenergic nucleus locus coeruleus (LC) is involved in various costly processes: arousal, stress, and attention. Recent work has pointed toward an implication in physical effort, and indirect evidence suggests that the LC could be also involved in cognitive effort. To assess the dynamic relation between LC activity, effort production, and difficulty, we recorded the activity of 193 LC single units in 5 monkeys performing 2 discounting tasks (a delay discounting task and a force discounting task), as well as a simpler target detection task where conditions were matched for difficulty and only differed in terms of sensory-motor processes. First, LC neurons displayed a transient activation both when monkeys initiated an action and when exerting force. Second, the magnitude of the activation scaled with the associated difficulty, and, potentially, the corresponding amount of effort produced, both for decision and force production. Indeed, at action initiation in both discounting tasks, LC activation increased in conditions associated with lower average engagement rate, i.e., those requiring more cognitive control to trigger the response. Decision-related activation also scaled with response time (RT), over and above task parameters, in line with the idea that it reflects the amount of resources (here time) spent on the decision process. During force production, LC activation only scaled with the amount of force produced in the force discounting task, but not in the control target detection task, where subjective difficulty was equivalent across conditions. Our data show that LC neurons dynamically track the amount of effort produced to face both cognitive and physical challenges with a subsecond precision. This works provides key insight into effort processing and the contribution of the noradrenergic system, which is affected in several pathologies where effort is impaired, including Parkinson disease and depression.

Effects of Introducing Rest Intervals in Functional Fitness Training

Background: Functional Fitness Training (FFT) is a new exercise modality prioritizing functional multi-joint movements executed at high intensity as a circuit. Objective: To examine the impacts of introducing rest intervals in a FFT workout compared to “rounds for time” (RFT) FFT. Materials and Methods: Participants were 25 resistance-trained adults who completed two FFT workouts 1 week apart. The study design was crossover such that in a given session half the participants completed the standard and the other half the adapted FFT (FFTadapted). The workouts consisted of the same exercises (circuit of four rounds of exercises), but one (FFTadapted) included preset rest intervals (three sets of 1 min after each completed round). Before and after the workouts, countermovement jump ability and blood lactate were measured. Heart rate (HR) and ratings of perceived exertion (RPE) were measured post-exercise. Results: For both the standard and adapted protocols, mean HR was 90% age-predicted maximum. Final RPE was also similar for both workouts (~15–15.5) and indicated a “hard” work intensity. Both FFTs took the same time to complete (~13 min). Furthermore, no significant differences were observed in jump ability between FFTs. In contrast, lactate (15.11 ± 3.64 vs. 13.48 ± 3.64 mmol·L−1, p < 0.05), measured 3 min post-exercise, was significantly lower in FFTadapted. Conclusions: In FFTadapted, there was a significant reduction in RPE and blood lactate concentrations after exercise, while there were no significant differences in either HR or jumping ability, compared to a FFT workout in RFT methodology.

The Effect of Static and Dynamic Stretching during Warm-Up on Running Economy and Perception of Effort in Recreational Endurance Runners

This randomized crossover counterbalanced study investigated, in recreational runners, the acute effects of pre-exercise stretching on physiological and metabolic responses, endurance performance, and perception of effort. Eight male endurance runners (age 36 ± 11 years) performed three running-until-exhaustion tests, preceded by three warm-ups, including the following different stretching protocols: static (SS), dynamic (DS), and no-stretching (NS). During the SS and DS sessions, the warm-up consisted of 10 min of running plus 5 min of SS or DS, respectively, while during the NS session, the warm-up consisted of 15 min of running. Physiological and metabolic responses, and endurance running performance parameters, were evaluated. The perception of effort was derived from the rating of perceived exertion (RPE). Running economy significantly improved after SS (p < 0.05) and DS (p < 0.01), and RPE values were significantly lower in SS (p < 0.05) and DS (p < 0.01), compared to NS. No differences in physiological and metabolic responses among the sessions were found. This study showed that including SS and DS within the warm-up ameliorated running economy and decreased the perception of effort during a running-until-exhaustion test, highlighting the benefits of stretching on endurance performance. These results should encourage recreational runners to insert stretching during warm-up, to optimize the running energy costs, reducing the perception of effort and making the training sessions more enjoyable.

Local Muscle Endurance and Strength Had Strong Relationship with CrossFit® Open 2020 in Amateur Athletes

This study analyzed the relationship between anthropometric measures, cardiorespiratory capacity, strength, power, and local muscle endurance with performance in the CrossFit^® Open 2020. For this, 17 volunteers (6 women) (29.0 ± 7.2 years) completed, on separate weeks, tests for body composition (dual-energy X-ray absorptiometry), maximal oxygen consumption (2 km row test), muscle strength (one repetition maximum (1 RM) back and front squat, isometric peak torque), muscle power (1 RM snatch and clean and jerk) and muscle endurance (Tibana test), which were compared with performance during the CrossFit^® Open 2020. Specific tests of localized muscular endurance and muscle strength had the strongest relationship with performance in the CrossFit^® Open 2020. On the other hand, the percentage of fat and cardiorespiratory capacity were not significantly correlated with CrossFit^® Open 2020 workout performance. Coaches and practitioners should therefore utilize these findings to assess physical fitness and organize the distribution of the training session based on less developed physical needs, in order to ensure an appropriate physiological adaptation for a given competition.

Comparison of Physiological Responses and Training Load between Different CrossFit® Workouts with Equalized Volume in Men and Women

The purpose of the present study was to compare the heart rate (HR), blood lactate and training load between different CrossFit^® workouts, with equalized total work volumes in men and women. The study included 23 individuals (13 men and 10 women) experienced in CrossFit^® training, who performed two workouts with different training types (as many reps as possible (AMRAP) and ‘for time’) but an equalized volume. Measurements of lactate, HR and rating of perceived exertion (RPE) were performed. The results show that there was no HR interaction between workout time and sex (p = 0.822; η² = 0.006) and between workout type and sex (p = 0.064, η² = 0.803). The HR significantly differed during each workout type (p < 0.001, η² = 0.621), but not between the two workout types (p = 0.552, η² = 0.017). Lactate showed no difference between the workout types (p = 0.474, η² = 0.768), although the training load was higher (p = 0.033, η² = 0.199) in women when they performed AMRAP. Altogether, the HR was not significantly different between training types or sex, while RPE, lactate and training load showed statistically significant differences depending on the group (women or men) or workout type (AMRAP or ‘for time’).

The Effect of Metformin on Self-Selected Exercise Intensity in Healthy, Lean Males: A Randomized, Crossover, Counterbalanced Trial

INTRODUCTION

In general, patients with type 2 diabetes have lower cardiorespiratory fitness levels and perform exercise at lower intensities compared to healthy controls. Since metformin (MET) has been shown to increase the rate of perceived exertion (RPE) during exercise with a fixed intensity, MET per se may reduce self-selected exercise intensity. The aim of this study was to assess the effect of MET on self-selected exercise intensity.

METHODS

Healthy males were eligible for this crossover, counterbalanced study with two treatment periods: MET and placebo (PLA), each lasting 17 days. Treatment dose was gradually increased and reached 2 g/day on treatment day 9, and continued at that level for the rest of the treatment period. The two periods were performed in randomized order. Two experimental days (A+B) were conducted on Day 15 (A) and Day 17 (B) of each period, respectively. Day A consisted of an exercise bout with self-selected exercise intensity (equal to RPE = 14-15 on the Borg Scale). Day B consisted of an exercise bout with fixed intensity (70% of VO₂peak). Oxygen consumption rate was assessed continuously during both exercise bouts.

RESULTS

Fifteen males (age 23.7 ± 0.6 years, BMI 22.3 ± 2.0, VO_2peak 3.5 ± 0.6 L/min) were included in the study. On Day B, RPE was higher in MET compared to PLA (14.8 ± 0.4 vs. 14.0 ± 0.3, P = 0.045). On Day A, no difference in self-selected exercise intensity measured by oxygen consumption rate (PLA 2.33 ± 0.09 L O₂/min, MET 2.42 ± 0.10 L O₂/min, P = 0.09) was seen between treatment periods.

CONCLUSIONS

Self-selected exercise intensity was not reduced by MET in healthy males, despite the fact that MET increased RPE during an exercise bout with fixed intensity.

Acute leucocyte, muscle damage, and stress marker responses to high-intensity functional training

BACKGROUND

High-intensity functional training (HIFT) has become more popular, and the number of practitioners has increased; however, it remains unclear whether perturbations in the immune parameters occur, even after one single bout. Our aim was to examine acute leucocyte, muscle damage, and stress marker responses following a single 'Cindy' workout session, and compare the results between novice and experienced participants.

MATERIAL AND METHODS

Twenty-three HIFT practitioners (age 31.0 ± 1.0 years) completed the 'Cindy' workout. They were categorized as novice (3-8 months of experience; n = 10) and experienced (≥18 months; n = 13). White blood cell (WBC) count, plasma creatine kinase (CK) activity, blood cortisol level, and lactate concentration were measured. Blood analysis was performed before (pre-ex), immediately after (post-ex), 30 min after (post-30 min), and 24 h after (post-24 h) a single 'Cindy' workout session.

RESULTS

WBC count was higher post-ex (6.8 to 11.8x103/μL) and returned to baseline values within post-30 min (p<0.01). Neutrophil (3.3 to 4.5x103/μL) and lymphocyte levels (2.8 to 5.9x103/μL) were higher post-ex and returned to baseline values after post-24 h, yet lymphocytopoenia (2.2x103/μL) was observed at post-30 min (p<0.01). CK increased post-ex (174.9 to 226.7 U.L-1) and remained elevated post-24 h. Cortisol (14.7 to 17.0 μg/dL) and lactate (1.9 to 13.5 mmol.l-1) responses increased post-ex, but only the lactate level was reduced at post-30 min (p<0.01). The experienced participants had higher WBC, lymphocyte, and cortisol concentrations post-ex than the novice ones (p<0.01).

CONCLUSIONS

A single HIFT session elicited significant acute perturbations in WBC count, stress markers, and muscle tissue, which is like other similar regimens. Importantly, the experienced participants showed greater lymphocyte and cortisol responses than the novice ones.

Characterization of Hormonal, Metabolic, and Inflammatory Responses in CrossFit® Training: A Systematic Review

Background: CrossFit® training is a high-intensity functional training program that aims to increase physical functional performance through biochemical responses, i.e., hormonal, metabolic, and inflammatory responses. Most hormonal, metabolic, and inflammatory changes induced by CrossFit® training have been reported in isolated clinical studies. The purpose of this review was to systematically explore the existing literature on characterization of hormonal, metabolic, and inflammatory responses resulting from CrossFit® training. Methods: A systematic search of the literature was conducted in PubMed, Web of Science and Scopus from August 2019 to October 2019. Studies were selected through critical review of the content. Using specific keywords, 623 articles were found, of which 597 were excluded for ineligibility, and 25 were eligible. The papers were separated according to subject area: hormonal (n = 8), metabolic (n = 19), and inflammatory (n = 6) changes. All were published between 2015 and 2019. Results: This review reveals potential effects of CrossFit® training on hormonal, metabolic, and inflammatory responses. However, studies had low levels of evidence and reliability due to methodological limitations. Conclusion: In summary, the results showed a greater volume and intensity of workouts accentuate the responses, that are of paramount importance for improving understanding of the effects of CrossFit® training and serve as a basis for prescribing future exercise protocols.

Session Rating of Perceived Exertion Is a Superior Method to Monitor Internal Training Loads of Functional Fitness Training Sessions Performed at Different Intensities When Compared to Training Impulse

Despite its increase in popularity, little is known about how to best quantify internal training loads from functional fitness training (FFT) sessions. The purpose of this study was to assess which method [training impulse (TRIMP) or session rating of perceived exertion (sRPE)] is more accurate to monitor training loads in FFT. Eight trained males (age 28.1 ± 6.0 years) performed an ALL-OUT FFT session and an intensity-controlled session (RPE of six out of 10). Internal load was determined via Edward's TRIMP (eTRIMP), Bannister's TRIMP (bTRIMP), and sRPE. Heart rate was measured continuously during the session, while blood lactate and rate of perceived exertion were measured at baseline, and immediately and 30 min after the sessions. ALL-OUT blood lactate and RPE were significantly higher immediately and 30 min after the session compared to the RPE6 condition. ALL-OUT training load was significantly different between conditions using bTRIMP (61.1 ± 10.6 vs. 55.7 ± 12.4 AU) and sRPE (91.7 ± 30.4 vs. 42.6 ± 14.9 AU), with sRPE being more sensitive to such differences [p = 0.045, effect size (ES) = 0.76 and p = 0.002, ES = 1.82, respectively]. No differences in the training loads of the different sessions were found using eTRIMP (93.1 ± 9.5 vs. 84.9 ± 13.7 AU, p = 0.085). Only sRPE showed a significant correlation with lactate 30 min post session (p = 0.015; p = 0.596, large). sRPE was more accurate than both TRIMP methods to represent the overall training load of the FFT sessions. While the use of sRPE is advised, further research is necessary to establish its ability to reflect changes in fitness, fatigue, and performance during a period of training.

The Relationship between CrossFit® Performance and Laboratory-Based Measurements of Fitness

To date, research has examined the physiological determinants of performance in standardized CrossFit^® (CF) workouts but not without the influence of CF familiarity. Therefore, the purpose of this present study was to examine the predictive value of aerobic fitness, body composition, and total body strength on performance of two standardized CF workouts in CF-naïve participants. Twenty-two recreationally trained individuals (males = 13, females = 9) underwent assessments of peak oxygen consumption (VO₂ peak), ventilatory thresholds, body composition, and one repetition maximum tests for the back squat, deadlift, and overhead press in which the sum equaled the CF Total. Participants also performed two CF workouts: a scaled version of the CF Open workout 19.1 and a modified version of the CF Benchmark workout Fran to determine scores based on total repetitions completed and time-to-completion, respectively. Simple Pearson’s r correlations were used to determine the relationships between CF performance variables (19.1 and modified Fran) and the independent variables. A forward stepwise multiple linear regression analysis was performed and significant variables that survived the regression analysis were used to create a predictive model of CF performance. Absolute VO₂ peak was a significant predictor of 19.1 performance, explaining 39% of its variance (adjusted R² = 0.39, p = 0.002). For modified Fran, CF Total was a significant predictor and explained 33% of the variance in performance (adjusted R² = 0.33, p = 0.005). These results suggest, without any influence of CF familiarity or experience, that performance in these two CF workouts could be predicted by distinct laboratory-based measurements of fitness.

Anxiety and Emotional Intelligence: Comparisons Between Combat Sports, Gender and Levels Using the Trait Meta-Mood Scale and the Inventory of Situations and Anxiety Response

The present study compared emotional intelligence and anxiety between six combat sports of lower, intermediate and high-level female and male athletes. The sample was composed by 444 athletes (age: 24.7 ± 8.8 years, body mass: 72.4 ± 12.1 kg, height: 1.82 ± 0.3 m, and practice time: 13.1 ± 7.4 years) separated by sex (male n = 273, female n = 171) from different combat sports (jiu-jitsu n = 142, judo n = 137, karate n = 57, kendo n = 63, taekwondo n = 25, and freestyle wrestling n = 20) of three levels (high-level n = 57, intermediate n = 137 and low-level n = 142). Inventory of situations and anxiety response (ISRA) provided an independent evaluation for the three systems: cognitive, motor and physiological, as well as a total with four factors of analysis (anxiety before the evaluation, interpersonal, phobic and before habitual, and daily situations). Trait Meta-Mood Scale (TMMS-24) verified emotional intelligence scales. Descriptive results are demonstrated by percentage or median (first quartile Q1; third quartile Q3), Kruskal-Wallis and Mann-Whitney tests were conducted to compare groups, p ≤ 0.05. The main results demonstrated 10% more total anxiety for wrestling and judo compared to the other groups (p ≤ 0.05). Female athletes showed 15% more anxiety than men, while emotional attention demonstrated 10% better results for women. Significant differences were observed between high- versus low-level athletes in the total anxiety with 85 (44; 143) versus 122 (69; 186) of ISRA index and emotional repair with 30 (25; 34) versus 27 (22; 32) of TMMS-24 index. Emotional intelligence seems to be higher in female and in higher level, while anxiety appears to be prevalent in judo and wrestling, low-level and in female athletes. These outcomes provide support for the hypothesis that emotional abilities are an important contributor to emotional intelligence, particularly differentiating high level athletes than other levels. Results can be incorporated into strategies for reducing anxiety and improving emotional intelligence, considering particularities of gender and level groups.

Carbohydrate supplementation and psychophysiological responses during moderate exercise in hypoxia

Background

Rating of Perceived Exertion (RPE) is a subjective scale to monitor overload and fatigue during exercise. Hypoxia may worsen the perception of fatigue, compromising the self-reported perception of effort and increasing RPE. The objective was to evaluate the effects of carbohydrate (CHO) supplementation on RPE during exercise in hypoxia simulating 4200 m.

Methods

Eight male physically active volunteers performed two exercises at 50% VO_2peak and 1% slope: exercise in hypoxia + placebo or exercise in hypoxia + CHO (6% maltodextrin) with supplementation at 20, 40, and 60 min during exercise. Oxygen Saturation (SaO₂%) was assessed at baseline and after exercise, while RPE and HR were measured each 10 min during the trial.

Results

SaO₂% decreased after exercise in both conditions of hypoxia compared to rest. The RPE did not differ between groups. However, the RPE increased in hypoxia after 20 min of exercise in relation to 10 min. The Area Under the Curve (AUC) of RPE was lower in hypoxia + CHO compared to hypoxia. The AUC of the HR/RPE ratio in the hypoxia + CHO group was higher in relation to hypoxia.

Conclusions

Our results indicate that CHO supplementation does not change RPE induced by 60 min of exercise at 50% VO_2peak in hypoxia equivalent to 4200 m at the different times analyzed. However, in hypoxia + CHO the (AUC)-60 min of total RPE decreased during exercise, while the heart rate/RPE ratio improved, indicating lower RPE in the hypoxic environment.

“Cross” modalities: are the AMRAP, RFT and EMOM models applicable to health?

Abstract Currently, training models based on the maximum number of repetitions/rounds or on the execution of a proposed task in the shortest possible time have been gaining ground among Physical Education professionals. However, in our opinion, these models have significant drawbacks that oppose their use in the health context. Thus, we provide an analysis of the problems related to the control and magnitude of the training load (volume and intensity), distribution, duration, and characteristics of the recovery intervals and, of course, the intra-session density. This analysis was made without having measured each of these proposals directly. It is based on the reflection of the dynamics of the efforts made and potential fatigue generated. We hope to be able to verify and provide accurate and reliable data that may support and confirm the hypothesis generated through this analysis.