Running Critical Power and W´: Influence of the Environment, Timing and Time Trial Order.

This study aimed to determine the influence of the testing environment (track vs. treadmill), time trial order (long-short vs. short-long), and timing (within-session vs. between-sessions) on the critical power (CP) and work over CP (W´), using the power metric in runners. Fifteen highly trained athletes performed three test sessions composed of two time trials of 9- and 3-min, separated by a 30-min rest period. One session was performed on a track, and two sessions on a treadmill, alternating the order of the time trials. The CP and W´ values determined on the track were significantly greater and lower than on the treadmill, respectively (p<0.001; CP≥89 W; W´≥3.7 kJ). Their degree of agreement was low (SEE CP>5%; W´>10%) and therefore was not interchangeable. There were no performance differences in the timing of the time trials (p=0.320). Lastly, performing the 9-min trial first resulted in a greater power output compared to when executed last (p<0.001; 4.9 W), although this resulted in similar CP and W´ values (Bias<5 and 10%, respectively). In conclusion, it is feasible to test CP and W´ in a single testing session, irrespective of the time trial order, although not interchangeably between track and treadmill.

Running Functional Threshold versus Critical Power: Same Concept but Different Values.

The aims of this study were (i) to estimate the functional threshold power (FTP) and critical power (CP) from single shorter time trials (TTs) (i. e. 10, 20 and 30 minutes) and (ii) to assess their location in the power-duration curve. Fifteen highly trained athletes randomly performed ten TTs (i. e. 1, 2, 3, 4, 5, 10, 20, 30, 50 and 60 minutes). FTP was determined as the mean power output developed in the 60-min TT, while CP was estimated in the running power meter platform according to the manufacturer's recommendations. The linear regression analysis revealed an acceptable FTP estimate for the 10, 20 and 30-min TTs (SEE≤12.27 W) corresponding to a correction factor of 85, 90 and 95%, respectively. An acceptable CP estimate was only observed for the 20-min TT (SEE=6.67 W) corresponding to a correction factor of 95%. The CP was located at the 30-min power output (1.0 [-5.1 to 7.1] W), which was over FTP (14 [7.0 to 21] W). Therefore, athletes and practitioners concerned with determining FTP and CP through a feasible testing protocol are encouraged to perform a 20-min TT and apply a correction factor of 90 and 95%, respectively.

Inter-repetition Rest Impact on Percentage of Repetition Completed at Certain Velocity Loss.

This study examined the impact of different inter-repetition rest (IRR) configurations (zero seconds [IRR0], three seconds [IRR3], and self-selected less than five seconds [SSIRR]) on estimating the number of repetitions (Nrep) and the percentage of completed repetitions relative to the maximum number of repetitions possible to failure (%rep) after reaching 10%, 20%, and 30% velocity loss thresholds (VLT). Eighteen men completed three sessions, each with a different IRR configuration, separated by 48-72 hours. Single sets of repetitions to momentary muscular failure were performed against 65%, 75%, and 85% of the one-repetition maximum during free-weight back squat and bench press exercises. No significant differences were reported between IRR configurations for the Nrep (P≥0.089) and %rep (P≥0.061), except for %rep after reaching the 20-30%VLT against 65%1RM and the 10-20%VLT against 75%1RM in the bench press exercise (P≤0.048). Additionally, both Nrep and %rep exhibited high interindividual variability (between-subject CV=14-79%) across the different IRR configurations. The individual %rep-%VLT relationships were slightly stronger than the general %rep-%VLT relationships (median R 2 =0.914-0.971 vs. 0.698-0.900). Overall, regardless of the IRR configuration, this novel velocity-based approach does not guarantee the same effort levels across subjects in the free-weight back squat and bench press sets.

The Variability of the Components of Fitness along the Menstrual Cycle.

This study aims to determine the variability of the components of fitness along the menstrual cycle (MC) of physically active eumenorrheic women. Fifteen subjects were monitored along two consecutive MCs through the calendar-based counting method in combination with a urine luteinizing hormone surge kit. Subjects were tested at the early follicular phase (EFP), pre-ovulatory or late follicular phase (LFP), and post-ovulatory or mid-luteal phase (MLP). In each session, the back squat one-repetition maximum (1-RM), maximum fat oxidation (MFO), maximum oxygen uptake (VO2max) and acute recovery capacity were determined. The results revealed a wide variability among components of fitness and a low to high variability among subjects (acute recovery: 3.6% [range 1.5 to 9.5%]; back squat 1-RM: 6.1% [range 2.2 to 11%]; VO2max: 6.6% [range 1.1 to 15%]; MFO: 23% [range 4.6 to 35%]). Despite the individual nature, considering the number and magnitude of the responses in each MC phase, VO2max and acute recovery capacity tended to be enhanced at the LFP, the MFO at the MLP, and the back squat 1-RM remained stable along the MC. Thus, practitioners are aware of which components are susceptible to change along the MC phase, but an individual monitoring is recommended.

Sex and Equipment Impact on Lifting Velocity and the Maximum Repetitions in Bench Press.

This study investigated how equipment and sex affect the prediction accuracy of the maximum number of repetitions performed to failure (RTF) using the fastest mean velocity of the set (MVfastest). Sixteen men and twelve women completed four sessions (two using free-weight equipment and two sessions using the Smith machine). Each session involved three sets of repetitions to failure against the 65%, 75%, and 85% of the one-repetition maximum, interspersed by 10-min of rest. The goodness-of-fit of the individualized RTF-MVfastest relationships was comparable between both equipment types and sexes (P≥0.510). Moreover, there were not significant differences in the MVfastest associated with RTF between equipment types (P≥0.258). However, the MVfastest associated with RTF was higher for men than for women in repetitions 6 to 15 (P≤0.043; ES≥0.69). In addition, the absolute errors when predicting RTF showed no significant differences between equipment types and loads (P<0.444). Specifically, these RTF estimates were within an acceptable range for men (<2 repetitions), but not for women (≥2 repetitions) (main effect of sex: P≤0.018; ES≥0.58). These findings suggest that individualized RTF-MVfastest equations estimate the RTF with an acceptable precision in men during bench press exercises in both equipment types but exhibit lower precision for women.

Can We Predict Long-Duration Running Power Output? Validity of the Critical Power, Power Law, and Logarithmic Models.

ABSTRACT: Ruiz-Alias, SA, Ñancupil-Andrade, AA, Pérez-Castilla, A, and García-Pinillos, F. Can we predict long-duration running power output? Validity of the critical power, power law, and logarithmic models. J Strength Cond Res 38(2): 306-310, 2024-Predicting long-distance running performance has always been a challenge for athletes and practitioners. To ease this task, different empirical models have been proposed to model the drop of the running work rate with the increase of time. Therefore, this study aims to determine the validity of different models (i.e., CP, power law, and Peronnet) to predict long-duration running power output (i.e., 30 and 60 minutes). In a 4-week training period, 15 highly trained athletes performed 7-time trials (i.e., 3, 4, 5, 10, 20, 30, and 60 minutes) in a randomized order. Then, their power-duration curves (PDCs) were defined through the work-time critical power model (CP work ), power-1/time (CP 1/time ), 2-parameter hyperbolic (CP 2hyp ), 3-parameter hyperbolic (CP 3hyp ), the undisclosed Stryd (CP stryd ), and Golden Cheetah (CP cheetah ) proprietary models, and the power law and Peronnet models using the 3 to 20 minutes time trials. These ones were extrapolated to the 30- and 60-minute power output and compared with the actual performance. The CP 2hyp , CP 3hyp , CP stryd , and CP cheetah provided valid 30- and 60-minute power output estimations (≤2.6%). The CP work and CP 1/time presented a large predicting error for 30 minutes (≥4.4%), which increased for 60 minutes (≥8.1%). The power law and Peronnet models progressively increased their predicting error at the longest duration (30 minutes: ≤-1.6%; 60 minutes: ≤-6.6%), which was conditioned by the endurance capability of the athletes. Therefore, athletes and practitioners are encouraged to applicate the aforementioned valid models to their PDC to estimate the 30-minute and 60-minute power output.

Acute Effect of Different Velocity-Based Training Protocols on 2000-meter Rowing Ergometer Performance.

ABSTRACT: Leandro Quidel-Catrilelbún, ME, Ruiz-Alias, SA, García-Pinillos, F, Ramirez-Campillo, R, and Pérez-Castilla, A. Acute effect of different velocity-based training protocols on 2000-m rowing ergometer performance. J Strength Cond Res 38(1): e8-e15, 2024-This study aimed to explore the acute effect of 4 velocity-based resistance training (VBT) protocols on 2000-m rowing ergometer (RE2000) time trial, as well as the behavior of the maximal neuromuscular capacities when RE2000 is performed alone or preceded by VBT protocols in the same session. Fifteen male competitive rowers (15-22 years) undertook 5 randomized protocols in separate occasions: (a) RE2000 alone (control condition); (b) VBT against 60% of 1 repetition maximum (1RM) with a velocity loss in the set of 10% followed by RE2000 (VBT60-10 + RE2000); (c) VBT against 60% 1RM with a velocity loss in the set of 30% followed by RE2000 (VBT60-30 + RE2000); (d) VBT against 80% 1RM with a velocity loss in the set of 10% followed by RE2000 (VBT80-10 + RE2000); (e) VBT against 80% 1RM with a velocity loss in the set of 30% followed by RE2000 (VBT80-30 + RE2000). The load-velocity relationship (load-axis intercept [L0], velocity-axis intercept [v0], and area under the load-velocity relationship line [Aline]) was used to evaluate the maximal neuromuscular capacities during the prone bench pull exercise before and after each protocol. The time trial was significantly longer for VBT60-30 + RE2000 and VBT80-30 + RE2000 than for RE2000, VBT60-10 + RE2000 and VBT80-10 + RE2000 (all p < 0.001; ES = 0.10-0.15). L0 and Aline were significantly reduced after all protocols (p < 0.001; ES = 0.10-0.13), with Aline reduction more accentuated for VBT60-10 + RE2000, VBT60-30 + RE2000, VBT80-30 + RE2000, and RE2000 (all p = 0.001; ES = 0.11-0.18) than for VBT80-10 + RE2000 (p = 0.065; ES = 0.05). Therefore, VBT protocols with greater velocity loss in the set (30% vs. 10%) negatively affected subsequent rowing ergometer performance, in line with impairment in Aline pulling performance.

Inter-Repetition Rest Impact on the Estimated Repetitions in Reserve at Various Loads and Proximities to Neuromuscular Failure.

ABSTRACT: Ruiz-Alias, SA, Ramirez-Campillo, R, Leando Quidel-Catrilelbún, ME, García-Pinillos, F, and Pérez-Castilla, A. Inter-repetition rest Impact on the estimated repetitions in reserve at various loads and proximities to neuromuscular failure . J Strength Cond Res XX(X): 000-000, 2024-The repetitions in reserve (RIR) estimation method allows for monitoring resistance training set volume. However, a significant bias is commonly observed when ending the set further from neuromuscular failure and using lower relative loads. Is unclear if implementing an IRR could improve its estimation validity. This study aimed to determine if the RIR estimation is influenced by the IRR at different relative loads and proximities to neuromuscular failure during the back squat (BQ) and bench press (BP) exercises. After a familiarization session, 19 male subjects (age, 21-26 years) completed an experimental session for each IRR configuration: IRR0 (without rest), IRR3 (3 seconds of rest), and SSIRR (self-selected rest [up to 5 seconds]). In each session, single sets to neuromuscular failure were performed at 3 relative loads (65% 1 repetition maximum [1RM], 75% 1RM, 85% 1RM) for BQ and BP exercises. Using the Estimated Repetitions to Failure scale, subjects estimated the RIR associated with a score of "5" and "2" (i.e., RIR-5 and RIR-2). The results revealed no interactions between the RIR estimation and IRR for BQ (RIR-5: p = 0.812; RIR-2: p = 0.084) or BP (RIR-5: p = 0.884; RIR-2: p = 0.944). Subjects provided valid estimations, with overestimation (BQ RIR-5: 0%; BQ RIR-2: 2.9%; BP RIR-5: 1.1%; BP RIR-2: 2.3%) or underestimation (BQ RIR-5: 14.9%; BQ RIR-2: 4%; BP RIR-5: 15.2% BP RIR-2: 8.2%) in few sets. In conclusion, the RIR estimation method seems valid, and the IRR (0-5 seconds) does not influence its validity at 65-85% 1RM loads nor proximities to neuromuscular failure (RIR-2, RIR-5).

Can we predict long-duration running power output? A matter of selecting the appropriate predicting trials and empirical model.

When facing a long-distance race, athletes and practitioners could develop an efficient pacing strategy and training paces if an accurate performance estimate of the target distance is achieved. Therefore, this study aims to determine the validity of different empirical models (i.e. critical power [CP], Power law and Peronnet) to predict long-duration power output (i.e. 60 min) when using two or three time trial configurations. In a 5-week training period, fifteen highly trained athletes performed nine-time trials (i.e. 1, 2, 3, 4, 5, 10, 20, 30, and 60 min) in a randomized order. Their power-duration curves were defined through the work-time (CPwork), power-1/time (CP1/time), two-parameter hyperbolic (CP2hyp), three-parameter hyperbolic (CP3hyp) CP models using different two- and three-time trial configurations. The undisclosed proprietary CP models of the Stryd (CPstryd) and Golden Cheetah training software (CPcheetah) were also computed as well as the non-asymptotic Power law and Peronnet models. These were extrapolated to the 60-min power output and compared to the actual performance. The shortest valid configuration (95% confidence interval < 12 W) for CPwork and CP1/time was 3-30 min (Bias: 8.3 [4.9 to 11.7] W), for CPstryd was 10-30 min (Bias: 4.2 [- 1.0 to 9.4] W), for CP2hyp, CP3hyp and CPcheetah was 3-5-30 min (Bias < 5.7 W), for Power law was 1-3-10 min (- 1.0 [- 11.9 to 9.9] W), and for Peronnet was 4-20 min (- 3.0 [- 10.2 to 4.3] W). All the empirical models provided valid estimates when the two or three predicting trial configurations selected attended each model fitting needs.

The Effect of Using Marathon Shoes or Track Spikes on Neuromuscular Fatigue caused by a Long-distance Track Training Session.

This study aims to compare the effect of the Nike ZoomX Dragonfly track spikes and the Nike ZoomX VaporflyNext% 2 marathon shoes on the fatigue manifestations present over and after a long-distance track training session. Thirteen highly trained athletes completed two training sessions (i. e., 9- and 3-minute time trials with complete recovery) with the aforementioned footwear models. The pace, ground contact time, and stride length were measured over the time trials, and maximal countermovement jumps were performed previously and after the training session. The results revealed that, although there was no significant interaction in the pace distribution (p≥0.072), athletes tend to be only able to increase the pace at the last lap with the marathon shoes (5.4 meters [-3.7 to 14.5 meters]) meanwhile with the track spikes it further decreased (-3.1 meters [-9.8 to 3.6 meters]). A reduced ground contact time over the session (p=0.025) and a tendency toward increasing stride length (p=0.09) in the last time trial were observed. The significant interaction on the countermovement jump height (p=0.023; Track spikes: -5.60%; Marathon shoes: 0.61%) also indicates that footwear influences the resulted allostatic load.

Running Critical Power: A Comparison Of Different Theoretical Models.

This study aimed (i) to compare the critical power (CP) and work capacity over CP (W´) values reported by the different CP models available in current analysis software packages (Golden Cheetah and Stryd platform), (ii) to locate the CP values in the power-duration curve (PDC), and (iii) to determine the influence of the CP model used on the W´ balance. Fifteen trained athletes performed four time trials (i. e., 3, 5, 10, 20 minutes) to define their PDC through different CP models: work-time (CPwork), power-1/time (CP1/time), Morton hyperbolic (CPhyp), Stryd platform (CPstryd), and Bioenergetic Golden Cheetah (CPCheetah). Three additional time trials were performed: two to locate the CP values in the PDC (30 and 60 minutes), and one to test the validity of the W' balance model (4 minutes). Significant differences (p<0.001) were reported between models for the estimated parameters (CP, W´). CPcheetah was associated with the power output developed between 10 to 20 minutes, CP1/time, CPstryd CPwork and CPhyp. The W´ reported by the three-parameter CP models overestimated the actual 4 minutes time to exhaustion, with CPwork (0.48 [- 0.19 to 1.16] minutes); and CP1/time (0.40 [- 0.13 to 0.94] minutes) being the only valid models (p≥0.240).

Level of Agreement between the MotionMetrix System and an Optoelectronic Motion Capture System for Walking and Running Gait Measurements.

Markerless motion capture systems (MCS) have been developed as an alternative solution to overcome the limitations of 3D MCS as they provide a more practical and efficient setup process given, among other factors, the lack of sensors attached to the body. However, this might affect the accuracy of the measures recorded. Thus, this study is aimed at evaluating the level of agreement between a markerless MSC (i.e., MotionMetrix) and an optoelectronic MCS (i.e., Qualisys). For such purpose, 24 healthy young adults were assessed for walking (at 5 km/h) and running (at 10 and 15 km/h) in a single session. The parameters obtained from MotionMetrix and Qualisys were tested in terms of level of agreement. When walking at 5 km/h, the MotionMetrix system significantly underestimated the stance and swing phases, as well as the load and pre-swing phases (p < 0.05) reporting also relatively low systematic bias (i.e., ≤ -0.03 s) and standard error of the estimate (SEE) (i.e., ≤0.02 s). The level of agreement between measurements was perfect (r > 0.9) for step length left and cadence and very large (r > 0.7) for step time left, gait cycle, and stride length. Regarding running at 10 km/h, bias and SEE analysis revealed significant differences for most of the variables except for stride time, rate and length, swing knee flexion for both legs, and thigh flexion left. The level of agreement between measurements was very large (r > 0.7) for stride time and rate, stride length, and vertical displacement. At 15 km/h, bias and SEE revealed significant differences for vertical displacement, landing knee flexion for both legs, stance knee flexion left, thigh flexion, and extension for both legs. The level of agreement between measurements in running at 15 km/h was almost perfect (r > 0.9) when comparing Qualisys and MotionMetrix parameters for stride time and rate, and stride length. The agreement between the two motion capture systems varied for different variables and speeds of locomotion, with some variables demonstrating high agreement while others showed poor agreement. Nonetheless, the findings presented here suggest that the MotionMetrix system is a promising option for sports practitioners and clinicians interested in measuring gait variables, particularly in the contexts examined in the study.

Velocity Loss Is Not an Accurate Predictor of the Percentage of Completed Repetitions During the Prone Bench Pull Exercise.

ABSTRACT: Pérez-Castilla, A, Miras-Moreno, S, Janicijevic, D, and García-Ramos, A. Velocity loss is not an accurate predictor of the percentage of completed repetitions during the prone bench pull exercise. J Strength Cond Res 37(5): 1001-1008, 2023-The primary aim of this study was to explore the goodness of fit and accuracy of both general and individual relationships between the magnitude of velocity loss (%VL) and the percentage of performed repetitions with respect to the maximal number of repetitions that can be completed to failure (%Rep) during the Smith machine prone bench pull exercise. Fifteen male sports science students completed a preliminary session to determine the bench pull one-repetition maximum (1RM) and 2 identical experimental sessions separated by 48-72 hours. In each experimental session, subjects randomly performed single sets of repetitions to failure separated by 10 minutes against the 60% 1RM, 70% 1RM, and 80% 1RM during the Smith machine bench pull exercise. Individual %Rep-%VL relationships presented a greater goodness of fit than general %Rep-%VL relationships at the 60% 1RM ( R2 = 0.85-0.97 vs. 0.79-0.85), 70% 1RM ( R2 = 0.84-0.99 vs. 0.77-0.84), and 80% 1RM ( R2 = 0.84-1.00 vs. 0.74-0.80). However, the accuracy (absolute errors) in estimating the %Rep during the second testing session based on the %Rep-%VL equations obtained in the first testing session did not differ between the individual and general %Rep-%VL equations in 8 of 9 comparisons ( p ≥ 0.102). The absolute errors between the actual and predicted %REP were unacceptable (>10%) in 11 of 18 comparisons, and acceptable (5-10%) in 7 of 18 comparisons. These results highlight that the %Rep cannot be estimated with high degree of accuracy from VL recordings during the Smith machine bench pull exercise, regardless of whether individual or general Rep-%VL relationships are considered.

Two-point Method Applied in Field Conditions: A Feasible Approach to Assess the Load-Velocity Relationship Variables During the Bench Pull Exercise.

ABSTRACT: Miras-Moreno, S, García-Ramos, A, Jukic, I, and Pérez-Castilla, A. Two-point method applied in field conditions: a feasible approach to assess the load-velocity relationship variables during the bench pull exercise. J Strength Cond Res 37(7): 1367-1374, 2023-This study explored the between-session reliability and concurrent validity of the load-velocity (L-V) relationship variables obtained from different methods during the Smith machine bench pull exercise. In a counterbalanced order, 23 resistance-trained male subjects performed 2 sessions against 6 different loads in one week and 2 sessions against the lightest and heaviest loads in another week. The L-V relationship variables (load-axis intercept [ L0 ], velocity-axis intercept [ v0 ], and area under the L-V relationship line [ Aline ]) were obtained using the mean and peak velocity by the standard multiple-point (all 6 loads were used for the L-V modeling), modified multiple-point (the data point that most reduced the coefficient of determination was omitted from the L-V modeling), and 2-point (only 2 loads were used for the L-V modeling) methods. The reliability of the L-V relationship variables was acceptable for all methods (within-subjects coefficient of variation [CV] = 2.09-9.21%). The standard multiple-point and 2-point methods provided greater reliability for all L-V relationship variables compared with the modified multiple-point method (CV ratio ≥ 1.27), while the 2-point method provided similar (CV ratio = 1.04 for Aline ) or greater (CV ratio = 1.50 for L0 and 1.62 for v0 ) reliability than the standard multiple-point method. The concurrent validity of the modified multiple-point and 2-point methods was acceptable for the L-V relationship variables (effect size ≤ 0.62; r ≥ 0.76). These results suggest that the 2-point method is not only a valid procedure but also more reliable, simpler, faster, and less prone to fatigue than multiple-point methods for assessing maximal neuromuscular capacities through the L-V relationship.

Relationship Between the Number of Repetitions in Reserve and Lifting Velocity During the Prone Bench Pull Exercise: An Alternative Approach to Control Proximity-to-Failure.

ABSTRACT: Pérez-Castilla, A, Miras-Moreno, S, Weakley, J, and García-Ramos, A. Relationship between the number of repetitions in reserve and lifting velocity during the prone bench pull exercise: an alternative approach to control proximity-to-failure. J Strength Cond Res 37(8): 1551-1558, 2023-This study aimed to explore the goodness-of-fit and accuracy of both general and individual relationships between the number of repetitions in reserve (RIR) and the repetition velocity during the Smith machine prone bench pull exercise. Fifteen male sports science students completed 3 sessions separated by 48-72 hours. The first session was used to determine the bench pull 1 repetition maximum (1RM). The second and third sessions were identical and consisted of 3 single sets (60, 70, and 80% 1RM) of repetitions to momentary muscular failure separated by 10 minutes during the Smith machine prone bench pull exercise. General (i.e., pooling together the data from the 15 subjects) and individual RIR-velocity relationships were constructed from the data collected in the second session by pooling the data from the 3 loads (multiple-loads) or specifically for each load (load-specific). The 4 RIR-velocity relationship models were ranked by their goodness-of-fit as follows: individual load-specific ( r = 0.93) > individual multiple-loads ( r = 0.83) > general multiple-loads ( r = 0.65) > general load-specific ( r = 0.61). The accuracy when predicting the RIR in the third session based on the RIR-velocity equations obtained in the second session was acceptable and comparable for the 4 RIR-velocity relationship models (absolute errors ≤2 RIR). However, the 4 RIR-velocity relationship models significantly underestimated the RIR for ≥1 RIR and overestimated the RIR for 0 RIR. These results suggest that the 4 RIR-velocity relationship models are equally effective to quantify proximity-to-failure during the Smith machine prone bench pull exercise.

Influence of the World Athletics Stack Height Regulation on Track Running Performance.

ABSTRACT: Ruiz-Alias, SA, Pérez-Castilla, A, Soto-Hermoso, VM, and García-Pinillos, F. Influence of the world athletics stack height regulation on track running performance. J Strength Cond Res 37(11): 2260-2266, 2023-A new footwear regulation based on limiting the stack height (i.e., amount of material between the feet and the ground) has been established by World Athletics to ensure that performance is achieved through the primacy of human effort over technology in running shoes. Analyzing the effect of legal and illegal shoes on running performance is therefore needed to determine its effectiveness. Thus, this study aimed (a) to compare the effect of 2 footwear models categorized as legal and illegal by the World Athletics regulation on track running performance and (b) to analyze the derived metrics of the athletes' biomechanics when using each footwear model at racing paces. Within 1 week, 14 highly trained athletes performed 2 testing sessions composed of 2 time trials of 9- and 3-minute duration with 30 minutes of recovery between them. The athletes wore the "Nike ZoomX Dragonfly" track spikes model and the "Nike ZoomX Vaporfly Next % 2" marathon shoe model in a counterbalanced randomized order. The results revealed that (a) there was only a small worthwhile improvement in the 3-minute time trial when using the marathon shoes of 0.97% (-0.04 to 1.98%) and (b) there was a main effect of footwear in 7 of the 9 biomechanical variables analyzed (p ≤ 0.050). The ground contact time was the unique performance predictor (p = 0.005, adjusted R2 = 0.476). Altogether, the use of legal and illegal running shoes altered the runners form, which only influenced the mid-distance performance.

Kinetic and Kinematic Assessment of the Band-Assisted Countermovement Jump.

ABSTRACT: Fernandes, JFT, Arede, J, Clarke, H, Garcia-Ramos, A, Perez-Castilla, A, Norris, JP, Wilkins, CA, and Dingley, AF. Kinetic and kinematic assessment of the band-assisted countermovement jump. J Strength Cond Res 37(8): 1588-1593, 2023-This study sought to elucidate kinetic and kinematic differences between unloaded and band-assisted countermovement jumps (CMJs). In a randomized order, 20 healthy subjects (mass 84.5 ± 18.6 kg) completed 3 repetitions of CMJs across 3 conditions: unloaded (at body mass), low, and moderate band (8.4 ± 1.9 and 13.3 ± 3.3 kg body mass reduction, respectively). For all repetitions, a force platform and linear position transducer were used to record and calculate kinetic and kinematic data. Body mass was significantly different between the unloaded, low, and moderate band conditions ( p < 0.05). Peak velocity, absolute peak, and mean force and movement duration displayed a trend that was mostly related to the condition (i.e., unloaded > low > moderate) ( p < 0.05). The opposing trend (i.e., moderate > low > unloaded) was generally observed for relative peak and mean force, reactive strength index modified, and flight time ( p < 0.05). No differences were observed for mean velocity, movement duration, and absolute and relative landing forces ( p > 0.05). The use of band assistance during CMJs can alter force, time, and velocity variables. Practitioners should be aware of the potential positive and negative effects of band assistance during CMJs.

Selective Effect of Different High-Intensity Running Protocols on Resistance Training Performance.

ABSTRACT: Pérez-Castilla, A, García-Pinillos, F, Miras-Moreno, S, Ramirez-Campillo, R, García-Ramos, A, and Ruiz-Alias, SA. Selective effect of different high-intensity running protocols on resistance training performance. J Strength Cond Res 37(6): e369-e375, 2023-This study aimed to explore the acute effect of 2 high-intensity running protocols (high-intensity interval training [HIIT] and sprint interval training [SIT]) on resistance training (RT) performance and their combined effect on the lower-body maximal neuromuscular capacities. Eighteen healthy subjects randomly completed 3 experimental protocols: only RT, HIIT + RT, and SIT + RT. Characteristics of the RT protocol include 3 back-squat sets of 10 repetitions or 20% velocity loss against 60% of 1 repetition maximum with 3 minutes of interset rest. Characteristics of the high-intensity running protocols include HIIT (4 intervals of 4 minutes at ∼110% of functional threshold power with 3 minutes of interinterval rest) and SIT (6 all-out sprints of 30 seconds with 4 minutes and 24 seconds of interinterval rest). The force-velocity relationship (maximal values of force [ F0 ], velocity [ v0 ], and power [P max ]) was evaluated at the beginning and at the end of each experimental protocol. The number of back-squat repetitions ( p = 0.006; effect size [ES] = -0.96), fastest velocity ( p = 0.003; ES = -0.63), and average velocity ( p = 0.001; ES = -0.73) were lower for the SIT + RT protocol compared with the RT protocol, but no significant differences were observed between the RT and HIIT + RT ( p ≥T0.057; ES ≤.-0.46, except -0.82 for the number of back-squat repetitions) and HIIT + RT and SIT + RT ( p ≥T0.091; ES .0-0.35) protocols. The 3 protocols induced comparable decreases in v0 and P max ( F(2,34) 2,0.96; p ≥ 0.393), but F0 tended to decrease after the SIT + RT protocol and to increase after the RT and HIIT + RT protocols ( F(2,34) = 4.37; p = 0.035). Compared with RT alone, the data suggest that SIT deteriorates RT quality and F0 capacity more than long-interval HIIT.

The Criterion Validity and Between-Day Reliability of the Perch for Measuring Barbell Velocity During Commonly Used Resistance Training Exercises.

ABSTRACT: Weakley, J, Munteanu, G, Cowley, N, Johnston, R, Morrison, M, Gardiner, C, Pérez-Castilla, A, and García-Ramos, A. The criterion validity and between-day reliability of the Perch for measuring barbell velocity during commonly used resistance training exercises. J Strength Cond Res 37(4): 787-792, 2023-This study aimed to assess the criterion validity and between-day reliability (accounting for technological and biological variability) of mean and peak concentric velocity from the Perch measurement system. On 2 testing occasions, 16 subjects completed repetitions at 20, 40, 60, 80, 90, and 100% of 1-repetition maximum in the free-weight barbell back squat and bench press. To assess criterion validity, values from the Perch and a 3-dimensional motion capture system (criterion) were compared. Technological variability was assessed by determining whether the differences between the Perch and criterion for each load were comparable for both testing sessions, whereas between-day reliability with both technological and biological variability was calculated from Perch values across days. Generalized estimating equations were used to calculate R2 and root mean square error, whereas Bland-Altman plots assessed magnitude of difference between measures. To support monitoring of athletes over time, standard error of measurement and minimum detectable changes (MDC) were calculated. There was excellent agreement between the Perch and criterion device, with mean velocity in both exercises demonstrating a mean bias ranging from -0.01 to 0.01 m·s -1 . For peak velocity, Perch underestimated velocity compared with the criterion ranging from -0.08 to -0.12 m·s -1 for the back squat and -0.01 to -0.02 m·s -1 for the bench press. Technological variability between-days were all less than the MDC. These findings demonstrate that the Perch provides valid and reliable mean and peak concentric velocity outputs across a range of velocities. Therefore, practitioners can confidently implement this device for the monitoring and prescription of resistance training.

Effect of a High-Intensity Handball-Specific Fatigue Protocol Focused on the Leg Contralateral to the Throwing Arm on Interlimb Asymmetries.

ABSTRACT: Janicijevic, D, Pérez-Castilla, A, Miras-Moreno, S, Ortega-Becerra, M, Morenas-Aguilar, MD, Smajla, D, Sarabon, N, and García-Ramos, A. Effect of a high-intensity handball-specific fatigue protocol focused on the leg contralateral to the throwing arm on interlimb asymmetries. J Strength Cond Res 37(7): 1382-1389, 2023-This study aimed to elucidate which countermovement jump (CMJ) variant (unilateral or bilateral) is more sensitive to detect the decrement in kinetic CMJ-derived variables of the leg more actively involved in a handball-specific fatigue protocol. Seventeen female handball players (age: 20.6 ± 2.5 years) performed a fatigue protocol consisting of 8 repetitions of the following circuit separated by 10 seconds: 10 m sprint, 180° change of direction with the leg contralateral to the throwing arm, 10 m sprint with ball reception at 7 m, and handball throw preceded by a jump over a 40 cm hurdle with the leg contralateral to the throwing arm. Before and after the fatigue protocol, 6 unilateral CMJs (3 with each leg) and 3 bilateral CMJs were performed on a dual Kistler force platform (model 9260AA6). Bilateral CMJ height was reduced by 5.4% after the fatigue protocol (p < 0.001). However, the fatigue protocol did not promote any significant change in peak force, mean force, and propulsive impulse or in their asymmetry values (17 of 18 comparisons). The decrement of 6.1% during the unilateral CMJ in the propulsive impulse developed by the leg ipsilateral to the throwing arm (less involved in the fatigue protocol) was the only variable that reached statistical significance (p = 0.038). The pre-post fatigue changes in asymmetry values presented negligible correlations between both CMJ variants (rs = 0.01 to -0.19). These results suggest that neither unilateral nor bilateral CMJs are able to detect changes in interlimb asymmetries after a high-intensity handball-specific fatigue protocol.