Optimizing resistance training intensity in supportive care for survivors of breast cancer: velocity-based approach in the row exercise.

PURPOSE: Resistance training mitigates side effects during and after cancer treatment. To provide a new approach for precisely and safely assessing and prescribing the intensity of resistance training in supportive cancer care, the purpose of this study was to evaluate the load-velocity relationship during the row exercise in women survivors of breast cancer. METHODS: Twenty women survivors of breast cancer who had undergone surgery and had completed core breast cancer treatment within the previous 10 years completed an incremental loading test until the one repetition maximum (1RM) in the row exercise. The velocity was measured during the concentric phase of each repetition with a linear velocity transducer, and their relationship with the relative load was analyzed by linear and polynomial regression models. RESULTS: A strong relationship was observed between movement velocity and relative load for all measured velocity variables using linear and polynomial regression models (R2 > 0.90; SEE < 6.00%1RM). The mean velocity and mean propulsive velocity of 1RM was 0.40 ± 0.03 m·s-1, whereas the peak velocity at 1RM was 0.64 ± 0.07 m·s1. CONCLUSION: In women survivors of breast cancer, monitoring movement velocity during the row exercise can facilitate precise assessment and prescription of resistance training intensity in supportive cancer care.

Examining Unilateral and Bilateral Exercises through the Load-velocity Relationship.

This study aimed to examine the load-velocity (L-V) relationship in the bench-press (BP) and leg-press (LP) exercises performed unilaterally, and compared this unilateral L-V relationship with the bilateral variants. Nineteen men (age=23.5±2.1 years) completed two incremental tests in BP and LP, performed bilaterally and unilaterally, across two sessions with a 48-hour rest period. We found a close relationship between medium propulsive velocity (MPV) and %1RM in unilateral BP (R2 =0.97, SEE=0.06 m·s-1) and LP (R2=0.96, SEE=0.06 m·s-1). No significant differences were observed between the preferred and non-preferred sides in the L-V relationship for either exercise. Additionally, higher velocities were achieved in unilateral exercises compared to bilateral exercises, particularly with light and moderate loads (30-70%1RM) in BP (p<0.05) and with light loads (30-45%1RM) in LP (p<0.05). Close L-V relationships were observed in unilateral exercises, without differences in the L-V relationships between preferred and non-preferred sides despite the interlimb asymmetries in the absolute strength values. Interestingly, lower velocities were observed at light loads (~30-45% 1RM) for bilateral compared to unilateral exercises, which could be explained by different strength deficits for these exercises.

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.

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.

Kinetic and Kinematic Characteristics Underpinning Change of Direction Performance in Basketball: A Comparative Study Between Sexes and Tests.

ABSTRACT: Baena-Raya, A, Díez-Fernández, DM, Martínez-Rubio, C, Conceição, F, and López-Sagarra, A. Kinetic and kinematic characteristics underpinning change of direction performance in basketball: A comparative study between sexes and tests. J Strength Cond Res 38(4): e182-e188, 2024-This study (a) evaluated the sex-specific kinetic and kinematic outcomes underpinning change of direction (COD) performance, (b) compared these outcomes across 3 different COD tests, and (c) examined the sex-specific and test-specific outcome most strongly related to COD performance in basketball players. Thirty young basketball players (17 males and 13 females) competing at the national level were assessed for the modified 505 test, modified T test, and V-cut test. The Local Positioning System technology (WIMU PRO, Realtrack Systems S.L., Almería, Spain) was used to measure the maximum values of acceleration (ACC max ), deceleration (DEC max ), velocity (VEL max ), and centripetal force (CentF max ) in each COD test. Male players displayed greater ACC max , VEL max , DEC max , and CentF max outputs for each section of the 505 test, T test, and V-cut test (all p < 0.05), resulting in a faster COD performance than females across tests (all ES > -1.42; 95% CI = -3.45 to -0.57). The 505 test demanded significantly greater kinematic outputs than T test and V-cut test for both sexes ( p < 0.01). The ACC max explained ∼26-58% of the variability in COD time for males across tests ( p < 0.05) and 40% in females' modified 505-test time ( p < 0.05). Likewise, in females, DEC max explained 38% of the modified T -test time variability, whereas VEL max explained 53% in the V-cut test time (both p < 0.05). These findings suggest that (a) COD data should not be used interchangeably across sexes, (b) test specificities should be considered for designing COD training, and (c) the kinematic outcomes explaining COD performance might vary across sexes.

Novel Curvilinear Sprint Test in Basketball: Reliability and Comparison With Linear Sprint.

ABSTRACT: Baena-Raya, A, Díez-Fernández, DM, López-Sagarra, A, Martínez-Rubio, C, Soriano-Maldonado, A, and Rodríguez-Pérez, MA. Novel curvilinear sprint test in basketball: reliability and comparison with linear sprint. J Strength Cond Res 37(9): e535-e540, 2023-This study (a) evaluated the reliability of a curvilinear sprint (CS) test to assess kinetic and kinematic outcomes in basketball players, (b) compared the kinetic and kinematic outcomes derived from curvilinear vs. linear sprints (LS), and (c) examined the association of both the CS and LS with change of direction (COD) performance. Thirty young basketball players (17 men and 13 women) competing at the national level (i.e., Spanish Basketball National League) performed a novel CS test around the 3-point line (the 3-point line CS test) to the right and left sides. The maximum and average values of acceleration (ACC), velocity (VEL), and centripetal force (CentF) were measured using Local Positioning System technology (WIMU PRO, Realtrack Systems S.L., Almería, Spain). All outcomes showed a high relative (intraclass correlations coefficient ≥ 0.90) and absolute (coefficient of variation [CV] < 5%) reliability, except the maximal CentF to the right (CV = 5.41%) and left sides (CV = 7.72%). Linear sprints displayed higher ACC and VEL outputs compared with the 3-point line CS test (all p < 0.001). Both sprinting tests were very large to nearly perfect associated with COD performance (LS r range from -0.71 to -0.86; CS r range from -0.68 to -0.94; p < 0.001), and the curvilinear ACC max was the kinematic outcome most strongly associated with COD performance ( r range from -0.73 to -0.94). In conclusion, the 3-point line CS test is reliable to measure CS performance in basketball and presents different kinetic and kinematic features than LS.

Delineating the potential of the vertical and horizontal force-velocity profile for optimizing sport performance: A systematic review.

The aims of this systematic review were to synthetize the current evidence about (i) the force-velocity (FV) profile parameters (maximal values of force [F0], velocity (V0), and power [Pmax]) obtained from the Samozino's method in different sports; (ii) the association of the FV profile parameters with sport performance outcomes; and (iii) the effects of specific training programmes on the FV profile parameters. PubMed, SportDiscus, Web of Science, and Medline databases were searched for articles published between October 2008 (conception of the Samozino's method) and October 2020. Twenty-one studies (10 descriptive, 6 correlational, and 5 longitudinal) met the inclusion criteria. The main findings revealed greater F0, Pmax, and V0 values and better jump/sprint performance for high-level athletes compared to their low-level counterparts. The vertical Pmax showed the highest correlation with jump height. The horizontal F0, Pmax, and V0 were nearly perfectly correlated with 5/10-m, 10/20-m and 30/40-m sprint times, respectively. Training programmes using heavy- or light-loads specifically enhanced F0 and V0, respectively. These results suggest that the FV profile parameters discriminate between athletes of different sport disciplines and levels of practice, present significant correlations with a number of sport performance outcomes, and can be modified after short-term training programmes.

Gender-Specific Association of the Sprint Mechanical Properties With Change of Direction Performance in Basketball.

ABSTRACT: Baena-Raya, A, Jiménez-Reyes, P, Romea, ES, Soriano-Maldonado, A, and Rodríguez-Pérez, MA. Gender-specific association of the sprint mechanical properties with change of direction performance in basketball. J Strength Cond Res 36(10): 2868-2874, 2022-We evaluated the gender-specific associations between the mechanical variables derived from the horizontal force-velocity (FV) profile (i.e., theoretical maximal force [ F0 ], velocity [ V0 ], maximal power output [ Pmax ], peak ratio of the effective horizontal component [ RFpeak ], and the force application technique index [ DRF ]) and the change of direction (COD) performance for basketball players. Seventy-one players (23 women and 48 men) were assessed for the horizontal FV profile and COD using the modified 505 and V-cut tests. The FV profile parameters were significantly higher for the men than those for the women. The F0 , RFpeak , and Pmax were strongly associated with performance in the 505 test (women rrange = -0.72 to -0.82; men: rrange = -0.67 to -0.75; p < 0.001) and the V-cut test (women rrange = -0.68 to -0.76; men rrange = -0.45 to -0.50; p < 0.001), as well as with a lower COD deficit (women rrange = 0.58 to 0.75 ( p < 0.01); men rrange = 0.49 to 0.54; all p < 0.001). For the women, a 1 N·kg -1 increase of the F0 was associated with -0.20 seconds and -0.56 seconds in the 505 and V-cut tests, respectively, and 0.16 seconds for the COD deficit. In the men, it was associated with -0.13 seconds and -0.37 seconds in the 505 and V-cut tests, respectively, and 0.10 seconds for the COD deficit. F0 , RFpeak , and Pmax are the most determinant sprint mechanical properties to successfully COD and reduce the COD deficit. The horizontal FV profile assessment is recommended for diagnosing and prescribing a training program for basketball players.

Effects of two drop-jump protocols with different volumes on vertical jump performance and its association with the force-velocity profile.

PURPOSE: This study aimed to evaluate the changes in countermovement jump (CMJ) height after two drop-jump (DJ) protocols with different volumes, and to explore the possibility of predicting the changes in CMJ height based on the vertical force-velocity (F-v) profile. METHOD: Thirty-four male athletes (age: 21.9 ± 2.0 years) were tested on three occasions. The F-v profile during the CMJ exercise was determined in the first session. Two DJ protocols (low-volume [1 set of 5 DJ trials from a 30 cm height] and high-volume [3 sets of 5 DJ trials from a 30 cm height]) were randomly performed during the second and third sessions, and the unloaded CMJ height was evaluated before (Pre), 4 min (Post4), 8 min (Post8), and 12 min (Post12) after the DJ protocol. RESULTS: CMJ height was significantly higher at Post4 (2.5 cm [95% confidence interval (CI) = 2.0-3.0 cm]; ES = 0.35), Post8 (2.1 cm [95% CI = 1.4-2.8 cm]; ES = 0.29) and Post12 (2.2 cm [95% CI = 1.4-3.0 cm]; ES = 0.30) compared to Pre. The only significant interaction (protocol × time) was caused by a higher increment in CMJ height at Post4 for the low-volume (8.1 ± 3.7%) compared to the high-volume (5.8 ± 3.9%) protocol. The F-v profile did not explain a significant part of the change in CMJ height (variance explained < 10%). CONCLUSIONS: These results suggest that low-volume DJ protocols could be more efficient to acutely increase CMJ performance, while the change in CMJ height was not affected by the F-v profile.

Estimating Repetitions in Reserve During the Bench Press Exercise: Should We Consider Sex and the Exercise Equipment?

BACKGROUND: Estimating repetitions in reserve (RIR) has been established as a valid and practical method for monitoring set configuration concerning proximity to failure in resistance training. However, factors such as sex and exercise equipment could interfere with the estimation process. Therefore, this study aimed to determine the influence of sex (female vs male) and exercise equipment (free-weight vs Smith machine) on the RIR estimation at different relative loads during the bench press exercise. HYPOTHESIS: Men would be more accurate than women in the RIR estimation, and participants would better perceive their actual effort at the Smith machine compared with the free-weight bench press exercise. STUDY DESIGN: Repeated measures design. LEVEL OF EVIDENCE: Level 3. METHODS: In a counterbalanced order, recreationally trained participants (12 female, 14 male) performed 2 identical sessions with the free-weight bench press exercise in 1 week and 2 identical sessions with the Smith machine bench press exercise in another week (first session for familiarization and second session for validity analysis). In each session, participants performed single sets of repetitions to failure against 3 relative loads (65%, 75%, and 85% of the 1-repetition maximum [1RM]). RESULTS: Results revealed a significant interaction between RIR and sex at 65% 1RM (P < 0.01; women: -1.2 [-1.7 to -0.6] repetitions; men: -0.1 [-0.6 to 0.3] repetitions), and between RIR and exercise equipment at 65% 1RM (P < 0.01; free-weight: -1.1 [-1.5 to -0.6] repetitions; Smith machine: -0.2 [-0.6 to 0.2] repetitions), but not at 75% and 85% 1RM. CONCLUSIONS: RIR estimation is a valid method for monitoring set configuration. However, this method tends to underestimate RIR at 65%1RM with female athletes and in the free-weight exercise for both sexes. CLINICAL RELEVANCE: Strength and conditioning coaches should help their athletes understand effort awareness in the aforementioned context.

Comparative efficacy of exercise, diet and/or pharmacological interventions on BMI, ovulation, and hormonal profile in reproductive-aged women with overweight or obesity: a systematic review and network meta-analysis.

BACKGROUND: The increasing prevalence of obesity worldwide poses a significant threat to reproductive function owing, in part, to hormonal disturbances caused by negative feedback between excess adiposity and the hypothalamic-pituitary-ovarian axis. Consequently, finding the most appropriate strategies to lose weight and improve ovulation in women with overweight or obesity is a clinically relevant matter that needs to be investigated. A comprehensive comparison of the independent and combined efficacy of lifestyle and/or pharmacological interventions on BMI, ovulation, and hormonal profile in women with overweight or obesity at risk of anovulatory infertility would facilitate improving fertility strategies in this population. OBJECTIVE AND RATIONALE: This study aimed to evaluate the comparative efficacy of exercise, diet, and pharmacological interventions on BMI, ovulation, and hormonal profile in reproductive-aged women with overweight or obesity. SEARCH METHODS: A systematic review was performed by searching PubMed, Scopus, Web of Science, PsycINFO, and Cochrane Library up to 14 December 2023, for randomized controlled trials assessing the effects of exercise, diet and/or pharmacological interventions (i.e. weight-lowering drugs or ovulation inducers) on BMI, ovulation, and/or hormonal profile in reproductive-aged women with overweight or obesity. We performed frequentist random-effect network meta-analyses and rated the certainty of the evidence. The primary outcomes were BMI and ovulation rate, and the secondary outcomes were serum reproductive hormone levels (gonadotrophins, androgens, or oestrogens). We performed sensitivity analyses, including the studies that only involved women with PCOS. OUTCOMES: Among 1190 records screened, 148 full texts were assessed for eligibility resulting in 95 trials (9910 women), of which 53% presented a high or unclear risk of bias. The network meta-analyses revealed that, compared to control: diet combined with weight-lowering drugs (mean difference (MD) -2.61 kg/m2; 95% CI -3.04 to -2.19; τ2 = 0.22) and adding exercise (MD -2.35 kg/m2; 95% CI -2.81 to -1.89; τ2 = 0.22) led to the greatest decrease in BMI; exercise combined with diet and ovulation inducers (risk ratio (RR) 7.15; 95% CI 1.94-26.40; τ2 = 0.07) and exercise combined with diet and weight-lowering drugs (RR 4.80; 95% CI 1.67-13.84; τ2 = 0.07) produced the highest increase in ovulation rate; and exercise combined with diet and weight-lowering drugs was the most effective strategy in reducing testosterone levels (standardized mean difference (SMD) -2.91; 95% CI -4.07 to -1.74; τ2 = 2.25), the third most effective strategy in increasing sex hormone-binding globulin levels (SMD 2.37; 95% CI 0.99-3.76; τ2 = 2.48), and it was coupled with being ranked first in terms of free androgen index reduction (SMD -1.59; 95% CI -3.18 to 0.01; τ2 = 1.91). The surface under the cumulative ranking curve scores suggested that: diet combined with weight-lowering drugs is the strategy most likely (94%) to produce the highest BMI reduction; and exercise combined with diet and ovulation inducers is the strategy most likely (89%) to produce the highest ovulation rate improvement. The sensitivity analyses, which exclusively included studies involving women diagnosed with PCOS, were consistent with the results presented above. WIDER IMPLICATIONS: Overall, the findings of this network meta-analysis indicate that the combination of exercise, diet, and pharmacological interventions is effective for weight loss, improving ovulation, and normalizing the androgen levels of women with overweight or obesity. Although higher quality studies are needed, these results support that the optimal treatment strategy for women with overweight or obesity wishing to conceive must consider exercise, diet, and pharmacological interventions during the shared decision-making process.

Optimizing exercise prescription during breast cancer rehabilitation in women: Analysis of the load-velocity relationship in the box squat exercise.

The aims of this study were to assess (i) the load-velocity relationship during the box squat exercise in women survivors of breast cancer, (ii) which velocity variable (mean velocity [MV], mean propulsive velocity [MPV], or peak velocity [PV]) shows stronger relationship with the relative load (%1RM), and (iii) which regression model (linear [LA] or polynomic [PA]) provides a greater fit for predicting the velocities associated with each %1RM. Nineteen women survivors of breast cancer (age: 53.2 ± 6.9 years, weight: 70.9 ± 13.1 kg, and height: 163.5 ± 7.4 cm) completed an incremental load test up to one-repetition maximum in the box squat exercise. The MV, MPV, and the PV were measured during the concentric phase of each repetition with a linear velocity transducer. These measurements were analyzed by regression models using LA and PA. Strong correlations of MV with %1RM (R2 = 0.903/0.904; the standard error of the estimate (SEE) = 0.05 m.s-1 by LA/PA) and MPV (R2 = 0.900; SEE = 0.06 m.s-1 by LA and PA) were observed. In contrast, PV showed a weaker association with %1RM (R2 = 0.704; SEE = 0.15 m.s-1 by LA and PA). The MV and MPV of 1RM was 0.22 ± 0.04 m·s-1, whereas the PV at 1RM was 0.63 ± 0.18 m.s-1. These findings suggest that the use of MV to prescribe relative loads during resistance training, as well as LA and PA regression models, accurately predicted velocities for each %1RM. Assessing and prescribing resistance exercises during breast cancer rehabilitation can be facilitated through the monitoring of movement velocity.

Exercise interventions following bariatric surgery are poorly reported: A systematic review and a call for action.

OBJECTIVES: This study assessed the transparency and replicability of exercise-based interventions following bariatric surgery by evaluating the content reporting of exercise-based clinical trials. DESIGN: The study design of the present article is a systematic review. DATA SOURCES: PubMed, Scopus, Web of Sciences, PsycINFO, and Cochrane were searched from their inception to May 2023. ELIGIBILITY CRITERIA: Eligible studies were clinical trials including exercise interventions in participants following bariatric surgery. There were 28 unique exercise interventions. Two independent reviewers applied the exercise prescription components of Frequency, Intensity, Time, and Type (FITT; four items) and the Consensus on Exercise Reporting Template (CERT; 19 items). Exercise interventions were organized into four major exercise components: aerobic training, resistance training, concurrent training, and "others." RESULTS: The FITT assessment revealed that 53% of the trials did not report the training intensity, whereas 25% did not indicate the duration of the major exercise component within the training session. The mean CERT score was 5 out of a possible score of 19. No studies reached CERT score >10, while 13 out of the total 19 CERT items were not adequately reported by ≥75% of the studies. CONCLUSION: This study highlights that the exercise interventions following bariatric surgery are poorly reported, non-transparent, and generally not replicable. This precludes understanding the dose-response association of exercise and health-related effects and requires action to improve this scientific field.

Physical-Performance Changes Over the Season: Are They Related to Game-Performance Indicators in Elite Men Volleyball Players?

BACKGROUND: The development and influence of physical capabilities and game action performance over the course of the season are a big challenge for coaches and players. PURPOSE: The aims of the present study were to examine (1) the seasonal changes in the physical capabilities (mechanical and kinematic) and game-performance indicators in top-level men volleyball players and (2) the relationship between these physical capabilities and game-performance indicators in official matches. METHODS: Eleven top-level players participated. Players were physically tested 3 times during the season. Before each test, players' match performance (11 sets) was analyzed according to the level of opposition and match location. The percentage of change, statistical differences over the season (Friedman and Wilcoxon tests), and associations between variables (Spearman r) were calculated (P < .05) among mechanical (force-velocity profile during vertical jump and bench press), kinematic (jump height and spike ball speed), and game action performance features (coefficient, efficacy, and percentage of errors in serve, attack, and block). RESULTS: The theoretical maximal force and velocity during vertical jump and bench press, respectively; the peak spike ball speed; and the serve efficacy significantly increased over the season. Moreover, there was a significant reduction in serve errors as the jump height increased (r = -.44; P = .026), as well as a significant increase in serve errors as the peak spike ball speed increased (r = -.62; P = .001). CONCLUSION: These findings reveal how the physical and game action performance variables evolve and interact during the season. This may help coaches and trainers to monitor and analyze the most relevant volleyball performance factors.

Interference Effects of Different Resistance-Training Protocols on Rowing Ergometer Performance: A Study on Semiprofessional Rowers.

PURPOSE: To evaluate the interference effects of various resistance-training (RT) protocols on rowing ergometer performance. METHODS: Fourteen semiprofessional male rowers randomly completed 5 protocols in separate sessions: (1) control-no RT session was performed, (2) upper-body high-fatigue-4 sets to failure during the bench pull exercise, (3) upper-body low-fatigue-4 sets of 6 repetitions during the bench pull exercise, (4) lower-body high-fatigue-4 sets to failure during the leg-press exercise, and (5) lower-body low-fatigue-4 sets of 6 repetitions during the leg-press exercise. All sets were performed against the 12-repetition-maximum load with 2 minutes of interset rest. Following the completion of the protocols, subjects performed an all-out 1000-m rowing ergometer test. RESULTS: Compared with the control condition, rowing ergometer performance was not significantly affected after the low-fatigue RT protocols (upper body: P ≥ .487; Δ = 0.0%-0.2%; lower body: P ≥ .200; Δ = -0.2%-0.5%), while it significantly declined following high-fatigue RT protocols (upper body: P ≤ .001; Δ = 1.0%-2.0%; lower body: P ≤ .002; Δ = 2.1%-2.5%). The average heart rate was significantly lower for the control condition compared with all RT protocols (P ≤ .043; Δ = 1.0%-1.5%). CONCLUSIONS: To minimize interference on rowing performance, coaches should prioritize the level of effort in RT protocols over specific exercises, specifically avoiding high-fatigue protocols that lead to failure before rowing practice.

Horizontal versus vertical force application: association with the change of direction performance in soccer players.

This study examined which mechanical variables derived from a vertical jump (i.e. concentric peak force [ConcPF] and eccentric peak force [EccPF], flight time [FT]: contraction time [CT], eccentric deceleration rate of force development [EccDecRFD]) and linear sprint (i.e. theoretical maximal force [F0] and velocity [V0], maximal power output [Pmax], the peak ratio of the effective horizontal component [RFpeak], and the index of force application technique [DRF]) determined the change of direction (COD) performance to a greater extent. Sixteen male soccer players (age: 21.8 ± 2.9 years; height: 175.94 ± 6.88 cm; weight: 73.23 ± 9.59 kg) were assessed for a countermovement jump, the horizontal force velocity (FV) profile, and the COD ZigZag test. The horizontal FV profile parameters were significantly associated with COD performance, while jump mechanical variables did not show any significant association (r = 0.08-0.19; p > 0.05). Specifically, F0 (r = -0.56), Pmax (r = -0.68), and RFpeak (r = -0.54) were strongly associated with COD performance. Moreover, a 1 N·kg-1 increase in F0 was associated with -0.11 s to complete the ZigZag test, whereas 1 W·kg-1 and 1% increase in Pmax and RFpeak were associated with -0.05 and -0.03 s, respectively, to complete the COD test. Horizontal force production during sprinting might play a key role in COD performance. Assessing the horizontal FV profile might help coaches to prescribe a specific training programme to maximize sprint acceleration, which might improve COD performance.

Assessing the Maximal Mechanical Capacities Through the Load-Velocity Relationship in Elite Versus Junior Male Volleyball Players.

BACKGROUND: Physical testing is crucial for athlete monitoring, talent identification, optimizing training, and tailoring programs to enhance game-performance in elite competitions. HYPOTHESIS: Load-velocity (L-V) relationship variables discriminate between elite and junior volleyball players, correlate with volleyball-specific performance, and are generalizable across lower- and upper-body exercises. STUDY DESIGN: Cross-sectional study. LEVEL OF EVIDENCE: Level 3. METHODS: A total of 9 elite and 11 junior volleyball players were assessed for the L-V relationship (load-axis intercept [L0], velocity-axis intercept [v0], and area under the L-V relationship line [Aline]) during the countermovement jump (CMJ) and bench press throw (BPT) exercises. Block and spike jump height, as well as standing and jumping spike speed were assessed 24 hours later. RESULTS: Elite players presented greater magnitude in the L-V variables (P ≤ 0.03; effect size [ES] ≥ 1.06) and higher volleyball-specific performance (P ≤ 0.03; ES ≥ 1.09) than juniors (except for CMJ v0 and Aline). The L-V relationship variables were significantly associated with the block and spike jump height and jumping spike speed only in elite players (r ≥ 0.703 and P ≤ 0.04 in 11 out of 18 correlations). No significant associations were observed between CMJ and BPT for any L-V relationship variable (r ≤ 581; P ≥ 0.08, except for Aline in junior players). CONCLUSION: The L-V relationship is a practical procedure to assess volleyball players' maximal mechanical capacities, which are associated with volleyball-specific performance in elite players. However, these data should not be used interchangeably between playing standards or exercises. CLINICAL RELEVANCE: This information might help strength and conditioning coaches to prescribe more effective training programs that focus on developing the specific physical capacities necessary for players to potentially advance to elite status.

Estimating the one-repetition maximum on the leg-press exercise in female breast cancer survivors.

We examined the accuracy of twelve different velocity-based methods for predicting the bilateral leg-press exercise one-repetition maximum (1RM) in breast cancer survivors. Twenty-one female breast cancer survivors (age 50.2 ± 10.8 years) performed an incremental loading test up to the 1RM. Individual load-velocity relationships were modeled by linear and quadratic polynomial regression models considering the mean velocity (MV) and peak velocity (PV) values recorded at five incremental loads (~45-55-65-75-85% of 1RM) (multiple-point methods) and by a linear regression model considering only the two distant loads (~45-85% of 1RM) (two-point method). The 1RM was always estimated through these load-velocity relationships as the load associated with a general (MV: 0.24 m/s; PV: 0.60 m/s) and an individual (MV and PV of the 1RM trial) minimal velocity threshold (MVT). Compared to the actual 1RM, the 1RMs estimated by all linear regression models showed trivial differences (Hedge's g ranged from 0.08 to 0.17), very large to nearly perfect correlations (r ranged from 0.87 to 0.95), and no heteroscedasticity of the errors (coefficient of determination (r2) < 0.10 obtained from the relationship of the raw differences between the actual and predicted 1RMs with their average value). Given the acceptable and comparable accuracy for all 1RM linear prediction methods, the two-point method and a general MVT could be recommended to simplify the testing procedure of the bilateral leg-press 1RM in breast cancer survivors.

Acute Mechanical and Skin Temperature Responses to Different Interrepetition Rest Intervals During Full-Squat Exercise.

PURPOSE: This study aimed to (1) evaluate the acute effects of different interrepetition rest full-squat protocols on countermovement jump (CMJ) height, velocity loss (VL), and skin temperature (Tsk) and (2) determine whether the VL, the changes in Tsk, or the individual strength level is associated with the change in CMJ height. METHODS: Sixteen resistance-trained men randomly performed 3 squat protocols at maximal intended velocity with 60% of the 1-repetition maximum (sets × repetitions [interrepetition rest]): traditional (2 × 6 [0 s]), cluster 2 (2 × 6 [30 s every 2 repetitions]), and cluster 1 (1 × 12; [36 s every repetition]), plus a control session. CMJ height was assessed before and 2, 4, and 8 minutes after the protocols. RESULTS: There was a significant main effect of protocol for the VL (F = 20.54, P < .001) and loss in mean power (F = 12.85, P < .001; traditional > cluster 2 > cluster 1). However, we found a comparable reduction of CMJ height after 8 minutes: traditional (-3.4% [4.2%]), cluster 2 (-5.3% [4.9%]), cluster 1 (-5.4% [2.9%]), and control (-4.2% [3.6%]). Overall, mean Tsk acutely decreased after all the protocols. Higher individual strength level (but not VL or the changes in Tsk) was associated with lower CMJ-height loss (P < .05). CONCLUSIONS: Although different interrepetition rest full-squat protocols may alter the loss in velocity and power, they result in a similar decrease in Tsk and CMJ height, which could be more influenced by individual strength level than VL or changes in Tsk.