Load-Time and Load-Speed Relationship in the Resisted Sled Sprint Exercise: What Independent Variable Most Accurately Determines the Relative Load?

ABSTRACT: Jiménez-Lozano, M, Yáñez-García, JM, Mora-Custodio, R, Valle-Salguero, A, Díez-Fernández, DM, Franco-Márquez, F, González-Badillo, JJ, and Rodríguez-Rosell, D. Load-time and load-speed relationship in the resisted sled sprint exercise: what independent variable most accurately determines the relative load? J Strength Cond Res 37(11): 2167-2177, 2023-The aims of this study were to analyze the load-speed and load-time relationships in the resisted sled sprint exercise using different variables as relative load and to estimate the decrement of speed sprint and the increase of sprint time across different loads. Thirty young healthy men performed a progressive loading test in the countermovement jump (CMJ) exercise to determinate the load that elicited a 2 m·s-1 peak velocity (PV2-load) and in the full squat exercise to obtain the 1 repetition maximum (1RM) value and the load that elicited a 1 m·s-1 mean velocity (V1-load). In addition, subjects performed a progressive loading test in the resisted sled sprint exercise, whereas time and instantaneous speed at 10 (T10 and V10) and 20 m (T20 and V20) were measured. The independent variables used were body mass (BM), 1RM and V1-load in the squat exercise, the PV2-Load in the loaded CMJ exercise, 1RM + BM, V1-Load + BM, and PV2-Load + BM. To analyze whether relationships were dependent on individual performance obtained in unloaded sprint, the total sample was divided into 3 subgroups: high performance (T20 < 3.00 s), medium performance (T20:3.00-3.12 s), and low performance (T20 > 3.12 seconds) groups. The independent variables showing the highest relationships with time and speed in 10 and 20 m were %BM, %BM + V1-load, and %BM + PV2-load. Statistically significant differences between performance groups in %DSS (decrease of sprint speed) and %IST (increase sprint time) in 20 m were found when %BM was used as relative load, whereas there were no significant differences between groups for %BM + PV2-load or %BM + V1-load. In conclusion, the use of %BM + PV2-load and %BM + V1-load should be considered as variables for monitoring the relative load in the resisted sled sprint exercise.

Movement Velocity as a Determinant of Actual Intensity in Resistance Exercise.

This study aimed to analyze the acute mechanical, metabolic and EMG response to five resistance exercise protocols (REP) in the full squat (SQ) exercise performed with two velocity conditions: maximal intended velocity (MaxV) vs. half-maximal velocity (HalfV). Eleven resistance-trained men performed 10 REP (5 with each velocity conditions) in random order (72-96 h apart). The REP consisted of three sets of 8-3 repetitions against 45-65% 1RM. The percent change in countermovement jump (CMJ) height, velocity attained with the load that elicited a ~1.00 m·s-1 (V1-load), surface EMG variables and blood lactate concentration were assessed pre- vs. post-exercise protocols. MaxV resulted in greater percent changes (Δ: 12-25%) and intra-condition effect sizes (ES: 0.76-4.84) in loss of V1-load and CMJ height compared to HalfV (Δ: 10-16%; ES: 0.65-3.90) following all REP. In addition, MaxV showed higher post-exercise lactate concentration than HalfV (ES: 0.46-0.83; p<0.05). For EMG variables, only the Dimitrov index resulted in relevant changes after each REP, with MaxV showing greater magnitude of changes (23-38%) than HalfV (12-25%) across all REP. These results suggest that voluntary movement velocity is a key aspect to consider since it clearly determines the overall training intensity during resistance exercise.

Can the Supido Radar Be Used for Measuring Ball Speed during Soccer Kicking? A Reliability and Concurrent Validity Study of a New Low-Cost Device.

The aim was to analyze the reliability and validity of a low-cost instrument, based on a radar system, to quantify the kicking ball speed in soccer. A group of 153 male soccer players (under-13, n = 53; under-15, n = 54; under-18, n = 46) participated in this study. Each player performed three kicks on the goal in a standardized condition while the ball speed was measured with three different devices: one Radar Stalker ATS II® (reference criterion) and two Supido Radar® (Supido-front of the goal and Supido-back of the goal). The standard error of measurement (SEM) expressed as a coefficient of variation (CV) and the intraclass correlation coefficient (ICC) were employed for assessing the reliability of each instrument. Stalker and Supido-back showed very high absolute (CV = 4.0-5.4%) and relative (ICC = 0.945-0.958) reliability, whereas Supido-front resulted in moderate to low reliability scores (CV = 7.4-15%, ICC = 0.134-0.693). In addition, Lin's concordance correlation coefficient (CCC) values revealed an 'almost perfect' agreement between Stalker and Supido-back for the average (r = 0.99) and maximal (r = 0.98) ball speed, regardless of the ball speed range analyzed. However, Supido-front resulted in a poor degree of concordance (CCC = 0.688) and a high magnitude of error (17.0-37.5 km·h-1) with the reference Stalker radar gun. The Supido Radar® placed behind the goal could be considered a reliable and valid device for measuring ball speed in soccer.

A Novel Strategy to Determine the 1-Repetition Maximum in the Jump Squat Exercise.

ABSTRACT: Loturco, I, McGuigan, MR, Rodríguez-Rosell, D, Pereira, LA, and Pareja-Blanco, F. A novel strategy to determine the 1-repetition maximum in the jump squat exercise. J Strength Cond Res 36(8): 2330-2334, 2022-This study aimed to determine the maximum relative load of the half-squat (HS; i.e., % HS 1-repetition maximum [1RM]) that can be used in its ballistic variation, namely, the jump squat (JS) exercise, and to examine whether this reference value varies in subjects with different strength levels. In total, 186 elite athletes from 10 distinct sport disciplines participated in this study. A progressive loading test up to HS 1RM was performed during the competitive phase of the season for all athletes. Mean propulsive velocity and propulsive phase duration were also assessed during the 1RM test. Athletes were divided into 3 distinct subgroups: "low," "middle," and "high" strength levels, based on their relative HS 1RM values (kg·kg -1 ). A 1-way analysis of variance was used to compare the variables assessed between the groups. Significance level was set at p < 0.05. The high group demonstrated the highest relative HS 1RM values, followed by the middle and low groups (all p < 0.05). No significant differences were observed between the groups for the remaining variables ( p > 0.05). It was observed that at 86.0 ± 5.4% 1RM, the full concentric action can already be considered as entirely propulsive in the HS exercise for all subjects, independent of their strength levels. Therefore, this relative strength value may be used as a reference for the 1RM in the JS exercise.

Changes in Muscle Strength, Jump, and Sprint Performance in Young Elite Basketball Players: The Impact of Combined High-Speed Resistance Training and Plyometrics.

ABSTRACT: Yáñez-García, JM, Rodríguez-Rosell, D, Mora-Custodio, R, and González-Badillo, JJ. Changes in muscle strength, jump, and sprint performance in young elite basketball players: the impact of combined high-speed resistance training and plyometrics. J Strength Cond Res 36(2): 478-485, 2022-This study aimed to compare the effect of a combined resistance training (RT) and plyometrics on strength, sprint, and jump performance in basketball players of different ages. Thirty three elite basketball players from the same academy were categorized into 3 groups by chronological age: under-13 (U13, n = 11); under-15 (U15, n = 11); and under-17 (U17, n = 11). Players participated in a 6-week strength training program that included 2 sessions each week and consisted of full squats with low loads (45-60% 1 repetition maximum) and low volume (2-3 sets and 4-8 repetitions), jumps, and sprint exercises. All repetitions were performed at maximal intended velocity. In addition to strength training sessions, subjects performed 4 on court basketball training sessions plus 2 official matches per week. After training program, all 3 experimental groups resulted in significant improvements (p < 0.05-0.001) in maximal strength (Δ: 9.2-27.3%; effect size [ES]: 0.38-0.82), countermovement jump height (Δ: 6.6-11.6%; ES: 0.37-0.95), and sprint time in 10 and 20 m (Δ: -3.9 to -0.3%; ES: 0.09-0.69) for all experimental groups. Comparison between groups showed that training program was more effective in inducing improvements in most variables assessed for U13 compared with U15 (ES: 0.11-0.42) and U17 (ES: 0.20-0.43), whereas differences between U15 and U17 were relevant in jump and strength parameters (ES: 0.20-0.35). Therefore, these findings suggest that high-speed RT combined with plyometrics produces increments in several important variables, including strength, jump, and sprint, to yield high performance during a match in young basketball players. However, training program used seems to be generally less effective as the age of the basketball players increased.

Effects of Different Loading Conditions During Resisted Sprint Training on Sprint Performance.

ABSTRACT: Rodríguez-Rosell, D, Sáez de Villarreal, E, Mora-Custodio, R, Asián-Clemente, JA, Bachero-Mena, B, Loturco, I, and Pareja-Blanco, F. Effects of different loading conditions during resisted sprint training on sprint performance. J Strength Cond Res 36(10): 2725-2732, 2022-The aim of this study was to compare the effects of 5 loading conditions (0, 20, 40, 60, and 80% of body mass [BM]) during weighted sled sprint training on unresisted and resisted sprint performance and jump ability. Sixty physically active men were randomly assigned into 5 groups according to the overload used during sled sprint training: 0% (G0%, n = 12), 20% (G20%, n = 12), 40% (G40%, n = 12), 60% (G60%, n = 12), and 80% BM (G80%, n = 12). Pretraining and post-training assessments included: countermovement jump (CMJ), 30-m sprint without extra load, and 20-m sprint with 20, 40, 60, and 80% BM. All 5 experimental groups trained once a week for a period of 8 weeks completing the same training program (number of sessions, number of bouts, running distance in each sprint, rest intervals between repetitions, and total running distance), but with different sled loads (0, 20, 40, 60, and 80% BM). There was a significant "time × group" interaction for resisted sprint performance at 80% BM condition, where the G40% group attained improvements in performance and G80% worsened. Moreover, G40% increased performance in unresisted and the rest of loading conditions. In addition, G0% and G60% showed statistically significant increases in unresisted sprint performance. No relevant changes were observed in the other experimental groups. All groups showed significant improvements ( p < 0.05-0.001) in CMJ height. Therefore, our findings suggest that resisted sprint training with moderate loads (i.e., 40% BM) may have a positive effect on unresisted and resisted sprint performance.

Characterization of the perioperative changes of exosomal immune-related cytokines induced by prostatectomy in early-stage prostate cancer patients.

BACKGROUND: Myeloid-derived suppressor cells (MDSCs) are relevant in prostate cancer microenvironment collaborating in tumor development. The main tumor marker used in this disease, prostate-specific antigen (PSA), does not provide information related to this tumor microenvironment. Cancer cells secrete exosomes carrying bioactive molecules contributing to MDSCs recruitment and induction. The aim of this study was to characterize the perioperative changes of exosomal cytokines relevant in MDSCs recruitment induced by prostatectomy in prostate cancer patients. METHODS: Blood was drawn from 26 early-stage prostate cancer patients before and after radical prostatectomy and from 16 healthy volunteers. Serum exosomes were separated by precipitation. Cytokines related with MDSC cell recruitment and activation CCL2, CXCL2, CXCL5, CXCL8, CXCL12, MIF, S100A9 and TGF-ß were measured in serum and serum-derived exosomes using immunometric assays. RESULTS: All cytokines were detected both in serum and exosomes, except for CXCL12, which was detected only in serum. Exosomes were enriched specially in MIF, TGF-ß and CXCL2. Presurgical MIF levels in exosomes correlated negatively with serum PSA. Also, presurgical TGF-ß decreased both in serum and exosomes as Gleason score rises. Patients presurgical exosomes had increased CCL2, CXCL5 and TGF-ß levels than exosomes from healthy controls. These differences were not observed when cytokines were analyzed in serum, except for TGF-ß. Cytokine levels of CCL2, CXCL5 decreased in patients' postsurgical exosomes, while TGF-ß further increased. On the contrary, S100A9 levels were lower in patients presurgical exosomes but increased after radical prostatectomy. CONCLUSIONS: Blood exosomal content in cytokines constitute an attractive source to evaluate MDSCs immunomodulators providing additional information related to tumor microenvironment in prostate cancer.

Effect of velocity loss during squat training on neuromuscular performance.

This study aimed to compare the effects of three resistance training (RT) programs differing in the magnitude of velocity loss (VL) allowed in each exercise set: 10%, 30%, or 45% on changes in strength, vertical jump, sprint performance, and EMG variables. Thirty-three young men were randomly assigned into three experimental groups (VL10%, VL30%, and VL45%; n = 11 each) that performed a velocity-based RT program for 8 weeks using only the full squat exercise (SQ). Training load (55-70% 1RM), frequency (2 sessions/week), number of sets (3), and inter-set recovery (4 min) were identical for all groups. Running sprint (20 m), countermovement jump (CMJ), 1RM, muscle endurance, and EMG during SQ were assessed pre- and post-training. All groups showed significant (VL10%: 6.4-58.6%; VL30%: 4.5-66.2%; VL45%: 1.8-52.1%; p < 0.05-0.001) improvements in muscle strength and muscle endurance. However, a significant group × time interaction (p < 0.05) was observed in CMJ, with VL10% showing greater increments (11.9%) than VL30% and VL45%. In addition, VL10% resulted in greater percent change in sprint performance than the other two groups (VL10%: -2.4%; VL30%: -1.8%; and VL45%: -0.5%). No significant changes in EMG variables were observed for any group. RT with loads of 55-70% 1RM characterized by a low-velocity loss (VL10%) provides a very effective and efficient training stimulus since it yields similar strength gains and greater improvements in sports-related neuromuscular performance (jump and sprint) compared to training with higher velocity losses (VL30%, VL45%). These findings indicate that the magnitude of VL reached in each exercise set considerably influences the observed training adaptations.

Role of CaMKII and sarcolipin in muscle adaptations to strength training with different levels of fatigue in the set.

Strength training promotes a IIX-to-IIA shift in myosin heavy chain (MHC) composition, likely due to changes in sarcoplasmic [Ca2+ ] which are sensed by CaMKII. Sarcoplasmic [Ca2+ ] is in part regulated by sarcolipin (SLN), a small protein that when overexpressed in rodents stimulates mitochondrial biogenesis and a fast-to-slow fiber type shift. The purpose of this study was to determine whether CaMKII and SLN are involved in muscle phenotype and performance changes elicited by strength training. Twenty-two men followed an 8-week velocity-based resistance training program using the full squat exercise while monitoring repetition velocity. Subjects were randomly assigned to two resistance training programs differing in the repetition velocity loss allowed in each set: 20% (VL20) vs 40% (VL40). Strength training caused muscle hypertrophy, improved 1RM and increased total CaMKII protein expression, particularly of the δD isoform. Phospho-Thr287 -CaMKII δD expression increased only in VL40 (+89%), which experienced greater muscle hypertrophy, and a reduction in MHC-IIX percentage. SLN expression was increased in VL20 (+33%) remaining unaltered in VL40. The changes in phospho-Thr287 -CaMKII δD were positively associated with muscle hypertrophy and the number of repetitions during training, and negatively with the changes in MHC-IIX and SLN. Most OXPHOS proteins remained unchanged, except for NDUFB8 (Complex I), which was reduced after training (-22%) in both groups. The amount of fatigue allowed in each set critically influences muscle CaMKII and SLN responses and determines muscle phenotype changes. With lower intra-set fatigue, the IIX-to-IIA MHC shift is attenuated.

Role of the Effort Index in Predicting Neuromuscular Fatigue During Resistance Exercises.

Rodríguez-Rosell, D, Yáñez-García, JM, Mora-Custodio, R, Torres-Torrelo, J, Ribas-Serna, J, and González-Badillo, JJ. Role of the effort index in predicting neuromuscular fatigue during resistance exercises. J Strength Cond Res XX(X): 000-000, 2020-This study aimed: (a) to analyze the acute mechanical, metabolic, and electromyographic (EMG) response to 16 resistance exercise protocols (REPs) defined by the first repetition's mean velocity and the percentage of velocity loss (%VL) over the set in the full-squat (SQ) exercise; and (b) to assess whether the effort index (EI, the product of the first repetition's mean velocity and the %VL in the set) could be used as an objective indicator of neuromuscular fatigue. Eleven resistance-trained men performed 16 REPs in the SQ exercise. For the configuration of the 16 REPs, 4 relative intensities (50, 60, 70, and 80% 1 repetition maximum) and 4 magnitudes of %VL (∼10, ∼20, ∼30, and ∼45%) were used. The induced fatigue after each REP was quantified using the percentage of change in (a) countermovement jump (CMJ) height, (b) mean propulsive velocity attained with the load that elicited an ∼1.00 m·s (V1 m·s load), and (c) changes in surface EMG variables. Blood lactate concentration was also collected. The EI presented very strong relationships with the %VL with the V1 m·s load, CMJ height, and post-exercise lactate concentration (r = 0.92, 0.93, and 0.91, respectively; p < 0.001). Moderate to strong relationships were found between the EI and the changes in amplitude (r = 054-0.58; p < 0.05), frequency (r = -0.55 to -0.83; p < 0.05-0.001), and time-frequency (r = 0.52-0.77; p < 0.05-0.001) EMG variables. In addition, the moderate to strong relationships found between the relative changes in mechanical, metabolic, and EMG variables after each REP reinforce the validity of the EI as an objective indicator of muscle fatigue, metabolic stress, and neural effect induced by typical resistance training sessions. Thus, by adjusting the EI in each session, it is possible to quantifying the actual level of effort experienced by each individual during resistance exercises.

Determining the One Repetition Maximum in the Ballistic Bench Press Exercise.

Loturco, I, McGuigan, MR, Suchomel, T, Freitas, TT, Rodríguez-Rosell, D, Pereira, LA, and Pareja-Blanco, F. Determining the one repetition maximum in the ballistic bench press exercise. J Strength Cond Res 34(12): 3321-3325, 2020-The purpose of this study was to determine the relative load (% of one repetition maximum [1RM]) at which the concentric action becomes entirely propulsive in the bench press (BP) exercise and verify whether this relative load varies between athletes with different strength levels. Twenty-eight professional athletes (Olympic boxers, professional mixed martial arts fighters, and elite rugby players) performed a progressive loading test up to their 1RM in the BP exercise (BP-1RM). Athletes were ordered according to their relative strength values and equally divided into 2 different groups: "low" (≤1.34) and "high" (≥1.38) strength levels. An independent t-test was used to compare the variables between groups. Significance level was set at p < 0.05. No significant differences were observed between the groups for the mean propulsive velocity attained at 1RM and for the maximum load that required braking action during the execution of the traditional BP exercise (effect size = 0.27 and 0.15, respectively; p > 0.05). Our results revealed that at 80% 1RM the concentric action can already be considered as 100% propulsive in the BP exercise. Importantly, this occurrence was independent of strength level. Therefore, this relative strength measure (i.e., 80% BP-1RM) may be used as a reference for the 1RM in the BP throw.

Relationship Between Velocity Loss and Repetitions in Reserve in the Bench Press and Back Squat Exercises.

Rodríguez-Rosell, D, Yáñez-García, JM, Sánchez-Medina, L, Mora-Custodio, R, and González-Badillo, JJ. Relationship between velocity loss and repetitions in reserve in the bench press and back squat exercises. J Strength Cond Res 34(9): 2537-2547, 2020-This study aimed to compare the pattern of repetition velocity decline during a single set to failure performed against 4 relative loads in the bench press (BP) and full back squat (SQ) exercises. After an initial test to determine 1 repetition maximum (1RM) strength and load-velocity relationships, 20 men performed one set of repetitions to failure (MNR test) against loads of 50, 60, 70, and 80% 1RM in BP and SQ, on 8 random order sessions performed every 6-7 days. Velocity against the load that elicited a ∼1.00 m·s (V1 m·s load) was measured before and immediately after each MNR test, and it was considered a measure of acute muscle fatigue. The number of repetitions completed against each relative load showed high interindividual variability in both BP (coefficient of variation [CV]: 15-22%) and SQ (CV: 26-34%). Strong relationships were found between the relative loss of velocity in the set and the percentage of performed repetitions in both exercises (R = 0.97 and 0.93 for BP and SQ, respectively). Equations to predict repetitions left in reserve from velocity loss are provided. For a given magnitude of velocity loss within the set (15-65%), the percentages of performed repetitions were lower for the BP compared with the SQ for all loads analyzed. Acute fatigue after each set to failure was found dependent on the magnitude of velocity loss (r = 0.97 and 0.99 for BP and SQ, respectively) but independent of the number of repetitions completed by each participant (p > 0.05) for both exercises. The percentage of velocity loss against the V1 m·s load decreased as relative load increased, being greater for BP than SQ. These findings indicate that monitoring repetition velocity can be used to provide a very good estimate of the number (or percentage) of repetitions actually performed and those left in reserve in each exercise set, and thus to more objectively quantify the level of effort incurred during resistance training.

Concurrent Training and Detraining: The Influence of Different Aerobic Intensities.

Sousa, AC, Neiva, HP, Gil, MH, Izquierdo, M, Rodríguez-Rosell, D, Marques, MC, and Marinho, DA. Concurrent training and detraining: the influence of different aerobic intensities. J Strength Cond Res 34(9): 2565-2574, 2020-The aim of this study was to verify the effects of different aerobic intensities combined with the same resistance training on strength and aerobic performances. Thirty-nine men were randomly assigned to a low-intensity group (LIG), moderate-intensity group (MIG), high-intensity group (HIG), and a control group. The training program consisted of full squat, jumps, sprints, and running at 80% (LIG), 90% (MIG), or 100% (HIG) of the maximal aerobic speed for 16-20 minutes. The training period lasted for 8 weeks, followed by 4 weeks of detraining. Evaluations included 20-m sprints (0-10 m: T10; 0-20 m: T20), shuttle run, countermovement jump (CMJ), and strength (1RMest) in full squat. There were significant improvements from pre-training to post-training in T10 (LIG: 4%; MIG: 5%; HIG: 2%), T20 (3%; 4%; 2%), CMJ (9%; 10%; 7%), 1RMest (13%; 7%; 8%), and oxygen uptake (V[Combining Dot Above]O2max; 10%; 11%; 10%). Comparing the changes between the experimental groups, 1RMest gains were significantly higher in the LIG than HIG (5%) or MIG (6%). Furthermore, there was a tendency for higher gains in LIG and MIG compared with HIG, with "possibly" or "likely" positive effects in T10, T20, and CMJ. Detraining resulted in performance decrements, but minimal losses were found for V[Combining Dot Above]O2max in LIG (-1%). Concurrent training seems to be beneficial for strength and aerobic development regardless of the aerobic training intensity. However, choosing lower intensities can lead to increased strength and is recommended when the cardiorespiratory gains should be maintained for longer.

Time Course of Recovery From Resistance Exercise With Different Set Configurations.

Pareja-Blanco, F, Rodríguez-Rosell, D, Aagaard, P, Sánchez-Medina, L, Ribas-Serna, J, Mora-Custodio, R, Otero-Esquina, C, Yáñez-García, JM, and González-Badillo, JJ. Time course of recovery from resistance exercise with different set configurations. J Strength Cond Res 34(10): 2867-2876, 2020-This study analyzed the response to 10 resistance exercise protocols differing in the number of repetitions performed in each set (R) with respect to the maximum predicted number (P). Ten males performed 10 protocols (R(P): 6(12), 12(12), 5(10), 10(10), 4(8), 8(8), 3(6), 6(6), 2(4), and 4(4)). Three sets with 5-minute interset rests were performed in each protocol in bench press and squat. Mechanical muscle function (countermovement jump height and velocity against a 1 m·s load, V1-load) and biochemical plasma profile (testosterone, cortisol, growth hormone, prolactin, IGF-1, and creatine kinase) were assessed at several time points from 24-hour pre-exercise to 48-hour post-exercise. Protocols to failure, especially those in which the number of repetitions performed was high, resulted in larger reductions in mechanical muscle function, which remained reduced up to 48-hour post-exercise. Protocols to failure also showed greater increments in plasma growth hormone, IGF-1, prolactin, and creatine kinase concentrations. In conclusion, resistance exercise to failure resulted in greater fatigue accumulation and slower rates of neuromuscular recovery, as well as higher hormonal responses and greater muscle damage, especially when the maximal number of repetitions in the set was high.

Effects of Resistance Training and Combined Training Program on Repeated Sprint Ability in Futsal Players.

The purpose of this study was to compare the effects of 6 weeks resistance training (RT) with combined RT and loaded change of direction (CD) exercise on muscle strength and repeated sprint ability (RSA) in futsal players. Thirty-four players (age: 23.7±4.1 years; height: 1.77±0.06 m; body mass: 74.1±8.2 kg) were randomly assigned into three groups: full squat group (SG, n=12), combined full squat and CD group (S+CDG, n=12), and control group (CG, n=10). The RT for SG consisted of full squat with low-load (~45-60% 1RM) and low-volume (2-3 sets and 4-6 repetitions), whereas the S+CDG performed the same RT program combined with loaded CD (2-5 sets of 10 s). Estimated one-repetition maximum (1RMest) and variables derived from RSA test including mean sprint time (RSAmean), best sprint time (RSAbest), percent sprint decrement (Sdec), mean ground contact time (GCTmean) and mean step length (SL) were selected as testing variables. Changes in sprint time and GCT in each sprint were also analysed. Both experimental groups showed significant (P<0.05-0.001) improvements for 1RMest, RSAbest and first and second sprint time. In addition, S+CDG achieved significant (P<0.05-0.001) improvements in RSAmean, sprint time (from fifth to ninth sprint) and GCT (from third to eighth sprint). These results indicate that only 6 weeks of low-load and low-volume RT combined with CD in addition to routine futsal training is enough to improve RSA and strength performance simultaneously in futsal players.

Effect of different inter-repetition rest intervals across four load intensities on velocity loss and blood lactate concentration during full squat exercise.

This study aimed to analyze the acute effect of inter-repetition rest (IRR) intervals on mechanical and metabolic response during four resistance exercise protocols (REPs). Thirty resistance-trained men were randomly assigned to: continuous repetitions (CR), 10 s (IRR10) or 20 s (IRR20) inter-repetition rest. The REPs consisted of 3 sets of 6, 5, 4 and 3 repetitions against 60, 70, 75 and 80% 1RM, respectively, in the full squat exercise. Muscle fatigue was assessed using: percentage of velocity loss over three sets, percentage of velocity loss against the ~1 m·s-1 load (V1 m·s-1), and loss of countermovement jump (CMJ) height pre-post exercise. Blood lactate was measured before and after exercise. The percentage of velocity loss over three sets and lactate concentration were significantly lower (P < 0.05) for IRR groups compared to CR in all REPs. The CR group showed a significantly higher (P < 0.05) velocity loss against V1 m·s-1 load and loss of CMJ height pre-post exercise than IRR groups in REP against 60% 1RM. In conclusion, both IRR groups produced a significant lower degree of fatigue compared to CR group. However, no significant differences were found in any measured variables between IRR configurations.

Concurrent Training Followed by Detraining: Does the Resistance Training Intensity Matter?

Sousa, AC, Marinho, DA, Gil, MH, Izquierdo, M, Rodríguez-Rosell, D, Neiva, HP, and Marques, MC. Concurrent training followed by detraining: does the resistance training intensity matter? J Strength Cond Res 32(3): 632-642, 2018-The aim of this study was to analyze the training and detraining (DT) effects of concurrent aerobic training and resistance training against 3 different external loads on strength and aerobic variables. Thirty-two men were randomly assigned to 4 groups: low-load (LLG, n = 9), moderate-load (MLG, n = 9), high-load (HLG, n = 8), and control group (CG, n = 6). Resistance training consisted of full squat (FS) with a low load (40-55% 1 repetition maximum [1RM]), a moderate load (55-70% 1RM), or a high load (70-85% 1RM) combined with jump and sprint exercises. Aerobic training was performed at 75% of the maximal aerobic speed for 15-20 minutes. The training period lasted for 8-week, followed by 4-week DT. Pretraining, post-training, and post-DT evaluations included 20-m running sprints (0-10 m: T10; 0-20 m: T20), shuttle run test, countermovement vertical jump (CMJ) test, and loading test (1RM) in FS. All the experimental groups showed improvements (p ≤ 0.05) in all the parameters assessed, except the LLG for T10 and the HLG for T20. The LLG, MLG, and HLG showed great changes in 1RM and V[Combining Dot Above]O2max compared with the CG (p ≤ 0.05), whereas the HLG and MLG showed a greater percentage change than the CG in T10 (p < 0.001) and CMJ (p ≤ 0.05). The 4-week DT period resulted in detrimental effects in all variables analyzed for all 3 experimental groups. In conclusion, our results suggest that strength training programs with low, moderate, or high external loads combined with low-intensity aerobic training could be effective for producing significant gains in strength and aerobic capacities. Moreover, the higher loads used increased gains in explosive efforts.

Effort Index as a Novel Variable for Monitoring the Level of Effort During Resistance Exercises.

Rodríguez-Rosell, D, Yáñez-García, JM, Torres-Torrelo, J, Mora-Custodio, R, Marques, MC, and González-Badillo, JJ. Effort index as a novel variable for monitoring the level of effort during resistance exercises. J Strength Cond Res 32(8): 2139-2153, 2018-This study aimed to analyze the acute mechanical and metabolic response to resistance exercise protocols (REPs) defined by 2 variables: the first repetition's mean velocity and the percentage of velocity loss (%VL) over the set. The product of these 2 variables was termed the effort index (EI) and was used as an indicator of the degree of fatigue induced during each REP. Twenty-one resistance-trained men (11 in full squat [SQ] and 10 in bench press [BP]) performed 16 REPs separated by 72 hours. Relative loads used (50, 60, 70, and 80% 1-repetition maximum) were determined from the load-velocity relationship for the SQ and BP, whereas volume was objectively determined using the %VL attained over the set (10, 20, 30, and 45% for SQ, and 15, 25, 40, and 55% for BP). Lactate concentration and velocity against the load that elicited a ∼1.00 m·s (V1 m·s load) were measured before and after each REP. Post-exercise velocity with the V1 m·s load and lactate concentration were significantly different (P < 0.01-0.001) from pre-exercise after all REPs. A very close relationship was found between the proposed EI and %VL with the V1 m·s load (r = 0.92-0.98) and post-exercise lactate concentration (r = 0.91-0.95) in both exercises. The correlations between this new index and fatigue indicators such as VL allow us to gain further insight into the actual degree of effort incurred during resistance exercise. In addition to being a valuable addition for training monitoring, the proposed EI could also be used as an independent variable in training studies by equalizing the effort between different interventions.

Velocity Loss as a Variable for Monitoring Resistance Exercise.

This study aimed to analyze: 1) the pattern of repetition velocity decline during a single set to failure against different submaximal loads (50-85% 1RM) in the bench press exercise; and 2) the reliability of the percentage of performed repetitions, with respect to the maximum possible number that can be completed, when different magnitudes of velocity loss have been reached within each set. Twenty-two men performed 8 tests of maximum number of repetitions (MNR) against loads of 50-55-60-65-70-75-80-85% 1RM, in random order, every 6-7 days. Another 28 men performed 2 separate MNR tests against 60% 1RM. A very close relationship was found between the relative loss of velocity in a set and the percentage of performed repetitions. This relationship was very similar for all loads, but particularly for 50-70% 1RM, even though the number of repetitions completed at each load was significantly different. Moreover, the percentage of performed repetitions for a given velocity loss showed a high absolute reliability. Equations to predict the percentage of performed repetitions from relative velocity loss are provided. By monitoring repetition velocity and using these equations, one can estimate, with considerable precision, how many repetitions are left in reserve in a bench press exercise set.

Light-load maximal lifting velocity full squat training program improves important physical and skill characteristics in futsal players.

This study aimed to compare the effect of 6 weeks of resistance training or combined resistance training and change of direction exercises on physical performance and motor skills in futsal players. Thirty-four futsal players were divided into full squat group (SG, n = 12), combined full squat and change of direction exercises group (S+CDG, n = 12) and control group (CG, n = 10). The resistance training for SG consisted of full squat with low load (~45-58% 1RM) and low volume (4-6 repetitions), whereas the S+CDG performed the same resistance training program combined with loaded change of direction. Sprint time in 10 and 20 m, change of direction test, countermovement vertical jump (CMJ) height, maximal strength and force-velocity relationship in full squat exercise, kicking speed ball (BSmean) and repeated sprint ability (RSAmean) were selected as testing variables. Both experimental groups showed significant improvements for CMJ, BSmean and all strength parameters. Only SG resulted in significant sprint gains, whereas S+CDG also achieved significant improvements in RSAmean. The CG remained unchanged after training period. No significant differences were found between both experimental groups. These findings suggest that only 12 sessions of either lightweight resistance training alone, lifting the load at maximal intended velocity or combined with change of direction exercises is enough to improve several physical and skills capacities critical to futsal performance in adult players.