Acute Responses to Different Velocity Loss Thresholds during Squat Exercise with Blood-Flow Restriction in Strength-Trained Men.

(1) Background: The aim of this paper is to analyze the acute effects of different velocity loss (VL) thresholds during a full squat (SQ) with blood-flow restriction (BFR) on strength performance, neuromuscular activity, metabolic response, and muscle contractile properties. (2) Methods: Twenty strength-trained men performed four protocols that differed in the VL achieved within the set (BFR0: 0% VL; BFR10: 10% VL; BFR20: 20% VL; and BFR40: 40% VL). The relative intensity (60% 1RM), recovery between sets (2 min), number of sets (3), and level of BFR (50% of arterial occlusion pressure) were matched between protocols. Tensiomyography (TMG), blood lactate, countermovement jump (CMJ), maximal voluntary isometric SQ contraction (MVIC), and performance with the absolute load required to achieve 1 m·s-1 at baseline measurements in SQ were assessed before and after the protocols. (3) Results: BFR40 resulted in higher EMG alterations during and after exercise than the other protocols (p < 0.05). BFR40 also induced greater impairments in TMG-derived variables and BFR10 decreased contraction time. Higher blood lactate concentrations were found as the VL within the set increased. BFR0 and BFR10 showed significantly increased median frequencies in post-exercise MVIC. (4) Conclusions: High VL thresholds (BFR40) accentuated metabolic and neuromuscular stress, and produced increased alterations in muscles' mechanical properties. Low VL could potentiate post-exercise neuromuscular activity and muscle contractile properties.

Myoelectric manifestations of fatigue of the finger flexor muscles and endurance capacity in experienced versus intermediate climbers during suspension tasks.

Climbing is a physically demanding discipline, placing significant loads on the finger flexors. Notwithstanding the documented greater endurance capacity of experienced climbers, the mechanisms explaining these training-induced adaptations remain unknown. We therefore investigate whether two non-competing strategies - muscle adaptation and alternate muscle recruitment - may explain the disparity in endurance capacity in participants with different climbing experience. We analysed high-density surface electromyograms (EMGs) from 38 Advanced and Intermediate climbers, during suspension exercises over three different depths (15, 20, 30 mm) using a half-crimp grip position. From the spatial distribution of changes in MeDian Frequency and Root Mean Square values until failure, we assessed how much and how diffusely the myoelectric manifestations of fatigue took place. Advanced climbers exhibited greater endurance, as evidenced by significantly longer failure time (p < 0.009) and lower changes in MDF values (p < 0.013) for the three grip depths. These changes were confined to a small skin region (nearly 25% of the grid size), centred at variable locations across participants. Moreover, lower MDF changes were significantly associated with longer suspension times. Collectively, our results suggest that muscle adaptation rather than load sharing between and within muscles is more likely to explain the improved endurance in experienced climbers.

The interplay between gastrocnemius medialis force-length and force-velocity potentials, cumulative EMG activity and energy cost at speeds above and below the walk to run transition speed.

NEW FINDINGS: What is the central question of the study? Are the changes in force potentials (at the muscle level) related with metabolic changes at speeds above and below the walk-to-run transition? What is the main finding and its importance? The force-length and force-velocity potentials of gastrocnemius medialis during human walking decrease as a function of speed; this decrease is associated with an increase in cumulative EMG activity and in the energy cost of locomotion. Switching from fast walking to running is associated to an increase in the force potentials, supporting the idea that the 'metabolic trigger' that determines the transition from walking to running is ultimately driven by a reduction of the muscle's contractile capacity. ABSTRACT: The aim of this study was to investigate the interplay between the force-length (F-L) and force-velocity (F-V) potentials of gastrocnemius medialis (GM) muscle fascicles, the cumulative muscle activity per distance travelled (CMAPD) of the lower limb muscles (GM, vastus lateralis, biceps femori, tibialis anterior) and net energy cost (Cnet ) during walking and running at speeds above and below the walk-to-run transition speed (walking: 2-8 km h-1 ; running: 6-10 km h-1 ). A strong association was observed between Cnet and CMAPD: both changed significantly with walking speed but were unaffected by speed in running. The F-L and F-V potentials decreased with speed in both gaits and, at 6-8 km h-1 , were significantly larger in running. At low to moderate walking speeds (2-6 km h-1 ), the changes in GM force potentials were not associated with substantial changes in CMAPD (and Cnet ), whereas at walking speeds of 7-8 km h-1 , even small changes in force potentials were associated with steep increases in CMAPD (and Cnet ). These data suggest that: (i) the walk to run transition could be explained by an abrupt increase in Cnet driven by an upregulation of the EMG activity (e.g., in CMAPD) at sustained walking speeds (>7 km h-1 ) and (ii) the reduction in the muscle's ability to produce force (e.g., in the F-L and F-V potentials) contributes to the increase in CMAPD (and Cnet ). Switching to running allows regaining of high force potentials, thus limiting the increase in CMAPD (and Cnet ) that would otherwise occur to sustain the increase in locomotion speed.

Evaluación de la respuesta aguda sobre distintas variables mecánicas, fisiológicas y metabólicas tras un ejercicio de subida de escaleras con equipo específico en bomberos profesionales / Avaliação da resposta aguda em diferentes variáveis mecânicas, fisiológicas e metabólicas após um exercíciode subida de escada com equipamentos específicos em bombeiros profissionais / Evaluation of the acute response on different mechanical, physiological and metabolic variables after a stair- climbing exercise with specific gear in professional firefighters

Objetivo: Analizar las respuestas agudas de una prueba de subida de escaleras con equipo especifico sobre distintas variables mecánicas, metabólicas yfisiológicas en un grupo de bomberos profesionales. Método: 34 bomberos (Edad: 42.7 ± 8.2 años; Peso: 76.16 ± 6.70 kg; Estatura: 177 ± 5 cm) realizaron una prueba de subida de una escalera de seisplantas con equipo específico a la máxima velocidad. Antes y después de dicha prueba, se evaluó su capacidad de salto vertical (CMJ) y la fuerza muscularde las piernas en el ejercicio de sentadilla completa con una carga similar a la carga del equipo específico (35 kg, VMP35kg); se analizaron tambiéndiferentes variables fisiológicas (saturación de oxígeno [O2] y frecuencia cardiaca [FC]) y metabólicas (lactato en sangre [La]). Los participantes seagruparon en 3 rangos de edad (G1: 26-35 años; G2: 36-45 años; G3: ≥ 46 años).Resultados: Se observó una pérdida significativa (p < 0.001) en la capacidad de salto CMJ y en la VMP35kg tras la prueba de subida de escaleras, junto conun aumento significativo (p < 0.001) en [La] y en la FC. Entre grupos de edad, se hallaron diferencias significativas (p < 0.05) en el salto CMJ y en la VMPde la sentadilla con 35 kg en los G1 y G2 con respecto al G3, siempre a favor de los grupos de menos edad.Conclusiones:El ejercicio de subida de escaleras con el equipo específico produjo una disminución significativa del rendimiento en la fuerza muscular delas piernas, así como un aumento significativo en las variables fisiológicas y metabólicas de FC y La, y una disminución significativa en la saturación de O2,indicando que este tipo de esfuerzo produce una fatiga elevada.(AU)

Objective: To analyse the acute response on different mechanical, physiological and metabolic variables after a stair-climbing exercise with specific gearin professional firefighters.Method: 34 professional firefighters (Age: 42.7 ± 8.2 years; Weight: 76.16 ± 6.70 kg; Heigh: 177 ± 5 cm) performed a stair-climbing exercise over 6 floorswith specific gear at maximum speed. Before and after this exercise, different mechanical variables: vertical jump capacity (CMJ) and lower limb strengthin full squat exercise with a load equivalent to that of the specific gear (35 kg, VMP35kg); and physiological and metabolic variables: oxygen saturation[O2], heart rate [FC] and lactate [La] were analysed. Participants were also grouped by age ranges (G1: 26-35 years; G2: 36-45 years; G3: ≥ 46 years).Results: A significant decrease (p < 0.001) in vertical jump capacity and lower limb strength in full squat after the stair-climbing exercise was observed. Inaddition, a significant increase (p < 0.001) in lactate and heart rate was also observed. When analysing by age ranges, significant differences (p < 0.05) invertical jump and squat exercise with 35kg were observed in G1 and G2 with respect to G3, always in favor of the younger age group. Conclusions: The stair-climbing exercise with specific gear showed a significant decrease in lower limb strength performance, as well as a significantincrease in heart rate and lactate variables, and a significant decrease in oxygen saturation. These results indicate that this type of effort induces highlevels of fatigue.(AU)

Objetivo: Analisar as respostas agudas de um teste de subida de escada com equipamento específico sobre diferentes variáveis mecânicas, metabólicas efisiológicas em um grupo de bombeiros profissionais.Método: 34 bombeiros (Idade: 42.7 ± 8.2 anos; Peso: 76.16 ± 6.70 kg; Altura: 177 ± 5 cm) realizaram um teste de subida de escada de seis andares comequipamento específico em velocidade máxima. Antes e após tal teste, foram avaliadas a capacidade de salto vertical (CMJ) e força muscular da perna noexercício de agachamento completo com carga semelhante à carga do equipamento específico (35kg, VMP35kg); Diferentes variáveis fisiológicas(saturação de oxigênio [O2] e frequência cardíaca [FC]) e metabólicas (lactato sanguíneo [La]) também foram analisadas. Os participantes foramagrupados em 3 faixas etárias (G1: 26-35 anos; G2: 36-45 anos; G3: ≥ 46 anos).Resultados: Foi observada uma perda significativa (p < 0,001) na capacidade de salto do CMJ e VMP35kg após o teste de subir escadas, juntamente comum aumento significativo (p < 0,001) na [La] e na FC. Entre as faixas etárias, foram encontradas diferenças significativas (p < 0,05) no salto CMJ e noagachamento VMP de 35kg no G1 e G2 em relação ao G3, sempre a favor das faixas etárias mais jovensConclusões: O exercício de subir escadas com o equipamento específico produziu uma diminuição significativa do desempenho na força muscular daspernas, assim como um aumento significativo nas variáveis fisiológicas e metabólicas de FC e La, e uma diminuição significativa na saturação de O2,indicando que este tipo de esforço produz alta fadiga.(AU)

Acute neuromuscular and hormonal responses to 20 versus 40% velocity loss in males and females before and after 8 weeks of velocity-loss resistance training.

NEW FINDINGS: What is the central question of this study? Do males and females differ in fatiguability during dynamic loadings, and what are the acute neuromuscular and hormonal responses to 20 versus 40% velocity-loss resistance loadings? How does an 8-week velocity-loss resistance training period modify acute neuromuscular and hormonal responses in males and females? What is the main finding and its importance? Using resistance training methods that regulated the within-set fatigue limit, males appeared to be more susceptible to fatigue than females before the training period. This between-sex difference was diminished after training. The predominant mechanisms of fatigue from 20 and 40% velocity-based resistance training appear to be within the musculature. ABSTRACT: Scientific examination of velocity-based resistance training (VBRT) has increased recently, but how males and females respond to different VBRT protocols or how these acute responses are modified after a period of training is unknown. Habitually resistance-trained males and females followed either a 20 or 40% velocity-loss programme for 8 weeks. Acute squat loading tests (five sets, 70% one-repetition maximum load, 3 min rest) were performed before and after the training period. Tests of maximum neuromuscular performance and blood sampling were conducted before, within 10 min of completion (POST) and 24 h after each acute loading test. Testing included countermovement jump, resting femoral nerve electrical stimulation and bilateral isometric leg press. Blood samples were analysed for whole-blood lactate, serum testosterone, cortisol, growth hormone and creatine kinase concentrations. Countermovement jump height, maximum isometric bilateral leg-press force and the force from a 10 Hz doublet decreased in all groups at POST after 20 and 40% velocity loss. Only males showed reduced force from the 100 Hz doublet and voluntary force over 100 ms at POST before training. The 40% velocity loss led to increased blood lactate and growth hormone responses before training in both males and females. After training, more systematic and equivalent responses in force over 100 ms, force from a 100 Hz doublet and blood lactate were observed regardless of sex/VBRT protocol. Overall, acute responses were greater from 40% VBRT, and males were more susceptible to acute loss in force production capacity before the training period. These VBRT protocol- and sex-related differences were diminished after training.

Influence of muscle-belly and tendon gearing on the energy cost of human walking.

This study combines metabolic and kinematic measurements at the whole-body level, with EMG and ultrasound measurements to investigate the influence of muscle-tendon mechanical behavior on the energy cost (Cnet ) of walking (from 2 to 8 km·h-1 ). Belly gearing (Gb = Δmuscle-belly length/Δfascicles length) and tendon gearing (Gt = ∆muscle-tendon unit length/∆muscle-belly length) of vastus lateralis (VL) and gastrocnemius medialis (GM) were calculated based on ultrasound data. Pendular energy recovery (%R) was calculated based on kinematic data, whereas the cumulative activity per distance travelled (CMAPD) was calculated for the VL, GM, tibialis anterior, and biceps femoris as the ratio between their EMG activity and walking speed. Finally, total CAMPD (CMAPDTOT ) was calculated as the sum of the CMAPD of all the investigate muscles. Cnet and CMAPDTOT showed a U-shaped behavior with a minimum at 4.2 and 4.1 km·h-1 , respectively; while %R, VL, and GM belly gearing showed an opposite trend, reaching a maximum (60% ± 5%, 1.1 ± 0.1 and 1.5 ± 0.1, respectively), between 4.7 and 5 km·h-1 . Gt was unaffected by speed in GM (3.5 ± 0.1) and decreased as a function of it in VL. A multiple stepwise linear regression indicated that %R has the greatest influence on Cnet, followed by CMAPDTOT and GM belly gearing. The role of Gb on Cnet could be attributed to its role in determining muscle work: when Gb increases, fascicles shortening decreases compared with that of the muscle-belly, thereby reducing the energy cost of contraction.

Do Faster, Stronger, and More Powerful Athletes Perform Better in Resisted Sprints?

ABSTRACT: Lizana, JA, Bachero-Mena, B, Calvo-Lluch, A, Sánchez-Moreno, M, Pereira, LA, Loturco, I, and Pareja-Blanco, F. Do faster, stronger, and more powerful athletes perform better in resisted sprints? J Strength Cond Res 36(7): 1826-1832, 2022-This study aimed to analyze the relationships between different strength, power, and speed abilities and resisted sprint performance across a wide range of sled loads (10, 30, and 50% body mass [BM]). Seventy-nine young physically active male sport science students (age: 22.8 ± 3.4 years, BM: 74.2 ± 9.1 kg, and height: 175.4 ± 8.5 cm) performed 2 testing sessions. Session 1 consisted of a 20 m sprint without any additional load and with 10, 30, and 50% BM. Session 2 consisted of countermovement jump and full squat (SQ) tests. The CMJ was performed without any additional load and with loads of 30 and 50% BM, and the SQ was performed with loads corresponding to 30, 50, 70, and 90% BM. Resisted sprint times were moderate to large correlated with unloaded sprint times (r = 0.79 to 0.89), unloaded and loaded jump height (r = -0.62 to -0.71), and SQ performance (r = -0.56 to -0.71). Negative relationships were observed between velocity loss induced by each sled load and jump and SQ performance. The magnitude of these relationships increased with increasing sled loads. In conclusion, differences in speed, strength, and power abilities may explain, at least partially, the individual response of each athlete during sprinting towing a sled, especially with heavier sled loads. Thus, faster, stronger, and more powerful athletes require heavier sled loads (relative to %BM) to experience similar exercise intensities.

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.

Acute Mechanical, Neuromuscular, and Metabolic Responses to Different Set Configurations in Resistance Training.

ABSTRACT: Piqueras-Sanchiz, F, Cornejo-Daza, PJ, Sánchez-Valdepeñas, J, Bachero-Mena, B, Sánchez-Moreno, M, Martín-Rodríguez, S, García-García, Ó, and Pareja-Blanco, F. Acute mechanical, neuromuscular, and metabolic responses to different set configurations in resistance training. J Strength Cond Res 36(11): 2983-2991, 2022-The aim of this study was to investigate the effect of set configuration on mechanical performance, neuromuscular activity, metabolic response, and muscle contractile properties. Sixteen strength-trained men performed 2 training sessions in the squat exercise consisting of (a) 3 sets of 8 repetitions with 5 minutes rest between sets (3 × 8) and (b) 6 sets of 4 repetitions with 2 minutes rest between sets (6 × 4). Training intensity (75% one repetition maximum), total volume (24 repetitions), total rest (10 minutes), and training density were equalized between protocols. A battery of tests was performed before and after each protocol: (a) tensiomyography (TMG), (b) blood lactate and ammonia concentration, (c) countermovement jump, and (d) maximal voluntary isometric contraction in the squat exercise. Force, velocity, and power output values, along with electromyography data, were recorded for every repetition throughout each protocol. The 6 × 4 protocol resulted in greater mechanical performance (i.e., force, velocity, and power) and lower neuromuscular markers of fatigue (i.e., lower root mean square and higher median frequency) during the exercise compared with 3 × 8, particularly for the last repetitions of each set. The 3 × 8 protocol induced greater lactate and ammonia concentrations, greater reductions in jump height, and greater impairments in TMG-derived velocity of deformation after exercise than 6 × 4. Therefore, implementing lower-repetition sets with shorter and more frequent interset rest intervals attenuates impairments in mechanical performance, especially in the final repetitions of each set. These effects may be mediated by lower neuromuscular alterations, reduced metabolic stress, and better maintained muscle contractile properties.

Load Index and Vertical Jump to Monitor Neuromuscular Fatigue in an Elite 800-m Athlete.

PURPOSE: To analyze the relationships between the evolution of training-load values and countermovement jump (CMJ) as an indicator of stress and fatigue in a high-level 800-m runner during a whole season, including indoor (ID) and outdoor season (OD). METHODS: Over 42 weeks, daily training load was quantified as the result of the product of the intensity and volume, and it was termed load index (LI). CMJ was measured in every running session after warm-up and immediately after the last effort of the session. Other jump-related variables such as CMJ height loss, average weekly CMJ, initial CMJ of the next consecutive session, and initial CMJ of the following week were studied. RESULTS: A significant negative relationship was observed between LI and weekly CMJ (ID: r = -.68, P < .001, common variance [CV] = 46%; OD: r = -.73, P < .001, CV = 53%), initial CMJ of the following week (OD: r = -.71, P < .01, CV = 50%), and CMJ height loss (ID: r = -.58, P < .01, CV = 34%; OD: r = -.52, P < .01, CV = 27%). A significant positive relationship was observed between LI and initial CMJ of the next consecutive session when LI values were <8 (OD: r = .72; P < .01, CV = 52%). However, from values ≥8, the relationship turned into a significant negative one (ID: r = -.74; P < .01, CV = 55%; OD: r = -64, P < .01, CV = 41%). CONCLUSIONS: CMJ may be a valid indicator of the degree of stress or fatigue generated by specific training sessions of a competitive athlete within a single session, a week, or even the following week. There could be an individual limit LI value from which the training volume does not allow a positive effect on high-speed actions such as a CMJ in the next consecutive session.

Effects of Resistance Training on Physical Performance in High-Level 800-Meter Athletes: A Comparison Between High-Speed Resistance Training and Circuit Training.

ABSTRACT: Bachero-Mena, B, Pareja-Blanco, F, and González-Badillo, JJ. Effects of resistance training on physical performance in high-level 800-meter athletes: a comparison between high-speed resistance training and circuit training. J Strength Cond Res 35(7): 1905-1915, 2021-This study compared the effects of 2 resistance training programs during 25 weeks on physical performance and hormonal response in high-level 800 m athletes. Thirteen male athletes (800-m personal best: 1:43-1:58 minutes:ss) were divided into 2 groups: high-speed resistance training group (RTG) (n = 6) and circuit training group (CTG) (n = 7). Three tests (T1, T2, and T3) including sprint and 800 m running, strength exercises, and blood hormones samples were performed. Both groups showed improvements in 800 m performance (RTG: likely positive, 80/20/0%; CTG: very likely positive, 98/2/0%); however, RTG showed an additional improvement in 200 m (likely positive, 85/15/0%), countermovement jump (CMJ) (very likely positive, 98/2/0%), and squat (likely positive, 91/9/0%), whereas CTG reached likely positive (88/11/1%) effects in CMJ and unclear/possibly negative effects in the rest of the strength variables analyzed. Concerning hormones, RTG resulted in a likely increase (83/15/3%) in testosterone from T1 to T3, and CTG showed a likely increase (79/17/4%) in cortisol from T2 to T3, remaining the rest of the hormones analyzed unclear. These results suggest that a resistance training characterized by high-speed and low-volume produced better improvements in both strength and running performance than a circuit training, accompanied by little changes in the hormonal response.

Mechanical and Metabolic Responses during High-intensity Training in Elite 800-m Runners.

The purpose of this study was to describe the mechanical and metabolic responses of a typical high-intensity training session in high-level 800-m athletes. Nine male high-level 800-m athletes (personal best 1:43-1:56 min:ss) performed a typical high-intensity interval training session consisting of 5×200 m with 4 min rest. Countermovement jump and blood lactate were measured at rest and after each running bout. Running times, ground contact times, and stride length were also measured. Running times and lactate (p<0.01) progressively increased from the first to the last running bout. Jump height (p<0.01) and stride length (p<0.05) progressively decreased from the first running bout to the last. A significant negative relationship (p<0.001; r =-0.83) was found between the individual values of jumping height and blood lactate concentration; and a significant positive relationship (p<0.01; r=0.67) was observed between the time in the 200 m and the contact times. In conclusion, the results demonstrated that the typical training session performed by 800-m athletes produced a high level of fatigue as evidenced by significant alterations in the mechanical and metabolic response. The impairments observed in the mechanical and metabolic parameters may indirectly reflect a state of energy deficit of the muscle contractile machinery and a reduction of the force-generating capacity.

Effects of Unloaded Sprint and Heavy Sled Training on Sprint Performance in Physically Active Women.

PURPOSE: This study aimed to compare the effects of unresisted versus heavy sled sprint training (0% vs 40% body mass [BM]) on sprint performance in women. Moreover, the effects of the aforementioned loads on resisted sprint and jump performance were analyzed. METHODS: Twenty-eight physically active women were randomly allocated into 2 groups: unloaded sprint training group (G0%, n = 14), and resisted sprint training with 40% BM group (G40%, n = 14). Pretraining and posttraining assessments included countermovement jump, unloaded 30-m sprint, and 20-m sprint with 20%, 40%, 60%, and 80% BM. Times to cover 0 to 10 (T10), 0 to 20 (T20), 0 to 30 (T30), 10 to 20 (T10-20), 20 to 30 (T20-30), and 10 to 30 m (T10-30) were recorded. Both groups were trained once a week for 8 weeks and completed the same training program, but with different loads (0% vs 40% BM). RESULTS: No significant time × group interactions were observed. For unloaded sprint performance, G0% showed significant (P = .027) decreases only in T10-20, while G40% attained significant decreases in T30 (P = .021), T10-30 (P = .015), and T20-30 (P = .003). Regarding resisted sprint performance, G0% showed significant (P = .010) improvements only for the 20% BM condition. The G40% group attained significant improvements in all loading conditions (20%, 40%, 60%, and 80% BM). Both groups showed significant improvements (P < .001) in countermovement jump height. CONCLUSIONS: In physically active women, no significant differences in sprint and countermovement jump performance were detected after 8 weeks of resisted and unresisted sprint training programs. Future studies should, therefore, be devoted to how sprint training should be individualized to maximize performance.

Effects of velocity loss in the bench press exercise on strength gains, neuromuscular adaptations, and muscle hypertrophy.

OBJECTIVE: This study aimed to compare the effects of four velocity-based training (VBT) programs in bench press (BP) between a wide range of velocity loss (VL) thresholds-0% (VL0), 15% (VL15), 25% (VL25), and 50% (VL50)-on strength gains, neuromuscular adaptations, and muscle hypertrophy. METHODS: Sixty-four resistance-trained young men were randomly assigned into four groups (VL0, VL15, VL25, and VL50) that differed in the VL allowed in each set. Subjects followed a VBT program for 8-weeks using the BP exercise. Before and after the VBT program the following tests were performed: (a) cross-sectional area (CSA) measurements of pectoralis major (PM) muscle; (b) maximal isometric test; (c) progressive loading test; and (d) fatigue test. RESULTS: Significant group x time interactions were observed for CSA (P < .01) and peak root mean square in PM (peak RMS-PM, P < .05). VL50 showed significantly greater gains in CSA than VL0 (P < .05). Only the VL15 group showed significant increases in peak RMS-PM (P < .01). Moreover, only VL0 showed significant gains in the early rate of force development (RFD, P = .05), while VL25 and VL50 improved in the late RFD (P ≤ .01-.05). No significant group × time interactions were found for any of the dynamic strength variables analyzed, although all groups showed significant improvements in all these parameters. CONCLUSION: Higher VL thresholds allowed for a greater volume load which maximized muscle hypertrophy, whereas lower VL thresholds evoked positive neuromuscular-related adaptations. No significant differences were found between groups for strength gains, despite the wide differences in the total volume accumulated by each group.

Acute and Short-Term Response to Different Loading Conditions During Resisted Sprint Training.

PURPOSE: To analyze the acute and short-term physical and metabolic responses to resisted sprint training with 5 different loading conditions (0%, 20%, 40%, 60%, and 80% body mass). METHODS: Fifteen male participants performed 8 × 20-m sprints with 2-minute rests between sprints with 5 different loading conditions. Subjects performed a battery of tests (creatine kinase and lactate concentrations, countermovement jump, 20-m sprint, and isokinetic knee extension and flexion contractions) at 3 different time points (preexercise [PRE], postexercise [POST], and 24-h postexercise [POST24H]). RESULTS: Results revealed significant increases in blood lactate for all loading conditions; however, as sled loadings increased, higher blood lactate concentrations and increments in sprint times during the training session were observed. Significant increases in creatine kinase concentration were observed from PRE to POST24H for all loading conditions. Concerning physical performance, significant decreases in countermovement-jump height from PRE to POST were found for all loading conditions. In addition, significant decreases in 20-m sprint performance from PRE to POST were observed for 0% (P = .05) and 80% (P = .02). No significant differences with PRE were observed for the physical-performance variables at POST24H, except for 20% load, which induced a significant decrease in mean power during knee flexion (P = .03). CONCLUSIONS: These results suggest that the higher the load used during resisted sprint training, the higher the physical-performance impairments and metabolic response produced, although all loading conditions led to a complete recovery of sprint performance at POST24H.

Velocity Loss as a Critical Variable Determining the Adaptations to Strength Training.

PURPOSE: This study aimed to compare the effects of four resistance training (RT) programs with different velocity loss (VL) thresholds: 0% (VL0), 10% (VL10), 20% (VL20), and 40% (VL40) on sprint and jump performance, muscle strength, neuromuscular, muscle hypertrophy, and architectural adaptations. METHODS: Sixty-four young resistance-trained men were randomly assigned into four groups (VL0, VL10, VL20, and VL40) that differed in the VL allowed in each set. Subjects followed an RT program for 8 wk (two sessions per week) using the full-squat (SQ) exercise, with similar relative intensity (70%-85% 1-repetition maximum), number of sets (3), and interset recovery period (4 min). Before and after the RT program, the following tests were performed: 1) muscle hypertrophy and architecture of the vastus lateralis (VLA), 2) tensiomyography, 3) 20-m running sprint, 4) vertical jump, 5) maximal voluntary isometric contraction in SQ, 6) progressive loading test in SQ, and 7) fatigue test. RESULTS: No between-group differences existed for RT-induced gains in sprint, jump, and strength performance despite the differences in the total volume performed by each group. VL20 and VL40 showed significant increases (P < 0.001) in muscle hypertrophy (group-time interaction, P = 0.06). However, only VL40 exhibited a significant slowing (P < 0.001) of the delay time in the VLA muscle (group-time interaction, P = 0.05). Moreover, VL40 showed a significant decrease in the early rate of force development (P = 0.04). CONCLUSIONS: Higher VL thresholds (i.e., VL20 and VL40) maximized hypertrophic adaptations, although an excessive VL during the set (i.e., VL40) may also induce negative neuromuscular adaptations. Therefore, moderate VL thresholds should be chosen to maximize strength adaptations and to prevent negative neuromuscular adaptations.

Enhanced Strength and Sprint Levels, and Changes in Blood Parameters during a Complete Athletics Season in 800 m High-Level Athletes.

The purpose of this study was to analyze changes in sprint, strength, hematological, and hormonal parameters in high-level 800 m athletes during a complete athletics season. Thirteen male athletes of national and international level in 800 m (personal best ranging from 1:43 to 1:58 min:ss) participated in this study. A total of 5 tests were conducted during a complete athletics season. Athletes performed sprint tests (20 and 200 m), countermovement jump (CMJ), jump squat (JS), and full squat (SQ) tests. Blood samples (red and white blood profile) and hormones were collected in test 1 (T1), test 3 (T3), and test 5 (T5). A general increase in the performance of the strength and sprint parameters analyzed (CMJ, JS, SQ, 20 m, and 200 m) during the season was observed, with a significant time effect in CMJ (P < 0.01), SQ (P < 0.01), and 200 m (P < 0.05). This improvement was accompanied by a significant enhancement of the 800 m performance from T3 to T5 (P < 0.01). Significant changes in some hematological variables: hematocrit (Hct) (P < 0.01), mean corpuscular volume (MCV) (P < 0.001), mean corpuscular hemoglobin content (MCHC) (P < 0.001), white blood cells count (WBC) (P < 0.05), neutrophils (P < 0.05), monocytes (P < 0.05), and mean platelet volume (MPV) (P < 0.05) were observed throughout the season. The hormonal response and creatin kinase (CK) did not show significant variations during the season, except for insulin-like growth factor I (IGF-1) (P < 0.05). In conclusion, our results suggest the importance of strength levels in middle-distance athletes. On the other hand, variations in some hematological parameters and a depression of the immune system occurred during the season. Therefore, monitoring of the mechanical, hematological and hormonal response in athletes may help coaches and athletes to optimize the regulation of training contents and may be useful to diagnose states of overreaching or overtraining in athletes throughout the season.

Relationships between Sprint, Jumping and Strength Abilities, and 800 M Performance in Male Athletes of National and International Levels.

This study analysed the relationships between sprinting, jumping and strength abilities, with regard to 800 m running performance. Fourteen athletes of national and international levels in 800 m (personal best: 1:43-1:58 min:ss) completed sprint tests (20 m and 200 m), a countermovement jump, jump squat and full squat test as well as an 800 m race. Significant relationships (p < 0.01) were observed between 800 m performance and sprint tests: 20 m (r = 0.72) and 200 m (r = 0.84). Analysing the 200 m run, the magnitude of the relationship between the first to the last 50 m interval times and the 800 m time tended to increase (1st 50 m: r = 0.71; 2nd 50 m: r = 0.72; 3rd 50 m: r = 0.81; 4th 50 m: r = 0.85). Performance in 800 m also correlated significantly (p < 0.01-0.05) with strength variables: the countermovement jump (r = -0.69), jump squat (r = -0.65), and full squat test (r = -0.58). Performance of 800 m in high-level athletes was related to sprint, strength and jumping abilities, with 200 m and the latest 50 m of the 200 m being the variables that most explained the variance of the 800 m performance.

Evolution of Determinant Factors of Repeated Sprint Ability.

The aim of this study was to investigate the changes in the relationships between repeated sprint ability (RSA) and anthropometric measures as well as fitness qualities in soccer players. Twenty-one professional soccer players performed several anthropometric and physical tests including countermovement vertical jumps (CMJs), a straight-line 30 m sprint (T30), an RSA test (6 x 20 + 20 m with 20 s recovery), a progressive isoinertial loading test in a full squat, a Yo-Yo Intermittent Recovery Test Level-1 (YYIRT-1) and a 20 m shuttle run test (20mSRT). The mean (RSAmean), the fastest (RSAbest), each single sprint time, and the percentage in a sprint decrease (%Dec) in the RSA test were calculated. RSAbest correlated significantly with RSAmean (r = .82) and with all single sprints (p < 0.05), showing a downward trend as the number of sprints performed increased. No significant relationship was observed between the %Dec and RSA performance. CMJs and the T30 also showed a correlation with RSA performance, whereas lower limb strength did not show any relationship with RSA performance. RSAmean showed significant (p < 0.05) relationships with body mass (r = .44), adiposity (r = .59) and the YYIRT-1 (r = -.62), increasing as the number of repeated sprints increased. The 20mSRT showed minimal relationships with RSA performance. In conclusion, maximal sprint capacity seems to be relevant for the RSA performance, mainly in the first sprints. However, high intermittent endurance capacity and low adiposity might help enhance the RSA performance when increasing the number of repeated sprints.

Relationships among repeated sprint ability, vertical jump performance and upper-body strength in professional basketball players

The repeated sprint ability (RSA), counter-movement jump (CMJ) performance and upper-body strength are very important variables in high-level basketball competition. However, the relationships among these variables are poorly studied in elite basketball players. Thus, the purpose of this research is to study the relationships among the Running-Based Anaerobic Speed Test (RAST), the CMJ and upper-body strength in professional male basketball players from the highest-level competition of Spain (League Endesa). Eleven, athletes (N=11, age = 24.5 ± 5.8 yrs, height = 200 ± 10.9 cm, weight = 98.4 ± 9 kg) were tested on the RAST, the CMJ before and after the RAST and the bench press strength in one single morning. The results show, high and statistically significant correlations between the RAST fatigue index (FI) and CMJ loss (the difference between pre and post RAST measures) (r = 0.78, p <0.01), the FI and the maximum force production on the bench press (r = -0.86, p <0.01), and the CMJ loss and the load at which peak power is produced on the bench press (r = -0.77, p <0.01). Our data highlights the remarkable relationship among repeated-sprint ability, the CMJ and upper-body strength in professional male basketball players. For this, it seems clear that elite basketball players may benefit from training programs designed to improve such variables simultaneously. This may be relevant for the strength & conditioning training of such athletes

La capacidad de repetir sprints cortos, los niveles de salto vertical con contramovimiento (CMJ) y la fuerza de miembros superiores tienen una gran importancia en la competición de alto nivel de baloncesto, aunque la relación entre estas variables no está clara en jugadores de elite. Así, el objetivo de esta investigación es estudiar las relaciones entre el test anaeróbico especifico de carrera (RAST), el CMJ y la fuerza de miembros superiores en jugadores profesionales de baloncesto de la liga de mayor nivel competitivo en Espana (Liga Endesa). Para ello, se midió el RAST, el salto con contramovimiento (CMJ) antes y después del RAST y la fuerza en press de banca a 10 deportistas (N=11, edad=24,51 ± 5,8 años, altura = 2001 ± 10,9 cm, peso corporal = 98,41 ± 9 kg) durante una sesión de entrenamiento. Los resultados muestran correlaciones altas y significativas entre el índice de fatiga en el RAST (IF) y la perdida de CMJ (diferencia entre la medición antes y después del RAST) (r = 0,78, p <0,01), el IF y la máxima producción de fuerza en el press de banca (r =-0,86, p <0,01), y la perdida de CMJ y la carga con la que se produce la potencia máxima en press de banca (r = -0,77, p <0,01). Estos datos evidencian la notable relación existente entre la capacidad de repetir sprints, el CMJ y la fuerza de miembros superiores en jugadores profesionales de baloncesto. Por ello, la elaboración de programas de entrenamiento que incidan en estas capacidades simultáneamente parece justifi cada en jugadores de baloncesto de elite. Estos hallazgos pueden ser relevantes para la preparación física de dichos deportistas