Preconditioning Strategies Before Maximum Clean Performance in Female Weightlifters.

ABSTRACT: Kelekian, GK, Zaras, N, Stasinaki, AN, Spiliopoulou, P, Karampatsos, G, Bogdanis, G, and Terzis, G. Preconditioning strategies before maximum clean performance in female weightlifters. J Strength Cond Res 36(8): 2318-2321, 2022-The aim of the study was to examine the acute effect of performing clean pulls with either 85% or 120% one repetition maximum (1RM), on subsequent clean performance, in female Olympic weightlifters. Eight competitive female Olympic weightlifters (age, 22.9 ± 5.8 years; height, 1.67 ± 0.06 m; training experience, 6.1 ± 3.9 years; clean performance, 66.3 ± 3.9 kg), performed clean pulls either with 85% or with 120% 1RM, 3 minutes before their maximum effort in clean, in 2 different days, in a counterbalanced order. The rate of perceived exertion (RPE) was provided after each intervention. Body composition (dual x-ray absorptiometry), countermovement jumping (CMJ) performance, leg press isometric rate of force development (RFD), and peak force (PF) were also evaluated on different days. Clean performance was increased by 6.1 ± 3.6% ( p = 0.002) after preconditioning with 85% 1RM and 4.7 ± 3.1% ( p = 0.004) after 120% 1RM. Rate of perceived exertion was lower after preconditioning with 85% 1RM, compared with 120% 1RM ( p = 0.015). No significant correlation was found between the changes in clean performance after 85% or 120% 1RM, with lean body mass, CMJ performance, and isometric leg press RFD, and leg press PF. These data suggest that lifting either 85% or 120% 1RM in clean pulls is an effective strategy for acute increase of clean performance in female Olympic weightlifters, whereas the use of 85% 1RM load may be performed with less exertion.

Effects of a 25-Week Periodized Training Macrocycle on Muscle Strength, Power, Muscle Architecture, and Performance in Well-Trained Track and Field Throwers.

ABSTRACT: Anousaki, E, Zaras, N, Stasinaki A-N, Panidi, I, Terzis, T, and Karampatsos, G. Effects of a 25-week periodized training macrocycle on muscle strength, power, muscle architecture, and performance in well-trained track and field throwers. J Strength Cond Res 35(10): 2728-2736, 2021-The purpose of the study was to investigate the effect of a 25-week macrocycle on strength, power, vastus lateralis (VL) muscle architecture, and competitive track and field throwing performance, in well-trained track and field throwers. Twelve well-trained throwers (age: 24.3 ± 5.5 years, mass: 96.6 ± 9.9 kg, and height: 1.82 ± 0.02 m), participated in the study. All athletes followed a 25-week periodized training program divided into 3 training phases: the hypertrophy/maximum strength phase, the maximum strength/power phase, and the power/speed phase. Measurements were performed at the beginning of the training period (T1), after the first training phase (T2), and after the end of the training period (T3). Measurements included the following: competitive track and field throwing performance; shot put throws; maximum strength (1-RM) in snatch, clean, and squat; countermovement jump (CMJ); and VL muscle architecture. Competitive track and field throwing performance and shot put throws increased from T1 to T3 by 10.9 ± 3.2% (p = 0.001) and 5.1 ± 6.4% (P = 0.049), respectively. 1 RM strength in snatch and squat increased significantly from T1 to T3 by 9.7 ± 8.9% (p = 0.001) and 9.9 ± 7.1% (p = 0.002), respectively. Countermovement jump height increased only from T1 to T2 by 10.9 ± 11.8% (p = 0.026). A significant increase was found for VL fascicle length between T1 and T3 (9.6 ± 11.1%, p = 0.049). Strong correlations were found between the percentage increase of competitive track and field throwing performance with 1 RM snatch (r = 0.571, p = 0.046) and with shot put throws (r = 0.715, p = 0.001). Twenty five weeks of training may increase performance and VL fascicle length, whereas increases in 1 RM snatch and in shot put throws are associated with competitive track and field throwing performance in well-trained throwers.

Fiber Type Composition and Rate of Force Development in Endurance- and Resistance-Trained Individuals.

Methenitis, S, Spengos, K, Zaras, N, Stasinaki, A-N, Papadimas, G, Karampatsos, G, Arnaoutis, G, and Terzis, G. Fiber type composition and rate of force development in endurance- and resistance-trained individuals. J Strength Cond Res 33(9): 2388-2397, 2019-The purpose of the study was to investigate the relationship between muscle fiber composition and the rate of force development (RFD) in well-trained individuals with different training background. Thirty-eight young men with different training background participated: 9 endurance runners, 10 power-trained individuals, 9 strength-trained individuals, and 10 sedentary individuals. They performed maximal isometric leg press for the measurement of RFD. Body composition (dual x-ray absorptiometry) and vastus lateralis fiber type composition were also evaluated. When all participants were examined as a group, moderate correlations were found between the percent of type II muscle fibers and RFD between 100 and 600 milliseconds (r = 0.321-0.497; p ≤ 0.05). The correlation coefficients were higher for the cross-sectional area (CSA) and the %CSA of type II and IIx muscle fibers (r = 0.599-0.847; p < 0.001). For the power group, RFD up to 250 milliseconds highly correlated with % type IIx muscle fibers and type IIx fiber CSA (r = 0.670-0.826; p ≤ 0.05), as well as with %CSA of type IIx fibers (r = 0.714-0.975; p ≤ 0.05). Significant correlations were found between the relative RFD (·kg lower extremities lean mass) and CSA-%CSA of type II and IIx fibers for the power group (r = 0.676-0.903; p ≤ 0.05). No significant correlations were found between muscle morphology and RFD for the other groups. In conclusion, the present data suggest that there is a strong link between the type IIx muscle fibers and early RFD and relative RFD in power-trained participants. Type II fibers seem to be moderately linked with RFD in non-power-trained individuals.

Role of Muscle Morphology in Jumping, Sprinting, and Throwing Performance in Participants With Different Power Training Duration Experience.

The aim of the study was to examine the correlation between muscle morphology and jumping, sprinting, and throwing performance in participants with different power training duration experience. Thirty-six power-trained young men were assigned to 3 groups according to the length of their power training: less experienced (<1 year), moderately experienced (1-3 years), and experienced (4-7 years). All participants performed countermovement and squat jumps, 60-m sprint, and shot throws twice. Lean body mass (LBM) was evaluated with dual-energy x-ray absorptiometry and thigh muscle cross-sectional area (CSA) with anthropometry. The vastus lateralis architecture and fiber type composition were evaluated with ultrasonography and muscle biopsies, respectively. When all subjects were considered as 1 group (n = 36), jumping performance was correlated with LBM, fascicle length, and type II fiber CSA; sprinting performance was correlated with estimated thigh muscle CSA alone; and shot throwing was correlated with LBM and type I, IIA fiber CSA. In the least experienced group, the LBM of the lower extremities was the most significant contributor for power performance, whereas in the moderately experienced group, the LBM, architectural properties, and type II fiber percentage CSA were the most significant contributors. For the experienced group, fascicle length and type II fiber percentage CSA were the most significant factors for power performance. These data suggest that jumping performance is linked with muscle morphology, regardless of strength or power training. The vastus lateralis muscle morphology could only partially explain throwing performance, whereas it cannot predict sprinting performance. Power performance in experienced participants rely more on the quality of the muscle tissue rather than the quantity.

Rate of Force Development, Muscle Architecture, and Performance in Young Competitive Track and Field Throwers.

The rate of force development (RFD) is an essential component for performance in explosive activities, although it has been proposed that muscle architectural characteristics might be linked with RFD and power performance. The purpose of the study was to investigate the relationship between RFD, muscle architecture, and performance in young track and field throwers. Twelve young track and field throwers completed 10 weeks of periodized training. Before (T1) and after (T2) training performance was evaluated in competitive track and field throws, commonly used shot put tests, isometric leg press RFD, 1 repetition maximum (1RM) strength as well as vastus lateralis architecture and body composition. Performance in competitive track and field throwing and the shot put test from the power position increased by 6.76 ± 4.31% (p < 0.001) and 3.58 ± 4.97% (p = 0.019), respectively. Rate of force development and 1RM strength also increased (p ≤ 0.05). Vastus lateralis thickness and fascicle length increased by 5.95 ± 7.13% (p = 0.012) and 13.41 ± 16.15% (p = 0.016), respectively. Significant correlations were found at T1 and T2, between performance in the shot put tests and both RFD and fascicle length (p ≤ 0.05). Close correlations were found between RFD, muscle thickness, and fascicle length (p ≤ 0.05). Significant correlations were found between the % changes in lean body mass and the % increases in RFD. When calculated together, the % increase in muscle thickness and RFD could predict the % increase in shot put throw test from the power position (p = 0.019). These results suggest that leg press RFD may predict performance in shot put tests that are commonly used by track and field throwers.

Muscle Strength, Power, and Morphologic Adaptations After 6 Weeks of Compound vs. Complex Training in Healthy Men.

The aim of the study was to compare the effects of compound vs. complex resistance training on strength, high-speed movement performance, and muscle composition. Eighteen young men completed compound (strength and power sessions on alternate days) or complex training (strength and power sets within a single session) 3 times per week for 6 weeks using bench press, leg press, Smith machine box squat, and jumping exercises. Pre- and posttraining, jumping and throwing performance and maximum bench press, leg press, and Smith machine box squat strength were evaluated. The architecture of vastus lateralis and gastrocnemius muscle was assessed using ultrasound imaging. Vastus lateralis morphology was assessed from muscle biopsies. Jumping (4 ± 3%) and throwing (9 ± 8%) performance increased only with compound training (p < 0.02). Bench press (5 vs. 18%), leg press (17 vs. 28%), and Smith machine box squat (27 vs. 35%) strength increased after both compound and complex training. Vastus lateralis thickness and fascicle angle and gastrocnemius fascicle angle were increased with both compound and complex training. Gastrocnemius fascicle length decreased only after complex training (-11.8 ± 9.4%, p = 0.006). Muscle fiber cross-sectional areas increased only after complex training (p ≤ 0.05). Fiber type composition was not affected by either intervention. These results suggest that short-term strength and power training on alternate days is more effective for enhancing lower-limb and whole-body power, whereas training on the same day may induce greater increases in strength and fiber hypertrophy.

Effects of tapering with light vs. heavy loads on track and field throwing performance.

The purpose of the study was to investigate the effects of power training with light vs. heavy loads during the tapering phases of a double periodized training year on track and field throwing performance. Thirteen track and field throwers aged 16-26 years followed 8 months of systematic training for performance enhancement aiming at 2 tapering phases during the winter and the spring competition periods. Athletes performed tapering with 2 different resistance training loads (counterbalanced design): 7 athletes used 30% of 1 repetition maximum (1RM) light-load tapering (LT), and 6 athletes used the 85% of 1RM heavy-load tapering (HT), during the winter tapering. The opposite was performed at the spring tapering. Before and after each tapering, throwing performance, 1RM strength, vertical jumping, rate of force development (RFD), vastus lateralis architecture, and rate of perceived exertion were evaluated. Throwing performance increased significantly by 4.8 ± 1.0% and 5.6 ± 0.9% after LT and HT, respectively. Leg press 1RM and squat jump power increased more after HT than LT (5.9 ± 3.2% vs. -3.4 ± 2.5%, and 5.1 ± 2.4% vs. 0.9 ± 1.4%, respectively, p ≤ 0.05). Leg press RFD increased more in HT (38.1 ± 16.5%) compared with LT (-2.9 ± 6.7%), but LT induced less fatigue than HT (4.0 ± 1.5 vs. 6.7 ± 0.9, p ≤ 0.05). Muscle architecture was not altered after either program. These results suggest that performance increases similarly after tapering with LT or HT in track and field throwers, but HT leads to greater increases in strength, whole body power, and RFD.

Lean Body Mass, Muscle Architecture and Powerlifting Performance during Preseason and in Competition.

Lean body mass (LBM) is correlated with powerlifting performance in athletes competing in different bodyweight classes. However, it remains unknown whether changes in LBM are correlated with performance changes in powerlifters preparing for a competition. The aim of this study was to investigate the changes in LBM and performance in powerlifters preparing for a competition. Eight male powerlifters (age 31.7 ± 9.8 years, height 1.77 ± 0.06 m, weight 99.2 ± 14.6 kg) and three female powerlifters (age 32.7 ± 16.3 years, height 1.54 ± 0.06 m, weight 66.6 ± 20.9 kg) participated in the study. The athletes followed individualized periodized training programs for 12 weeks, aiming to maximize their performance for the national championship. The maximum strength (1-RM) in the squat, bench press, and deadlift, body composition, handgrip strength, anaerobic power, quadriceps' cross-sectional area and vastus lateralis muscle architecture were measured before and after the training period. Significant increases were found after the training period in the squat (5.8 ± 7.0%, p < 0.05), bench press (4.9 ± 9.8%, p = 0.05) and deadlift (8.3 ± 16.7%, p < 0.05). Significant correlations were found between the 1-RM and LBM before and after the training period (r > 0.75, p < 0.05). The changes in the 1-RM after the training intervention correlated with the changes in the total LBM (p < 0.05). These results suggest that individual changes in LBM due to systematic resistance training for a competition may dictate increases in the 1-RM strength in powerlifters.

Muscle Ultrasound Echo Intensity and Fiber Type Composition in Young Females.

Ultrasonography has been extensively used to evaluate skeletal muscle morphology. The echo intensity, i.e., the mean pixel intensity of a specific region of interest in an ultrasound image, may vary among muscles and individuals with several intramuscular parameters presumed to influence it. The purpose of this study was to investigate the correlation between muscle echo intensity and muscle fiber type composition in humans. Thirteen female physical education students (age: 22.3 ± 5.4 years, height: 1.63 ± 0.06 m, body mass: 59.9 ± 7.4 kg) with no history of systematic athletic training participated in the study. Body composition with dual X-ray absorptiometry, leg-press maximum strength (1-RM), echo intensity, and the cross-sectional area (CSA) of the vastus lateralis (VL) muscle according to ultrasonography were measured. Muscle biopsies were harvested from the VL site where the echo intensity was measured. VL echo intensity was not significantly correlated with the percentage of type I muscle fibers or with the percentage area of type I muscle fibers. However, when VL echo intensity was corrected for the subcutaneous fat thickness at the site of the measurement, it was significantly correlated with the percentage of type I muscle fibers (r = 0.801, p < 0.01) and the percentage area of type I muscle fibers (r = 0.852, p < 0.01). These results suggest that the echo intensity of the vastus lateralis muscle corrected for the subcutaneous fat thickness at the measurement site may provide an estimate of the muscle fiber type composition, at least in young moderately trained females.

Effect of Inter-Repetition Rest Vs. Traditional Resistance Training on The Upper Body Strength Rate of Force Development and Triceps Brachii Muscle Architecture.

The purpose of the study was to examine the effect of seven-week inter-repetition rest vs. traditional resistance training on upper body maximum strength, the rate of force development and triceps brachii muscle architecture. Sixteen male participants were equally assigned into the inter-repetition rest and the traditional group. In both groups, training included the bench press exercise performed with 4 sets of 6 maximum repetitions, two training sessions per week. Twenty-second inter-repetition rest was employed for the inter-repetition rest group only. Measurements before and after the training period included maximum strength in the bench press, the isometric upper body rate of force development and peak force and triceps brachii muscle architecture. Maximum strength increased significantly in both groups (inter-repetition rest group: 21.5 ± 5.7% vs. traditional group: 13.5 ± 7.2%, p < 0.05), however, the maximum strength percentage increase was greater in the inter-repetition rest group compared to the traditional group (p = 0.027). Upper body isometric peak force increased only after inter-repetition rest training (10.7 ± 10.3%, p = 0.009). The rate of force development remained unchanged for both groups (p > 0.05), although percentage changes in time frames of 0-80 and 0-100 milliseconds were greater for the inter-repetition rest group compared to the traditional training group (p = 0.024 and p = 0.044, respectively). Triceps brachii thickness increased similarly for both groups (p < 0.05). These results suggest that inter-repetition rest may induce greater increases in maximum strength and the rate of force development compared to traditional training during the initial weeks of resistance training.

Biological Determinants of Track and Field Throwing Performance.

Track and field throwing performance is determined by a number of biomechanical and biological factors which are affected by long-term training. Although much of the research has focused on the role of biomechanical factors on track and field throwing performance, only a small body of scientific literature has focused on the connection of biological factors with competitive track and field throwing performance. The aim of this review was to accumulate and present the current literature connecting the performance in track and field throwing events with specific biological factors, including the anthropometric characteristics, the body composition, the neural activation, the fiber type composition and the muscle architecture characteristics. While there is little published information to develop statistical results, the results from the current review suggest that major biological determinants of track and field throwing performance are the size of lean body mass, the neural activation of the protagonist muscles during the throw and the percentage of type II muscle fiber cross-sectional area. Long-term training may enhance these biological factors and possibly lead to a higher track and field throwing performance. Consequently, coaches and athletes should aim at monitoring and enhancing these parameters in order to increase track and field throwing performance.

Rate of Force Development, Muscle Architecture, and Performance in Elite Weightlifters.

PURPOSE: The purpose of the present study was to investigate the relationship between weightlifting performance and the rate of force development (RFD), muscle architecture, and body composition in elite Olympic weightlifters. METHODS: Six male Olympic weightlifters (age 23.3 [3.4] y, body mass 88.7 [10.2] kg, body height 1.76 [0.07] m, snatch 146.7 [15.4] kg, clean and jerk 179.4 [22.1] kg), all members of the national team, participated in the study. Athletes completed a 16-week periodized training program aiming to maximize their performance at the national competition event. Measurements, including maximal strength (1-repetition maximum) in snatch, clean and jerk, back and front squat, isometric leg press RFD and peak force, countermovement jump, vastus lateralis muscle architecture, and body composition, were performed before and after the training period. RESULTS: Weightlifting performance increased significantly after training (P < .05). Leg press RFD increased only in time windows of 0 to 200 and 0 to 250 milliseconds after training (8.9% [8.5%] and 9.4% [7.7%], respectively, P < .05) while peak force remained unaltered (P < .05). Front squat strength increased significantly (P < .05), while countermovement jump power increased 2.3% (2.1%) (P < .05). No changes were observed for muscle architecture and lean body mass (P > .05). Significant correlations were observed between performance in snatch and clean and jerk with isometric leg press RFD, at all time windows, as well as with lean body mass and squat 1-repetition maximum. CONCLUSIONS: These results suggest that regular examination of RFD, lean body mass, and lower extremities' 1-repetition maximum may be useful performance predictors in elite Olympic weightlifters.

Weak Association Between Vastus Lateralis Muscle Fiber Composition and Fascicle Length in Young Untrained Females.

The aim of the study was to investigate the relationships between vastus lateralis muscle fiber length and fiber type composition in individuals with minimal exposure to systematic resistance/power training. In sixty female physical education students (age: 21.03 ± 2.1 years, body weight: 59.8 ± 9.7 kg, body height: 166.2 ± 6.5 cm), with no experience in systematic training, lean body mass, VL muscle architecture and fiber composition type, countermovement jumping (CMJ) performance, and isometric leg press rate of force development were evaluated. Data were analyzed for all participants, as well as two equally numbered groups assigned according to their maximum countermovement jumping power (High-Power or Low-Power group). Significant but low correlations were found between type II muscle fiber percentage and fascicle length (N = 60, p < 0.05). Significant correlations were found between type IIa and IIx muscle fiber percentage cross-sectional area (%CSA) and fascicle length (N = 60; r = 0.321, and r = 0.378; respectively, p < 0.05). These correlations were higher for the High-Power group (r = 0.499, and r = 0.522; respectively, p < 0.05), and lower, and nonsignificant, for the Low-Power group. The best predictor of strength/power performance was the lean body mass of the lower extremities (r = 0.389-0.645, p < 0.05). These results suggest that in females with minimal exposure to systematic training, fascicle length may be weakly linked with type II fiber areas, only in females with high-power profiles.

Lean Body Mass, Muscle Architecture, and Performance in Well-Trained Female Weightlifters.

Lean mass and quadriceps muscle architecture have been associated with performance in male well-trained weightlifters, but no data exist for female weightlifters. The aim of the study is to investigate the relationship between lean mass, quadriceps cross sectional area (CSA), and muscle architecture with weightlifting performance in female weightlifters. Eight well-trained female weightlifters (age 23.5 ± 6.3 years, maximum total lifting performance = 147.4 ± 34.1 kg) participated in the study. Five of the athletes were members of the national team and three were among the nation's top-five performers of the respective body-weight category. Measurements included maximum lifting performance in snatch and clean and jerk, body composition (dual x-ray absorptiometry), vastus lateralis (VL) muscle architecture, vastus intermedius (VI) muscle thickness and quadriceps muscles' CSA and countermovement jump (CMJ). Very large to nearly perfect correlations were found between snatch and clean and jerk for trunk lean body mass (r = 0.959 and 0.929), for total CSA (r = 0.732 and 0.608), and CMJ power (r = 0.933 and 0.896). These results suggest that lean body mass, quadriceps' CSA and CMJ should be monitored regularly in female weightlifters to detect potential modifications in lifting performance.

Muscle fiber composition, jumping performance, and rate of force development adaptations induced by different power training volumes in females.

This study aimed to investigate the effect of 3 different eccentric-only power training volumes on muscle fiber type composition and power performance. Twenty-nine females were assigned into 3 groups and performed 10 weeks of either 3 (low volume), 6 (moderate volume), or 9 (high volume) sets/session of 4 fast-velocity eccentric-only half-squats against 70% of concentric 1-repetition maximum (1RM), followed by 3 maximum countermovement jumps (CMJs) after each set. Half-squat 1RM, CMJ height/power, maximum isometric force, rate of force development (RFD) and muscle fiber cross-sectional area (CSA) were increased in all groups (p = 0.001). Low-volume training induced higher increases in CMJ height/power and early RFD, compared with the moderate- and high-volume training programs (p < 0.001). Significant reductions in type IIx muscle fiber percentages and %CSAs were found after moderate- and high-volume training, with concomitant increases in type IIa fibers (p = 0.001). Significant correlations were found between the changes in type IIa and type IIx percentages, fiber CSA, %CSA, and the changes in performance (r: -0.787 to 0.792; p < 0.05). These results suggest that relatively large eccentric power training volumes may result in detrimental neuromuscular adaptations, minimal changes in early RFD, and a reduction of type IIx muscle fiber percentage. Novelty Low but not high volume of power training maintains type IIx muscle fibers. Early rate of force development increases after a low- or moderate-power training volume, but not after a high-power training volume. Training-induced changes in type IIx muscle fiber percentage is related with changes in early rate of force development.

Intramuscular fibre conduction velocity and muscle fascicle length in human vastus lateralis.

Muscle fascicle length and muscle fibre conduction velocity (MFCV) are thought to be important parameters for power performance. It might be expected that faster muscle fibre conduction velocities would compensate for longer fascicle lengths to increase the speed of action potential propagation along the elongated fibres. However, the relationship between muscle fascicle length and MFCV remains unknown. The aim of the present study was to explore the relationship between average vastus lateralis MFCV and average fascicle length. In 17 moderately trained, healthy, male, physical education students (age, 23.4 ± 3.1 years; body height, 178 ± 5.5 cm; body mass, 82.7 ± 6.9 kg; body mass index, 24.6 ± 1.5 kg·m-2) resting MFCV was measured with intramuscular microelectrodes while muscle architecture was evaluated with ultrasonography. Fascicle length was highly correlated with total MFCV (r = 0.923, p = 0.000), maximum MFCV (r = 0.949, p = 0.000), and MFCV of the fastest (r = 0.709, p = 0.001), but not of the slowest fibres (r = 0.131, p = 0.616). No significant correlations were also found between vastus lateralis thickness or fascicle angle with any of MFCV parameters (r = 0.145-0.430; R2 < 0.130; p > 0.05). These data indicate that average MFCV is associated with average fascicle length in vastus lateralis muscle in different individuals. It seems that participants with longer fascicle lengths have also higher MFCVs.

Rate of Force Development and Muscle Architecture after Fast and Slow Velocity Eccentric Training.

The aim of the study was to investigate the rate of force development (RFD) and muscle architecture early adaptations in response to training with fast- or slow-velocity eccentric squats. Eighteen young novice participants followed six weeks (two sessions/week) of either fast-velocity (Fast) or slow-velocity (Slow) squat eccentric-only training. Fast eccentric training consisted of nine sets of nine eccentric-only repetitions at 70% of 1-RM with <1 s duration for each repetition. Slow eccentric training consisted of five sets of six eccentric-only repetitions at 90% of 1-RM with ~4 sec duration for each repetition. Before and after training, squat 1-RM, countermovement jump (CMJ), isometric leg press RFD, and vastus lateralis muscle architecture were evaluated. Squat 1-RM increased by 14.5 ± 7.0% (Fast, p < 0.01) and by 5.4 ± 5.1% (Slow, p < 0.05). RFD and fascicle length increased significantly in the Fast group by 10⁻19% and 10.0 ± 6.2%, p < 0.01, respectively. Muscle thickness increased only in the Slow group (6.0 ± 6.8%, p < 0.05). Significant correlations were found between the training induced changes in fascicle length and RFD. These results suggest that fast eccentric resistance training may be more appropriate for increases in rapid force production compared to slow eccentric resistance training, and this may be partly due to increases in muscle fascicle length induced by fast eccentric training.

Changes in Muscle Power and Muscle Morphology with Different Volumes of Fast Eccentric Half-Squats.

The aim of the study was to evaluate power performance and muscle morphology adaptations in response to 5 weeks of fast-eccentric squat training (FEST) performed twice per week, with three different training volumes. Twenty-five moderately trained females were assigned into three groups performing eight repetitions of FEST of either four sets (4 × 8 group; N = 9), 6 sets (6 × 8 group; N = 8) or eight sets (8 × 8 group, N = 8). Before and after the intervention, countermovement jumping height (CMJh) and power (CMJp), half squat maximal strength (1-RM), quadriceps cross-sectional area (QCSA) and vastus lateralis (VL) architecture and fiber type composition were evaluated. Significant increases (p < 0.05) were found for all groups, with no differences among them in 1-RM (4 × 8: 14.8 ± 8.2%, 6 × 8: 13.1 ± 9.2% and 8 × 8: 21.6 ± 7.0%), CMJh (4 × 8: 12.5 ± 8.5%, 6 × 8: 11.3 ± 9.3% and 8 × 8: 7.0 ± 6.2%), CMJp (4 × 8: 9.1 ± 6.0%, 6 × 8: 7.1 ± 5.2% and 8 × 8: 5.0 ± 3.9%) and QCSA (4 × 8: 7.7 ± 4.7%, 6 × 8: 9.0 ± 6.8% and 8 × 8: 8.2 ± 6.5%). Muscle fiber type distribution remained unaltered after training in all groups. VL fascicle length increased and fascicle angle decreased only in 6 × 8 and 8 × 8 groups. In conclusion, four sets of eight fast-eccentric squats/week increase lower body power and strength performance and maintain type IIX muscle fibers after 5 weeks, at least in moderately trained females.

The Importance of Lean Body Mass for the Rate of Force Development in Taekwondo Athletes and Track and Field Throwers.

The rate of force development (RFD) is vital for power athletes. Lean body mass (LBM) is considered to be an essential contributor to RFD, nevertheless high RFD may be achieved by athletes with either high or low LBM. The aim of the study was to describe the relationship between lower-body LBM and RFD, and to compare RFD in taekwondo athletes and track and field (T&F) throwers, the latter having higher LBM when compared to taekwondo athletes. Nine taekwondo athletes and nine T&F throwers were evaluated for countermovement jumping, isometric leg press and leg extension RFD, vastus lateralis (VL), and medial gastrocnemius muscle architecture and body composition. Lower body LBM was correlated with RFD 0-250 ms (r = 0.81, p = 0.016). Taekwondo athletes had lower LBM and jumping power per LBM. RFD was similar between groups at 30-50 ms, but higher for throwers at 80-250 ms. RFD adjusted for VL thickness was higher in taekwondo athletes at 30 ms, but higher in throwers at 200-250 ms. These results suggest that lower body LBM is correlated with RFD in power trained athletes. RFD adjusted for VL thickness might be more relevant to evaluate in power athletes with low LBM, while late RFD might be more relevant to evaluate in athletes with higher LBM.

Intramuscular fiber conduction velocity, isometric force and explosive performance.

Conduction of electrical signals along the surface of muscle fibers is acknowledged as an essential neuromuscular component which is linked with muscle force production. However, it remains unclear whether muscle fiber conduction velocity (MFCV) is also linked with explosive performance. The aim of the present study was to investigate the relationship between vastus lateralis MFCV and countermovement jumping performance, the rate of force development and maximum isometric force. Fifteen moderately-trained young females performed countermovement jumps as well as an isometric leg press test in order to determine the rate of force development and maximum isometric force. Vastus lateralis MFCV was measured with intramuscular microelectrodes at rest on a different occasion. Maximum MFCV was significantly correlated with maximum isometric force (r = 0.66, p < 0.01), nevertheless even closer with the leg press rate of force development at 100 ms, 150 ms, 200 ms, and 250 ms (r = 0.85, r = 0.89, r = 0.91, r = 0.92, respectively, p < 0.01). Similarly, mean MFCV and type II MFCV were better correlated with the rate of force development than with maximum isometric leg press force. Lower, but significant correlations were found between mean MFCV and countermovement jump power (r = 0.65, p < 0.01). These data suggest that muscle fiber conduction velocity is better linked with the rate of force development than with isometric force, perhaps because conduction velocity is higher in the larger and fastest muscle fibers which are recognized to contribute to explosive actions.