Sebastián Marín Toro, Marc Schalles, Pavo Vrdoljak
En los procesos industriales, la lectura de los termómetros puede variar con el tiempo. Para minimizar el riesgo de estos errores no detectados en la medición de la temperatura es necesario recalibrar periódicamente los termómetros fuera del proceso. En este artículo se propone una alternativa más simple, compacta y duradera basada en un nuevo enfoque que utiliza la temperatura de Curie Tc de los materiales ferroeléctricos. En esta temperatura, el material pasa de la fase paraeléctrica a la ferroeléctrica. Uno de estos materiales se integró en un termómetro industrial compacto, proporcionando una temperatura de referencia de Tc ≈ 118 °C, que permite calibraciones automatizadas, cada vez que la temperatura del proceso industrial desciende por debajo de esta temperatura de referencia. En las pruebas de laboratorio, realizadas a largo plazo con 10 termómetros y cerca de 2500 calibraciones de cada uno, se obtuvo una desviación estándar de la Tc inferior a 45 mK. La alta estabilidad y reproducibilidad de los termómetros fue confirmada también en pruebas de campo realizadas en las industrias farmacéutica y alimenticia. La incertidumbre de la Tc, con un factor de cobertura de k = 2, se calculó en U = 349 mK.
Abstract McMahon, G, and Kennedy, R. The effects of palm cooling on physiological and metabolic responses, exercise performance, and total volume during high-intensity bench press exercise in resistance-trained men. J Strength Cond Res 37(11): 2122–2129, 2023—Previous research suggests that cooling distal to the working agonist muscles during the interset rest periods of high-intensity resistance exercise may facilitate improved performance by means of improving metabolic conditions of contractile machinery. However, these studies have not directly measured indicators of metabolic conditions. Therefore, the aim of this study was to compare 2 palm-cooling conditions with a thermoneutral condition during high-intensity resistance exercise and subsequent effects on physiological and metabolic responses and exercise performance. Eleven healthy, resistance-trained, young men (20–36 years old) performed 4 sets of bench press exercise to exhaustion at 80% 1 repetition maximum each separated by 3 minutes of passive recovery. Palm cooling (10° C [TEN] or 15° C [FTN]) or thermoneutral (28° C [CON]) condition was applied for 60 seconds during the recovery interval of each set in a randomized, double-blind fashion, with 4 days recovery between the experimental conditions. There were no differences (p > 0.05) in volume load between the experimental conditions across all sets. Mean repetition velocity and force of the bench press declined significantly following set 1 in all conditions (p 0.05) between any of the conditions. Palm cooling at either 10 or 15° C had no observable effects on physiological and metabolic responses during exercise, nor has it any effect on bench press performance or volume load compared with a thermoneutral condition. Therefore, cooling cannot be currently recommended as an ergogenic strategy to enhance acute bench press performance or mitigate fatigue during high-intensity resistance training.
Abstract Nakamura, M, Konrad, A, Kasahara, K, Yoshida, R, Murakami, Y, Sato, S, Aizawa, K, Koizumi, R, and Wilke, J. The combined effect of static stretching and foam rolling with or without vibration on the range of motion, muscle performance, and tissue hardness of the knee extensor. J Strength Cond Res 37(2): 322–327, 2023—Although the combination of static stretching (SS) and foam rolling (FR) is frequently used for warm-up in sports, the effect of the intervention order is unclear. This study compared mechanical tissue properties, pain sensitivity, and motor function after SS and FR (with and without vibration) performed in different orders. Our randomized, controlled, crossover experiment included 15 healthy male subjects (22.5 ± 3.3 years) who visited the laboratory 5 times (inactive control condition, FR + SS, FRvibration + SS, SS + FR, and SS + FRvibration) with an interval of ≥48 hours. In each session, subjects completed three 60-second bouts of FR and SS, targeting the anterior thigh. Pressure pain threshold, tissue hardness, knee flexion range of motion (ROM), maximal voluntary isometric (MVC-ISO), and concentric (MVC-CON) torque, as well as countermovement jump height, were determined before and after the intervention. All interventions significantly (p < 0.01) increased knee flexion ROM (d = 0.78, d = 0.87, d = 1.39, and d = 0.87, respectively) while decreasing tissue hardness (d = −1.25, d = −1.09, d = −1.18, and d = −1.24, respectively). However, MVC-ISO torque was significantly reduced only after FR + SS (p = 0.05, d = −0.59). Our results suggest that SS should be followed by FR when aiming to increase ROM and reduce tissue hardness without concomitant stretch-induced force deficits (MVC-ISO, MVC-CON, and countermovement jump height). Additionally, adding vibration to FR does not seem to affect the magnitude of changes observed in the examined outcomes.
Abstract Morgan, B, Mirza, AM, Gimblet, CJ, Ortlip, AT, Ancalmo, J, Kalita, D, Pellinger, TK, Walter, JM, and Werner, TJ. Effect of an 11-week resistance training program on arterial stiffness in young women. J Strength Cond Res 37(2): 315–321, 2023—The current investigation was conducted to determine the effect of 2 resistance training models on indices of arterial stiffness in young, healthy women. Twenty-four women, untrained college students, aged 18–22 years were randomized into 1 of 3 groups: control (CON) group (n = 8), high-intensity (HI) resistance exercise group (n = 8), and high-volume (HV) resistance exercise group (n = 8). Subjects randomized to resistance training groups were required to perform strength training exercises 3–5 days a week for 11 weeks. The exercise regimen consisted of 2–3 sets of 3–8 repetitions (80–90% of 1 repetition maximum [1RM]) for the HI group and 3–4 sets of 10–15 repetitions (50–70% of 1RM) for the HV group. All subjects were instructed to continue their normal diet and avoid cardiovascular exercise during the study. After the intervention, there was a significant increase in carotid femoral pulse wave velocity (PWV) (6.39 ± 0.73 to 8.40 ± 2.31 m·s−1; p < 0.05) and carotid radial PWV (9.77 ± 1.74 to 12.58 ± 2.09 m·s−1; p < 0.05) in the CON group alone. Both the HI and HV groups increased their maximum squat (36.6 ± 7.9 vs. 41.3 ± 31.8 percent change; p < 0.05), bench press (34.4 ± 12.6 vs. 23.4 ± 11.1 percent change; p < 0.05), and seated row (22.0 ± 12.6 vs. 21.9 ± 12.5 percent change; p < 0.05), respectively. Our findings support the use of resistance training exercise without undue impact on vascular compliance in otherwise healthy women.
Jakob D. Lauver, A. Moran, Justin P Guilkey
et al.
Abstract Lauver, JD, Moran, A, Guilkey, JP, Johnson, KE, Zanchi, NE, and Rotarius, TR. Acute responses to cycling exercise with blood flow restriction during various intensities. J Strength Cond Res 36(12): 3366–3373, 2022—The purpose of this study was to investigate the acute physiological responses during cycling at various intensities with blood flow restriction (BFR). Subjects (N = 9; V̇o2peak = 36.09 ± 5.80 ml·kg−1·min−1) performed 5 protocols: high-intensity (HIGH), control (CON-90), 90% of ventilatory threshold (VT) work rate with BFR (90-BFR), 70% of VT with BFR (70-BFR), and 30% V̇o2peak with BFR (30-BFR). Protocols consisted of five 2-minute work intervals interspersed with 1-minute recovery intervals. Blood flow restriction pressure was 80% of limb occlusion pressure. V̇o2, muscle excitation, tissue oxygen saturation (StO2), discomfort, and level of perceived exertion (RPE) were assessed. Muscle excitation was higher during HIGH (302.9 ± 159.9 %BSL [baseline]) compared with 70-BFR (99.7 ± 76.4 %BSL) and 30-BFR (98.2 ± 70.5 %BSL). StO2 was greater during 90-BFR (40.7 ± 12.5 ∆BSL), 70-BFR (34.4 ± 15.2 ∆BSL), and 30-BFR (31.9 ± 18.7 ∆BSL) compared with CON-90 (4.4 ± 11.5 ∆BSL). 90-BFR (39.6 ± 12.0 ∆BSL) resulted in a greater StO2-Avg compared with HIGH (20.5 ± 13.8 ∆BSL). Also, HIGH (23.68 ± 5.31 ml·kg−1·min−1) resulted in a greater V̇o2 compared with 30-BFR (15.43 ± 3.19 ml·kg−1·min−1), 70-BFR (16.65 ± 3.26 ml·kg−1·min−1), and 90-BFR (18.28 ± 3.89 ml·kg−1·min−1); 90-BFR (intervals: 4 = 15.9 ± 2.3; intervals: 5 = 16.4 ± 2.5) resulted in a greater RPE compared with 30-BFR (intervals: 4 = 13.3 ± 1.4; intervals: 5 = 13.7 ± 1.7) during intervals 4 and 5. These results suggest that when adding BFR to various intensities of aerobic exercise, consideration should be given to peak work and VT to provide a balance between high local physiological stress and perceptual responses.
Samuel T. Orange, James W. Metcalfe, Andreas Liefeith
et al.
Orange, ST, Metcalfe, JW, Liefeith, A, Marshall, P, Madden, LA, Fewster, CR, and Vince, RV. Validity and reliability of a wearable inertial sensor to measure velocity and power in the back squat and bench press. J Strength Cond Res XX(X): 000-000, 2018-This study examined the validity and reliability of a wearable inertial sensor to measure velocity and power in the free-weight back squat and bench press. Twenty-nine youth rugby league players (18 ± 1 years) completed 2 test-retest sessions for the back squat followed by 2 test-retest sessions for the bench press. Repetitions were performed at 20, 40, 60, 80, and 90% of 1 repetition maximum (1RM) with mean velocity, peak velocity, mean power (MP), and peak power (PP) simultaneously measured using an inertial sensor (PUSH) and a linear position transducer (GymAware PowerTool). The PUSH demonstrated good validity (Pearson's product-moment correlation coefficient [r]) and reliability (intraclass correlation coefficient [ICC]) only for measurements of MP (r = 0.91; ICC = 0.83) and PP (r = 0.90; ICC = 0.80) at 20% of 1RM in the back squat. However, it may be more appropriate for athletes to jump off the ground with this load to optimize power output. Further research should therefore evaluate the usability of inertial sensors in the jump squat exercise. In the bench press, good validity and reliability were evident only for the measurement of MP at 40% of 1RM (r = 0.89; ICC = 0.83). The PUSH was unable to provide a valid and reliable estimate of any other criterion variable in either exercise. Practitioners must be cognizant of the measurement error when using inertial sensor technology to quantify velocity and power during resistance training, particularly with loads other than 20% of 1RM in the back squat and 40% of 1RM in the bench press.
Kubo, K, Ikebukuro, T, and Yata, H. Effects of 4, 8, and 12 repetition maximum resistance training protocols on muscle volume and strength. J Strength Cond Res XX(X): 000-000, 2020-The purpose of this study was to determine skeletal muscle adaptations (strength and hypertrophy) in response to volume-equated resistance training with divergent repetition strategies. Forty-two men were randomly assigned to 4 groups: higher load-lower repetition group performing 4 repetition maximum (RM) for 7 sets (4RM, n = 10), intermediate load-intermediate repetition group performing 8RM for 4 sets (8RM, n = 12), lower load-higher repetition group performing 12RM for 3 sets (12RM, n = 10), and nonexercising control group (CON, n = 10). The volume of the pectoralis major muscle (by magnetic resonance imaging) and 1RM of the bench press were measured before and after 10 weeks of training (2 times per week). No significant difference was observed in the relative increase in the muscle volume among the 4RM, 8RM, and 12RM groups. The relative increase in 1RM was significantly lower in the 12RM group than in the 4RM group (p = 0.029) and the 8RM group (p = 0.021). The relative increase in 1RM was significantly correlated with that in the muscle volume in the 12RM group (r = 0.684, p = 0.042), but not in the 4RM (r = -0.265, p = 0.777) or 8RM (r = -0.045, p = 0.889) groups. These results suggest that the increase in muscle size is similar among the 3 training protocols when the training volume was equated, whereas the increase in muscle strength is lower with the 12RM protocol than the other protocols.
Abstract Nonnato, A, Hulton, AT, Brownlee, TE, and Beato, M. The effect of a single session of plyometric training per week on fitness parameters in professional female soccer players. A randomized controlled trial. J Strength Cond Res 36(4): 1046–1052, 2022—As the interest and popularity of female soccer has increased over the last few decades, there still lacks research conducted with the elite population, specifically ecological training interventions during the competitive season. Therefore, the aim of this study was to compare the effectiveness of 12 weeks (undertaken once a week) of plyometric (PLY) training on physical performance in professional female soccer players during the season. Using a randomized controlled trial design, 16 players were included in the current study (mean ± SD; age 23 ± 4 years, weight 60.3 ± 4.9 kg, height 167 ± 3.7 cm) and randomized in PLY (n = 8) and Control groups (CON, n = 8), respectively. Squat jump (SJ), counter movement jump (CMJ), long jump (LJ), single-leg triple jump distance test (triple jump test), changes of direction 505 test (505-COD), and sprint 10 and 30 m were performed before and after 12 weeks of PLY training. Significant within-group differences were found in triple jump test dominant (p = 0.031, effect size [ES] = moderate) and nondominant limb (p = 0.021, ES = moderate) and sprint 10 m (p = 0.05, ES = large), whereas the CON did not report any positive variation. However, neither group reported significant variation in SJ, CMJ, LJ, 505-COD, and sprint 30 m (underlining the difficulties in obtain meaningful variation in season). These findings have strong practical applications because this study showed for the first time that a single session a week of plyometric training can significantly increase sport-specific fitness parameters in professional female soccer players during the season.
Uthoff, A, Oliver, J, Cronin, J, Harrison, C, and Winwood, P. Sprint-specific training in youth: Backward running vs. forward running training on speed and power measures in adolescent male athletes. J Strength Cond Res XX(X): 000-000, 2018-This study compared the effects of 2 sprint-specific training programs against the natural development of speed, power, and stiffness in a group of adolescent male athletes. Forty-three male adolescents (aged 13-15 years) were randomly assigned to 1 of 2 training groups; backward running training (BRT = 26), or forward running training (FRT = 17). A physical education class (n = 24) of similar age constituted a control (CON) group. Both training groups performed running sessions matched for distance and intensity biweekly for 8 weeks. Parametric and magnitude-based inferences were used to analyze within group (pre-post measures) and between group (gain scores) for 10-m, 10- to 20-m, and 20-m sprint times, vertical countermovement jump (CMJ) height, and vertical leg stiffness. Both running groups significantly improved (p ≤ 0.05) in all performance tests from pre-training to post-training, with effect sizes ranging from -1.25 to 0.63. When the groups were compared, the BRT and FRT groups improved significantly (p ≤ 0.01) on all sprint performances and stiffness relative to the CON group. The BRT group demonstrated favorable effects for 10-m and 20-m sprint performances (effect size [ES] = -0.47 and -0.26, respectively) and CMJ height (ES = 0.51) compared with the FRT group. These results demonstrate that forward and backward sprint-specific training programs enhance speed and power measures more than natural development in adolescent male athletes. Furthermore, the greater training responses in sprint performance and CMJ ability indicate that BRT is a useful tool for improving concentric strength and power and may be classified as a sprint-specific training method.
Jefferson da Silva Novaes, Luiz Guilherme da Silva Telles, E. R. Monteiro
et al.
Abstract da Silva Novaes, J, da Silva Telles, LG, Monteiro, ER, da Silva Araujo, G, Vingren, JL, Silva Panza, P, Reis, VM, Laterza, MC, and Vianna, JM. Ischemic preconditioning improves resistance training session performance. J Strength Cond Res 35(11): 2993–2998, 2021—The aim of this study was to investigate the acute effect of ischemic preconditioning (IPC) in a resistance exercise (RE) training session on the number of repetitions performed, total volume, and rating of perceived exertion in recreationally trained and normotensive men. Sixteen recreationally trained and normotensive men completed 3 RE sessions in a counterbalanced and randomized order: (a) IPC protocol using 220 mm Hg followed by RE (IPC), (b) IPC cuff control protocol with 20 mm Hg followed by RE (CUFF), and (c) no IPC (control) followed by RE (CON). RE was performed with 3 sets of each exercise (bench press, leg press, lateral pulldown, hack machine squat, shoulder press, and Smith back squat) until concentric muscular failure, at 80% of one repetition maximum, with 90 seconds of rest between sets and 2 minutes of rest between exercises. Ischemic preconditioning and CUFF consisted of 4 cycles of 5 minutes of occlusion/low pressure alternating with 5 minutes of no occlusion (0 mm Hg) using a pneumatic tourniquet applied around the subaxillary region of the upper arm. For each condition, the number of repetitions completed, total volume of work performed, and rating of perceived exertion were determined. No significant difference was found for rating of perceived exertion between any experimental protocol. Ischemic preconditioning significantly (p < 0.05) increased the number of repetitions across exercises. Consequently, total volume performed (sum of total number of repetitions x load for each exercise) was significantly higher in IPC (46,170 kg) compared with CON (34,069 kg) and CUFF (36,590 kg) across all exercises. This work may have important implications for athletic populations because it demonstrates increase in muscle performance outcomes during a single RE session. Therefore, performing IPC before RE could be an important exercise prescription recommendation to increase maximum repetition performance and total volume of work performed and thus potentially increase desired training adaptations (i.e., strength and hypertrophy).
Bustos, A, Metral, G, Cronin, J, Uthoff, A, and Dolcetti, J. Effects of warming up with lower-body wearable resistance on physical performance measures in soccer players over an 8-week training cycle. J Strength Cond Res XX(X): 000-000, 2020-Warm-ups provide an opportune time to integrate specific movements to improve performance. This study aimed to examine the effects of adding wearable resistance (WR) lower-limb loading to a warm-up on physical performance measures in soccer athletes. Thirty-one national-level soccer players (aged 16-18 years) were matched for speed and allocated to either a WR training (WRT = 15) or an unloaded (CON = 16) group. Both groups performed the same warm-up 2-3x·wk for 8 weeks with the WRT group wearing 200- to 600-g loads on their calves. Pre-training, mid-training, and post-training data were collected for 10- and 20-m sprint times, repeated sprint ability, and vertical countermovement jump (CMJ) and horizontal countermovement jump (standing long jump [SLJ]) performance. Wearable resistance training improved pre-training to post-training 10- and 20-m sprint times more than the unloaded training (effect size [ES] = -1.06 to -0.96, respectively; 60.0-66.7 vs. 18.8-37.5% > smallest worthwhile change [SWC]). Both groups decreased CMJ over the first 4 weeks (ES ≥ 0.45) and increased CMJ performance over the second 4 weeks of training (ES ≥ 0.27). Both the WRT and CON groups improved SLJ performance after the 8-week training block (ES = 0.85 and 0.93, respectively; 86.7 and 62.5% > SWC, respectively), yet no differences were identified between groups. These findings indicate that 8 weeks (23 sessions) of WR training appears to elicit practically meaningful improvements in accelerated sprinting and horizontal jumping performance. Strength and conditioning practitioners should consider including WR in sports where sprinting and horizontal force production are critical performance indicators.
Abstract Nunes, ACCA, Cattuzzo, MT, Faigenbaum, AD, and Mortatti, AL. Effects of integrative neuromuscular training and detraining on countermovement jump performance in youth volleyball players. J Strength Cond Res 35(8): 2242–2247, 2021—The purpose of this study was to analyze the effect of integrative neuromuscular training (INT) on countermovement vertical jump height (CVJH) performance in youth volleyball players before and after a detraining period. Thirty-two novice volleyball players were cluster randomized into 2 groups: intervention group—INT (age: 13.1 ± 0.4 years; body mass: 55.3 ± 12.1 kg; and height: 161.1 ± 6.4 cm) and control group—CON (age: 12.8 ± 0.7 years; body mass: 51.8 ± 13.6 kg; and height: 160.1 ± 10.7 cm). The subjects were evaluated for somatic maturation (years from peak height velocity) and for CVJH performance at 4 time points during the 20-week study period: baseline, 6 weeks of INT, 12 weeks of INT, and 8 weeks after INT (detraining). The analysis used repeated-measures analysis of variance and Bonferroni post hoc test to identify possible differences in the CVJH delta in both groups. Spearman correlation was performed to verify the association between the values of the vertical jump tests and maturational levels found. The INT showed a significant improvement in the CVJH from baseline to 12 weeks and maintained training-induced gains after detraining period (p > 0.001). Significant increase in CVJH was found in the percentage of change (Δ%) from baseline to 6 weeks (p < 0.005), 12 weeks (p < 0.001), and detraining (p < 0.001) in INT compared with the CON. The results of this study indicate that INT was able to improve CVJH performance in novice youth volleyball players and these gains were sustained during the detraining period. These findings indicate that regular participation in supervised INT can enhance jumping performance in young volleyball players, and that this type of neuromuscular program may be particularly beneficial for youth with limited fundamental motor skill performance.
Abstract Alves, RR, Viana, RB, Silva, MH, Guimarães, TC, Vieira, CA, Santos, DdAT, and Gentil, PRV. Postactivation potentiation improves performance in a resistance training session in trained men. J Strength Cond Res 35(12): 3296–3299, 2021—This study aims to analyze the influence of postactivation potentiation (PAP) on performance during a resistance training (RT) session in trained individuals. Fourteen trained men (25.0 ± 3.5 years; 89.9 ± 16.3 kg; 1.77 ± 0:08 m; 28.0 ± 4.0 kg·m−2; and 5 ± 4 years of RT experience) were tested in 2 situations: with PAP and without PAP (CON). Both situations involved 3 sets of the bench press exercise performed to muscle failure at 75% of the 1 repetition maximum load and with 1.5-minute interval between sets. Total work was greater (p < 0.001) for PAP (1,601 ± 504 kg) than for CON (1,379 ± 364 kg). The number of repetitions performed in the first and second sets of PAP (11.5 ± 3.1 and 6.5 ± 1.9, respectively) were greater (p < 0.05) than those performed in CON (10.4 ± 2.7, 5.5 ± 1.8, respectively). No significant difference was found in the number of repetitions in the last set between the situations. The present study suggests that PAP might be beneficial to improve total work and performance during multiple sets of RT in trained men. Therefore, PAP might be used during RT to promote higher total work and potentially increase results over long term. Thus, the protocol can use in sports centers, fitness centers, and gyms per coaches and athletes to increase performance and total work in trained individuals.
We consider possible high temperature superconductivity (high-T$_c$) in transition metal compounds with a cubic zinc-blende lattice structure. When the electron filling configuration in the d-shell is close to d$^7$, all three t$_{2g}$ orbitals are near half filling with strong nearest neighbor antiferromagnetic (AFM) superexchange interactions. We argue that upon doping, this electronic environment can be one of "genes" to host unconventional high T$_c$ with a time reversal symmetry broken $d_{2z^2-x^2-y^2} \pm i d_{x^2-y^2}$ pairing symmetry. With gappless nodal points along the diagonal directions, this state is a direct three dimensional analogue to the two dimensional $B_{1g}$ d-wave state in cuprates. We suggest that such a case may be realized in electron doped CoN, such as CoN$_{1-x}$O$_x$ and (H, Li)$_{1-x}$CoN.
We improve the Bardeen-Cooper-Schrieffer wave function with a fixed particle number so as to incorporate many-body correlations beyond the mean-field treatment. It is shown that the correlations lower the ground-state energy far more than Cooper-pair condensation in the weak-coupling region. Moreover, they naturally bring a superposition over the number of condensed particles. Thus, Cooper-pair condensation is special among the various bound-state formations of quantum mechanics in that number fluctuations are necessarily present in the condensate through the dynamical exchange of particles with the non-condensate reservoir. On the basis of this result, we propose $\varDelta N_{\rm con}\cdot \varDelta φ\gtrsim 1$ as the uncertainty relation relevant to the number-phase fluctuations in superconductors and superfluids, where the number of condensed particles $N_{\rm con}$ is used instead of the total particle number $N$. The formula implies that a macroscopic phase $φ$ can be established even in number-fixed superconductors and superfluids since $\varDelta N_{\rm con}\gg 1$.
Abstract Lum, D. Effects of various warm-up protocol on special judo fitness test performance. J Strength Cond Res 33(2): 459–465, 2019—The purposed of this study was to compare the effects of postactivation potentiation (PAP) on Special Judo Fitness Test (SJFT) performance using explosive exercises that activates upper and lower limbs muscles. Eleven male judo athletes (mean ± SD, age, 16–29 years; height, 170 ± 7 cm; body mass, 73 ± 16 kg) attended 4 separate sessions. The first session was used to familiarize the subjects to the experimental procedure, the SJFT, the high pull test (HPT), and the 2 explosive exercises including resistance band pull and standing broad jump. Subsequently, subjects were randomly assigned in a counterbalanced manner to either perform the upper and lower body (ULB) PAP, lower body (LB) PAP or usual competition (CON) warm-up routine before performing the HPT and SJFT. The following variables were quantified: throws performed during series A, B, and C; total number of throws; heart rate immediately and 1 minute after the test; test index; peak power; and RPE after warm-up. During series 1, number of throws performed in LB and ULB were significantly greater than CON (p ⩽ 0.05). Only ULB resulted in significantly greater number of total throws (p < 0.01) and higher peak power (p < 0.01) than CON. The RPE for both LB and ULB were significantly lower than CON (p < 0.01). Peak power was moderately correlated to total number of throws performed (r = 0.4, p ⩽ 0.05). This study suggest that performing ULB before SJFT can result in improved performance and peak power.
Abstract Jarvis, MM, Graham-Smith, P, and Comfort, P. A Methodological approach to quantifying plyometric intensity. J Strength Cond Res 30(9): 2522–2532, 2016—In contrast to other methods of training, the quantification of plyometric exercise intensity is poorly defined. The purpose of this study was to evaluate the suitability of a range of neuromuscular and mechanical variables to describe the intensity of plyometric exercises. Seven male recreationally active subjects performed a series of 7 plyometric exercises. Neuromuscular activity was measured using surface electromyography (SEMG) at vastus lateralis (VL) and biceps femoris (BF). Surface electromyography data were divided into concentric (CON) and eccentric (ECC) phases of movement. Mechanical output was measured by ground reaction forces and processed to provide peak impact ground reaction force (PF), peak eccentric power (PEP), and impulse (IMP). Statistical analysis was conducted to assess the reliability intraclass correlation coefficient and sensitivity smallest detectable difference of all variables. Mean values of SEMG demonstrate high reliability (r ≥ 0.82), excluding ECC VL during a 40-cm drop jump (r = 0.74). PF, PEP, and IMP demonstrated high reliability (r ≥ 0.85). Statistical power for force variables was excellent (power = 1.0), and good for SEMG (power ≥0.86) excluding CON BF (power = 0.57). There was no significant difference (p > 0.05) in CON SEMG between exercises. Eccentric phase SEMG only distinguished between exercises involving a landing and those that did not (percentage of maximal voluntary isometric contraction [%MVIC] = no landing −65 ± 5, landing −140 ± 8). Peak eccentric power, PF, and IMP all distinguished between exercises. In conclusion, CON neuromuscular activity does not appear to vary when intent is maximal, whereas ECC activity is dependent on the presence of a landing. Force characteristics provide a reliable and sensitive measure enabling precise description of intensity in plyometric exercises. The present findings provide coaches and scientists with an insightful and precise method of measuring intensity in plyometrics, which will allow for greater control of programming variables.