This study examined the acute influence of a bench press (BP) loading on the explosive squat (SQ) performance and vice versa.
Nineteen strength-trained men completed 2 experimental sessions ...consisting of either a SQ+BP loading or a BP+SQ loading with 3 × 5 + 3 × 3 repetitions at 80% of the 1-repetition maximum in a randomized order. SQ and BP mean propulsive velocity (MPV) were assessed during both loadings, at baseline (T0) as well as immediately after the first (T1) and second strength loading (T2).
Both BP and SQ MPV decreased between T0 and T1 in SQ+BP (-6.13 ± 6.13%, p = .014, g = 0.485 and -9.11 ± 7.23%,
< .001, g = 0.905, respectively) and BP+SQ (-15.15 ± 7.69%,
< .001, g = 1.316 and -7.18 ± 6.16%,
< .001, g = 0.724, respectively). Mean BP MPV was lower in set 2 to set 6 in SQ+BP when compared to BP+SQ (-7.90% - 9.88%, all
< .05, g = 0.523-0.808). Mean SQ MPV was lower in set 1 and set 4 in BP+SQ when compared to SQ+BP (-4.94% - 5.22%, all
< .001, g = 0.329-0.362).
These results demonstrate that the presence of non-local muscle fatigue affects the movement velocity. Therefore, if a training program aims to perform strength training exercises with maximal movement velocity, it is essential to carefully evaluate whether upper and lower body exercises should be carried out within close proximity.
This study investigated how joint angle influences fascicle shortening dynamics of gastrocnemius medialis (GM) during explosive contractions and the resulting impact on rate of torque development ...(RTD). Sixteen participants performed six sets of five maximal explosive voluntary isometric plantar flexions at -20°, -10°, 0° (neutral position), 10°, 20°, and 30° of ankle angle and five no-load ballistic plantar flexions. RTD assessed over all time windows (from 0 to 200 ms) was significantly lower in extreme plantar flexed (≥20°) and dorsiflexed (-20°) positions compared with -10, 0° (475 ± 105 N·m·s
), and 10°. At these neutral positions, RTD was maximal and muscle fascicles mainly operated over the plateau of the force-length relationship. At 0°, fascicle shortening velocity peaked at 9.26 ± 2.85 cm/s (i.e., 28.2% of maximal shortening velocity measured during no-load ballistic condition). At 112 ms after RTD onset, fascicle force reached 208 ± 78 N (i.e., 85.6% of the theoretical maximum force at the corresponding shortening velocity) and was thereafter comprised within the 95% confidence interval of the force-velocity curve. This clearly indicates that muscle force reached the maximal force that accounts for the fascicle shortening velocity. These findings suggest that the dynamic behavior of muscle fascicles, and the associated fascicle shortening velocity, may influence the rapid force-generating capacity mainly from 100 ms of RTD onset. The present study provides important information for better understanding of the determinants of human muscle performance during explosive tasks.
Ankle angle influences the operating muscle fascicle lengths of gastrocnemius medialis and the rate of torque development during explosive isometric plantar flexions. The rate of torque development peaks in neutral angles where muscle fascicles shorten over the plateau of the force-length relationship. When fascicles operate over the plateau of the force-length relationship (neutral ankle positions), the force-velocity properties represent a limiting factor for the rapid force-generating capacity from 100 ms after the onset of explosive contractions.
In this paper, an Apriori association rule optimization model based on the combination of transaction compression and Hash technology is proposed for the relationship between core strength exercises ...and the explosive strength quality of throwing track and field athletes. In order to improve the efficiency of mining, the Hash function is set on the basis of the FP-growth algorithm, and its grouping strategy is improved by the load optimization algorithm of the greedy strategy, and it is fused with the improved Apriori algorithm. Finally, we set up an athletic training comparison experiment with or without core strength exercises to explore the effect of core strength exercises on the improvement of explosive strength quality with the help of the fusion algorithm. After core strength exercises, the grip strength and vertical jump events of throwing athletes increased from 30.94 and 36.03 to 33.52 and 38.28, respectively, and the quality of explosive force was significantly improved. While comparing with the conventional strength exercises, the athletes who performed core strength exercises had a P-value of less than 0.05 in all the other five test items except static squat jump; the effect of the exercises was significantly better than that of the conventional strength exercises, and the lower limbs, trunk and waist and abdominal muscle groups, and the upper limbs explosive strength were also effectively improved.
Purpose
Neural drive and contractile properties are well-defined physiological determinants of explosive strength, the influence of muscle architecture and related morphology on explosive strength is ...poorly understood. The aim of this study was to examine the relationships between
Quadriceps
muscle architecture (pennation angle Θ
P
and fascicle length F
L
) and size (e.g., volume; Q
VOL
), as well as patellar tendon moment arm (PT
MA
) with voluntary and evoked explosive knee extension torque in 53 recreationally active young men.
Method
Following familiarisation, explosive voluntary torque at 50 ms intervals from torque onset (T
50
, T
100
, T
150
), evoked octet at 50 ms (8 pulses at 300-Hz; evoked T
50
), as well as maximum voluntary torque, were assessed on two occasions with isometric dynamometry. B-mode ultrasound was used to assess Θ
P
and F
L
at ten sites throughout the quadriceps (2–3 sites) per constituent muscle. Muscle size (Q
VOL
) and PT
MA
were quantified using 1.5 T MRI.
Result
There were no relationships with absolute early phase explosive voluntary torque (≤ 50 ms), but θ
P
(weak), Q
VOL
(moderate to strong) and PT
MA
(weak) were related to late phase explosive voluntary torque (≥ 100 ms). Regression analysis revealed only Q
VOL
was an independent variable contributing to the variance in T
100
(34%) and T
150
(54%). Evoked T
50
was also related to Q
VOL
and θ
P.
When explosive strength was expressed relative to MVT there were no relationships observed.
Conclusion
It is likely that the weak associations of θ
P
and PT
MA
with late phase explosive voluntary torque was via their association with MVT/Q
VOL
rather than as a direct determinant.
The main aim of the present study was to evaluate the acute effects of ischemia used during rest periods on bar velocity changes during the bench press exercise at progressive loads, from 20 to 90% ...of 1RM. Ten healthy resistance trained men volunteered for the study (age = 26.3 ± 4.7 years; body mass = 89.8 ± 6.3 kg; bench press 1RM = 142.5 ± 16.9 kg; training experience = 7.8 ± 2.7 years). During the experimental sessions the subjects performed the bench press exercise under two different conditions, in a randomized and counterbalanced order: (a) ischemia condition, with ischemia applied before the first set and during every rest periods between sets, and (b) control condition where no ischemia was applied. During each experimental session eight sets of the bench press exercise were performed, against loads starting from 20 to 90% 1RM, increased progressively by 10% in each subsequent set. A 3-min rest interval between sets was used. For ischemia condition the cuffs was applied 3 min before the first set and during every rest period between sets. Ischemia was released during exercise. The cuff pressure was set to ∼80% of full arterial occlusion pressure. The two-way repeated measures ANOVA showed a statistically significant interaction effect for peak bar velocity (
p
= 0.04) and for mean bar velocity (
p
= 0.01). There was also a statistically significant main effect of condition for peak bar velocity (
p
< 0.01) but not for mean bar velocity (
p
= 0.25). The
post hoc
analysis for interaction showed significantly higher peak bar velocity for the ischemia condition compared to control at a load of 20% 1RM (
p
= 0.007) and at a load of 50% 1RM (
p
= 0.006). The results of the present study indicate that ischemia used before each set even for a brief duration of <3 min, has positive effects on peak bar velocity at light loads, but it is insufficient to induce such effect on higher loads.
This study investigated the association between explosive force production during isometric squats and athletic performance (sprint time and countermovement jump height). Sprint time (5 and 20 m) and ...jump height were recorded in 18 male elite-standard varsity rugby union players. Participants also completed a series of maximal- and explosive-isometric squats to measure maximal force and explosive force at 50-ms intervals up to 250 ms from force onset. Sprint performance was related to early phase (≤100 ms) explosive force normalised to maximal force (5 m, r = −0.63, P = 0.005; and 20 m, r = −0.54, P = 0.020), but jump height was related to later phase (>100 ms) absolute explosive force (0.51 < r < 0.61; 0.006 < P < 0.035). When participants were separated for 5-m sprint time (< or ≥ 1s), the faster group had greater normalised explosive force in the first 150 ms of explosive-isometric squats (33-67%; 0.001 < P < 0.017). The results suggest that explosive force production during isometric squats was associated with athletic performance. Specifically, sprint performance was most strongly related to the proportion of maximal force achieved in the initial phase of explosive-isometric squats, whilst jump height was most strongly related to absolute force in the later phase of the explosive-isometric squats.
Study purpose. High-intensity aerobic capacity (HIAC) is essential for soccer players because they have to perform sprints of short duration in the shortest possible time. At the same time, they need ...to quickly change direction with and without the ball, which requires agility. The purpose of the study was to investigate the effect of a periodized (8-week) training plan that combines interval training (IT), explosive strength (ES), speed, and game-like situations on agility and HIAC in youth soccer players.
Materials and methods. This research is an experimental study in which the population was male youth soccer players (N = 23) (aged 16.7±2.1). The Arrowhead Agility Test and the HIAC Yo-Yo Intermittent Recovery Test Level 1 (YYIR1) have taken the pre- and post-data of agility. By using the formula for YYIR1 test: VO₂max (mL kg-1 min-1) = IR1 distance (m) × 0.0084 + 36.4, we get an estimation of the volume of maximum oxygen consumption (VO₂max). The data analysis used a t-test at 0.05% as the significance level.
Results. Based on the results, the mean of the pre-tests in agility, YO-YO IR1, and VO₂max showed 17.911, 14.8100, and 55.25510. After training for eight weeks, there was an improvement: the mean showed 16.667, 15.9750, and 60.06960. As per the results of the data on the hypothesis in the study, it was found that there was a significant effect of periodized IT in combination with ES and speed on agility performance and HIAC of the youth soccer players.
Conclusions. There was a significant effect of periodized IT in combination with ES and speed on improving youth soccer players’ agility performance and HIAC.
This study aimed to examine the associations between lower-body explosive strength (squat jump-SJ, and countermovement jump-CMJ), speed (10- and 35-m linear sprints), and agility (
-test) capacities, ...after controlling for crucial predictors such as chronological age (CA) and body composition. The sample was composed of 164 adolescent male football players from under 19, under 17, and under 15 age groups. Body fat percentage (BF%) was significantly and positively related to body mass, speed, and agility. In contrast, BF% was a significant negative predictor of lower-body explosive strength. Sprint and
-test times were significantly and negatively correlated with lower-body explosive strength. After controlling for CA and body composition, SJ was the most significant predictor, accounting for 36 to 37% of the variance observed in the 35 m linear sprint and the
-test performance. Our main results suggest that lower-body explosive strength, particularly in the SJ, is a significant predictor of male adolescent male football players' speed and agility capacities. Conversely, detrimental relationships between BF% and these outcomes were observed. Sports agents should consider lower-body explosive strength development as part of the youth football training process, particularly to improve maximal sprint and change of direction times, which are crucial to game performance.
While heat exposure has been shown to increase the rate of force development (RFD), the underlying processes remain unknown. This study investigated the effect of heat on gastrocnemius medialis (GM) ...muscle-tendon properties and interactions. Sixteen participants performed electrically-evoked and voluntary contractions combined with ultrafast ultrasound under thermoneutral (CON: 26°C, core temperature 37.0±0.3°C, muscle temperature 34.0±1.1°C) and passive heat exposure (HOT: 47°C, core temperature 38.4±0.3°C, muscle temperature 37.0±0.8°C) conditions. Maximal voluntary force was unchanged while voluntary activation decreased (-4.6±8.7%, P=0.038) in HOT. Heat exposure increased RFD before 100 ms from contraction onset (+48.2±62.7%; P=0.013), without further changes after 100 ms. GM fascicle dynamics during electrically-evoked and voluntary contractions remained unchanged between conditions. Joint velocity at a given force was higher in HOT (+7.1±6.6%; P=0.004), while the fascicle force-velocity relationship was unchanged. Passive muscle stiffness and active tendon stiffness were lower in HOT than CON (P≤0.030). This study showed that heat-induced increases in early RFD may not be attributed to changes in contractile properties. Late RFD was unaltered, probably explained by decreased soft tissues' stiffness in heat. Investigations are required to explore the possible influence of neural drive and motor unit recruitment in the enhancement of explosive strength elicited by heat exposure.
The purpose of this systematic review and meta-analysis was to compare changes in explosive power between blood flow restriction training and traditional resistance training protocols. Searches of ...PubMed, Scopus, Web of Science, and OVID Medline were conducted for studies. Inclusion criteria were: (a) healthy people; (b) randomized controlled or controlled trials; (c) outcome measures of explosive performance (peak power, rate of force development, jump performance, sprint performance, etc.); (d) involving a comparison between blood flow restriction training and traditional resistance training. Quality assessment was conducted using the Physiotherapy Evidence Database (PEDro) scale. A total of 12 studies (262 subjects) were finally included for analysis. The PEDro scale score had a median of 5 of 10 points (range: 3-6 points). Significant small to moderate improvements were observed in blood flow restriction training jump: standard mean difference (SMD) of 0.36 (95% CI: 0.02; 0.69); sprint: SMD of 0.54 (95% CI: 0.00; 1.07); power: SMD of 0.72 (95% CI: 0.17; 1.27) when compared to traditional resistance training. The findings indicate that blood flow restriction training is more effective in improving explosive power of lower limbs compared to traditional resistance training in healthy people. In addition, blood flow restriction with a wide cuff (≥ 10 cm) during training improved explosive power better than with a narrow cuff or during the rest interval. Blood flow restriction training is very suitable for athletes in short competitive seasons and those who are not able to tolerate high loads (i.e., rehabilitators and the elderly).
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