Skills and Expertise
Research Items (94)
This study aimed (i) to explore the relationship between vertical (jumping) and horizontal (sprinting) force–velocity–power (FVP) mechanical profiles in a large range of sports and levels of practice, and (ii) to provide a large database to serve as a reference of the FVP profile for all sports and levels tested. A total of 553 participants (333 men, 220 women) from 14 sport disciplines and all levels of practice participated in this study. Participants performed squat jumps (SJ) against multiple external loads (vertical) and linear 30–40 m sprints (horizontal). The vertical and horizontal FVP profile (i.e., theoretical maximal values of force ( F0 ), velocity ( v0 ), and power ( Pmax )) as well as main performance variables (unloaded SJ height in jumping and 20-m sprint time) were measured. Correlations coefficient between the same mechanical variables obtained from the vertical and horizontal modalities ranged from −0.12 to 0.58 for F0 , −0.31 to 0.71 for v0 , −0.10 to 0.67 for Pmax , and −0.92 to −0.23 for the performance variables (i.e, SJ height and sprint time). Overall, results showed a decrease in the magnitude of the correlations for higher-level athletes. The low correlations generally observed between jumping and sprinting mechanical outputs suggest that both tasks provide distinctive information regarding the FVP profile of lower-body muscles. Therefore, we recommend the assessment of the FVP profile both in jumping and sprinting to gain a deeper insight into the maximal mechanical capacities of lower-body muscles, especially at high and elite levels.
Database of force-velocity profile from horizontal and vertical modalities in various sports modalities, level and sex. F0, theoretical maximal force; v0, theoretical maximal velocity; Pmax, theoretical maximal power; LL, low level or amateur; ML, medium level or semi-professional; HL, high level or professional; EL, elite level or international.
This study aimed to analyse fatigue-induced changes in mechanical sprinting properties during a specific repeated-sprint test in elite rugby sevens athletes. Twenty elite rugby sevens players performed ten 40 m sprints on a 30 s cycle with participant’s running back and forth in a marked lane. Radar was used to assess maximal overground sprint performance over each 40 m. Macroscopic mechanical properties (maximal horizontal force (F0), maximal horizontal power (Pmax), maximal ratio of horizontal force (RFpeak), decrease in the ratio of horizontal-to-total force (DRF), total force and maximal sprinting velocity (v0)) were drawn from horizontal force velocity relationships, using a validated method applied to the speed–time data. Fatigue-induced changes were analysed comparing the first sprint to an average of 2nd-4th, 5th-7th and 8th-10th. Repeated-sprint ability (RSA) testing induced substantial changes in the maximal velocity component, with a decrease (–15%) in v0 (effect size (ES) = –2.46 to –4.98), and to a lower extent (–5.9%) in the maximal force component F0 (ES = –0.59). DRF moderately decreased (14%; ES=–0.76–1.11), and RFpeak largely decreased in the later sprints (ES = –0.32 to –1.27). Fatigue observed in this RSA test appeared to have a greater effect on the technical ability to produce horizontal force at high velocities, likely due to an alteration in the ability to maintain horizontally oriented force application when velocity increases rather than during the initial acceleration phase, but also the overall force production capacity. The ability to maintain forward-oriented force at high velocities is of central importance for identifying fatigue and monitoring load.
Aim: Hamstring muscle injury is the main injury related to sports requiring sprint acceleration. In addition, hamstring muscles have been reported to play a role in horizontal force production during sprint acceleration performance. The aim of the present study was to analyze (i) the determinants of horizontal force production and (ii) the role of hip extensors, and hamstring muscles in particular, for horizontal force production during repeated sprint-induced fatigue conditions. Method: In this experimental laboratory setting study including 14 sprint-trained male athletes, we analyzed (i) the changes in sprint mechanics, peak torque of the knee and hip extensors and flexors, muscle activity of the vastus lateralis, rectus femoris, biceps femoris, and gluteus, and sagittal plane lower limb motion, before and after twelve 6-s sprints separated by 44 s rest on an instrumented motorized treadmill, and (ii) the determinants of horizontal force production (F H) during the sprint acceleration in a fatigue state (after 12 sprints). Results: The repeated-sprint protocol induced a decrease in maximal power output (Pmax) [−17.5 ± 8.9%; effect size (ES): 1.57, large] and in the contact-averaged horizontal force component (F H) (−8.6 ± 8.4%; ES: 0.86, moderate) but not meaningful changes in the contact-averaged resultant (total) force (F Tot) (−3.4 ± 2.9%; ES: 0.55, small) and vertical force component (F V) (−3.1 ± 3.2%; ES: 0.49, small). A decrease was found in concentric peak torque of the knee flexors and extensors and in gluteus and Frontiers in Physiology | www.frontiersin.org 1 November 2018 | Volume 9 | Article 1706 Edouard et al. Sprint Mechanics in Fatigue Conditions vastus lateralis muscle activity during entire swing and end-of-swing phase. An increase was found in contact time and swing time, while step frequency and knee speed before ground contact decreased. Muscular determinants associated with F H and its decrease after the repeated-sprint protocol were concentric peak torque of the hip extensors (p = 0.033) and a decrease in gluteus maximus activity at the end-of-swing (p = 0.007), respectively. Conclusion: Sprint-induced fatigue lead to changes in horizontal force production muscular determinants: hamstring muscle seems not to have the same role than in non-fatigue condition. Horizontal force production seems to be more dependent on the hip extensors and gluteus maximus function. Given the fatigue-induced decrease in hamstring muscle strength, we can hypothesize that muscle compensatory and kinematic strategies reported in a fatigued state could be an adaptation to allow/maintain performance and a protective adaptation to limit hamstring muscles constraints.
This study analysed the acute mechanical and metabolic responses to a sprint training session focused on maintaining maximal speed until a given speed loss was reached. Nine male high-level sprinters performed 60 m running sprints up to a 3% in speed loss with 6 min rests between sets. Mechanical responses (countermovement jump (CMJ) height and speed loss) and metabolic responses (blood lactate and ammonia concentrations) were measured pre-exercise and after each set was performed. Jump height loss showed almost perfect relationships with both lactate (r = 0.91) and ammonia (r = 0.91) concentrations. In addition, nearly perfect relationships were observed for each athlete between CMJ height loss and lactate (r = 0.93–0.99) and ammonia (r = 0.94–0.99). Very large correlations were found between speed loss and lactate (r = 0.83), and ammonia (r = 0.86) concentrations. Furthermore, close relationships were observed for each athlete between speed loss and lactate (r = 0.86–0.99), and ammonia (r = 0.88–0.98). These results suggest that the CMJ test may allow more accurate setting of training loads in sprint training sessions, by using an individualised sprint dose based on mechanical and physiological responses rather than a standard fixed number of sprints for all athletes.
This study aimed to compare the between-session reliability of three typically measured velocity variables (mean velocity [MV], mean propulsive velocity [MPV], and maximum velocity [Vmax]) to assess vertical jump performance. Twenty-three men had their squat jump (SJ) and countermovement jump (CMJ) tested against five different loading conditions (17, 30, 45, 60 and 75 kg) during two consecutive weeks. The two sessions of each jump type were performed within the same week separated by 48-72 hours. The main finding was a significant difference in reliability between the variables, which were ranked from the highest to the lowest reliable as follow (median coefficient of variation [CV] and range): Vmax (CV=2.35% [1.85%-3.23%]) > MV (CV=3.29% [2.18%-4.40%]) > MPV (CV=3.69% [2.08%-5.17%]). A significant variable × exercise interaction was also observed showing that the differences in reliability between the variables were meaningful during the SJ (MV: CV=3.93% [3.06%-4.40%], MPV: CV=4.61% [4.07%-5.17%], and Vmax: CV=2.14% [1.85%-2.71%]), while no significant differences were observed for the CMJ (MV: CV=2.43% [2.18%-3.70%], MPV: CV=2.71% [2.08%-3.63%], and Vmax: CV=2.40% [1.97%-3.23%]). These results suggest that the Vmax should be the recommended variable for obtaining a reproducible measure of lower-body ballistic performance, especially during the SJ exercise.
Background The ability to jump has been related to muscle strength and power, speed and amplitude of the lower limbs movements, and specifically for the elderly, the vertical jump has been shown to be a good predictor of functional capacity and risk of falling. The use of a mobile application ( App ) which can measure the vertical jump (i.e., iPhone App My Jump ) has recently emerged as a simple, cheap and very practical tool for evaluation of jump ability. However, the validity of this tool for the elderly population has not been tested yet. The elderly usually perform very low jumps and therefore the signal-to-noise ratio may compromise the validity and reliability of this method. Thus, the aim of the current study was to verify the validity and reliability of the iPhone App “ My Jump ” for the evaluation of countermovement jump (CMJ) height within an elderly population. Methods After familiarization, 41 participants performed three CMJs assessed via a contact mat and the My Jump App . The intraclass correlation coefficient (ICC) was used to verify the relative reliability, while the coefficient of variation (CV%) and the typical error of measurement (TEM) were used to verify the absolute reliability. Pearson’s correlation coefficient was used to verify the strength of the relationship between methods (i.e., concurrent validity), a Bland–Altman plot to show their agreement, and the Student’s t -test to identify systematic bias between them. For reliability analyses, all jumps were considered (i.e., 123). All jumps (i.e., 123), the average height of each attempt (i.e., 41), and the highest jump, were considered for validity analyses. Results The CMJ height of the highest jump was 10.78 ± 5.23 cm with contact mat, and 10.87 ± 5.32 with My Jump App , with an identified systematic bias of 0.096 cm ( P = 0.007). There was a nearly perfect correlation between methods ( r = 0.999; P = 0.000, in all cases) with a very good agreement observed (0.3255 to −0.5177 cm, 0.2797 to −0.5594 cm, and 0.3466 to −0.6264 cm, for highest jump height, average jump height, and all jump heights, respectively). The ICC of the My Jump App was 0.948, the TEM was 1.150 cm, and the CV was 10.10%. Conclusion Our results suggest that the My Jump App is a valid and reliable tool compared to the contact mat for evaluating vertical jump performance in the elderly. Therefore, it allows a simple and practical assessment of lower limbs’ power in this population. For the elderly, as well as for other populations with low jumping heights, the highest jump height and the average jump height could be used indistinctly.
Purpose:: This study aimed to compare the sprint mechanical force-velocity (F-V) profile between soccer and futsal players. A secondary aim was, within each sport, to study the differences in sprint mechanical F-V profile between sexes and players of different levels. Methods:: 102 soccer players (63 men) and 77 futsal players (49 men) that were competing from the elite to amateur levels in the Spanish league participated in this investigation. The testing procedure consisted of 3 unloaded maximal 40-m sprints. The velocity-time data recorded by a radar device was used to calculate the variables of the sprint acceleration F-V profile (maximal theoretical force [F0], maximal theoretical velocity [V0], maximal power [Pmax], decrease in the ratio of horizontal-to-resultant force [DRF], and maximal ratio of horizontal-to-resultant force [RFpeak]). Results:: Futsal players showed a higher F0 than soccer players (effect size [ES] range: 0.11 to 0.74), while V0 (ES range: -0.48 to -1.15) and DRF (ES range: -0.75 to -1.45) was higher for soccer players. No significant differences were observed between soccer and futsal players for Pmax (ES range: -0.43 to 0.19) and RFpeak (ES range: -0.49 to 0.30). Men and high-level players presented an overall enhanced F-V profile compared to women and their lower-level counterparts, respectively. Conclusions:: The higher F0 and lower V0 of futsal players could be caused by the specific game's demand (larger number of accelerations but of shorter distances compared to soccer). These results show that the sprint mechanical F-V profile is able to distinguish between soccer and futsal players.
KEY POINTS 1. Despite a widespread use, we contended that jump height as measured during vertical jump tests is not a good indicator of lower limb power or maximal power output capability. 2. We showed this based on several confounding factors: body mass, push-off distance, individual force-velocity profile and optimal force-velocity profile. Some experimental data were also shown and discussed to further illustrate the not very-good correlation between jump height and power output. 3. Finally, in order to address this issue, we discussed the possible practical solutions, and advocate for the use of a simple, accurate computation method based on jump height as an input.
- Jul 2018
Background: The aim of the present study was to evaluate the changes in a panel of biomarkers including lactate, ferritin and uric acid in saliva of untrained and trained subjects after repeated explosive effort sequences, and to analyse the differences in interpretation of these biomarkers depending on the way the data is expressed (without any correction or corrected by protein content or flow). Methods: Eighteen volunteers (11 untrained and 7 trained) performed 8 consecutive explosive effort sequences (60 m sprints). Blood and saliva samples were collected before and after each sequence. Salivary data was analysed as absolute concentration and after correcting by their protein content and flow. Results: Lactate in saliva showed increases with acute exercise, being these increases of higher magnitude in non-trained subjects. In addition, when corrected by total protein, lactate in saliva correlates with blood lactate in non-trained subjects. Ferritin and uric acid in saliva did not show changes after the effort sequences. Conclusions: From the biomarkers evaluated, the measurement of lactate in saliva corrected by total protein could be useful for the assessment of fatigue induced during repeated explosive effort sequences and could be potentially used as a non-invasive alternative to blood lactate. This report also points out that way of reporting the saliva analytes could greatly influence the interpretation of the results and that lactate in saliva has a different dynamic in trained and non-trained individuals that should be further explored.
The purpose of this investigation was to analyze the validity and reliability of an iPhone app (named: Dorsiflex) for the measurement of weight-bearing ankle dorsiflexion. To do this, twelve healthy participants (age = 28.6 ± 2.3 years) performed a weight-bearing lunge test with each leg in five separate occasions, while dorsiflexion angle was simultaneously registered using a professional digital inclinometer and the Dorsiflex iPhone app, which was specifically developed for this study. A total of 120 angles measured both with the digital inclinometer and the app were then compared for validity, reliability and accuracy purposes using several statistical tests. There was an almost perfect correlation between the digital inclinometer and the Dorsiflex app for the measurement of ankle dorsiflexion (r = 0.989, 95% CI = 0.986–0.993, SEE = 0.48º), with trivial, non-significant differences between devices (SMD = 0.17, p = 0.10). When analyzing the reliability of the app for the measurement of five different trials for each participant, similar coefficients of variation (CV) were observed in comparison with those obtained with the digital inclinometer (Dorsiflex app: CV = 5.1 ± 2.3%; Digital inclinometer: CV = 4.9 ± 2.5%). The results of the present study show that weight-bearing ankle dorsiflexion can be easily, accurately, and reliably evaluated using the Dorsiflex iPhone app.
Purpose: The aims of this study were (I) to quantify the magnitude of the association between the same variables of the force-velocity (FV) profile and the performance variables (unloaded squat jump [SJ] height and 20 m sprint time) obtained during the jumping and sprinting testing procedures, and (II) to determine which mechanical capacity (i.e., maximum force [F0], maximum velocity [V0] or maximum power [Pmax]) presents the highest association with the performance variables. Methods: The FV profile of 19 elite female soccer players (age: 23.4±3.8 years, height: 166.4±5.6 cm, body mass: 59.7±4.7 kg) was determined during the jumping and sprinting tasks. The F0, V0, FV slope, Pmax, and FV imbalance (difference respect to the optimal FV profile in jumping and the decrease in the ratio of horizontal force production in sprinting) were determined for each task. Results: Very large correlations between both tasks were observed for Pmax (r= 0.75) and the performance variables (r= -0.73), moderate correlations for V0 (r= 0.49), while the F0 (r= -0.14), the FV slope (r= -0.09), and the FV imbalance (r= 0.07) were not significantly correlated between both tasks. The Pmax obtained during each specific task was the mechanical capacity most correlated with its performance variable (r= 0.84 in jumping and r= 0.99 in sprinting). Conclusions: The absence of significant correlations between some of the FV relationship parameters suggests that for an individualized training prescription based on the FV profile both jumping and sprinting testing procedures should be performed with elite female soccer players.
This study explored the acute and delayed (24 and 48 h post-exercise) effects of a resistance training session leading to muscular failure. Eleven resistance-trained men completed a training session consisting on 3 sets of repetitions to failure during the back squat exercise performed at the maximum possible speed with a load equivalent to a mean propulsive velocity (MPV) of 1 m·s-1 (≈ 60% of 1-repetition maximum). A number of mechanical (number of repetitions and starting MPV of the set, MPV achieved against the 1MPV load, countermovement jump [CMJ] height, and handgrip strength), metabolic (lactate, uric acid, and ammonia concentrations), and perceptual (OMNI-RES perceived exertion) variables were measured. The results revealed (I) a decrease of 38.7% in set 2 and 54.7% in set 3 of the number of repetitions performed compared to the first set (P<0.05), (II) a reduction in the MPV of the repetitions and an increase in lactate concentration and OMNI-RES values with the succession of sets (P<0.05), (III) comparable decrements in CMJ height after the 3 sets (25-32%), (IV) a decrease in CMJ height (P<0.05; 6.7-7.9%) and in the MPV attained against the 1MPV load (P<0.05; 13-14%) after 24 and 48 hours of completing the training session, but no significant changes were observed in handgrip strength (P>0.05; < 2%), and (V) uric acid and ammonia concentrations above the basal levels (P<0.05). The large decrements in mechanical performance together with the high metabolic stress discourage the frequent use of resistance training sessions leading to muscular failure.
Aims In the current study we investigated the effects of resisted sprint training on sprinting performance and underlying mechanical parameters (force-velocity-power profile) based on two different training protocols: (i) loads that represented maximum power output (Lopt) and a 50% decrease in maximum unresisted sprinting velocity and (ii) lighter loads that represented a 10% decrease in maximum unresisted sprinting velocity, as drawn from previous research (L10). Methods Soccer [n = 15 male] and rugby [n = 21; 9 male and 12 female] club-level athletes were individually assessed for horizontal force-velocity and load-velocity profiles using a battery of resisted sprints, sled or robotic resistance respectively. Athletes then performed a 12-session resisted (10 × 20-m; and pre- post-profiling) sprint training intervention following the L10 or Lopt protocol. Results Both L10 and Lopt training protocols had minor effects on sprinting performance (average of -1.4 to -2.3% split-times respectively), and provided trivial, small and unclear changes in mechanical sprinting parameters. Unexpectedly, Lopt impacted velocity dominant variables to a greater degree than L10 (trivial benefit in maximum velocity; small increase in slope of the force-velocity relationship), while L10 improved force and power dominant metrics (trivial benefit in maximal power; small benefit in maximal effectiveness of ground force orientation). Conclusions Both resisted-sprint training protocols were likely to improve performance after a short training intervention in already sprint trained athletes. However, widely varied individualised results indicated that adaptations may be dependent on pre-training force-velocity characteristics.
- Apr 2018
Practical duration stretching after aerobic activities is a recommended component of the first part of warm-up due to its effects on performance. However, its effects on proprioceptive skills are unknown. This study aimed to analyze the effects of running and practical duration static and dynamic stretching on postural balance and the joint position sense of national sprinters. Thirty-two national sprinters were randomly classified into a static stretching group (SS) (n=11), dynamic stretching group (DS) (n=11), or control group (n=10). SS carried out five minutes of running and shortduration (20 seconds) static stretches; DS carried out five minutes of running and short-duration dynamic (20 seconds) stretches; and the control group carried out five minutes of running. Before and after the intervention, unipedal static postural balance and knee joint position sense (JPS) were evaluated. SS exhibited a more centralized center of pressure in the medial-lateral plane for unipedal static postural balance in right-leg support after stretching (p = 0.005, d = 1.24), while DS showed values further from the center after stretching for the same unipedal support compared to baseline (p = 0.042, d = 0.49), and the control group remained stable (p > 0.05). JPS did not show significant differences in any group (p > 0.05). In conclusion, combining running and practical duration static stretching may be beneficial for right-leg postural stabilization, while dynamic stretching may be partly and slightly deleterious. Both static and dynamic stretching combined with running and running alone have neutral effects on knee joint position sense. Sports professionals should consider running and practical duration static stretching as part of the warm-up of sprinters to partly improve unipedal static postural balance.
The aim of this study was to look at differences in countermovement jump (CMJ) performance and selected kinetic parameters in athletes of different training backgrounds and to examine the relationships between these parameters. The subjects were 14 endurance athletes, 12 sprinters, and 13 fire-fighter aspirants (controls); each performed two CMJ on a force plate. The best jump of two attempts was selected and the following parameters were calculated: CMJ height (h), peak power (PP), normalized vertical stiffness (Kvert), rate of force development (RFD), peak RFD (pRFD) during concentric phase, and the ratio between pRFD and the time of its occurrence (iRFD). Sprinters exhibited greater h, PP, Kvert and RFD values than the other groups. A strong correlation was revealed between PP and h, and between pRFD and Kvert in all groups. The magnitude of correlations improved with iRFD when compared to pRFD (.5-.6 vs. .7-.9). There were strong correlations (r>.7) between PP, Kvert, and both pRFD and iRFD only for the endurance athletes group. From these results, it would be recommended to record different RFD calculations during CMJ evaluations, including the new RFD index (iRFD), in athletes of different training backgrounds.
This study aimed to compare the between-session reliability of three velocity variables (mean velocity [MV], mean propulsive velocity [MPV], and maximum velocity [Vmax]) to assess bench press throw (BPT) performance. Twenty-one men were tested during two consecutive weeks in two variants of the BPT exercise (concentric-only and eccentric-concentric) against five different loading conditions (17, 27, 37, 47, and 57 kg). The two sessions of each BPT variant were performed within the same week separated by 48-72 hours. The main findings revealed that (1) the highest reliability was observed for Vmax (median coefficient of variation [CV] and range) (CV = 2.14% [1.43%, 4.02%]), followed by MV (CV = 3.18% [1.47%, 5.22%]), and finally the MPV was the least reliable variable (CV = 4.27% [1.98%, 6.38%]), (2) all velocity variables demonstrated a higher reliability during the eccentric-concentric BPT (CV = 2.41% [1.43%, 5.30%]) when compared to the concentric-only BPT (CV = 4.02% [1.74%, 6.38%]), and (3) the reliability tended to decrease with the increment of the load: 17 kg (CV = 2.12% [1.43%, 4.68%]), 27 kg (CV = 1.96% [1.74%, 3.86%]), 37 kg (CV = 2.98% [2.47%, 5.67%]), 47 kg (CV = 4.59% [2.32%, 6.38%]), and 57 kg (CV = 3.92% [1.95%, 5.52%]). These results indicate that the assessment of the Vmax should be performed with a light loading condition during the eccentric-concentric BPT for obtaining the most reproducible measure of upper-body ballistic performance.
Background: Eccentric actions allows to apply 20-50% greater strength than concentric. This effort may induce a more rapid protein synthetic response and greater increase in anabolic signalling (Franchi et al., 2014). Moreover, ECC actions produces disruption to contractile, structural, and supportive elements (Enoka, 1996), due to specific force demands on fewer active fibers, being susceptible to tear when resisting dynamic lengthening (Schoenfeld et al., 2017). While serum is still the most common method used, some research proposes saliva as alternative to measure the responses induced by exercise (Deminice et al., 2010). Despite the large number of studies examining the effect of eccentric training on strength, neither the behaviour of the biochemical response of certain enzymes during post-training points or the comparison of response between genders, and changes of muscle enzymes in saliva after this training are known. Objectives: The aim of this study was to examine the response of muscle damage markers until 96 h post training in men and women using serum and saliva. Methods: Sixteen men (n=10) and women (n=6), (age 23.04±2.56), after two familiarization session and test of 1RM, participated in eccentric training session which consisted in 8 set of 5 repetitions with 120% of RM in squat with 5 min of resting. Serum and saliva measures were taken at baseline, 24, 48, 72 and 96 h post-training. Data were analysed by descriptive analysis, Pearson correlation and ANOVA. Results: Data showed significant differences for serum CK values between pre-training and all post-training points for men and women (p<.01 and p<.05, respectively), decreasing as longer time-points were analysed in men. Similar findings were found for serum AST and LDH values in both genders. In addition, Saliva CK values showed significant differences in pre-post 96h for men (p<.05). However, we could not find significant differences for AST and LDH related to timeline in saliva in any of both genders. Finally, there was a main effect of gender in CK serum for pre-training and pre-post 24h values (Frange= 4.73-4.85; p<.05). Conclusions: It seems that this type of exercise can produce acute muscle damage, A significant increase in CK in saliva in males were found at 96 h. No significant changes in other enzymes in saliva were found although some individuals showed increases after the effort. This lack of changes could be due probably to the high interindivual variability found. Further studies would be recommended to further investigate the reasons for this variability Practical Applications: We believe that our current results could help to adjust, dosify and design training programs employing squat exercises for specific eccentric training
Purpose: Our aim was to quantify the mechanical outputs developed during horizontal squat jumps, and notably the movement velocity, in comparison to vertical squat jumps with and without loads. Methods: Thirteen healthy male athletes performed squat jumps without additional loads (SJ0), with a load of ~60% of body mass (SJ60) and during horizontal squat jumps performed lying down on a roller device with (AHSJ) and without (HSJ) a rubber band assistance. Instantaneous lower limb extension velocity, force and power output were measured and averaged over the push-off phase. Results: The force was significantly higher during SJ60 than during SJ0, which was higher than during HSJ and AHSJ. Extension velocity was significantly different across all conditions with 0.86 ± 0.07, 1.29 ± 0.10, 1.59 ± 0.19 and 1.83 ± 0.19 m.s-1 for SJ60, SJ0, HSJ and AHSJ conditions, respectively. Differences in force and velocity values between SJ0 and the other conditions were large to extremely large. Differences were observed in power values only between SJ60 and SJ0, SJ60 and AHSJ and SJ0 and HSJ. Conclusion: Horizontal squat jump modalities allow athletes to reach very to extremely largely higher limb extension velocities (HSJ: +24.0±16%, AHSJ: +42.8±17.4%) than during SJ0. HSJ and AHSJ modalities are cheap and practical modalities to train limb extension velocity capabilities, i.e. the ability of the neuromuscular system to produce force at high contraction velocities.
- Nov 2017
Context. New methods are being validated to easily evaluate the knee joint position sense (JPS) due to its role in sports movement and the risk of injury. However, no studies to date have considered the open kinetic chain (OKC) technique, despite the biomechanical differences compared to closed kinetic chain movements. Objective. To analyze the validity and reliability of a digital inclinometer to measure the knee JPS in the OKC movement. Design. The validity, inter-tester and intra-tester reliability of a digital inclinometer for measuring knee JPS were evaluated. Setting. Sports research laboratory. Participants. Eighteen athletes (11 males and 7 females; 28.4 ± 6.6 years; 71.9 ± 14.0 kg; 1.77 ± 0.09 m; 22.8 ± 3.2 kg/m2) voluntary participated in this study. Main Outcomes Measures. Absolute angular error (AAE), relative angular error (RAE) and variable angular error (VAE) of knee JPS in an OKC. Results. Intraclass correlation coefficient (ICC) and standard error of the mean (SEM) were calculated to determine the validity and reliability of the inclinometer. Data showed excellent validity of the inclinometer to obtain proprioceptive errors compared to the video analysis in JPS tasks (AAE: ICC = 0.981, SEM = 0.08; RAE: ICC = 0.974, SEM = 0.12; VAE: ICC = 0.973, SEM = 0.07). Inter-tester reliability was also excellent for all the proprioceptive errors (AAE: ICC = 0.967, SEM = 0.04; RAE: ICC = 0.974, SEM = 0.03; VAE: ICC = 0.939, SEM = 0.08). Similar results were obtained for intra-tester reliability (AAE: ICC = 0.861, SEM = 0.1; RAE: ICC = 0.894, SEM = 0.1; VAE: ICC = 0.700, SEM = 0.2). Conclusions. The digital inclinometer is a valid and reliable method to assess the knee JPS in OKC. Sport professionals may evaluate the knee JPS to monitor its deterioration during training or improvements throughout the rehabilitation process.
This study aimed (1) to analyze the accuracy of mean propulsive velocity to predict the percentage of the 1-repetition maximum in the seated military press exercise and (2) to test the effect of gender and of a resistance training program on the load–velocity profile. The load–velocity relationships of 26 men and 13 women were evaluated by means of an incremental loading test up to the individual 1-repetition maximum. Additionally, the load–velocity relationships of 24 of those 26 men were measured again after a six-week resistance training program. Individual load–velocity relationships had very high coefficients of determination and low standard errors of the estimate (R2 = 0.987; standard error of the estimate = 0.04 m/s). Differences higher than 10% between the individual and the general load–velocity profiles as well as a high between-participants’ variability for the mean propulsive velocity attained at each 1-repetition maximum (coefficient of variation = 12.9–24.6%) were identified. The load–velocity profiles proved to be affected by both the gender (higher mean propulsive velocity at each %1-repetition maximum for men) and the resistance training program (lower mean propulsive velocity at each %1-repetition maximum after training). Taken together, these results speak in favor of creating individual profiles instead of using general equations when using the load–velocity relationship to estimate relative load.
The aim was to determine the position of the one-repetition maximum (1RM) squat point on the force-velocity (F-V) relationship obtained during squat jump (SJ). Ten healthy athletes performed a 1RM squat during which ground reaction force and lower-limb extension velocity were measured, and six loaded SJs to determine individual F-V relationship. The goodness of fit of the linear F-V relationship with or without the 1RM point was tested. The vertical and horizontal coordinates were determined relative to the theoretical maximal force (F0) and the highest loaded SJ (load of 44.5±4.6% 1RM). The goodness of fit of the individual F-V relationship did not differ with or without the 1RM condition, even if the 1RM point was slightly below the curve (−5±5%, P=0.018). The 1RM point can be considered as a point of the F-V relationship. The velocity (0.22±0.05 m.s−1) of the 1RM point corresponded to ~30% of the velocity reached during the highest loaded SJ. The force developed in the 1RM condition was ~16% higher than during the highest loaded SJ and ~11% lower than F0. This finding underlines the difference between F0 and the 1RM condition and it also suggests that 1RM permorfance is (slightly) influenced by velocity capacities (V0).
This study aimed to compare mechanical and metabolic responses between traditional (TR) and cluster (CL) set configurations in the bench press exercise. In a counterbalanced randomized order, 10 men were tested with the following protocols (sets × repetitions [inter-repetition rest]): TR1: 3×10 [0-s], TR2: 6×5 [0-s], CL5: 3×10 [5-s], CL10: 3×10 [10-s], and CL15: 3×10 [15-s]. The number of repetitions (30), inter-set rest (5 min), and resistance applied (10RM) were the same for all set configurations. Movement velocity and blood lactate concentration were used to assess the mechanical and metabolic responses, respectively. The comparison of the first and last set of the training session revealed a significant decrease in movement velocity for TR1 (Effect size [ES]: -0.92), CL10 (ES: -0.85) and CL15 (ES: -1.08) (but not for TR2 [ES: -0.38] and CL5 [ES: -0.37]); while blood lactate concentration was significantly increased for TR1 (ES: 1.11), TR2 (ES: 0.90) and CL5 (ES: 1.12) (but not for CL10 [ES: 0.03] and CL15 [ES: -0.43]). Based on velocity loss, set configurations were ranked as follows: TR1 (-39.3±7.3%) > CL5 (-20.2±14.7%) > CL10 (-12.9±4.9%), TR2 (-10.3±5.3%) and CL15 (-10.0±2.3%). The set configurations were ranked as follows based on the lactate concentration: TR1 (7.9±1.1 mmol·l-1) > CL5 (5.8±0.9 mmol·l-1) > TR2 (4.2±0.7 mmol·l-1) > CL10 (3.5±0.4 mmol·l-1) and CL15 (3.4±0.7 mmol·l-1). These results support the use of TR2, CL10 and CL15 for the maintenance of high mechanical outputs, while CL10 and CL15 produce less metabolic stress than TR2.
The aim of this study was to assess the relationship between strength variables and maximum velocity (Vmax) in the squat jump (SJ) in sprinting and jumping athletes. Thirty-two sprinting and jumping athletes of national level (25.4 ± 4.5 years; 79.4 ± 6.9 kg and 180.4 ± 6.0 cm) participated in the study. Vmax in the SJ showed significant relationships with peak force 1 (PF1) (r = 0.82, p ≤ 0.001), peak force 2 (PF2) (r = 0.68, p ≤ 0.001), PF2 by controlling for PF1 (r = 0.30, non-significant), the maximum rate of force development at peak force 1 (RFDmax1) (r = 0.62, p ≤ 0.001), mean RFD 1 (RFDmean1) (r = 0.48, p ≤ 0.01), mean RFD 2 (RFDmean2) (r = 0.70, p ≤ 0.001), force at RFDmax1 (r = 0.36, p ≤ 0.05), force at RFDmax2 (r = 0.83, p ≤ 0.001) and force at RFDmax2 by controlling for PF1 (r = 0.40, p ≤ 0.05). However, Vmax in the SJ was associated negatively with the ratio PF2/PF1 (r = -0.54, p ≤ 0.01), time at peak force 2 (Tp2) (r = -0.64, p ≤ 0.001) and maximum rate of force development at peak force 2 (RFDmax2) (r = -0.71, p ≤ 0.001). These findings indicate that the peak force achieved at the beginning of the movement (PF1) is the main predictor of performance in jumping, although the RFDmax values and the ratio PF2/PF1 are also variables to be taken into account when analyzing the determinant factors of vertical jumping.
This study aimed to compare mechanical, metabolic, and perceptual responses between two traditional (TR) and four cluster (CL) set configurations. In a counterbalanced randomized order, 11 men were tested with the following protocols in separate sessions (sets × repetitions [inter-repetition rest]): TR1: 3×10 [0-s]; TR2: 6×5 [0-s]; CL1: 3×10 [10-s]; CL2: 3×10 [15-s]; CL3: 3×10 [30-s]); CL4: 1×30 [15-s]). The exercise (full-squat), number of repetitions (30), inter-set rest (5 min), and resistance applied (10RM) was the same for all set configurations. Mechanical fatigue was quantified by measuring the mean propulsive velocity during each repetition, and the change in countermovement jump height observed after each set and after the whole training session. Metabolic and perceptual fatigue were assessed via the blood lactate concentration and the OMNI perceived exertion scale measured after each training set, respectively. The mechanical, metabolic, and perceptual measures of fatigue were always significantly higher for the TR1 set configuration. The two set configurations that most minimized the mechanical measures of fatigue were CL2 and CL3. Perceived fatigue did not differ between the TR2, CL1, CL2 and CL3 set configurations. The lowest lactate concentration was observed in the CL3 set configuration. Therefore, both the CL2 and CL3 set configurations can be recommended because they maximize mechanical performance. However, the CL2 set configuration presents two main advantages with respect to CL3: (1) it reduces training session duration, and (2) it promotes higher metabolic stress, which to some extent may be beneficial for inducing muscle strength and hypertrophy gains.
This study aimed to analyze various fitness qualities in handball players of different ages, and to determine the relationships between these parameters and throwing velocity. Forty-four handball players participated, pooled by age groups: ELITE (n = 13); under-18 (U18, n = 16); under-16 (U16, n = 15). The following tests were completed: 20-m running sprints; countermovement jumps (CMJ); jump squat to determine the load that elicited ~20 cm jump height (JSLOAD-20cm); a progressive loading test in full-squat and bench-press to determine the load that elicited ~1 m[middle dot]s-1 (SQ-V1-LOAD and BP-V1-LOAD), and handball throwing (Jump Throw and 3-Step Throw). ELITE showed greater performance in almost all sprint distances, CMJ, JSLOAD-20cm and bench-press strength than U18 and U16. The differences between U18 and U16 were unclear for these variables. ELITE also showed greater (P < 0.001) performance for squat strength and throwing than U18 and U16, and U18 attained greater performance (P < 0.05) for these variables than U16. Throwing performance correlated (P < 0.05) with sprint times (r = -.31; -.51) and jump ability (CMJ: r = .39; .56 and JSLOAD-20cm: r = .57; .60). Muscle strength was also associated (P < 0.001) with both types of throw (SQ-V1-LOAD: r = .66; .76; and BP-V1-LOAD: r = .33; .70). These results indicate handball throwing velocity is strongly associated with lower-limb strength, although upper-limb strength, jumping and sprint capacities also play a relevant role in throwing performance, suggesting the need for coaches to include proper strength programs to improve handball players' throwing velocity.
Background: The aim of this study was to evaluate changes in the enzymes creatine kinase (CK), lactate dehydrogenase (LDH) and aspartate aminotransferase (AST) in saliva before and after an intense exercise consisting of a futsal match. Methods: CK, LDH and AST were analyzed in saliva and serum samples of eleven, injury-free, amateur young men before and 30 minutes, 12 hours and 36 hours after a futsal match. Results: A significant increase in CK, LDH and AST was observed after the game in serum samples. In saliva, although a high interindividual variability was found with some individuals no showing increases, significant increases in CK and LDH were observed after the game.. No significant changes were observed in saliva AST after the game. Conclusions: Our study showed for first time that CK and LDH can increase in saliva after an intensive exercise consisting on a futsal match. Results suggest that measurements of CK and LDH in saliva could be potentially used to evaluate possible muscle stress or damage in cases of intensive exercise.
Ballistic performances are determined by both the maximal lower limb power output (P max) and their individual force-velocity (F-v) mechanical profile, especially the F-v imbalance (FV imb): difference between the athlete's actual and optimal profile. An optimized training should aim to increase P max and/or reduce FV imb. The aim of this study was to test whether an individualized training program based on the individual F-v profile would decrease subjects' individual FV imb and in turn improve vertical jump performance. FVimb was used as the reference to assign participants to different training intervention groups. Eighty four subjects were assigned to three groups: an " optimized " group divided into velocity-deficit, force-deficit, and well-balanced subgroups based on subjects' FV imb , a " non-optimized " group for which the training program was not specifically based on FV imb and a control group. All subjects underwent a 9-week specific resistance training program. The programs were designed to reduce FV imb for the optimized groups (with specific programs for subgroups based on individual FV imb values), while the non-optimized group followed a classical program exactly similar for all subjects. All subjects in the three optimized training subgroups (velocity-deficit, force-deficit, and well-balanced) increased their jumping performance (12.7 ± 5.7% ES = 0.93 ± 0.09, 14.2 ± 7.3% ES = 1.00 ± 0.17, and 7.2 ± 4.5% ES = 0.70 ± 0.36, respectively) with jump height improvement for all subjects, whereas the results were much more variable and unclear in the non-optimized group. This greater change in jump height was associated with a markedly reduced FV imb for both force-deficit (57.9 ± 34.7% decrease in FV imb) and velocity-deficit (20.1 ± 4.3%) subjects, and unclear or small changes in P max (−0.40 ± 8.4% and +10.5 ± 5.2%, respectively). An individualized training program specifically based on FV imb (gap between the actual and optimal F-v profiles of each individual) was more efficient at improving jumping performance (i.e., unloaded squat jump height) than a traditional resistance training common to all subjects regardless of their FV imb. Although improving both FV imb and P max has to be considered to improve ballistic performance, the present results showed that reducing FV imb without even increasing P max lead to clearly beneficial jump performance changes. Thus, FV imb could be considered as a potentially useful variable for prescribing optimal resistance training to improve ballistic performance.
- Feb 2017
Background The hamstring muscles are the most injured muscles in athletes practicing sprints. In addition, they seem greatly contributing to the production of horizontal force, a key element in the sprint acceleration performance. Objective To experimentally analyse the relationship between horizontal force production and hamstrings strength during maximum-velocity treadmill sprints with and without fatigue. Design Descriptive cross-sectional study. Setting Laboratory study on competitor-level athletes. Participants 14 healthy male athletes trained for sprint running. Main Outcome Measurements Comparison analyses of the following parameters before and after 12 6-seconds sprints separated by 44 seconds of recovery on an instrumented treadmill sprint: horizontal ground force production, EMG activity of the vastus lateralis, rectus biceps femoris and gluteus muscles, maximum isokinetic strength of the flexors and extensors of the hip and knee measured at 120°/s in concentric and eccentric before and just after the 12 sprints. Results For the best performance sprint, the multiple linear regression analysis showed a significant relationship (p=0.02) between the horizontal force and the combination of EMG activity of the biceps femoris in late swing phase of the stride and the eccentric isokinetic strength of the knee flexors. After the 12 sprints, there was a significant decrease (p<0.05) in sprint performance (−6.6%), horizontal force (−8.6%), isokinetic strength (−5.8 to -11.9%) and muscle activity (−5.0 to −38.9%), and there was a significant correlation between the horizontal force and eccentric strength of the knee extensors (r=0.640; p<0.02), and concentric strength of hip extensors (r=0.676; p<0.01). Conclusions For a high-performance acceleration, it would seem necessary to be able both to strongly activate the hamstrings just before ground contact and have a great capacity eccentric strength of the hamstrings. In fatigue conditions, horizontal force reduction would seem not only related to the strength of decreased hamstring, but with the knee extensors eccentric strength decrease.
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.
Lower limb isometric strength is a key parameter to monitor the training process or recognise muscle weakness and injury risk. However, valid and reliable methods to evaluate it often require high-cost tools. The aim of this study was to analyse the concurrent validity and reliability of a low-cost digital dynamometer for measuring isometric strength in lower limb. Eleven physically active and healthy participants performed maximal isometric strength for: flexion and extension of ankle, flexion and extension of knee, flexion, extension, adduction, abduction, internal and external rotation of hip. Data obtained by the digital dynamometer were compared with the isokinetic dynamometer to examine its concurrent validity. Data obtained by the digital dynamometer from 2 different evaluators and 2 different sessions were compared to examine its inter-rater and intra-rater reliability. Intra-class correlation (ICC) for validity was excellent in every movement (ICC > 0.9). Intra and inter-tester reliability was excellent for all the movements assessed (ICC > 0.75). The low-cost digital dynamometer demonstrated strong concurrent validity and excellent intra and inter-tester reliability for assessing isometric strength in the main lower limb movements.
Background: Sprint running acceleration is a key feature of physical performance in team sports, and recent literature shows that the ability to generate large magnitudes of horizontal ground-reaction force and mechanical effectiveness of force application are paramount. The authors tested the hypothesis that very-heavy loaded sled sprint training would induce an improvement in horizontal-force production, via an increased effectiveness of application. Methods: Training-induced changes in sprint performance and mechanical outputs were computed using a field method based on velocity-time data, before and after an 8-wk protocol (16 sessions of 10- × 20-m sprints). Sixteen male amateur soccer players were assigned to either a very-heavy sled (80% body mass sled load) or a control group (unresisted sprints). Results: The main outcome of this pilot study is that very-heavy sled-resisted sprint training, using much greater loads than traditionally recommended, clearly increased maximal horizontal-force production compared with standard unloaded sprint training (effect size of 0.80 vs 0.20 for controls, unclear between-groups difference) and mechanical effectiveness (ie, more horizontally applied force; effect size of 0.95 vs -0.11, moderate between-groups difference). In addition, 5-m and 20-m sprint performance improvements were moderate and small for the very-heavy sled group and small and trivial for the control group, respectively. Practical Applications: This brief report highlights the usefulness of very-heavy sled (80% body mass) training, which may suggest value for practical improvement of mechanical effectiveness and maximal horizontal-force capabilities in soccer players and other team-sport athletes. Results: This study may encourage further research to confirm the usefulness of very-heavy sled in this context.
The purpose of this study was to assess validity and reliability of sprint performance outcomes measured with an iPhone application (named: MySprint) and existing field methods (i.e. timing photocells and radar gun). To do this, 12 highly trained male sprinters performed 6 maximal 40-m sprints during a single session which were simultaneously timed using 7 pairs of timing photocells, a radar gun and a newly developed iPhone app based on high-speed video recording. Several split times as well as mechanical outputs computed from the model proposed by Samozino et al. [(2015). A simple method for measuring power, force, velocity properties, and mechanical effectiveness in sprint running. Scandinavian Journal of Medicine & Science in Sports. https://doi.org/10.1111/sms.12490] were then measured by each system, and values were compared for validity and reliability purposes. First, there was an almost perfect correlation between the values of time for each split of the 40-m sprint measured with MySprint and the timing photocells (r=0.989–0.999, standard error of estimate=0.007–0.015 s, intraclass correlation coefficient (ICC)=1.0). Second, almost perfect associations were observed for the maximal theoretical horizontal force (F0), the maximal theoretical velocity (V0), the maximal power (Pmax) and the mechanical effectiveness (DRF – decrease in the ratio of force over acceleration) measured with the app and the radar gun (r= 0.974–0.999, ICC=0.987–1.00). Finally, when analysing the performance outputs of the six different sprints of each athlete, almost identical levels of reliability were observed as revealed by the coefficient of variation (MySprint: CV=0.027–0.14%; reference systems: CV=0.028–0.11%). Results on the present study showed that sprint performance can be evaluated in a valid and reliable way using a novel iPhone app.
- Sep 2016
- Annals of Physical and Rehabilitation Medicine
Objective The hamstring muscles are the most injured muscles in athletes practicing sprints. However, they seem greatly contributing to the production of horizontal force, a key element in the sprint acceleration performance. The aim of our study was to experimentally analyse the link between the production of horizontal force and strength of the hamstrings at maximum sprints on a treadmill and in fatigue conditions. Patients and methods Fourteen male subjects accustomed to sprint participated in the experiment consisting in 12 6-seconds sprints separated by 44 seconds of recovery on an instrumented treadmill sprint for measuring the horizontal force, coupled with the simultaneous recording of the EMG activity of the vastus lateralis, rectus biceps femoris and gluteus muscles. Before and after the 12 sprints, the maximum isokinetic strength of the flexors and extensors of the hip and knee was measured on isokinetic dynamometer type CONTREX with 3 maximum repetitions at 120°/s in concentric and eccentric. A comparison before and after analysis and correlation between the parameters was carried out. Results At the maximum sprint, the multiple linear regression analysis showed a significant relationship (P = 0.02) between the horizontal force and the combination of EMG activity of the biceps femoris in late swing phase of the stride and the eccentric isokinetic strength of the knee flexors. After the 12 sprints, there was a significant decrease (P < 0.05) in the sprint performance, horizontal force, isokinetic strength and muscle activity. And there was a significant correlation between the horizontal force and eccentric strength of the knee extensors, and concentric strength of hip extensors. Discussion/Conclusion For a high-performance acceleration, it would seem necessary to be able both to strongly activate the hamstrings just before ground contact and have a great capacity eccentric strength of the hamstrings. In fatigue conditions, horizontal force reduction would seem not only related to the strength of decreased hamstring, but with d knee extensors eccentric strength decrease.
AIM: Ballistic performances, notably jumping, are key factors in many sport activities. They are mostly determined by the maximal power (Pmax) that lower limbs can generate but also by the individual Force-velocity (F-v) mechanical profile characterizing the ratio between maximal force and maximal unloaded extension velocity capabilities. An individually optimal F-v profile has been shown to characterize the best balance between force and velocity capabilities(Samozino et al 2012, 2013). A F-v imbalance (FVimb) being associated to lower performances. The F-v profile could be sensitive to specific and optimized training in order to improve ballistic performances. So training has to aim at increasing Pmax and/or optimizing the F-v profile. Thus, the aim of this study was to determine the effects of an individual specific force-velocity profiling based-training. METHODS: Sixty-three subjects were assigned to three groups according to FVimb classification: a velocity and a force imbalance deficit groups and a control group(no consideration of FVimb). Mean push-off force, velocity and power were calculated from jump height (Samozino ́s method, 2008). From this data, actual and optimal F-v profiles were computed for each subject to quantify FVimb and organize groups accordingly. Participants underwent a 9-week specific resistance training program designed according to FVimb classification to reduce imbalances for the intervention groups versus a one-size-fits-all program with no FVimb consideration for the control group. RESULTS: A greater increase in jump performance(16.6% and 13.3% in force and velocity groups, respectively)was observed in the intervention group, with a decrease in FVimb (-38.3% and -83.2% in force and velocity groups, respectively) compared to controls. CONCLUSION: An optimized and individualized training program specifically addressing the force/velocity imbalance is more efficient in improving jumping performance than a traditional resistance training common to all subjects, regardless of their force/velocity imbalance and optimal force-velocity profile. Thus, FVimb could be considered as a potentially useful variable for prescribing optimal resistance training to improve ballistic (e.g. jumping) performance. References: Samozino Pet al (2008) J Biomech41(14): 2940-5 SamozinoPet al(2013) IJSM35(6): 505-10 Samozino P et al (2012)MSSE44(2): 313-22
The purpose of this study was to evaluate the effects of a warm-up and fatigue protocol on the vertical jump and knee joint position sense of sprinters. Thirty-two sprinters were randomly allocated to either a control group (CONT) or a plyometric group (PLYO) that performed a warm-up, followed by a high-intensity plyometric protocol. Absolute (AAE), relative (RAE), and variable (VAE) angular errors and vertical jump were evaluated before and after the warm-up, as well as after the plyometric protocol and again 5 min later. After the warm-up, athletes improved RAE and jump performance. After the plyometric protocol, scores on the RAE, VAE, and the vertical jump performance worsened compared to the control group and to the values obtained after the warm-up. Five minutes later, RAE and vertical jump continued to be impaired. AAE did not show significant differences. The vertical jump is improved after the warm-up, although it is deteriorated after high-intensity plyometry. Regarding knee proprioception, the lack of impairments in the AAE make unclear the effects of the plyometric exercises on knee proprioception.
- Jun 2016
This study aimed to analyze perceptual, metabolic and mechanical responses to sprint training sessions. 9 male high-level sprinters performed 40 m running sprints up to a loss of 3% in speed, with 4 min rests between sets. Perceptual (rating of perceived exertion, RPE), mechanical (speed and countermovement jump height loss) and metabolic (blood lactate and ammonia) parameters were measured pre-exercise and after each sprint was performed. Relationships between the variables were calculated with a 90% confidence interval. Jump height loss showed almost perfect relationships with both blood lactate (r=0.96 (0.95 to 0.97)) and ammonia (r=0.95 (0.94 to 0.95)), whereas speed loss, number of sprints performed and RPE values showed large-very large relationships with blood lactate and ammonia. Furthermore, an almost perfect curvilinear relationship was observed between lactate and ammonia concentrations (R2=0.96 (0.95 to 0.97)). These results suggest that countermovement jump (CMJ) height can be used to quantify the fatigue induced during a typical sprint training session, and may prove a useful tool to facilitate individualized load monitoring. The results indicate that the CMJ is a better monitor of metabolic fatigue than traditional measures. © Georg Thieme Verlag KG Stuttgart · New York.
Purpose: 1) to analyze the reliability and validity of a simple computation method to evaluate force (F), velocity (v) and power (P) output during a countermovement jump (CMJ) suitable for use in field conditions; and 2) to verify the validity of this computation method to compute the CMJ Force-velocity (F-v) profile (including unloaded and loaded jumps) in trained athletes. Methods: Sixteen high-level male sprinters and jumpers performed maximal CMJs under six different load conditions (from 0 to 87 kg). A force-plate sampling at 1000 Hz was used to record vertical ground reaction force and derive vertical displacement data during CMJ trials. For each condition, mean F, v, and P of the push-off phase were determined from both force plate data (reference method) and simple computation measures based on body mass, jump height (from flight time), and push-off distance, and used to establish linear F-v relationship for each individual. Results: Mean absolute bias values were 0.9% (±1.6), 4.7% (±6.2), 3.7% (±4.8), and 5% (±6.8) for F, v, P and slope of the F-v relationship (SFv), respectively. Both methods showed high correlations for F-v profile related variables (r = 0.985 - 0.991). Finally, all variables computed from the simple method showed high reliability with ICC > 0.980 and CV < 1.0%. Conclusions: These results suggest that the simple method presented here is valid and reliable for computing CMJ force, velocity, power, and force-velocity profiles in athletes and could be used in practice under field conditions when body mass, push-off distance, and jump height are known.
- Mar 2016
The aim of this study is to evaluate the physical and physiological load imposed on amateur football players in a simulated game situation on different artificial turf systems. For that purpose, 20 football players (21.65±3.10 years old) were monitored with Global Positioning Systems and heart rate bands during 45 minute games on four selected artificial turf systems. The results show more covered distance in highintensity ranges on the system with lower levels of damping and higher rates of rotational traction (p<0.05). Likewise, this system of artificial turf demonstrated a high number of sprints (12.65±5.67), as well as more elevated maximum speed peaks during the last part of the game (28.16±2.90 km/h) in contrast to the systems with better damping capacity (p<0.05). On the other hand, the physiological load was similar across the four artificial turf systems (p>0.05). Finally, the regression analysis demonstrated a significant influence of the mechanical properties of the surface on global distance (15.4%), number (12.6%) and maximum speed (16.6%) of the sprints. To conclude, the mechanical variability of the artificial turf systems resulted in differences in the activity profiles and the players' perceptions during simulated football games.
Context: Knee joint position sense (JPS) is a key parameter for optimum performance in many sports, but is frequently negatively affected by injuries and/or fatigue during training sessions. Although evaluation of JPS may provide key information to reduce the risk of injury, it often requires expensive and/or complex tools that make monitoring proprioceptive deterioration difficult. Objective: This study sought to analyze the validity and reliability of a digital inclinometer to measure knee JPS in a closed kinetic chain (CKC). Design: The validity and inter-tester and intra-tester reliability of a digital inclinometer for measuring knee JPS were assessed. Setting: Biomechanics laboratory. Participants: Ten athletes (5 males and 5 females; 26.2 ± 1.3 years, 71.7 ± 12.4 kg; 1.75 ± 0.09 m; 23.5 ± 3.9 kg/m2) participated in this study. Intervention: Knee JPS was measured in a CKC. Main outcome measures: Absolute Angular Error (AAE) of knee JPS in a CKC was the main outcome measure. Results: Intraclass correlation coefficient (ICC) and standard error of the mean (SEM) were calculated to determine the validity and reliability of the inclinometer. Data showed that the inclinometer had a high level of validity compared to an isokinetic dynamometer (ICC = 1.0, SEM = 1.39, p < 0.001), and there was very good intra- and inter-tester reliability for reading the inclinometer (ICC = 1.0, SEM = 0.85, p < 0.001). Compared with AutoCAD video analysis, inclinometer validity was very high (ICC = 0.980, SEM = 3.46, p < 0.001) for measuring AAE during the knee JPS task in a CKC. Also, the inter-tester reliability of the inclinometer for obtaining AAE was very high (ICC = 0.994, SEM = 1.67, p < 0.001). Conclusion: The inclinometer provides a valid and reliable method for assessing knee JPS in a CKC. Health and sports professionals could take advantage of this tool to monitor proprioceptive deterioration in athletes.
Introduction: One of the main problems faced by strength and conditioning coaches is the issue of how to objectively quantify and monitor the actual training load undertaken by athletes in order to maximize performance. It is well known that performance of explosive sports activities is largely determined by mechanical power. Objective: This study analysed the height at which maximal power output is generated and the corresponding load with which is achieved in a group of male-trained track and field athletes in the test of countermovement jump (CMJ) with extra loads (CMJEL). Methods: Fifty national level male athletes in sprinting and jumping performed a CMJ test with increasing loads up to a height of 16 cm. The relative load that maximized the mechanical power output (Pmax) was determined using a force platform and lineal encoder synchronization and estimating the power by peak power, average power and flight time in CMJ. Results: The load at which the power output no longer existed was at a height of 19.9 ± 2.35, referring to a 99.1 ± 1% of the maximum power output. The load that maximizes power output in all cases has been the load with which an athlete jump a height of approximately 20 cm. Conclusion: These results highlight the importance of considering the height achieved in CMJ with extra load instead of power because maximum power is always attained with the same height. We advise for the preferential use of the height achieved in CMJEL test, since it seems to be a valid indicative of an individual's actual neuromuscular potential providing a valid information for coaches and trainers when assessing the performance status of our athletes and to quantify and monitor training loads, measuring only the height of the jump in the exercise of CMJEL.
Recent literature supports the importance of horizontal ground reaction force (GRF) production for sprint acceleration performance. Modeling and clinical studies have shown that the hip extensors are very likely contributors to sprint acceleration performance. We experimentally tested the role of the hip extensors in horizontal GRF production during short, maximal, treadmill sprint accelerations. Torque capabilities of the knee and hip extensors and flexors were assessed using an isokinetic dynamometer in 14 males familiar with sprint running. Then, during 6-s sprints on an instrumented motorized treadmill, horizontal and vertical GRF were synchronized with electromyographic (EMG) activity of the vastus lateralis, rectus femoris, biceps femoris, and gluteus maximus averaged over the first half of support, entire support, entire swing and end-of-swing phases. No significant correlations were found between isokinetic or EMG variables and horizontal GRF. Multiple linear regression analysis showed a significant relationship (P = 0.024) between horizontal GRF and the combination of biceps femoris EMG activity during the end of the swing and the knee flexors eccentric peak torque. In conclusion, subjects who produced the greatest amount of horizontal force were both able to highly activate their hamstring muscles just before ground contact and present high eccentric hamstring peak torque capability.
The purpose of this study was to investigate the relationship between movement velocity and relative load in three lower limbs exercises commonly used to develop strength: leg press, full squat and half squat. The percentage of one repetition maximum (%1RM) has typically been used as the main parameter to control resistance training; however, more recent research has proposed movement velocity as an alternative. Fifteen participants performed a load progression with a range of loads until they reached their 1RM. Maximum instantaneous velocity (Vmax) and mean propulsive velocity (MPV) of the knee extension phase of each exercise were assessed. For all exercises, a strong relationship between Vmax and the %1RM was found: leg press (r(2)adj = 0.96; 95% CI for slope is [-0.0244, -0.0258], P < 0.0001), full squat (r(2)adj = 0.94; 95% CI for slope is [-0.0144, -0.0139], P < 0.0001) and half squat (r(2)adj = 0.97; 95% CI for slope is [-0.0135, -0.00143], P < 0.0001); for MPV, leg press (r(2)adj = 0.96; 95% CI for slope is [-0.0169, -0.0175], P < 0.0001, full squat (r(2)adj = 0.95; 95% CI for slope is [-0.0136, -0.0128], P < 0.0001) and half squat (r(2)adj = 0.96; 95% CI for slope is [-0.0116, 0.0124], P < 0.0001). The 1RM was attained with a MPV and Vmax of 0.21 ± 0.06 m s(-1) and 0.63 ± 0.15 m s(-1), 0.29 ± 0.05 m s(-1) and 0.89 ± 0.17 m s(-1), 0.33 ± 0.05 m s(-1) and 0.95 ± 0.13 m s(-1) for leg press, full squat and half squat, respectively. Results indicate that it is possible to determine an exercise-specific %1RM by measuring movement velocity for that exercise.
The aim of this study was to determine what variables determine the differences in performance on 2 tests of squat jump (SJ) performed under light load in highly trained athletes using maximal velocity (Vmax) or flight time (FT) as the discriminating factor of SJ performance. Thirty-two participants performed two maximal SJ-weighted jumps using a force platform synchronized with a linear transducer. Mean force (Fmean), mean and maximal power (Pmean, Pmax), peak force (PF), maximal rate of force development (RFDmax), and time required to attain PF (TPF) and RFDmax (TRFDmax) were analyzed. SJ was divided into two segments: 1) from the initiation of force application to PF1; and 2) from the moment following PF1 to Vmax. Traditional significant statistics revealed significant differences in the same variables between Best and Worst to use both FT and Vmax. However, to use an approach based on the magnitude of the effect, Best showed greater Pmax (83/17/0%), Pmean (85/15/0%), Fmean (71/29/0%), RFDmax1 (73/27/0%), and PF1 (53/47/0%), and lower TPF2 (0/61/39%) than Worst when Vmax was used to discriminate the SJ performance. However, to use FT to differentiate SJ performance, any difference was observed between Best and Worst. Although jump height assessed through FT is a valid measure, these results suggest that Vmax is a more sensitive variable than FT to detect differences in loaded SJ performance.
The development of muscular power is often a key focus of sports performance enhancement programs. The purpose of this meta-analysis was to examine the effect of load on peak power during the squat, jump squat, power clean, and hang power clean, thus integrating the findings of various studies to provide the strength and conditioning professional with more reliable evidence upon which to base their program design. A search of electronic databases [MEDLINE (SPORTDiscus), PubMed, Google Scholar, and Web of Science] was conducted to identify all publications up to 30 June 2014. Hedges' g (95 % confidence interval) was estimated using a weighted random-effect model. A total of 27 studies with 468 subjects and 5766 effect sizes met the inclusion criterion and were included in the statistical analyses. Load in each study was labeled as one of three intensity zones: Zone 1 represented an average intensity ranging from 0 to 30 % of one repetition maximum (1RM); Zone 2 between 30 and 70 % of 1RM; and Zone 3 ≥70 % of 1RM. These results showed different optimal loads for each exercise examined. Moderate loads (from >30 to <70 % of 1RM) appear to provide the optimal load for power production in the squat exercise. Lighter loads (≤30 % of 1RM) showed the highest peak power production in the jump squat. Heavier loads (≥70 % of 1RM) resulted in greater peak power production in the power clean and hang power clean. Our meta-analysis of results from the published literature provides evidence for exercise-specific optimal loads for power production.
The purpose of this study was to analyze the immediate effects of a plyometric training protocol on unipedal postural balance and countermovement jumps. Additionally, we analyzed the effects of a warm-up on these parameters. Thirty-two amateur male sprinters (24.9 +/- 4.1 years old, 72.3 +/- 10.7 kg, 1.78 +/- 0.05 m, 22.6 +/- 3.3 kg/m2) were randomly sorted into a control group (n = 16) (they did not perform any physical activity) and a plyometric training group (n = 16) (they performed a 15 minute warm-up and a high-intensity plyometric protocol consisting of 10 sets of 15 vertical jumps). Before and after the warm-up, and immediately after and five minutes after the plyometric protocol, all athletes indicated the perceived exertion on calf and quad regions on a scale from 0 (no exertion) to 10 (maximum exertion). They also carried out a maximum countermovement jump and a unipedal postural balance test (athletes would remain as still as possible for 15 seconds in a left leg and right leg support stance). Results showed that, in the plyometric group, length and velocity of center-of-pressure movement in right leg support stance increased compared to baseline (p = .001 and p = .004, respectively) and to the control group (p = .035 and p = .029, respectively) immediately after the plyometric protocol. In addition, the countermovement jump height decreased right after the plyometric protocol (p < .001). The perceived exertion on calf and quad regions increased after the plyometry (p < .001). Five minutes later, these parameters remained deteriorated despite a slight recovery (length: p = .044; velocity: p = .05; countermovement jump height: p < .001; local exertion: p < .001). Data also showed that countermovement jump height improved following the warm-up (p = .021), but unipedal postural balance remained unaltered. As a conclusion, high-intensity plyometric exercises blunt unipedal postural balance and countermovement jump performance. The deterioration lasts at least five minutes, which may influence future exercises in the training session. Coaches should plan the training routine according to the immediate effects of plyometry on postural balance and vertical jumps, which play a role in injury prevention and sports performance.
The aim of this study is to examine the relationship between the relative load in full-squats and the height achieved in jump squat exercises, and to discover the load which maximizes the power output of high-level athletes. Fifty-one male high-level track and field athletes (age = 25.2 ± 4.4 years, weight = 77. ± 6.2 kg, height = 179.9 ± 5.6 cm) who competed in sprinting and jumping events, took part in the study. Full-squat one repetition maximum (1-RM) and jump squat height with loads from 17 to 97 kg were measured in two sessions separated by 48 h. Individual regression analyses showed that jump squat height (JH) (R2 = 0.992 ± 0.005) and the jump decrease (JD) that each load produced with respect to the unloaded countermovement jump (CMJ) (R2 = 0.992 ± 0.007) are highly correlated with the full-squat %1-RM, which means training intensities can be prescribed using JH and JD values. We also found that the load that maximizes jump squat's power output was 0%RM (i.e., unloaded CMJ). These results highlight the close relationship between jump squat performance and relative training intensity in terms of %1-RM. We also observed that the load that maximizes power output was 0%1-RM. Monitoring jump height during jump squat training could help coaches and athletes to determine and optimize their training loads.
PURPOSE: The aim of this study is to examine the relationship between the relative load in full-squats and the height achieved in jump squat exercises, and to discover the load which maximizes the power output of high-level athletes. METHOD: Fifty-one male high-level track and field athletes (age = 25.2 ± 4.4 years, weight = 77. ± 6.2 kg, height = 179.9 ± 5.6 cm) who competed in sprinting and jumping events, took part in the study. Full-squat one repetition maximum (1-RM) and jump squat height with loads from 17 to 97 kg were measured in two sessions separated by 48 h. RESULTS: Individual regression analyses showed that jump squat height (JH) (R2 = 0.992 ± 0.005) and the jump decrease (JD) that each load produced with respect to the unloaded countermovement jump (CMJ) (R2 = 0.992 ± 0.007) are highly correlated with the full-squat %1-RM, which means training intensities can be prescribed using JH and JD values. We also found that the load that maximizes jump squat's power output was 0%RM (i.e., unloaded CMJ). CONCLUSIONS: These results highlight the close relationship between jump squat performance and relative training intensity in terms of %1-RM. We also observed that the load that maximizes power output was 0%1-RM. Monitoring jump height during jump squat training could help coaches and athletes to determine and optimize their training loads.
- Dec 2014
This study analysed the acute metabolic and mechanical responses to a specific Repeated Sprint Ability (RSA) test. Eighteen male professional soccer players from a team of the First Division of Spanish National League participated. A 12x30m RSA test with 30 s recovery together with countermovement jump test (CMJ) pre a post RSA test was performed. Mechanical responses (i.e. height performance in CMJ and speed loss) and metabolic responses (i.e. blood lactate, and ammonia concentrations) were measured pre-exercise and post-exercise. A related samples t-test was used to analyse CMJ height pre-post changes as well as to compare pre- and post-exercise lactate and ammonia levels. CMJ height loss pre-post session (8%) was significant, and fatigue, measured as CMJ height loss, was strongly correlated to lactate (r = 0.97; p<0.001) and ammonia (r = 0.92; p<0.001) for all players. The relationships between the variables studied were determined by calculating the Pearson correlation coefficients. The metabolic stress developed during the effort can be estimated by controlling CMJ because of the high correlation between CMJ and blood lactate and ammonia concentrations. The high correlations found between mechanical (speed and CMJ height losses) and metabolic (lactate and ammonia) measures of fatigue highlight the utility and validity of using CMJ to monitor training load and quantify objectively neuromuscular fatigue during RSA.
Demographic data indicate that the populations of most nations are growing older. A deterioration of skeletal muscle function is the main consequence of ageing. Muscular strength and power gradually decrease with age and this decline accelerates after the age of 60–65 yrs (Häkkinen et al., 1995, EJAP, 70, 518–527). Resistance training improves muscle force production and contributes for maintaining functional autonomy in elderly. The aim of our study was to analyse the effects of an 8-week resistance training program on muscle force production and functional autonomy in older individuals. Forty-seven elderly (69 ± 4y) volunteered for the study and were randomly assigned into two groups: Experimental Group (EG: n = 27, 10 males and 17 females) and Control Group (CG: n = 20, 9 males and 11 females). Before and after the training intervention all participants performed tests of functional autonomy in accordance to GDLAM protocol and 1RM estimation. EG performed a personalised and individualised training (three times weekly; 60–80% 1RM, 3 sets of 6 to 15 reps) in a circuit. A related samples t-test was used to analyse functional autonomy and 1RM performance pre-post 8-wk training intervention and independent t-tests and 1-way with repeated measures ANOVA to compare differences between EG and CG groups. There was no difference before intervention between groups. After completing the 8-wk intervention, autonomy GDLAM index and 1RM performances improved significantly for EG (as males as females participants) group, respectively (p < 0.05; p < 0.001) compared to CG (did not improve at all) showing a higher improvement in females (60%; p < 0.001) compared to males (50%; p < 0.01). This study highlights the benefit of a specific training program for preventive and rehabilitative strategies in elderly by improving functional autonomy and muscle strength.
Ability to sprint is a key parameter (Faude et al., J Sports Sci, 2012, 30:625–31) and is the most frequent action in goal situations. Previously, other authors have established linear relationship between countermovement jump, leg power and percentage body fat, and team success (Arnason et al. MSSE, 2014, 36(2), 278–85). The body composition, as seen through a large content of muscle and low content of fat tissue, could be a particularly strong predictor of rapid movement performance, as jumping performance or sprint (Copic et al., JSCR, 2014). Thus, our principal aim is to explore potential relationships between anthropometric measures and athletic performance, focusing on strength related variables. Twelve young soccer player (age 22 ± 2 y, body mass 69.5 ± 7.1 kg, height 179 ± 8 cm; body fat 7.6 ± 2.2%) performed a CMJ, CMJ-BW loaded, 40 m sprint (analysing partial times at 15 and 30 m) and one Repetition Maximum (RM) in back squat test. Main interesting findings from this study were the strong associations between anthropometric measures and relevant strength variables related to physical condition performance in soccer. CMJ and CMJ-BW Loaded was strongly correlated with 1 RM, 40 m sprint performance and shuttle sprint at 15 and 30 m (r from 0.64 to 0.89; p < 0.05 to <0.001). Likewise BF was surprisingly highly correlated to CMJ, 1RM and different sprint times (r from 0.54 to 0.86; p < 0.05 to <0.001). In accordance to (Comfort et al., JSCR, 2013, 28(1), 173–7; Brocherie et al. (2014) J Sports Sci 17: 1–12), the results of this study illustrates the importance of developing high levels of strength in order to enhance sprint and jump performance in youth soccer players. Besides, Nikolaidis (CEJM, 2012, 7(6), 783–9) evidenced that a threshold exists in BF, above which muscular power output is affected to a great extent. Therefore, BF was negatively associated with physical fitness parameters.
INTRODUCTION Soccer is a complex sport requiring the repetition of many different activities such as jogging, sprinting and jumping (1). It is essential to know how manage variables such as intensity, rest time or number of players in order to organize the well known “Small Sided Games” (SSG). Besides, the ability to sprint is a key parameter (2) and is the most frequent action in goal situations. In the review, we haven´t found any research which relates specific SSG with simple mechanical parameters associated to fatigue neither the influence of repetition of this SSG sequences. Thus, the purpose of this study were: Firstly, to know the fatigue level produced by a SSG and investigate relationships between mechanical parameters related to jump and maximal sprint running before and after this specific situations. METHODS Sixteen trained soccer players performed a maximal sprint of 30-m before the specific SSG. Instantaneous running velocity (v in m•s-1) over time and distance was recorded with a radar Stalker ATS SystemTM. As well, a countermovement jump (CMJ) and a standing long jump (SLJ) were performed before the SSG. The SSG was composed by 4 repetitions of: a straight sprint over 20-m (without ball), a change of direction and 20-m of 2-on-1 situation finishing with a shot. Immediately after the SSG, players performed a 30-m maximal sprint, CMJ and SLJ in order to check the decrease in performance. RESULTS CMJ height and SLJ performance loss pre-post SSG were highly significant and were strongly correlated (r = 0.87; p<0.001). The speed losses produced by the specific SSG presented a high relation with CMJ and SLJ exercises (r = 0.78 – 0.89; p<0.001). Besides, top speed and the moment which is achieved in the maximal sprint running significantly decreased (p<0.001). DISCUSSION High correlations found between mechanical responses (speed, CMJ height and SLJ performance losses) and the marked alterations observed in this study during a specific SSG, could be useful as indicators of fatigue. This could highlight the utility and validity of using CMJ and SLJ to monitor training load in different specific workouts, as has been proposed by Jiménez-Reyes et al (3). This data provides trainers a simple tool to monitor players fatigue and individual load which would then be used to design optimal training routines to improve players’ training session.
Introduction: Sprints, jumps and kicking are considered relevant factors for successful performance and widely related to strength. Traditionally, the training protocols used for increasing strength training consisted in a set of exercises in which athletes lifted heavy weights (nearly 1RM) with difficulties for considering the real effort of athletes. However, several authors have stressed the importance of movement velocity in the prescription and control of resistance training, establishing for some exercises that by measuring movement velocity it is possible to determine the %1RM and real effort. Considering the aforementioned above strength programming training, the main purpose of this study was to investigate the effects of using a traditional strength training (TST) with a fixed intensity and a velocity-based strength training (VST) monitoring real intensity in professional Spanish soccer players. Methods: Eighty professional soccer players (4 teams) took part in the study (24.4 6 5.21 year, body mass 73 6 4.6 kg, height 177.4 6 5.4 cm, body fat 9.3 6 2.3%), who play in the Spanish first and second division leagues were distributed in a TST and VST groups, doing a personalized and individualized training (twice weekly; 6RM, and 1 m$s21 movement velocity and 20 cm in CMJ for TST and VST, respectively). Four teams were evaluated at the beginning of the competitive period, and at the end of the first half of the regular season. The following were evaluated: the strength of the lower extremities by CMJ, CMJ loaded until the jump height was around 20 cm (CMJ20cm) and full squat until the execution speed was 1$m$s21 (Sq1ms) and the sprint time 20 meters. Results: CMJ and Sq1ms performances improved significantly for TST and VST groups, respectively (p # 0.05; p , 0.001) showing a surprisingly higher improvement in the VST (12%; p , 0.001; effect size (ES) of 1.24 in CMJ; 14%; p , 0.001; ES of 1.37 in Sq1ms) compared to the TST (4%; p # 0.05; ES of 0.49 in CMJ; 7%; p # 0.05; ES of 0.73 in Sq1ms). For CMJ20cm and 20-m sprint only the VST improved significantly (15%; p , 0.001; ES of 1.98 in CMJ20cm; 5%; p # 0.05; ES of 0.61 in 20-m sprint). Discussion: These findings indicate that VST produces better physical performance effects than TST and a specific improvement in power output related patterns, suggesting that this methodology is more adequate for strength improvement for in-season training in professional soccer.
The aim of this research was to evaluate the influence of the mechanical properties of artificial turf systems on soccer players’ performance. A battery of perceptive physiological and physical tests were developed on four different structural systems of artificial turf (System 1: Compacted gravel sub-base without elastic layer; System 2: Compacted gravel sub-base with elastic layer; System 3: Asphalt sub-base without elastic layer; System 4: Asphalt sub-base with elastic layer). The sample was composed of 18 soccer players (22.44±1.72 years) who typically train and compete on artificial turf. The artificial turf system with less rotational traction (S3) showed higher total time in the Repeated Sprint Ability test in comparison to the systems with intermediate values (49.46±1.75 s vs 47.55±1.82 s (S1) and 47.85±1.59 s (S2); p<0.001). The performance in jumping tests (countermovement jump and squat jump) and ball kicking to goal decreased after the RSA test in all surfaces assessed (p<0.05), since the artificial turf system did not affect performance deterioration (p>0.05). The physiological load was similar in all four artificial turf systems. However, players felt more comfortable on the harder and more rigid system (S4; visual analogue scale = 70.83±14.28) than on the softer artificial turf system (S2; visual analogue scale = 54.24±19.63). The lineal regression analysis revealed a significant influence of the mechanical properties of the surface of 16.5%, 15.8% and 7.1% on the mean time of the sprint, the best sprint time and the maximum mean speed in the RSA test respectively. Results suggest a mechanical heterogeneity between the systems of artificial turf which generate differences in the physical performance and in the soccer players’ perceptions.
- Oct 2014
Different warm-up protocols (WUP) have been most commonly researched and it has been clearly demonstrated that some of these WUP elicit PAP however limited data are available about the best pre-conditioning activity (type of exercise, duration, volume, intensity). Therefore, our aim was to analyse 4 different WUP in order to examine the subsequent performance in countermovement jump (CMJ) and sprint performance at the same time, together with lactate along with performance in CMJ and sprint, what would be important and interesting information of the PAP-fatigue relationship for each one of protocols. Twelve high level sprinters (age 22 ± 2 y, body mass 70.2 ± 3.6 kg, height 181 ± 5 cm; body fat 7.4 ± 3.1%) took part in this study. Four different pre-conditioning activities (PCA) were designed, and after that, athletes randomly assigned to each one during 4-wk. PCA were squat (SQ) with 80% 1RM, (CMJ) with loads of 100% of body weight (BW), traditional WUP with three progressive sprint races and a specific sprint-based WUP composed by progressive sprint races. PAP effect was verified on CMJ and sprint performance in 0, 4, and 6 min after each WUP and group. CMJ height increased significantly at 0 and 4 min after all PCA protocols, showing a higher improvement in the specific sprint-based WUP (4.3%; p < 0.001; ES 0.93). Also a reduction in sprint time performance at 0 and 4 min was checked, with 2.6% (p < 0.01) with sprint-based WUP too. An interesting finding was that lactate values between 5.25 mmol·L-1 and 7.74 mmol·L-1 elicited PAP on sprint and CMJ performances for different WUP. Using a specific potentiation protocol that could enhance sprint performance would provide vital information, because running speed is critical in many athletic events. The knowledge of acute effects of PAP can be used to improve performance by including resistance exercises, jumps with extra load or sprint in an athlete’s warm-up (Mitchell and Sale, 2011, EJAP, 111: 1957–63).
A simple method for evaluating force (F), velocity (V) and power (P) output during a squat jump (SJ) was validated by Samozino et al. (2008, J Biomech, 41: 2940–5), who also showed the existence of an optimal force-velocity profile during SJ (2012, MSSE, 44(2):313–22). Counter Movement Jump (CMJ) is a very common test in sports training and testing (Markström and Olsson 2013, JSCR, 27:944–53). The aims of this study was to test the validity of this simple calculation method to evaluate muscle mechanical characteristics of lower limb extension (F, V and P) during a CMJ from three simple parameters: body mass, CMJ height and height of push off (Hpo). Sixteen high-level sprinters performed maximal CMJ against five additional loads (from 17 to 87 kg). Vertical ground reaction force was recorded and synchronised with vertical displacement (1000 Hz). For each condition and from both force plate measurements and the proposed simple computation method (Samozino et al. 2008), mean F, V, and P were determined over the entire push-off phase, and used to determine individual linear F-V relationships and associated maximal force (F0), velocity (V0) and power (Pmax) values. The absolute bias was calculated for each parameter: Bias = (Simple Method-Reference Method)/Reference Method ·100. Mean absolute bias were 1.47% (±0.01), 4.73% (±0.04), 3.19% (±0.03), and 5.84% (±0.04) for F0, V0 and Pmax, respectively. Correlations between the two methods were significant for all parameters (r from 0.97 to 0.99, p < 0.001). These results, and Bland and Altman analyses, support the validity of this simple method in CMJ. Consequently, the proposed method, based on three simple parameters only (body mass, jump height and Hpo), allows to accurately evaluate lower limbs force, velocity and power properties during loaded CMJ in field conditions. Coaches could use this method to quantify individual athlete Pmax and FV profile, and individualise their training regimens accordingly
An observation that is apparent during traditional strength or power training is the speed and power loss as fatigue increases (Lawton et al. 2006). Training with this structure can be very stressful and it would be very important to monitor the speed loss during sets repetition (Sánchez-Medina 2011). A solution to this issue would be the inter-repetition rest manipulation (Hardee et al. 2012). Thus, an alternative model to performing a designated number of fatiguing continuous repetitions is to introduce an inter-repetition rest, that is, a rest interval after every repetition or after a certain number of repetitions (Lawton et al. 2006). Therefore, the aims of this study were (i) to analyse the mechanical response examining power and speed associated with continuous-repetition (CR) and inter-repetition rest (IRR), and (ii) to examine lactate concentration comparing CR and different IRR protocols. Eleven sport science students and well-trained in strength participated in this study. Subjects performed 2 CR protocols and 4 IRR protocols with the same volume (30 repetitions) in squat. The movement velocity and power output for each repetition was recorded using a linear encoder sampling each 1ms (1000 Hz). CR consisted in 3 sets of 10 repetitions and 6 sets of 5 repetitions compared to 5 IRR protocols of 3 sets of 10 repetitions 10 sec (IRR10), 15 sec (IRR15), 30 sec (IRR30) and other of 30 repetitions with 15 sec (IRR30x15). Each protocol (IRR10, IRR15, IRR30, IRR30x15) was performed on different days each separated by at least 72 hours. A timer was used to follow all IRR protocols Significantly (p < 0.001) greater repetition power outputs (25–49%) were observed in the later repetitions (4–6) of the IRR10, IRR15, IRR30, IRR30x15 in comparison to CR. Mean propulsive velocity significantly decreased by 39% and 23% in CR of 10 and 5 repetitions, respectively in comparison to decreases between 16% to 9% in IRR protocols. CR resulted in increased blood lactate concentrations significantly (p<0.01). These findings demonstrate IRR periods allow for maintenance of power and this may have implications for improved training adaptations, and thus, using IRR could enable greater power output in comparison to CR. Coaches should quantify and consider IRR to determine and individualize training loads and exercises to optimize the power output while not fatiguing so much athletes, and in turn performance.
González-Hernández, J.M.1 , Andrés-López, R.1, García-Peñuela, A.J.1, Jiménez-Reyes, P.2 1University Alfonso X, UAX, Madrid, Spain 2Catholic University San Antonio - UCAM, Murcia, Spain An observation that is apparent during traditional strength or power training is the speed and power loss as fatigue increases (Lawton et al. 2006). Training with this structure can be very stressful and it would be very important to monitor the speed loss during sets repetition (Sánchez-Medina 2011). A solution to this issue would be the inter-repetition rest manipulation (Hardee et al. 2012). Thus, an alternative model to performing a designated number of fatiguing continuous repetitions is to introduce an inter-repetition rest, that is, a rest interval after every repetition or after a certain number of repetitions (Lawton et al. 2006). Therefore, the aims of this study were (i) to analyse the mechanical response examining power and speed associated with continuous-repetition (CR) and inter-repetition rest (IRR), and (ii) to examine lactate concentration comparing CR and different IRR protocols. Eleven sport science students and well-trained in strength participated in this study. Subjects performed 2 CR protocols and 4 IRR protocols with the same volume (30 repetitions) in squat. The movement velocity and power output for each repetition was recorded using a linear encoder sampling each 1ms (1000 Hz). CR consisted in 3 sets of 10 repetitions and 6 sets of 5 repetitions compared to 5 IRR protocols of 3 sets of 10 repetitions 10 sec (IRR10), 15 sec (IRR15), 30 sec (IRR30) and other of 30 repetitions with 15 sec (IRR30x15). Each protocol (IRR10, IRR15, IRR30, IRR30x15) was performed on different days each separated by at least 72 hours. A timer was used to follow all IRR protocols Significantly (p < 0.001) greater repetition power outputs (25–49%) were observed in the later repetitions (4–6) of the IRR10, IRR15, IRR30, IRR30x15 in comparison to CR. Mean propulsive velocity significantly decreased by 39% and 23% in CR of 10 and 5 repetitions, respectively in comparison to decreases between 16% to 9% in IRR protocols. CR resulted in increased blood lactate concentrations significantly (p<0.01). These findings demonstrate IRR periods allow for maintenance of power and this may have implications for improved training adaptations, and thus, using IRR could enable greater power output in comparison to CR. Coaches should quantify and consider IRR to determine and individualize training loads and exercises to optimize the power output while not fatiguing so much athletes, and in turn performance
Purpose To study the effect of a countermovement on the lower limb force–velocity (F–v) mechanical profile and to experimentally test the influence of F–v mechanical profile on countermovement jump (CMJ) performance, independently from the effect of maximal power output (P max). Methods Fifty-four high-level sprinters and jumpers performed vertical maximal CMJ and squat jump (SJ) against five to eight additional loads ranging from 17 to 87 kg. Vertical ground reaction force data were recorded (1,000 Hz) and used to compute center of mass vertical displacement. For each condition, mean force, velocity, and power output were determined over the entire push-off phase of the best trial, and used to determine individual linear F–v RELATIONSHIPS and P max. From a previously validated biomechanical model, the optimal F–v profile maximizing jumping performance was determined for each subject and used to compute the individual mechanical F–v imbalance (Fv IMB) as the difference between actual and optimal F–v profiles. Results A multiple regression analysis clearly showed (r 2 = 0.952, P < 0.001, SEE 0.011 m) that P max, Fv IMB and lower limb extension range (h PO) explained a significant part of the interindividual differences in CMJ performance (P < 0.001) with positive regression coefficients for P max and h PO and a negative one for Fv IMB. Conclusion Compared to SJ, F–v relationships were shifted to the right in CMJ, with higher P max, maximal theoretical force and velocity (+35.8, 20.6 and 13.3 %, respectively). As in SJ, CMJ performance depends on Fv IMB, independently from the effect of P max, with the existence of an individual optimal F–v profile (Fv IMB having an even larger influence in CMJ).
The aim of this study was to investigate the relationships between repeated explosive effort sequences (20 + 20 m shuttle sprint with change of direction, kicking and jumping), metabolic response (lactate and ammonia), and fitness qualities (strength and endurance) in under-19 soccer players. 21 players completed: 1) sprint test: 30 m (T30) and 40 m (20 + 20 m) shuttle sprints; 2) countermovement jumps (CMJ); 3) maximal kicking; and 4) 9 repeated-explosive effort sequences (RES); 4) a progressive isoinertial loading test in full squat to determine the load which subjects achieved ~1 m • s − 1 (V1- load); 6) Yo-Yo Intermittent Recovery Test Level 1 (YYIRT-1). Mean sprint time of the 9 repeated sprints (RSAmean1–9) showed correlation with V1- load (r = − 0.52 [− 0.79, − 0.25]) metabolic response (lactate, r = 0.67 [0.47, 0.87] and ammonia, r = 0.53 [0.27, 0.79]). YYIRT-1 correlated with RSAmean1-9 (rw = − 0.78 [− 0.92, − 0.64]) when the body weight was controlled. Furthermore, the 3 first sprints (RSAmean1-3) correlated with RSAbest (r = 0.93 [0.88, 0.98]), V1-load (r = − 0.64 [ − 0.86, − 0.42]), and T30 (r = 0.63 [0.41, 0.85]). These results suggest that the soccer player’s lower body strength (V1-load, jumping and sprinting) explains a large part of the performance in the first sequences, whereas the aerobic capacity, estimated through YYIRT-1, becomes more important to performance as the number of sprints is increases
- Jun 2014
Relatively few studies have explored the effects of body composition on jumping performance. Recently, Copic et al. (2014, JSCR, in press) showed that percent of body fat and body muscle could be predictors of jumping performance in non-trained women. Since power capabilities depends on both force and velocity mechanical qualities, the effect of body composition on power or performance can be associated to effect on maximal force and/or velocity. The aim of this study was to experimentally test the influence of body composition on lower limb force–velocity (FV) mechanical properties. Squat jump (SJ) (Samozino et al., 2010, J Theor Biol, 264(1):11–18) and countermovement jump (CMJ) (Jiménez-Reyes et al, 2014, EJAP, in press) FV profiles were computed in healthy subjects and related to lean mass (LM) adjusted for whole mass (body weight) and percent of body fat (BF). 26 subjects (27 + 4 y) with different physical condition performed maximal SJ and CMJ against additional loads. From vertical ground reaction force and displacement data individual linear F-V relationships (SFv, slope of the F-V curve, in N.s.kg−1.m−1) were determined using the best trial for each condition and used to compute individual maximal power, force and velocity. Dual-energy X-ray absorptiometry (Norland XR-46) were performed by the same qualified researcher. BF is inversely related to SJ-maximal height (hmax) (r = 0.27, p = 0.191) and CMJ-hmax (r = 0.376, p = 0.064), which is in line with Slinde et al. (2008, JSCR, 22(2):640–4). LM is related to SJ-hmax (r = 0.276, p = 0.18), CMJ-hmax (r = 0.428, p = 0.033) which is expected according to Copic et al (2014, JSCR, in press). We found an interesting relationship between LM and SJ-SFv (R = 0.424, p = 0.035) but not in CMJ-SFv (R = 0.089, p = 0.672). It indicates that SJ-SFv could depend on LM meanwhile CMJ-SFv could be influenced by other biological features.
Question - Could anyone help me with any ideas, articles, and/or data sets on how to build up the 200m and/or 400m sprint in light of actual performance levels?
I think it could be very interesting to analyze changes in CMJ height pre-post and blood lactate and ammonia concentrations observed during real competition and very specific training sessions. The decrease in jump capacity pattern is mainly related to high levels of blood lactate and ammonia and with this information you have a very simple way in order to estimate metabolic stress developed during the effort in real competition and training sessions by measuring the CMJ because of the high correlation between CMJ and blood lactate and ammonia concentrations.
Rhythmic gymnastics (RG) has evolved considerably, characterized, at the present time by the continuous repetition of specific elements (jumps, twists, balance…) and is defined by its high intensity, constant repetition and the capacity of recovery (Douda et al. IJSPP 2008;3:41-54). There is a lack of experimental data on the determinant factors related to performance and the effect of general routines of training in gymnastics. The main aim of this study was to measure the relationship between mechanical, physiological and psychological measures and performance in a specific task in RG. Ten elite gymnasts and ten non-elite took part in this study. A specific test of RG with two minutes of duration was performed. Jumping test values (CMJ and SJ), blood lactate, heart rate and RPE were measured before and after (immediately after finishing, and in the intervals of time 0-1 and 1-3 min). The main result of this study was a highly significant correlation between CMJ and SJ height loss pre-post in a specific test in RG and blood lactate concentration, elite gymnastics (r=0.82-0.87; p<0.01) and non-elite (r=0.97-0.98; p<0.001). One another important finding was a difference in the recovery of jump capacity pattern between elite and non-elite gymnastics (p<0.001), which was higher in elite in the interval time 0-1 post test. The loss of CMJ and SJ height could be considered as an indicator of the level of effort and fatigue because of the high correlation between CMJ and blood lactate and ammonia concentrations (Gorostiaga, et al. JSCR 2010;24:1138-1149; Jiménez-Reyes, et al. MSSE 2012;44(5):582) as previously shown in other tasks of high intensity, and could be useful and applicable to a specific test in RG. This fact would support the utility and validity of using CMJ and SJ to monitor and quantify objectively the level of effort and fatigue during training in RG.
Intermittent exercise with short bouts (30-500 m) of high intensity exercise (90-100% of running intensity) separated by different recovery periods (3-15 minutes) are habitually used by sprinters during training sessions (Gorostiaga et al. JSCR 2010;24:1138-1149). Repetition of sprints may induce neuromuscular fatigue (NMF). The aim of the present study was to quantify the extent of NMF while performing sprint workouts (SW) by analysing the acute metabolic and mechanical response to different SW. Nine high level sprinters (age 23±4 y, body mass 73.7±4.6 kg, height 177.6±5.9 cm; body fat 9.6±2.9%) performed eight SW separated by a week. SW with different number of repetitions (R) for each subject in short distance travelled (DT) [(x)RxDT] and SW with same number of R in long DT [3xDT]. Mechanical responses (i.e. height performance in CMJ and speed loss) and metabolic responses (i.e. blood lactate and ammonia concentrations) were measured pre-exercise, during exercise each repetition performed and post-exercise. CMJ height loss pre-post session were significant for all sprint workouts and competitions analysed and highly correlated to metabolic responses (r=0.86-0.98). These losses were between 9% for 40 m and 26% for 500 m. The fatigue, measured as CMJ height loss, increases with DT, and is strongly correlated to lactate (r=0.93) and ammonia (r=0.98). The metabolic stress developed during the effort can be estimated by controlling CMJ because of the high correlation between CMJ and blood lactate and ammonia concentrations (Jiménez-Reyes et al. MSSE 2012;44(5):582). The high correlations found between mechanical (speed and CMJ height losses) and metabolic (lactate and ammonia) measures of fatigue highlight the utility and validity of using CMJ to monitor training load in different sprint workouts and quantify objectively NMF during SW and competitions.
The 400 m run is one of the most demanding athletic events. In 400 m, muscle acidosis decreases force production. A large number of both biochemical and biophysical changes occur at the same time that fatigue is developing (Nummela et al. JSS 1992;10:217-228). The aim of this study was to investigate relationships between changes in CMJ height pre-post and blood lactate and ammonia concentrations observed during real competition. Sixteen high level sprinters (age 23±4 y, body mass 72.6±3.7 kg, height 181.2±5.3 cm; body fat 7.4±2.7%) performed six competitions (including National Track and Field Championships). Mechanical responses (i.e. height performance in CMJ and speed loss) and metabolic responses (i.e. blood lactate and ammonia concentrations) were measured before and at 1, 3, 5, 7 and 9 minutes after exercise. The main result of this study was a highly significant correlation between CMJ height loss pre-post competition and metabolic responses (r=0.86-0.94). The decrease in jump capacity pattern was mainly related to higher blood lactate and ammonia responses. These losses were about 17% for 200 m and 27% for 400 m. Fatigue, measured as CMJ height loss, increased with performance level of athletes, and, was strongly correlated to lactate (r=0.87) and ammonia (r=0.91). Gorostiaga et al. JSCR 2010;24:1138-1149) which examined CMJ height loss following typical sprint-training workouts in 400 m elite runners (60-300 m), although were not performed at maximal intensity or real competition. Metabolic stress developed during the effort in real competition can be estimated by measuring the CMJ because of the high correlation between CMJ and blood lactate and ammonia concentrations (Jiménez-Reyes et al. MSSE 2012;44(5):582), without the necessity of measuring blood metabolites.
Question - If we use nonspecific training on 400m runners, what kind of transfer can we expect to the competitive performance?
I agree with Andrew and even if lactate concentrations, HR, and others indicator would be the same in the non-specific training, there are other variables to consider that are more important for optimizing performance in 400-m running sprint and one of them and one of the most important is the running pace!! and I think that this aspect must be trained in a specific way always!
Hope to help you
Recently, GPS tracking systems have been used to assess the physical demands in some sports. The validity of GPS devices for measuring distance traveled in team sport and endurance athletes have been investigated and there have been studies for assessing speed in active subjects, but none so far has used GPS of 15 Hz. PurPose: To analyze and compare two GPS system device to asses speed and acceleration in sprint races. metHoDs: Ten physically active male subjects (age: 19.3 ± 2.3 years, stature: 1.77 ± 0.07 m, body mass: 72.7 ± 9.6 kg) randomly chosen from a population of physically active students and sport team athletes were selected. The correlations between peak acceleration and peak speed obtained from a GPS 1 Hz and 15 Hz with sprint time (at 5, 10 and 30-m) measured with timing lights were determined. Forty-three individual sprints were recorded concurrently with timing lights (Microgate, Bolzano, Italy), a GPSports SPI Elite (1 Hz) and GPSports SPI PRO X (15 Hz) (GPSports System, Canberra, Australia). The light sensors were set at 0, 5, 10 and 15-m for the sprints of 15-m and at 0, 30, 40 and 50-m for the sprints of 50-m. From a standing start 40-cm behind the starting gates, the subjects performed a maximal effort sprint over 15m and 50-m. The subjects were instructed before the sprint to produce maximal efforts for the sprint. To determine the test-retest reliability of the GPS device, each subject completed at least two sprints of each distance on two separate. Pearson’s correlation coefficients and 90% confidence intervals (90%CI) were calculated according to the methods of Hopkins. resuLts: The correlation coefficients between measures of GPS 1 Hz and GPS 15 Hz in sprints of 15m and 50m were 0.02 in acceleration, and for peak speed were significant for 15m (0.68) and 0.50m (0.96). Correlations coefficients between times 5, 10 and 15m measured with timing lights and maximum acceleration and speed measured with GPS were highly significant (r=0.95-0.98). ConCLusions: The results of this study demonstrated a close correlation between peak speeds measured with GPS (1 and 15 Hz) and sprint time in 30, 40 and 50m. The use of GPS may be an alternative to timing lights for assessing sprint performance in 30m and longer distances, however the low sampling rate (1 and 15 Hz) reduce the sensitivity of these measures, especially over shorter distances.
The study of training load has always provoked controversy and it is still unresolved as to which is the optimal training load to achieve peak performance. Most studies simultaneously analyze training's acute effects and the relationships between the different variables, though in many cases there is no scientific evidence about the most suitable loads and their effects on performance. Our aim was to provide relevant and useful information to monitor and organize athletic training in a rational way, by obtaining more complete information about the effects of the training process. Twentyfour sprinters took part in the study. The subjects' physical condition was tracked weekly using the countermovement jump (CMJ) and by collecting other data about the weekly training load for 71 weeks. We highlight the progression of CMJ and training load dynamics in the four weeks before competition in which the best performance was obtained during the 71 weeks of the study. In conclusion, if training load and its relationship to physical and athletic performance is exhaustively monitored, it would allow for adequately adjusting training loads and it would also provide relevant, useful information for a rational training plan.
The study of training load has always provoked controversy and it is still unresolved as to which is the optimal training load to achieve peak performance. Most studies simultaneously analyze training's acute effects and the relationships between the different variables, though in many cases there is no scientific evidence about the most suitable loads and their effects on performance. Our aim was to provide relevant and useful information to monitor and organize athletic training in a rational way, by obtaining more complete information about the effects of the training process. Twentyfour sprinters took part in the study. The subjects' physical condition was tracked weekly using the countermovement jump (CMJ) and by collecting other data about the weekly training load for 71 weeks. We highlight the progression of CMJ and training load dynamics in the four weeks before competition in which the best performance was obtained during the 71 weeks of the study. In conclusion, if training load and its relationship to physical and athletic performance is exhaustively monitored, it would allow for adequately adjusting training loads and it would also provide relevant, useful information for a rational training plan.
Introduction In response to the need to adjust training loads of sprinters in speed sessions, caused by great variability in the number of series that coaches use and ignorance about how many series realize, when to stop training or what tool to use to control optimally speed session training, was carried out this study, in which we tried to approach the relationship between the degree of load and the fatigue, measured through speed losses and jump capacity and for the metabolic stress. Methods Eighteen high level sprinters (age 23.1 ± 4.4 yr, body mass 73.7 ± 4.6 kg, height 177.6 ± 5.9 cm; body fat 9.6 ± 2.9%) took part in the study. They realized sprints of 40, 60 and 80m made to the maximum speed possible up to lose 3% of the speed. It was carried out in three different sessions separated by a week. Before and after each run they made 3 "Countermovement jumps" (CMJ) and blood lactate and ammonia were measured each two repetitions performed.
Introduction The study of training load´s dose always has provoked controversies and there is not solved which is the optimal training load to achieve the highest performance (Cronin and Sleivert, 2005). Most studies analyse the training's immediate effects without a scientific evidence exists, in many cases, on the most suitable loads and their effects in performance. Our aim was to obtain a more complete and actual information on training processéffects, verifying the evolution in time of these variables and their relationship to athletic performance. Methods Twenty four high level sprinters (age 25.4 ± 4.5 yr, body mass 75.5 ± 7.3 kg, height 179.9 ± 5.6 cm; body fat 9.9 ± 2.3%) took part in the study. Over seventy-one training´s week, subjects' physical condition was weekly tracked using "Countermovement Jump" (CMJ) and by collecting other data of weekly training load athletes performed, strength and power measurements and the results in competition.
In response to the need to adjust training loads of sprinters in speed sessions, due to the large variability in the number of repetitions that coaches use and their ignorance of how many repetitions to execute, when to stop training, or what tools to use to optimally monitor speed session training, this study was carried out, in which we assess the relationship between the degree of load and fatigue, which was measured through speed loss and jump ability as well as metabolic stress. Eighteen national- and internationallevel sprinters participated. They completed 40m, 60m, and 80m sprints at maximum speed until they lost 3% of their speed. This was carried out in three different sessions with one week between each session. Before and after each sprint they executed three countermovement jumps (CMJ), and lactate was measured in the first and last repetitions. The losses produced in the successive sprints presented a strong relationship between the distances and the reduction in CMJ height. For the 40m run, this loss was equivalent to the speed loss, 3.1% for 40m, though it increased to 6.7% for 60m and to 8.3% for 80m. This relationship between reduction in CMJ height and distances run could be used as an indicator of the degree of fatigue produced by various types of efforts, and, therefore, it would be useful for monitoring and dosage of training load.
- Jul 2011
Power output is acknowledged as an indicator of physical condition for athletes. Vertical jump height is a good predictor of muscle strength (power output), and therefore several types of vertical jump tests have been used to evaluate athletic performance. The aimof this study was to analyse the relationship between jumping and acceleration abilities in sprinters. Thirty-six sprinters from the national and international level took part in this study, completing Squat Jumps (SJ), Counter movement jumps (CMJ), and CMJ with progressive loads (CMJLoad), as well as 20m and 30m sprints. In this study, we obtained significant relationships between the CMJ (r=-0.65, p
- Jun 2011
The aims of this study were to assess (a) the validity of total body load (TBL)-obtained from the global position system (GPS) devices-to quantify soccer training load, assessing its relationship with session rating of perceived exertion (session-RPE) and (b) to analyze the differences in terms of TBL and session-RPE among defenders, midfielders, and forwards. Twenty-two professional soccer players (Spanish first division, season 2007-2008; 26.74 ± 4.2 years; height 179.74 ± 4.04 cm; weight 73.7 ± 3.35 kg) participated in the study. During 13 training sessions composed predominantly of small-sided games, TBL and RPE multiplied by the minutes of session duration were determined using GPS and the 21-point scale, respectively. In each session, data from 10 players randomly selected and classified according to player position (defenders, midfielders, and forwards) were collected. Although session-RPE was a significant predictor of TBL (β = 0.23, p < 0.05), this method only accounted for 5% of the variance in TBL. No significant differences in terms of TBL and session-RPE were found regarding player position. The results of this study suggest that TBL is not a valid measure to quantify training load because it is not strongly correlated with session-RPE. Furthermore, TBL and session-RPE in small-sided soccer games do not vary according to player positions.
- Nov 2009
Electromechanical delay (EMD) and rate of force development (RFD) are determinants of explosive neuromuscular performance. We may expect a contrast in EMD and RFD between explosive power athletes, who have a demonstrable ability for explosive contractions, and untrained individuals. However, comparison and the neuromuscular mechanisms for any differences have not been studied. The neuromuscular performance of explosive power athletes (n = 9) and untrained controls (n = 10) was assessed during a series of twitch, tetanic, explosive, and maximum voluntary isometric knee extensions. Knee extension force and EMG of the superficial quadriceps were measured in three 50-ms time windows from their onset and were normalized to strength and maximal M-wave (Mmax), respectively. Involuntary and voluntary EMD were determined from twitch and explosive voluntary contractions, respectively, and were similar for both groups. The athletes were 28% stronger, and their absolute RFD in the first 50 ms was twofold that of controls. Athletes had greater normalized RFD (4.86 ± 1.46 vs 2.81 ± 1.20 MVC·s(-1)) and neural activation (mean quadriceps, 0.26 ± 0.07 vs 0.15 ± 0.06 Mmax) during the first 50 ms of explosive voluntary contractions. Surprisingly, the controls had a greater normalized RFD in the second 50 ms (6.68 ± 0.92 vs 7.93 ± 1.11 MVC·s-1) and a greater change in EMG preceding this period. However, there were no differences in the twitch response or normalized tetanic RFD between groups. The differences in voluntary normalized RFD between athletes and controls were explained by agonist muscle neural activation and not by the similar intrinsic contractile properties of the groups.
There is evidence of a relationship between muscular rate of force development (RFD) and neural activation (De Ruiter et al., 2004), and therefore it might be expected that explosive power athletes have a greater RFD than non-athletes due to enhanced neural activation, but this has not yet been investigated. The present study compared differences in RFD, neural activation, and electromechanical delay (EMD) between elite explosive power athletes (ATH; n = 9) and aged-matched controls (CON; n = 10). During 3 separate trials (each separated by 1 week) participants sat in a custom built isometric rig (hip and knee angle 90 and 80° respectively), and completed a series of involuntary and voluntary isometric contractions of the knee extensors of their dominant leg. Force was measured from a strain gauge, sampled at 2000 Hz, and electromyography (EMG) was recorded from the rectus femoris (RF), vastus lateralis (VL), and vastus medialis (VM). The maximum M-wave of each muscle was established by supramaximal stimulation of the femoral nerve with single pulse (100 µs) twitch contractions. Maximum voluntary force (MVF) and root mean squared (RMS) of the EMG signal at MVF (RMSmax) was established from four 3-s isometric maximal voluntary contractions (iMVC), each separated by 30 s. To assess RFD parameters participants performed 10 explosive iMVC (the instruction was to push as fast and hard as possible for 1-2 s), separated by 20 s. The three contractions with the highest peak RFD (RFDp) were analysed to establish average RFD from 0-40 ms (RFD40) and 0-100 ms (RFD100), and each of these variables was normalised to MVF. The RMS of the EMG signal was analysed in three consecutive 50-ms time windows (0-50, 50-100, and 100-150 ms), commencing from EMG signal onset, and was normalised to both maximum M-wave (RMS:M) and RMSmax (RMS: RMSmax). Maximum EMD (EMDmax) was classified as the longest EMD of the 3 knee extensor muscles. A mean of the second and third trials was used for analysis. The ATH had a greater MVF than CON (+28%; P<0.01). The ATH also had a greater RFD40, RFD100, and RFDp (+145%, +39%, and +48%, respectively; P<0.01), however, when these variables were normalised to MVF only RFD40 remained greater in ATH (3.4 ± 1.2 vs. 1.8 ± 0. 9 MVFs-1; P<0.01). During the 0-50 ms window the ATH had a greater RMS:M ratio in all muscles, and a greater RMS:RMSmax ratio in the RF and VL (P<0.05). There was also a trend for CON to record a longer EMDmax than the ATH (19.1 ± 4.3 and 15.9 ± 2.8 ms, respectively; P = 0.08). The results of this study suggest there may be a difference in EMD between ATH and CON. A greater normalised RFD40 in ATH was found and appeared to be due to a greater neural activation during the initial phase of the contraction. Conversely, any difference in absolute RFD during the later phases of the contraction appearded to be due to the greater strength of the ATH. References. De Ruiter et al (2004). J Appl Physiol 97: 1693-1701
Knowledge of acute effects of training load in sprint training sessions is essential for improving performance. The ultimate goal of training is to prepare athletes to perform at their best at important competitions. Therefore, it´s a need the training load´s individualization for sprint training. PURPOSE: To analyze the acute metabolic and mechanical response to different sprint workouts (SW). SW with different number of repetitions (R) for each subject in short distance traveled (DT) and SW with same number of R in long DT. METHODS: Eighteen high level sprinters (age 23.1 ± 4.4 yr, body mass 73.7 ± 4.6 kg, height 177.6 ± 5.9 cm; body fat 9.6 ± 2.9%) took part in this study. Six sessions separated by a week were performed. Three sessions for 40, 60 and 80m performed at highest posible speed up to lose 3% of speed with 4, 6 and 8 minutes rest between sets (same ratio work/recovery for different DT); thus, different R for the same DT [(x)RxDT]. Other three sessions performed over 150, 250 and 500m with the same R and DT for all subjects: 3xDT with 15 minutes rest between sets. Mechanical responses (i.e. height performance in countermovementjump (CMJ) and speed loss) and metabolic responses (i.e. blood lactate, uric acid and ammonia concentrations) were measured pre-exercise, during exercise each repetition performed and post-exercise. RESULTS: CMJ height loss pre-post session were significant for all sprint workouts analized and highly correlated to metabolic responses (r = 0.86-0.98). The speed losses produced in the successive sprints presented a high relation between the distances and reduction in CMJ height. These losses were between 9.1% for 40m and 26.3% for 500m. The fatigue, measured as CMJ height loss, increases with DT, and, is strongly correlated to lactate (r = 0.93), uric acid (r = 0.86) and ammonia (r = 0.98). CONCLUSIONS: The metabolic stress developed during the effort can be estimated by controlling CMJ because of the high correlation between CMJ and blood lactate, uric acid and ammonia concentrations. The high correlations found between mechanical (speed and CMJ height losses) and metabolic (lactate, uric acid and ammonia) measures of fatigue highlight the utility and validity of using CMJ to monitor training load in different sprint workouts and quantify objectively neuromuscular fatigue during sprint workouts.