Force-velocity Profile Research Articles

Sex influence on muscle synergies in a ballistic force-velocity test during the delayed recovery phase after a graded endurance run

The acute and delayed phases of the functional recovery pattern after running exercise have been studied mainly in men. However, it seems that women are less fatigable and/or recover faster than men, at least when tested in isometric condition. After a 20 km graded running race, the influence of sex on the delayed phase of recovery at 2–4 days was studied using a horizontal ballistic force-velocity test. Nine female and height male recreational runners performed maximal concentric push-offs at four load levels a week before the race (PRE), 2 and 4 days (D2 and D4) later. Ground reaction forces and surface electromyographic (EMG) activity from 8 major lower limb muscles were recorded. For each session, the mechanical force-velocity-power profile (i.e. theoretical maximal values of force (F¯ 0), velocity (V¯ 0), and power (P¯ max)) was computed. Mean EMG activity of each recorded muscle and muscle synergies (three for both men and women) were extracted. Independently of the testing sessions, men and women differed regarding the solicitation of the bi-articular thigh muscles (medial hamstring muscles and rectus femoris). At mid-push-off, female made use of more evenly distributed lower limb muscle activities than men. No fatigue effect was found for both sexes when looking at the mean ground reaction forces. However, the force-velocity profile varied by sex throughout the recovery: only men showed a decrease of both V¯ 0 (p < 0.05) and P¯ max (p < 0.01) at D2 compared to PRE. Vastus medialis activity was reduced for both men and women up to D4, but only male synergies were impacted at D2: the center of activity of the first and second synergies was reached later. This study suggests that women could recover earlier in a dynamic multi-joint task and that sex-specific organization of muscle synergies may have contributed to their different recovery times after such a race.

Power-Force-Velocity Profiling as a Function of Used Loads and Task Experience.

To evaluate cohort-specific reliability and concurrent validity of 3 different vertical power-force-velocity (P-F-v) profiles to determine force, velocity, maximal power, and the slope of the force-velocity relationship using squat jumps. Fifteen male sport students and 15 elite ski jumping athletes (male = 11; female = 4) conducted 2 block-randomized test-retest sessions with 5-point-method or 2-point-method loading conditions. A third P-F-v profile was established by excluding the data point most declining the coefficient of determination (r2) of the 5-point method. Acceptable absolute and relative reliability were found across methods in ski jumping athletes (intraclass correlation coefficient [ICC] ≥ .79, coefficient of variation [CV] ≤ 6.2%). However, force values were significantly lower in the retest (≤2.1%, d ≤ 0.75). In contrast, no systematic differences (P ≥ .461), but unacceptable absolute and relative reliability, were found in sport students (ICC ≥ .63, CV ≤ 14.8%). The P-F-v parameters of the different collecting and evaluating approaches yielded high to excellent correlations (ski jumping athletes: r ≥ .64; sport students: r ≥ .61), but maximal power (≤4.6%) and velocity (<6.2%,) values of sport students revealed significant differences. The similarity of P-F-v testing and basic ski jumping training daily exercises seems to be more significant to obtain reliable force-velocity parameters than the methodological approach. Accordingly, P-F-v profiles seem to be reliable with the proposed methods only in highly task-experienced athletes but not in less task-experienced cohorts like sport students.

Assessing the Sprint Force-Velocity Profile in International Football Players with Cerebral Palsy: Validity, Reliability and Sport Class' Profiles.

This study assessed and described the Sprint Force-velocity (SFv) profile, and its validity and reliability in international cerebral palsy (CP) football players. Twenty international male CP football players (age: 26.9±7.4) performed a 30-m sprint, a vertical jump (CMJ), a change of direction (MAT), a dribbling and an intermittent endurance (Yo-YoIR1) test. The SFv profile and physical performance variables were shown according to the players’ sport class with the estimation of the effect sizes between classes. The SFv showed high reliability (ICC=0.77 to 0.99; SEM=0.89 to 8.66%). Validity for the SFv was provided by its positive correlation with the players’ sport class (r=0.53 to 0.75; p=.02 to <.01) and the rest of the physical performance tests (r=0.45 to 0.99; p=.04 to <.01). The RFmax was the main SFv profile variable that explained players’ performance in the rest of the tests (β=0.77 to 1.0; p<.05; R2=0.59 to 0.99). The SFv profile seems to be an efficient test to assess international CP football players’ physical performance. This provides information about the players’ individual sprint mechanical characteristics and their sprint strengths and weaknesses, allowing coaches and conditioning trainers to individualize their training interventions to optimize sprint performance.

Mechanical paramaters of sprint in female soccer players at different skill levels

Aim: The purpose of the present study was to evaluate the relationships between sprint mechanical parameters and sprint performance among female soccer players at different skill levels. The second objective was to assess a potential differences in force-velocity profiles between players from higher and lower sport skill level. Materials and methods: Sixty-six female soccer players (age = 23.1 5.1 years) performed a 30-m sprint to assess sprint performance and mechanical variables. Speed was measured by radar technology for 5, 10, 20, and 30 m and was used to calculate the theoretical maximal velocity (V0), theoretical maximal horizontal force (F0), maximal horizontal power (Pmax), decrease in the ratio of horizontal to resultant force (DRF), and peak ratio of horizontal to resultant force (RFpeak). Results: Different force-velocity (F-V) profile parameters are determinants of sprint performance at various distances. RFpeak (r =-0.99), Pmax (r = -0.93), and F0 (r = 0.92) had the strongest associations with sprint performance at shorter (5-m) distances, while at longer (20-m) distances, V0 (r = -0.73), Pmax (r = -0.94), and RFpeak (r = -0.88) were largely associated with sprint performance. The players from higher sports skill level showed higher levels of F0, RFpeak, Pmax and time to 10 meter distance. Conclusion: The results of this study suggest that depending on sprint distance used for testing and training procedures in female soccer players, the most informative parameters are Pmax, RFpeak, F0, and V0. As the skill level in female soccer players increases, an increase in maximal theoretical horizontal force during sprinting can be observed.

Effectiveness of individualized training based on force-velocity profiling on physical function in older men.

The study aimed to investigate the effectiveness of an individualized power training program based on force–velocity (FV) profiling on physical function, muscle morphology, and neuromuscular adaptations in older men. Forty‐nine healthy men (68 ± 5 years) completed a 10‐week training period to enhance muscular power. They were randomized to either a generic power training group (GPT) or an individualized power training group (IPT). Unlike generic training, individualized training was based on low‐ or high‐resistance exercises, from an initial force–velocity profile. Lower‐limb FV profile was measured in a pneumatic leg‐press, and physical function was assessed as timed up‐and‐go time (TUG), sit‐to‐stand power, grip strength, and stair‐climbing time (loaded [20kg] and unloaded). Vastus lateralis morphology was measured with ultrasonography. Rate of force development (RFD) and rate of myoelectric activity (RMA) were measured during an isometric knee extension. The GPT group improved loaded stair‐climbing time (6.3 ± 3.8 vs. 2.3% ± 7.3%, p = 0.04) more than IPT. Both groups improved stair‐climbing time, sit to stand, and leg press power, grip strength, muscle thickness, pennation angle, fascicle length, and RMA from baseline (p < 0.05). Only GPT increased loaded stair‐climbing time and RFD (p < 0.05). An individualized power training program based on FV profiling did not improve physical function to a greater degree than generic power training. A generic power training approach combining both heavy and low loads might be advantageous through eliciting both force‐ and velocity‐related neuromuscular adaptions with a concomitant increase in muscular power and physical function in older men.

Long-Term Monitoring of Training Load, Force-Velocity Profile, and Performance in Elite Weightlifters: A Case Series With Two Male Olympic Athletes

Sandau, I and Granacher, U. Long-term monitoring of training load, force-velocity profile, and performance in elite weightlifters: a case series with two male Olympic athletes. J Strength Cond Res 36(12): 3446-3455, 2022-The aim of this case series approach was to analyze weekly changes in force-velocity relationship (FvR) parameters (v̅0, F̅0, P̅max) and theoretical snatch performance (snatchth) assessed through a specific snatch pull test in preparation of the European and World Championships in 2 male elite weightlifters. A second aim was to examine associations of training load (volume, volume load, average load), barbell FvR-parameters, and snatchth over a period of 2 macrocycles in preparation of the same competitions. FvR-parameters, snatchth, training load data, and body mass were assessed weekly over 40 weeks. Using the smallest real difference approach, significant (p ≤ 0.05) decreases in v̅0 and increases in F̅0, P̅max, and snatchth were found within macrocycles. However, the large significant loss in body mass (≈11%) in athlete 1 during macrocycle 2 represents most likely a main factor for diminished P̅max, and snatchth in macrocycle 2. Based on cross-correlation analyses, barbell FvR-parameters and snatchth were significantly (p ≤ 0.05) associated with maximal strength, muscle power, and speed training load variables. Moderate correlations (0.31-0.47) were found between training load and P̅max and snatchth in athlete 2. It can be concluded that the applied training loads elicits improvements in P̅max and snatchth because the athlete approached the main competitions. However, because of the large loss in body mass, the relations between training load and barbell FvR-parameters and snatchth were less clear in athlete 1. It seems that a loss in body mass as a result of a change in bodyweight category mitigates P̅max development during the macrocycle and hindered to reach peak snatchth at the main competitions.

Anaerobic Speed Reserve, Sprint Force-Velocity Profile, Kinematic Characteristics, and Jump Ability among Elite Male Speed- and Endurance-Adapted Milers.

This study aimed to compare sprint, jump performance, and sprint mechanical variables between endurance-adapted milers (EAM, specialized in 1500–3000-m) and speed-adapted milers (SAM, specialized in 800–1500 m) and to examine the relationships between maximal sprint speed (MSS), anaerobic speed reserve (ASR), sprint, jump performance, and sprint mechanical characteristics of elite middle-distance runners. Fifteen participants (8 EAM; 7 SAM) were evaluated to obtain their maximal aerobic speed, sprint mechanical characteristics (force–velocity profile and kinematic variables), jump, and sprint performance. SAM displayed greater MSS, ASR, horizontal jump, sprint performance, and mechanical ability than EAM (p < 0.05). SAM also showed higher stiffness in the 40-m sprint (p = 0.026) and a higher ratio of horizontal-to-resultant force (RF) at 10 m (p = 0.003) and RFpeak (p = 0.024). MSS and ASR correlated with horizontal (r = 0.76) and vertical (r = 0.64) jumps, all sprint split times (r ≤ −0.85), stiffness (r = 0.86), and mechanical characteristics (r ≥ 0.56) during the 100-m sprint, and physical qualities during acceleration (r ≥ 0.66) and sprint mechanical effectiveness from the force–velocity profile (r ≥ 0.69). Season-best times in the 800 m were significantly correlated with MSS (r = −0.86). Sprint ability has a crucial relevance in middle-distance runners’ performance, especially for SAM.

Sprint Performance and Mechanical Force-Velocity Profile among Different Maturational Stages in Young Soccer Players.

The aim of the present study was to determine the influence of maturation status on the components of the sprint force-velocity (F-V) profile in young soccer players. Sixty-two young male soccer players from the same professional soccer academy took part in the present study. A cross-sectional design was implemented to compare the main components of the sprint F-V profile (i.e., maximal theoretical force (F0), velocity (V0), power (Pmax), and ratio of horizontal-to-resultant force (RFpeak), and decrease in the ratio of horizontal-to-resultant force (DRF)) and sprint performance (5, 20, and 30 m sprint time) among participants’ maturation stages (i.e., pre-, mid- and post-peak height velocity (PHV) groups). The results show that the ES of differences in 5 min sprint performance, F0, and RFpeak (i.e., strength- and acceleration-related components of the sprint F-V profile) were greater between pre- and mid-PHV groups than those between mid- and post-PHV groups (i.e., large and very large effects (1.24 ≤ ES ≤ 2.42) vs. moderate, small, and zero effects (0 ≤ ES ≤ 0.69), respectively). However, the ES of differences in V0 and DRF (i.e., peak speed-related components of the sprint F-V profile) were greater between mid- and post-PHV groups than those between pre- and mid-PHV groups (i.e., large effects (1.54 ≤ ES ≤ 1.92) vs. moderate effects (−0.59 ≤ ES ≤ 1), respectively). Once the strength development is achieved to a great extent from the pre- to mid-PHV groups, specific strength training methods may be used for young soccer players to improve their sprint performance.

Comparison of two measurement devices for obtaining horizontal force-velocity profile variables during sprint running

This study established the magnitude of systematic bias and random error of horizontal force-velocity (F-v) profile variables obtained from a 1080 Sprint compared to that obtained from a Stalker ATS II radar device. Twenty high-school athletes from an American football training group completed a 30 m sprint while the two devices simultaneously measured velocity-time data. The velocity-time data were modelled by an exponential equation fitting process and then used to calculate individual F-v profiles and related variables (theoretical maximum velocity, theoretical maximum horizontal force, slope of the linear F-v profile, peak power, time constant tau, and horizontal maximal velocity). The devices were compared by determining the systematic bias and the 95% limits of agreement (random error) for all variables, both of which were expressed as percentages of the mean radar value. All bias values were within 6.32%, with the 1080 Sprint reporting higher values for tau, horizontal maximal velocity, and theoretical maximum velocity. Random error was lowest for velocity-based variables but exceeded 7% for all others, with slope of the F-v profile being greatest at ±12.3%. These results provide practitioners with the information necessary to determine if the agreement between the devices and the magnitude of random error is acceptable within the context of their specific application.

Differences in the Force-Velocity profile between Judoist and freestyle wrestlers

Background: The aim of this study was to gain new knowledge about the force-velocity (F-V) profile in Judoist and freestyle wrestlers, investigating if there were any differences between sports and which physical demands have which fighting modalities. Participants: 24 athletes (male) took part in this study. Twelve Judoist (age: 20.3 ± 3.9 years, weight: 76.4 ± 10.4 kg; height: 179.4 ± 5.3 cm; BMI: 32.2 ±1.9 kg/m2) and twelve freestyle wrestlers (age: 19.6 ± 4.5 years, weight: 65.3 ± 13.6 kg; height: 177.5 ±5.7 cm; BMI: 23.8 ± 1.8 kg/m2) participated. Methods: To evaluate the F-V profile, the participants performed a squat jump (SJ) without load, as well as with different load conditions (0, 25, 50, 75, and 100% of athlete’s body mass). To assess the height of the jump, the OptoGait system was used. Consequently, the theoretical maximal force (F 0); the theoretical maximal velocity (V 0); maximal mechanical power output (Pmax); slope of the linear F-V relationship (Sfv); optimal F-V profile (Sfvopt ); and the differences between Sfv and Sfvopt (FV imb% ) were obtained. Results: A higher F 0 and lower V 0 were found in Judo athletes compared to wrestlers. Significant differences were found in Sfv and FV imb (p&lt;0.001). Conclusion: The F-V profile is an accurate, reliable, and economical method that facilitates the evaluation of the current state of the athlete individually. Practical applications: The F-V profile method allows coaches and athletes to adjust their training objectives to achieve a higher level in their sport.

Influence of individualized training based on mechanical force-velocity profile on the bilateral vertical jump performance

A detailed review of literature revealed that there is no study of the influence of different types of loads on the performance of a bilateral vertical jump examined on subjects of the same type of F-v profile. Therefore, the aim of this study was to evaluate the influence of two different load-types on the squat-jump performance in force-deficient subjects. During the seven-week training program, the 15 participants of force group performed a half back squat with a load of 80-85% 1RM, while the 15 participants of velocity group performed squat jumps with an unloading of 25% of body weight during the same period of time. The force group significantly improved height of the squat jump (+12.43 ± 6.98%; p &amp;lt;0.001), with a large effect (ES = 1.92 ± 0.72), while in the velocity group were recorded non-significant change (+2.02 ± 5.92%; p = 0.26), with a small effect (ES = 0.30 ± 0.60). These results in the force group were accompanied by a significant optimization of the F-v profile (+31.53 ± 34.91%; p = 0.003), with the attribute of large effect (ES = 1.10 ± 0.65), and the velocity group again recorded non-significant change (-2.20 ± 34.34%; p = 0.70), with a trivial effect (ES = -0.13 ± 0.60). The results of the force group support the hypothesis of the effectiveness of a training program aimed at developing a deficient component of the F-v profile.

Horizontal versus vertical force application: association with the change of direction performance in soccer players.

ABSTRACT This study examined which mechanical variables derived from a vertical jump (i.e. concentric peak force [ConcPF] and eccentric peak force [EccPF], flight time [FT]: contraction time [CT], eccentric deceleration rate of force development [EccDecRFD]) and linear sprint (i.e. theoretical maximal force [F0] and velocity [V0], maximal power output [Pmax], the peak ratio of the effective horizontal component [RFpeak], and the index of force application technique [DRF]) determined the change of direction (COD) performance to a greater extent. Sixteen male soccer players (age: 21.8 ± 2.9 years; height: 175.94 ± 6.88 cm; weight: 73.23 ± 9.59 kg) were assessed for a countermovement jump, the horizontal force velocity (FV) profile, and the COD ZigZag test. The horizontal FV profile parameters were significantly associated with COD performance, while jump mechanical variables did not show any significant association (r = 0.08–0.19; p > 0.05). Specifically, F0 (r = −0.56), Pmax (r = −0.68), and RFpeak (r = −0.54) were strongly associated with COD performance. Moreover, a 1 N·kg−1 increase in F0 was associated with −0.11 s to complete the ZigZag test, whereas 1 W·kg−1 and 1% increase in Pmax and RFpeak were associated with −0.05 and −0.03 s, respectively, to complete the COD test. Horizontal force production during sprinting might play a key role in COD performance. Assessing the horizontal FV profile might help coaches to prescribe a specific training programme to maximize sprint acceleration, which might improve COD performance.

Comparison of movement velocity and force-velocity parameters using a free video analysis software and a linear position transducer during unilateral and bilateral ballistic leg press

Abstract Study aim: This study compared movement velocity and force-velocity profile parameters measured by a free video analysis software program, with the use of a high-speed video recording, and a validated linear position transducer (LPT). Material and methods: Ten team-sports athletes performed double-leg and single-leg ballistic lower limb extensions on a leg press machine against a wide range of resistive loads. Each repetition was recorded by the LPT a high-speed camera (300 fps), and later analysed with a free video analysis software program. Results: Mean and peak movement velocity presented high reliability (ICC: 0.990 and 0.988, p &lt; 0.001) and agreement between the two measuring systems (systematic bias: –0.06 ± 0.04 and –0.01 ± 0.03 m/s, respectively). Force-velocity profile parameters were also similar: maximum velocity at zero load (Vo: 1.79 ± 0.15 vs. 1.78 ± 0.12 m/s, p = 0.64), slope (b: –1585 ± 503 vs. –1562 ± 438 N · s/m, p = 0.43), maximum force at zero velocity (Fo: 2835 ± 937 vs. 2749 ± 694 N, p = 0.41) and maximum power (1274 ± 451 vs 1214 ± 285 W, p = 0.38). Both measuring systems could similarly detect the individual force or velocity deficit (p=0.91). Conclusion: In conclusion, a free video analysis software combined with a high-speed camera was shown to be a reliable, accurate, low bias and cost-effective method in velocity-based testing.

Relationships between Strength and Step Frequency with Fatigue Index in Repeated Sprint Ability.

Force−velocity profile (FVP) and repeated-sprint ability (RSA) tests are indicators of physical capacities in most team sport players. The purpose of this study was to examine the stride kinematics during a repeated-sprint ability (RSA) test and to analyze the relationship between Bosco’s force−velocity profile (FVP) and RSA performance in elite female field hockey players. Thirteen elite-female players performed both RSA (six 30 m maximal sprints) and jumping (CMJ weighted and body weight) tests. Sprinting time fatigue indexes during a 30 m RSA test were correlated with step frequency fatigue indexes (r > 0.7; p < 0.01). CMJ50 showed a large relationship with sprint time fatigue indexes. FV50 showed a very large relationship with sprint time fatigue indexes (r > 0.7; p < 0.01), and a large relationship with the step frequency fatigue indexes (r > 0.5; p < 0.05). This study highlighted two possible ways to improve fatigue indexes in RSA, with the aim of maximizing the distances covered at high-intensities during the matches: (a) strength training and (b) focusing on step frequency during speed training.

A Novel Approach of Modelling and Predicting Track Cycling Sprint Performance

In cycling, performance models are used to investigate factors that determine performance and to optimise competition results. We present an innovative and easily applicable mathematical model describing time-resolved approaches for both the physical aspects of tractional resistance and the physiological side of propelling force generated by muscular activity and test its validity to reproduce and forecast time trials in track cycling. Six elite track cyclists completed a special preparation and two sprint time trials in an official velodrome under continuous measurement of crank force and cadence. Fatigue-free force-velocity profiles were calculated, and their fatigue-induced changes were determined by non-linear regression analysis using a monoexponential equation at a constant slope. Model parameters were calibrated based on pre-exercise performance testing and the first of the two time-trials and then used to predict the performance of the second sprint. Measured values for power output and cycling velocity were compared to the modelled data. The modelled results were highly correlated to the measured values (R2&gt;0.99) without any difference between runs (p&gt;0.05; d&lt;0.1). Our mathematical model can accurately describe sprint track cycling time trial performance. It is simple enough to be used in practice yet sufficiently accurate to predict highly dynamic maximal sprint performances. It can be employed for the evaluation of completed runs, to forecast expected results with different setups, and to study various contributing factors and quantify their effect on sprint cycling performance.

Validity of a simple sit-to-stand method for assessing force-velocity profile in older adults.

Lower limb muscle strength is an important determinant of physical function in older adults. However, its measure in clinical settings is limited because of the requirement for large-scale and costly equipment. A new simple protocol based on sit-to-stand test (STS) is developed to measure force velocity (F-v) and power velocity (P-v) profile in the community-dwelling older adults. The objective of this study was to assess the validity of this new methodology for measuring F-v and P-v profile compared to the gold standard isokinetic BIODEX. 46 older people aged 65-85years (M=73.7; SD=7.7). F-v and P-v profiles were assessed in participants on their dominant leg. The concurrent validity of STS was tested using Spearman's rank correlation coefficient and Passing Bablok: maximal power output Pmax, optimal velocity and force Vopt and Fopt, maximal force at null velocity F0, maximal unloaded velocity V0 and coefficient of F-v (SFV) and P-v equation (a_poly, b_poly). No proportional difference for F0 and b_poly and a low significant correlation for Pmax (r=0.314), Sfv (r=0.229), a_poly (r=0.335) and b_poly (r=0.226) whereas the other parameters were non correlated significantly. STS method is moderately reliable on force and power parameters whereas further improvements are needing for velocity parameters. However, its feasibility, portability and lower cost compared to other methods makes it very affordable in clinical context and will allow easy investigation of aging population.

Optimal mechanical force-velocity profile for sprint acceleration performance.

The aim was to determine the respective influences of sprinting maximal power output ( ) and mechanical Force-velocity (F-v) profile (ie, ratio between horizontal force production capacities at low and high velocities) on sprint acceleration performance. A macroscopic biomechanical model using an inverse dynamics approach applied to the athlete's center of mass during running acceleration was developed to express the time to cover a given distance as a mathematical function of and F-v profile. Simulations showed that sprint acceleration performance depends mainly on , but also on the F-v profile, with the existence of an individual optimal F-v profile corresponding, for a given , to the best balance between force production capacities at low and high velocities. This individual optimal profile depends on and sprint distance: the lower the sprint distance, the more the optimal F-v profile is oriented to force capabilities and vice versa. When applying this model to the data of 231 athletes from very different sports, differences between optimal and actual F-v profile were observed and depend more on the variability in the optimal F-v profile between sprint distances than on the interindividual variability in F-v profiles. For a given sprint distance, acceleration performance (<30m) mainly depends on and slightly on the difference between optimal and actual F-v profile, the weight of each variable changing with sprint distance. Sprint acceleration performance is determined by both maximization of the horizontal power output capabilities and the optimization of the mechanical F-v profile of sprint propulsion.

Delineating the potential of the vertical and horizontal force-velocity profile for optimizing sport performance: A systematic review

ABSTRACT The aims of this systematic review were to synthetize the current evidence about (i) the force-velocity (FV) profile parameters (maximal values of force [F 0], velocity (V 0), and power [Pmax ]) obtained from the Samozino’s method in different sports; (ii) the association of the FV profile parameters with sport performance outcomes; and (iii) the effects of specific training programmes on the FV profile parameters. PubMed, SportDiscus, Web of Science, and Medline databases were searched for articles published between October 2008 (conception of the Samozino’s method) and October 2020. Twenty-one studies (10 descriptive, 6 correlational, and 5 longitudinal) met the inclusion criteria. The main findings revealed greater F0, Pmax , and V0 values and better jump/sprint performance for high-level athletes compared to their low-level counterparts. The vertical Pmax showed the highest correlation with jump height. The horizontal F0, Pmax , and V0 were nearly perfectly correlated with 5/10-m, 10/20-m and 30/40-m sprint times, respectively. Training programmes using heavy- or light-loads specifically enhanced F0 and V0 , respectively. These results suggest that the FV profile parameters discriminate between athletes of different sport disciplines and levels of practice, present significant correlations with a number of sport performance outcomes, and can be modified after short-term training programmes.

Uphill sprinting load– and force–velocity profiling: Assessment and potential applications

ABSTRACT This study aimed to quantify the validity and reliability of load–velocity (LV) relationship of hill sprinting using a range of different hill gradients and to describe the effect of hill gradient on sprint performance. Twenty-four collegiate-level athletes performed a series of maximal sprints on either flat terrain or hills of gradients 5.2, 8.8 and 17.6%. Velocity–time curves were recorded using a radar device. LV relationships were established using the maximal velocity achieved in each sprinting condition, whilst force–velocity–power (FVP) profiles were established using only the flat terrain sprint. LV profiles were shown to be valid (R2 = 0.99) and reliable (TE < 4.4%). For every 1-degree increase in slope, subjects’ velocity decreased by 1.7 ± 0.1% on average. All the slopes used represented low resistance relative to the entire LV spectrum (<25% velocity loss). Subjects who exhibited greater horizontal force output at higher velocities on flat terrain were most affected by the gradient of the hill. Hills of gradients up to 17.6% do not provide sufficient resistance to optimize power development. However, such hills could be used to develop late-stage technical ability, due to the prolonged horizontally oriented body position that occurs as subjects attempt to overcome the acceleration due to gravity.

Inter-Rater Reliability and Intra-Rater Reliability Testing of My Jump 2 Mobile Application in Measuring Countermovement Jump

My Jump 2 is a mobile application that is objectively valid and reliable to measure vertical jumping height. The objectives of this study are to find the inter-rater and intra-rater reliability of the My Jump 2 mobile application in measuring countermovement jump (CMJ) height. A total of 25 male recreational athletes performed CMJ for five attempts and was recorded by using iPhone 7 Plus in 240 frames per second. The videos were then rated by three raters and rated again seven days later using the My Jump 2 mobile application. An excellent degree of reliability was found between rater measurements. The average measure ICC was 1.00 with a 95% confidence interval from 1.00 to 1.000 (F(124,248)= 18867201.171, p<.001). An excellent degree of reliability was found within rater measurements. The average measure ICC was 1.00 with a 95% confidence interval from 1.00 to 1.00 (F (124,124) = 44750598.291, p<.001). This study provides evidence in supporting the use of the My Jump 2 mobile application to measure the height of the countermovement jump in a research setting. Future research is needed to study the validity and reliability of other parameters possibly measured by the My Jump 2 mobile application like force-velocity profile, jumping launch force, and power.