Does ground-reaction force influence post-impact ball speed in the tennis forehand groundstroke?

Motion of the rear leg during a tennis forehand was previously reported to influence the ball speed. However, impact of a kinetic measure such as the ground-reaction force (GRF) on forehand ball speed has not been investigated. The aim of this study was to investigate the influence of GRF on forehand ball speed and identify the most influential component of GRF related to overall higher ball speeds. Nine tennis players (eight males, one female) were invited to participate. Three testing sessions were conducted. Each session consisted of maximal forehand ball-speed testing and seven forehands at three ball speeds; fast (100%), medium (90%) and slow (80%). GRF and post-impact ball speed were measured for each stroke. Of all the individual GRF vectors, peak anterior-posterior force best explained the changes in ball speed, where 26% (R2 = 0.26) of ball speed variance can be explained by this force vector alone. In a stepwise fashion, adding peak lateral force to the model explained a further 7% (R2 = 0.33). Combining peak anterior-posterior, medial-lateral and vertical forces explained a total of 37% (R2 = 0.37). Peak anterior-posterior force appears to be the most influential ground-reaction force affecting forehand post-impact ball speed.

Thigh loaded wearable resistance increases sagittal plane rotational work of the thigh resulting in slower 50-m sprint times.

This study determined the acute changes in rotational work with thigh attached wearable resistance (WR) of 2% body mass during 50-m sprint-running. Fourteen athletes completed sprints with, and without, WR in a randomised order. Sprint times were measured via timing gates at 10-m and 50-m. Rotational kinematics were obtained over three phases (steps 1-2, 3-6 and 7-10) via inertial measurement unit attached to the left thigh. Quantification of thigh angular displacement and peak thigh angular velocity was subsequently derived to measure rotational work. The WR condition was found to increase sprint times at 10-m (1.4%, effect size [ES] 0.38, p 0.06) and 50-m (1.9%, ES 0.55, p 0.04). The WR condition resulted in trivial to small increases in angular displacement of the thigh during all phases (0.6-3.4%, ES 0.04-0.26, p 0.09-0.91). A significant decrease in angular velocity of the thigh was found in all step phases (-2.5% to -8.0%, ES 0.17-0.51, p < 0.001-0.04), except extension in step phase 1 with the WR. Rotational work was increased (9.8-18.8%, ES 0.35-0.53, p < 0.001) with WR in all phases of the sprint. Thigh attached WR provides a means to significantly increase rotational work specific to sprinting.

Effects of forearm wearable resistance during accelerated sprints: From a standing start position.

Fusiform weighted garments enable specific loading strategies during sport-specific movements. Loading the arms over during accelerated sprinting from a 2-point start position is pertinent to a variety of sporting performances. Fourteen sprint-trained individuals (age = 20.61 ± 1.16 years; height = 1.73 m ± 3.85 cm; body mass 65.33 ± 4.86 kg; personal best 100-m race time 11.40 ± 0.39 s) performed unloaded/loaded wearable resistance (WR) sprints. Between-condition step kinematics and kinetics were compared over four acceleration phases: steps 1-4, 5-8, 9-12 and 13-16. Sprint performance did not differ between unloaded and loaded WR at 10-m (-1.41%; ES = -0.32), or 30-m (-0.76%; ES = -0.24). Sprinting with forearm WR significantly decreased step frequency during phase two (p < 0.05, -3.42%; ES = -0.81) and three (-3.60%; ES = -0.86) and step velocity during phase four of the 30 m sprinting task (p < 0.05, -3.61%; ES: 0.91) only. There were no significant differences (p ≤ 0.05) between step kinetics amongst the two conditions. Findings indicate that arm-loaded WR may provide specific sprinting overload for 2-point starting positions. This may be relevant to a wider sporting context such as field and team sport performances.

Acceleration mechanics during forward and backward running: A comparison of step kinematics and kinetics over the first 20 m.

Backward running (BR) and forward running (FR) are unique movements utilized by athletes in many sports. Importantly, this investigation provides further insights on BR and benchmarking against more commonly researched FR capacity. Twenty-one collegiate soccer players (age 20.0 ± 0.8 years, body mass 65.6 ± 7.7 kg, body height 1.70 ± 0.07 m) performed maximal effort BR and FR along 20 m of in-ground force platforms. Step kinematics and kinetics were compared between BR and FR over four relative acceleration phases (BR = steps 1-6, 7-12, 13-18 and 19-23; FR = steps 1-4, 5-8, 9-12, 13-15). The primary findings of this study were that BR speeds were 29% slower than FR (p < 0.001), all step kinematics differed between BR and FR (p < 0.01), except contact time from the second to fourth step phases (p > 0.05), and most step kinetics were lower during BR (p < 0.05), with the exceptions of peak vertical force (p > 0.05). These findings indicate that lower running speeds over the acceleration phases of BR appear to be primarily due to lower horizontal ground reaction force application, resulting in shorter stride lengths and decreased flight times compared to FR.

Pacing and stroke kinematics in 200-m kayak racing.

Pacing profiles of 19 elite and sub-elite 200-m kayak athletes were examined through stroke-by-stroke analysis, using GPS/accelerometer methodology. Stroke rates and lengths were also quantified across multiple race segments. Whilst athletes reached peak velocity at between 40 and 60 m, it was not possible to determine specifically whether an all-out or positive strategy was employed. Race times were strongly and negatively correlated with the acceleration over the first ~25% of race distance (r = -0.95 ± 0.04) as well as average velocity over the first 30 m of the race (r>-0.9), i.e. faster starts were associated with faster finishing times. Furthermore, the maintenance of velocity, stroke rate and stroke length after reaching their maxima were strongly associated with race times. Stroke rates were higher (Cohen's d = 5.19) in the elite than sub-elite athletes (group categorisation based on race times), but there were no substantial differences in stroke rates between athletes within the elite cohort. Nonetheless, longer stroke lengths were associated with faster race times within the elite cohort (r = -0.48 to -0.85). The current study suggests that faster rates of acceleration and the ability to exhibit greater stroke lengths at relatively high stroke rates are determinants of 200-m kayak race performance.

Relationships Between Midthigh Pull Force Development and 200-m Race Performance in Highly Trained Kayakers.

ABSTRACT: Pickett, CW, Nosaka, K, Zois, J, and Blazevich, AJ. Relationships between midthigh pull force development and 200-m race performance in highly trained kayakers. J Strength Cond Res 35(10): 2853-2861, 2021-While increased lower-limb force production during kayaking has been shown to be related to increased boat velocity, poor relationships between maximal deadlift test performances and 200-m race time have been observed previously. This discrepancy may result from either a lack of movement pattern or temporal force production specificity between the test and kayak paddling. The isometric midthigh pull (MTP) test is commonly used in strength testing and quantifies temporal and peak force production, with the lower limbs positioned in a more kayak-specific manner than the deadlift test. Midthigh pull force data collected from 11 high-level kayak athletes were analyzed for both reliability and correlations with 200-m race time and deadlift isoinertial strength 3 repetition maximum (3RM). Strong consideration was given to the collection, processing, and analysis of the MTP data, which markedly affected the study results. Correlations between race time and MTP peak force and rates of force development were poor to moderate (r = -0.49 to 0.07). Strong to very strong relationships (r = 0.66-0.79) were found between forces developed early in the MTP (<0.15 seconds) and deadlift 3RM strength tests but were poor for later time-specific force development (r ≤ 0.12). However, poor reliability was found for force measured up to ≤0.25 seconds from the point of force onset (intraclass correlation coefficient >0.8). Owing to the relatively weak relationships with 200-m race time, and the large variability of the data, it may not be wise to include the MTP in the testing and training of 200-m kayak athletes.

Seasonal changes in physical capacities of basketball players according to competitive levels and individual responses.

PURPOSE: The aim of this study was to quantify changes in physical capacities of thirty-eight basketball players selected from different teams, as well as from varying competitive levels (i.e. Division I, Division II and Division III) during the preparation and in-season periods. METHODS: Pre (T1) and post (T2) preparation period and during regular season (T3), the players completed a Yo-Yo Intermittent Recovery test-level 1. Following a 3 to 8 days-break, players performed a 6-min continuous running test (Mognoni's test), a counter-movement jump test and a 5-min high-intensity intermittent running test. RESULTS: Blood lactate concentration measured after the Mognoni's test was significantly reduced from T1 to T2, and from T2 to T3 (P<0.001, ƞ2 = 0.424). The distance covered during the Yo-Yo Intermittent Recovery test was significantly increased only from T1 to T2 in Division II and III (P<0.001, ƞ2 = 0.789). Similarly, the physiological responses to high-intensity intermittent running test were improved only from T1 to T2 (all P<0.001, ƞ2 = 0.495 to 0.652). Despite significant changes observed in running tests from T1 to T2, at individual level 35-55% of players did not show a very likely improvement. Relative peak power produced during vertical jumps at T3 by Division I players was increased compared to T1 (ANOVA interaction, P = 0.037, ƞ2 = 0.134). CONCLUSIONS: The main improvements in physical capacities occurred during the preparation period, when the aerobic fitness and the ability to sustain high-intensity intermittent efforts were moderately-to-largely improved. However, it appears that the preparation period does not consistently impact on vertical jump variables. Aerobic fitness and force/power production during vertical jumps appear to improve across the competitive season (slightly-to-moderately). Physical tests should be used to identify weaknesses in physical performance of players and to monitor their fatigue status, with the aim to develop individualized training programs.

Comparison of Physical Profiles of State-Level Netball Players by Position.

Graham, S, Duthie, G, Aughey, R, and Zois, J. Comparison of physical profiles of state-level netball players by position. J Strength Cond Res 34(9): 2654-2662, 2020-Understanding the physical profiles of state-level netball athletes provides conditioning professionals with testing norms and an understanding of important capacities within particular positions. The purpose was to examine positional differences in physical capacities of state-level netball athletes. Forty-six state-level netball athletes completed physical capacity assessments in the second week of their preseason, over 2 seasons. Tests included stature, 20-m sprint (with 5 and 10 m splits), 505 change-of-direction, countermovement jump, single-leg bounding, and the Yo-Yo intermittent recovery test level one. A linear mixed-model with fixed and random effects was used in conjunction with magnitude-based inferences to determine meaningful differences with 90% confidence limits (CLs). Midcourt athletes were shorter in stature than shooters (effect size [ES]: 1.26, CL 0.88-1.63) and defenders (-2.58, -3.35 to -1.80). Midcourt athletes were faster than shooters and defenders in linear acceleration over 5 and 10 m distances and 505 change-of-direction (ES range: -0.34 to -0.59). Shooters presented poorer intermittent endurance than midcourt (-0.82, -1.34 to -0.31) and defenders (-0.56, -1.19 to 0.07). Defenders jumped higher than midcourt athletes (-0.56, -1.30 to 0.19) and shooters (-0.61, -1.18 to -0.04), and possessed greater bounding ability compared with shooters (ES range: -0.23 to -0.57). Midcourt athletes require a more holistic set of physical capacities including acceleration, change-of-direction, jumping, and intermittent endurance. For defender and shooter positions, results indicate physical requirements that may be more specific to their positions. Conditioning professionals can use these findings to target specific physical qualities to maximize position-specific performance.

Force-velocity profile changes with forearm wearable resistance during standing start sprinting.

Abstract Horizontal force-velocity (F-V) profiling is a strategy to assess athletes' individual performance capabilities during sprinting. This study investigated the acute changes in F-V profiles during sprinting of fourteen collegiate male sprinters with a mean 100-m sprint time of 11.40 ± 0.39 s, from a split-stance starting position. The subjects sprinted 30-m with, and without, wearable resistance (WR) equivalent to 2% body mass, attached to their forearms. Sprinting time at 5, 10, 20, and 30-m was assessed using laser technology. External horizontal F-V relationships were calculated via velocity-time signals. Maximal theoretical velocity (V 0), theoretical relative and absolute horizontal force (F 0), and horizontal power (P max) were determined from the F-V relationship. Paired t-tests were used to determine statistical differences (p ≤ 0.05) in variables across conditions with Cohen's d as effect sizes (ES) calculated to assess practical changes. Sprint times at 10-m and beyond were significantly increased (1.9-3.3%, p 0.01-0.03, ES 0.46-0.60) with WR compared to unloaded sprinting. The only significant change in F-V with the WR condition was found in relative P max system (-6.1%, p 0.01, ES 0.66). A small decrease was reported in V 0 (-1.0%, p 0.11, ES 0.27), with small to medium ES decreases reported in F 0 (-4.8% to -6.1%, p 0.07-0.21, ES 0.25-0.51) and P max (-4.3% to -4.6%, p 0.06-0.08, ES 0.32-0.45). The greater changes to F 0 and P max suggest that forearm WR may be a possible training tool for athletes who wish to focus on force and power adaptation during sprint acceleration from a standing start.

The peak player load™ of state-level netball matches.

OBJECTIVES: To investigate the peak accelerometer-derived intensity of state-level netball matches and compare differences between positional groupings. Findings will provide guidance for sport science professionals on how to best replicate the most intense passages of play in training settings. DESIGN: Longitudinal (one season). METHOD: Twenty-eight netball athletes across three teams from the same club wore an accelerometer (S5 Optimeye, Catapult sports) for all matches, in one season. Raw acceleration data were downloaded and converted into a vector magnitude (Player Load™) we then quantified the peak intensity over 30-s and one to ten-minute time periods. Positional groupings were created based on the number of thirds on a netball court that a particular position can enter, as this was deemed more appropriate for the current study than the traditional combinations based on tactical requirements. A linear mixed-model with fixed and random effects was utilised along with magnitude-based inferences to determine meaningful differences with 90 % confidence limits (CL). RESULTS: Across all time periods post 30-s, only one comparison was not meaningfully different i.e. three-thirds v two-thirds at the one-minute timepoint (effect size: 0.27, CL -0.05 to 0.60). CONCLUSIONS: Findings justify that netball athletes, depending on positional group defined by this study, should train at different intensities dependent on a specified duration. Conditioning professionals and coaches should design training drills that best replicate the peak intensity of match play. This may improve an athlete's physical performance capacity during highly exertive periods of competition, which regularly occur at critical moments in play.

The efficacy and characteristics of warm-up and re-warm-up practices in soccer players: a systematic review.

INTRODUCTION: This review aimed 1) to evaluate the current research that examines the efficacy of warm-up (WU) and re-warm-up (RWU) on physical performance; and 2) to highlight the WU and RWU characteristics that optimise subsequent performance in soccer players. EVIDENCE ACQUISITION: A computerized search was performed in the PubMed, ScienceDirect and Google Scholar (from 1995 to December 2015) for English-language, peer-reviewed investigations using the terms "soccer" OR "football" AND "warm-up" OR "stretching" OR "post-activation potentiation" OR "pre-activity" OR "re-warm-up" AND "performance" OR "jump" OR "sprint" OR "running". EVIDENCE SYNTHESIS: Twenty seven articles were retrieved. Particularly, 22 articles examined the effects of WU on soccer performance and 5 articles focused on the effects of RWU. Clear evidence exists supporting the inclusion of dynamic stretching or postactivation potentiation-based exercises within a WU as acute performance enhancements were reported (pooled estimate changes of +3.46% and +4.21%, respectively). The FIFA 11+ WU also significantly increases strength, jump, speed and explosive performances (changes from 1% to 20%). At half-time, active RWU protocols including postactivation potentiation practices and multidirectional speed drills attenuate temperature and performance reductions induced by habitual practice. The data obtained in the present review showed that the level of play did not moderate the effectiveness of WU and RWU on soccer performance. CONCLUSIONS: This review demonstrated that a static stretching WU reduced acute subsequent performance, while WU activities that include dynamic stretching, PAP-based exercises, and the FIFA 11+ can elicit positive effects in soccer players. The efficacy of an active RWU during half-time is also justified.

Maximal Upper-Body Strength and Oxygen Uptake Are Associated With Performance in High-Level 200-m Sprint Kayakers.

Pickett, CW, Nosaka, K, Zois, J, Hopkins, WG, and Blazevich, AJ. Maximal upper-body strength and oxygen uptake are associated with performance in high-level 200-m sprint kayakers. J Strength Cond Res 32(11): 3186-3192, 2018-Current training and monitoring methods in sprint kayaking are based on the premise that upper-body muscular strength and aerobic power are both important for performance, but limited evidence exists to support this premise in high-level athletes. Relationships between measures of strength, maximal oxygen uptake (V[Combining Dot Above]O2max), and 200-m race times in kayakers competing at national-to-international levels were examined. Data collected from Australian Canoeing training camps and competitions for 7 elite, 7 national, and 8 club-level male sprint kayakers were analyzed for relationships between maximal isoinertial strength (3 repetition maximum bench press, bench row, chin-up, and deadlift), V[Combining Dot Above]O2max on a kayak ergometer, and 200-m race time. Correlations between race time and bench press, bench row, chin-up, and V[Combining Dot Above]O2max were -0.80, -0.76, -0.73, -0.02, and 0.71, respectively (90% confidence limits ∼±0.17). The multiple correlation coefficient for 200-m race time with bench press and V[Combining Dot Above]O2max was 0.84. Errors in prediction of 200-m race time in regression analyses were extremely large (∼4%) in relation to the smallest important change of 0.3%. However, from the slopes of the regressions, the smallest important change could be achieved with a 1.4% (±0.5%) change in bench-press strength and a 0.9% (±0.5%) change in V[Combining Dot Above]O2max. Substantial relationships were found between upper-body strength or aerobic power and 200-m performances. These measures may not accurately predict individual performance times, but would be practicable for talent identification purposes. Training aimed at improving upper-body strength or aerobic power in lower performing athletes could also enhance the performance in 200-m kayak sprints.

High-intensity warm-ups: effects during subsequent intermittent exercise.

High-intensity, short-duration warm-up techniques improve acute physical performance, but sparse research has examined their consequence when followed by intermittent activity, which is pertinent to team sports. The authors compared a 5-repetitionmaximum (5RM) leg-press, a small-sided game (SSG), and a current team-sport warm-up in 10 semiprofessional soccer players after 2 intermittent-activity protocols consisting of 15 repetitions of a 60-s circuit that included sprinting, slalom, walking, jogging, decelerations, changes of direction, backward running, and striding activities. There was a large improvement in countermovement-jump height in the 5RM after the 1st intermittent-activity protocol (mean, ±90% CL 6.0, ±4.0%, P=.03) and a small improvement after the 2nd (4.6, ±4.0%, P=.04) compared with team sport. Reactive agility was moderately faster via 5RM after the 1st intermittent-activity protocol (3.1, ±2.6%: P=.04) and the 2nd (5.7, ±2.7%, P=.001) than via SSG. There was a small improvement in reactive agility after the 1st intermittent-activity protocol in the 5RM, compared with team sport (3.3, ±2.9%, P=.04). There was a small improvement in mean 20-m-sprint times after both intermittent-activity protocols in the 5RM, compared with SSG (4.2, ±2.0%, P=.01, and 4.3, ±2.0%, P=.01) and, after the 1st intermittent-activity protocol only, compared with team sport (4.2, ±2.1%, P=0.02). Small increases in blood lactate concentration were observed (46.7, ±18.6%, P=.01) in the 5RM compared with the SSG after the 2nd intermittent-activity protocol. Improved performances after the 5RM warm-up should encourage practitioners to reduce activity time and include high-intensity tasks in team-sport warmups aimed at inducing a potentiating effect.

The role of rotational mobility and power on throwing velocity.

Sound rotational power and mobility are an integral component in functional performances, such as throwing and striking. The purpose of this study was to examine the role of rotational power and mobility on cricket ball-throwing velocity. Eleven professional cricketers and 10 under-19 club-level cricketers performed the chop and lift, seated and standing cricket ball throw, seated and standing side medicine ball throw, and seated active thoracic rotation range of motion (ROM) and hip rotation ROM on one occasion. Participants were divided into 2 groups (fast and slow) based on their standing cricket ball-throwing velocity. The seated and standing cricket ball throw on the dominant side was significantly different (p < 0.00) between fast and slow throwers (11.03 and 10.7 km·h(-1), respectively). Muscular performance measures, such as bilateral thoracic rotation ROM, hip external rotation ROM on the dominant side, and force and work required in the chop, were significantly different (p ≤ 0.05) between fast and slow throwers. Faster throwers in this study displayed greater force (18.4%) and work (31.2%) outputs in the chop compared with the slower throwers; however, slower throwers showed significantly greater ROM in the thoracic (13.4-16.8%) and hip regions (11.8%). It was concluded that greater ROM at proximal segments, such as hips and thoracic, may not increase throwing velocity in cricket as reduced ROM at proximal segments can be useful in transferring the momentum from the lower extremity in an explosive task such as throwing.

High-intensity warm-ups elicit superior performance to a current soccer warm-up routine.

OBJECTIVES: This study investigated the acute effects of a currently implemented team-sport warm-up and two alternative, high-intensity, short-duration protocols - 5 repetition maximum leg press and small-sided games. DESIGN: Ten male soccer players participated in a randomised, cross-over study. METHODS: Participants performed a team-sport, a leg-press, or a small-sided game warm-up. Subsequent performance tests included counter-movement jump, reactive agility, and 15×20 m sprints embedded in an intermittent exercise task. Physiological measures included core temperature, blood lactate concentration, heart rate and rating of perceived exertion. Data were analysed using the effect size statistic with 90% confidence intervals, and percentage change, to determine magnitude of effects. RESULTS: Counter-movement jump height improved following the small-sided game (6%, ES: 0.8±0.8) and leg-press warm-up (2%, ES: 0.3±0.5), but not after the team-sport warm-up ('unclear' effect). Reactive agility improved after the small-sided game (4%, ES: 0.8±0.7) and leg-press warm-ups only (5%, ES: 1.1±0.7), when compared to baseline. Mean 20-m sprint times during the intermittent exercise task improved following the leg-press warm-up, when compared with the small-sided game (9%, ES: 0.9±0.3) and team-sport warm-ups (7%, ES: 0.6±0.6). Core temperature was lower following the leg-press warm-up compared to small-sided game (1%, ES: 0.9±0.7) and the team-sport WUs (2%, ES: 2.4±0.8). Blood lactate was highest following the small-sided game (67%, ES: 2.7±0.8) and team-sport warm-ups (66%, ES: 2.9±0.9). CONCLUSIONS: A leg-press and small-sided game warm-up may improve acute team-sport performance tests when compared to a traditional warm-up protocol.

Effects of secondary warm up following stretching.

Evidence suggests that static stretching inhibits muscular power. However, research does not reflect practice whereby individuals follow up stretching with secondary activity. This study investigated muscular power following stretching, and after a second bout of activity. Participants (n = 13) completed 3 randomized testing sessions which included a 5 min warm-up, followed by a vertical jump (VJ) on a force platform; an intervention (static stretching, dynamic, or control), followed by a second VJ. Participants then completed a series of movements, followed by a VJ, up to 60 min post activity. Immediately following the intervention, there was a 10.7% difference in VJ between static and dynamic stretching. The second warm up bout increased VJ height following the dynamic intervention, whereas the static stretching condition did not show any differences. The novel finding from this study demonstrates a second exercise bout does not reverse the effects of static stretching and is still detrimental to VJ.