High-velocity Running Research Articles

Fish in the fast lane: the stressful consequences of speeding through a flume

Understanding the swimming ability of different fish species is essential for assessing their ecological niche, behaviour and overall fitness. Changes in swimming ability can relate to the overall health of aquatic ecosystems, as it can be affected by water quality, temperature or habitat quality changes. Our study investigated the effects of stress on swimming performance in wild vairone (Telestes muticellus) in an experimental flume. The obtained data was analysed using k-means clustering to identify stress response patterns. Our findings demonstrate that k-means clustering effectively identified distinct subgroups of fish with similar stress responses in groups with physiological stress responses with high individual variability. We found that short-term exposure to a stress source such as high-velocity running water can increase swimming endurance in this species concerning the velocity in the setup, which was mainly seen in the cortisol and MDA levels in the muscle tissue of the fish. The velocity of the water showed limitations on swimming ability tests and highlighted that fish have a specific range of swimming speeds that they can sustain.

Relationship Between External Training Load and Session Rating of Perceived Exertion Training Impulse in Elite Sprinters.

To quantify the change in session rating of perceived exertion training impulse (RPE-TRIMP) that may occur in response to increased running distance at 3 running velocity ranges in elite sprinters. We monitored training load in elite sprinters (women: n = 7; men: n = 11) using wearable Global Positioning System technology and RPE-TRIMP for a total of 681 individual training sessions during a 22-week competition-preparation period. Internal training load was operationalized by RPE-TRIMP, and external training load was operationalized by distance covered in 3 velocity ranges. A linear mixed-effects model with athlete as a random effect was fit to RPE-TRIMP with total distance covered at ≤69.99% (low-velocity running [LVR]), 70% to 84.99% (high-velocity running [HVR]), and 85% to 100% (very-high-velocity running [VHVR]) of individual maximum velocity. Increased running distance in all 3 velocity ranges (LVR, HVR, and VHVR) resulted in a significant (P < .001) increase in RPE-TRIMP. Coefficients (95% CIs) were .10 (.08-.11) for LVR, .23 (.18-.28) for HVR, and .44 (.35-.53) for VHVR. A 50-m increase in running distance covered in the LVR, HVR, and VHVR velocity ranges was associated with increases in RPE-TRIMP of 5, 11.5, and 22 arbitrary units, respectively. Internal training load, calculated as RPE-TRIMP, increased with increases in total distance covered in the LVR, HVR, and VHVR velocity ranges (P < .001). RPE-TRIMP can be a practical solution for monitoring global training-session load in elite sprinters.

Frontal plane pelvic kinematics during high velocity running: Association with hamstring injury history

IntroductionHamstring injuries are the most prevalent non-contact soft tissue injury in sports, with a larger portion of injuries being recurrent. The sagittal plane running kinematics correlated to hamstring injury history has been well documented. However, analysis of frontal plane kinematics allows for observation of stability and symmetry. This study aimed to examine the frontal plane running kinematics of elite collegiate level sprinters, with and without previous hamstring injury, compared to healthy counterparts. MethodsThirty-nine participants performed three 50-m sprints, with three inertial measurement unit sensors placed on the pelvis: one on each iliac crest and one on the sacrum. Participants were classified based on sex, competitive status, and injury history. To investigate differences based on group classification, the data were used to analyze mediolateral motion (relative magnitude of mediolateral acceleration) and asymmetry (difference in acceleration between right and left iliac crests) during each stance phase throughout the run. ResultsInjured sprinters displayed significantly greater mediolateral motion and asymmetry during stances than healthy counterparts. ConclusionsThis study demonstrates that frontal plane running stance dynamics are different in athletes with previous hamstring injury than healthy athletes. These athletes may benefit from rehabilitation strategies targeting postural control and stability during dynamic tasks.

Physical Match Demands of International Women’s Rugby Union: A Three-Year Longitudinal Analysis of a Team Competing in The Women’s Six Nations Championship

There is a paucity of studies describing the physical match demands of elite international women's rugby union, which limits coaches' ability to effectively prepare players for the physical demands required to compete at the elite level. Global positioning system technologies were used to measure the physical match demands of 53 international female rugby union players during three consecutive Women's Six Nations Championships (2020-2022), resulting in 260 individual match performances. Mixed-linear modelling was used to investigate differences in physical match demands between positions. Significant effects (p < 0.05) of the position were observed for all variables, with the exception of relative distances (m.min-1) at velocities of 1.01-3.00 m·s-1 (p = 0.094) and 3.01-5.00 m·s-1 (p = 0.216). This study provides valuable data on the physical match demands of elite international women's rugby union match play that may aid practitioners in the physical preparation of players to compete at this level. Training methodologies for elite-level female rugby union players should consider the unique demands across positional groups with specific considerations of high-velocity running and collision frequency.

Influence of Repeated-Sprint Ability on the in-Game Activity Profiles of Semiprofessional Rugby Union Players According to Position

This study investigated the influence of repeated-sprint ability (RSA) on the activity of rugby union players in a competitive situation according to their position. Thirty-three semiprofessional rugby union players (age, 25.6 ± 4.3; height, 184.0 ± 8.0 cm; weight, 98.9 ± 13.9 kg, ~20 h training a week), divided into two position subgroups (forwards n = 20, backs n = 13) or four positional subgroups (front row and locks n = 13, back row n = 7, inside backs n = 6, outside backs n = 7), were tested. Their RSA was assessed with a 12 × 20 m sprint test over a 20 s cycle. GPS data (distance, acceleration, number of sprints, maximum velocity, and high-velocity running) and technical data were collected on 18 semiprofessional division rugby union games. In forwards, players with lower cumulated sprint time in the RSA test produced significantly more accelerations (ρ = −0.85, p < 0.001) and more combat actions per match minute (ρ = −0.69, p < 0.001). In backs, RSA was significantly correlated with high-intensity running [distance (ρ = −0.76), Vmax (ρ = −0.84), sprints frequency (ρ = −0.71), high-velocity running (ρ = −0.76), all p < 0.01]. Then, the players were divided into four subgroups (front row and locks, back row, inside backs and outside backs). RSA was significantly associated with the number of accelerations (ρ = −0.96, p <001) and combat actions in front row and locks (ρ = −0.71, p = 0.007). In the back row, RSA was correlated with distance (ρ = −0.96, p = 0.003) and the frequency of combat actions (ρ = −0.79, p = 0.04). In inside backs, RSA was significantly (all p < 0.01) correlated with distance (ρ = −0.81), number of accelerations (ρ = −0.94) and high-velocity running (ρ = −0.94), while in outside backs, RSA was associated with sprint frequency (ρ = −0.85) and the maximal in-game velocity reached (ρ = −0.89). These results demonstrate that RSA is associated with match running and combat activity performance (i) regardless of the position on the pitch and (ii) specifically for each player's position by improving the corresponding activity profile.

In-match physical demands on elite Japanese rugby union players using a global positioning system

ObjectivesOur aim of this study was to quantify the physical demands of elite rugby union players by each position as a step towards designing position-specific training programme using a Global...

Determinants of hamstring fascicle length in professional rugby league athletes

ObjectivesInvestigate the determinants of hamstring fascicle length in professional rugby league players. DesignRetrospective cohort study MethodsThirty-three elite male athletes underwent testing in the pre-season and in-season periods. Fascicle length measurements of the biceps femoris long head, 3D kinematics and elapsed time-periods at thigh angular velocities between 20°/s to peak velocity during a single-leg Nordic hamstring strength test, GPS-derived running loads, age and previous injury history were all recorded. Fixed effect determinants for fascicle length were analyzed using multiple linear regression. ResultsSignificant determinants of hamstring fascicle length were observed. Multivariate regression analysis showed modifiable factors including chronic (56 days) running volumes >80% of measured peak velocity and maximum velocity itself collectively explained 43% of the variability in the fascicle length data, whilst peak eccentric strength and elapsed time under load from 20°/s to peak thigh angular velocity collectively contributed an additional 44%. Chronic running volumes >90% of individually measured peak velocity and the ‘break angle’ during a Nordic eccentric contraction were not significant contributors to the final model. Non-modifiable risk factors (age and previous injury) contributed the remaining 13%. ConclusionsManaging high velocity running exposure as well as eccentric strength allows for ˜90% of the controllable determinants in fascicle length within elite athlete populations. An important contributor to the explained variability within fascicle length (superseded only by chronic velocity exposure and peak eccentric strength) was an athletes ability to achieve a prolonged contraction at long lengths during eccentric strength training rather than the angle of failure during the contraction in itself.

Repeated High-Intensity Effort Activity in International Male Rugby Sevens.

Couderc, A, Gabbett, TJ, Piscione, J, Robineau, J, Peeters, A, Igarza, G, Thomas, C, Hanon, C, and Lacome, M. Repeated high-intensity effort activity in international male Rugby Sevens. J Strength Cond Res 35(6): 1720-1726, 2023-Rugby Sevens is characterized by repeated high-intensity accelerations, sprinting, and collisions, commonly referred to as repeated high-intensity effort (RHIE) activity. Although repeated acceleration and sprinting activity of Rugby Sevens has been investigated, to date, no study has investigated the repeated running and collision activity of international Rugby Sevens during competitive events. In this study, 15 elite players competed in 44 matches during the HSBC World Sevens Series. Global positioning systems and match analysis software were used to quantify the frequency of repeated running and collision efforts. High acceleration (≥2.5 m·s -2 ), high speed (above maximal aerobic speed), sprint (above 85% of maximal sprint speed), and collision efforts (tackles, ruck, and contact) were considered as high-intensity effort activities. An RHIE bout was defined as 3 or more high-intensity efforts with less than 21 seconds recovery between efforts. The difference between positional groups (forward and backs) and first and second halves was compared using magnitude-based inferential statistics. One hundred twelve individual match observations were analyzed. On average, players performed 27 high-intensity effort events across the game. The distribution of high-intensity efforts included the following: 37% collisions, 34% accelerations, 27.5% high-velocity running, and 1.5% sprints. An average of 3.7 RHIE bouts was performed per player. The difference in high-intensity efforts and number of RHIE bouts performed were trivial/small when compared between first and second halves, and between forward and back positional groups. Repeated high-intensity effort bouts play an important role in the activity profile of elite Rugby Sevens players. This study could provide a framework for performance analysts and coaches to analyze match-related performance of elite Rugby Sevens players, taking into account both the high-intensity running and collision components of the game. Coaches should implement training interventions to ensure the maintenance of RHIE performance during competitive events.

Relationship Between Running Performance and Recovery-Stress State in Collegiate Soccer Players.

Coker, NA, Wells, AJ, Ake, KM, Griffin, DL, Rossi, SJ, and McMillan, JL. Relationship between running performance and recovery-stress state in collegiate soccer players. J Strength Cond Res 31(8): 2131-2140, 2017-The purpose of this study was to evaluate the relationship between changes in running performance and the stress-recovery state in collegiate soccer players. Running performance was evaluated in 7 National Collegiate Athletic Association Division I male soccer players (179.39 ± 5.24 cm; 75.46 ± 5.98 kg; 20.37 ± 1.41 years) through global positioning systems over the course of 12 competitive games in a single season. The regular season was divided into 4 competitive blocks: B1 (n = 3), B2 (n = 3), B3 (n = 3), and B4 (n = 3). Total distance and distance covered while engaging in walking, jogging, low-speed running, high-speed running, sprinting, low-intensity running, and high-intensity running were assessed during each block. The Recovery-Stress Questionnaire (RESTQ) 52 Sport was administered twice during each block to evaluate measures of stress and recovery. Total distance was greater during B4 compared with B1 (p = 0.027). Jogging and low-speed running were greater during B4 compared with all other time points (p's ≤ 0.05). Low-intensity running distance was greater during B4 compared with B1 (p = 0.034). Sport-specific recovery decreased significantly during B4 compared with B1 (p = 0.035). Correlational analysis indicated that high-velocity running was associated with increased stress, whereas low-velocity running was associated with greater recovery. However, changes in sport-specific recovery did not correlate with changes in running performance from B1 to B4. Results of this study indicate that running performance decreased across the season. Changes in running performance coincided with a decrease in sport-specific recovery. Practitioners may benefit from including the RESTQ as part of an assessment battery to monitor the stress/recovery state of athletes.

When Is a Sprint a Sprint? A Review of the Analysis of Team-Sport Athlete Activity Profile.

The external load of a team-sport athlete can be measured by tracking technologies, including global positioning systems (GPS), local positioning systems (LPS), and vision-based systems. These technologies allow for the calculation of displacement, velocity and acceleration during a match or training session. The accurate quantification of these variables is critical so that meaningful changes in team-sport athlete external load can be detected. High-velocity running, including sprinting, may be important for specific team-sport match activities, including evading an opponent or creating a shot on goal. Maximal accelerations are energetically demanding and frequently occur from a low velocity during team-sport matches. Despite extensive research, conjecture exists regarding the thresholds by which to classify the high velocity and acceleration activity of a team-sport athlete. There is currently no consensus on the definition of a sprint or acceleration effort, even within a single sport. The aim of this narrative review was to examine the varying velocity and acceleration thresholds reported in athlete activity profiling. The purposes of this review were therefore to (1) identify the various thresholds used to classify high-velocity or -intensity running plus accelerations; (2) examine the impact of individualized thresholds on reported team-sport activity profile; (3) evaluate the use of thresholds for court-based team-sports and; (4) discuss potential areas for future research. The presentation of velocity thresholds as a single value, with equivocal qualitative descriptors, is confusing when data lies between two thresholds. In Australian football, sprint efforts have been defined as activity >4.00 or >4.17 m·s−1. Acceleration thresholds differ across the literature, with >1.11, 2.78, 3.00, and 4.00 m·s−2 utilized across a number of sports. It is difficult to compare literature on field-based sports due to inconsistencies in velocity and acceleration thresholds, even within a single sport. Velocity and acceleration thresholds have been determined from physical capacity tests. Limited research exists on the classification of velocity and acceleration data by female team-sport athletes. Alternatively, data mining techniques may be used to report team-sport athlete external load, without the requirement of arbitrary or physiologically defined thresholds.

Soccer activity profile of altitude versus sea-level natives during acclimatisation to 3600 m (ISA3600)

ObjectivesWe investigated the effect of high altitude on the match activity profile of elite youth high altitude and sea level residents.MethodsTwenty Sea Level (Australian) and 19 Altitude-resident (Bolivian) soccer players...

Activity profiles of professional soccer, rugby league and Australian football match play

We compared the match activity profiles of elite footballers from Australian football (AF), rugby league (RL) and soccer (SOC), using identical movement definitions. Ninety-four elite footballers from AF, RL or SOC clubs in Australia participated in this study. Movement data were collected using a 5-Hz global positioning system from matches during the 2008–2011 competitive seasons, including measures of velocity, distance, acceleration and bouts of repeat sprints (RS). Australian footballers covered the greatest relative running distances (129 ± 17 m.min−1) compared to RL (97 ± 16 m.min−1) and SOC (104 ± 10 m.min−1) (effect size [ES]; 1.0–2.8). The relative distance covered (4.92 ± 2.10 m.min−1 vs. 5.42 ± 2.49 m.min−1; 0.74 ± 0.78 m.min−1 vs. 0.97 ± 0.80 m.min−1) and the number of high-velocity running (0.4 ± 0.2 no.min−1 vs. 0.4 ± 0.2 no.min−1) and sprint (0.06 ± 0.06 no.min−1 vs. 0.08 ± 0.07 no.min−1) efforts between RL and SOC players were similar (ES; 0.1–0.3). Rugby league players undertook the highest relative number of accelerations (1.10 ± 0.56 no.min−1). RS bouts were uncommon for all codes. RL and SOC players perform less running than AF players, possibly due to limited open space as a consequence of field size and code specific rules. While training in football should be code specific, there may be some transference of conditioning drills across codes.

Lower Running Performance and Exacerbated Fatigue in Soccer Played at 1600 m

This study investigated the decrement in running performance of elite soccer players competing at low altitude and time course for abatement of these decrements. Twenty elite youth soccer players had their activity profile, in a sea-level (SL) and 2 altitude (Alt, 1600 m, d 4, and d 6) matches, measured with a global positioning system. Measures expressed in meters per minute of match time were total distance, low- and high-velocity running (LoVR, 0.01-4.16 m/s; HiVR, 4.17-10.0 m/s), and frequency of maximal accelerations (>2.78 m/s2). The peak and subsequent stanza for each measure were identified and a transient fatigue index calculated. Mean heart rate (HR) during the final minute of a submaximal running task (5 min, 11 km/h) was recorded at SL and for 10 d at Alt. Differences were determined between SL and Alt using percentage change and effect-size (ES) statistic with 90% confidence intervals. Mean HR almost certainly increased on d 1 (5.4%, ES 1.01 ± 0.35) and remained probably elevated on both d 2 (ES 0.42 ± 0.31) and d3 (ES 0.30 ± 0.25), returning to baseline at d 5. Total distance was almost certainly lower than SL (ES -0.76 ± 0.37) at d 4 and remained probably reduced on d 6 (ES -0.42 ± 0.36). HiVR probably decreased at d 4 vs SL (-0.47 ± 0.59), with no clear effect of altitude at d 6 (-0.08 ± 0.41). Transient fatigue in matches was evident at SL and Alt, with a possibly greater decrement at Alt. Despite some physiological adaptation, match running performance of youth soccer players is compromised for at least 6 d at low altitude.

Widening margin in activity profile between elite and sub-elite Australian football: A case study

It is not known if the activity profile of elite Australian football players changes across two levels of competition. The aims of this study were therefore to: (1) classify the activity profile of elite and sub-elite Australian football for players from one elite Australian football club; and (2) compare the activity profile of elite footballers across both elite and sub-elite competitions. Quantitative case-study approach. Movement was recorded by 5Hz global positioning system and expressed relative to game time for total; and high-velocity running distance (4.17-10.00ms(-1)) and maximal accelerations (2.78-10.00ms(-2)). The difference was expressed as a percentage and effect size statistic with confidence intervals. Elite Australian football players had 8% greater total 11% more high intensity running; and 16% more maximal accelerations during matches in 2009 compared to 2008. Players at a sub-elite level had no change in total; 9% less high intensity running but 23% greater maximal accelerations during the same period. In 2008 there was a 5% lower total covered by players in sub-elite competition; no difference in high intensity running; and 28% less maximal accelerations compared to elite. In 2009 the gap was larger for distance of running as sub-elite had 15% less total and 20% less high intensity running than elite. Similar to 2008, sub-elite players had 23% less maximal accelerations in 2009. The activity profile of players in the elite competition has increased over these two seasons, but not in the sub-elite. This has implications for teams where players must move between competitions during the season.

Acceleration Profiles in Elite Australian Soccer

We quantified the acceleration and high-velocity running of elite Australian soccer players. We hypothesised that high-intensity activity would be underestimated when excluding acceleration during match analysis given its high metabolic demand and occurrence at low velocities. Player movements were observed from 29 players (forwards and central and wide defenders and midfielders) during domestic Australian competition using 5-Hz global positioning system. Effort occurrence were determined for high-velocity running, sprinting and maximal accelerations. The commencement and final velocity of maximal accelerations were also identified. Players undertook an 8~fold greater number of maximal accelerations than sprints per game (65±21 vs. 8±5). Of maximal accelerations ~98% commenced from a starting velocity lower than what would be considered high-velocity running while ~85% did not cross the high-velocity running threshold. The number of efforts performed in all categories were position dependent (P<0.001). Wide defenders performed more maximal accelerations (P<0.006) and central defenders and midfielders performed less sprints compared to all other positions (P<0.02). Maximal accelerations are frequently undertaken during a match often occurring at low velocities. Excluding maximal accelerations in match analysis research may underestimate the amount of high-intensity movements undertaken. Additionally positional differences in high-intensity movements should be accounted for when developing specific conditioning drills.

Current Match-Analysis Techniques’ Underestimation of Intense Periods of High-Velocity Running

To compare the peak 5-min period of high-velocity running (HiVR) during a soccer match using a predefined vs a rolling time interval. Player movement data were collected from 19 elite Australian soccer players over 11 competitive matches (77 individual match files) using a 5-Hz global-positioning system. Raw velocity data were analyzed to determine the period containing the greatest HiVR distance per match half and the distance covered in the subsequent epoch. Intervals were identified using either a predefined (distance covered in 5 min at every 5-min time point) or rolling (distance covered in 5 min from every time point) method. The percentage difference ± 90% confidence limits were used to determine differences between methods. Predefined periods underestimated peak distance covered by up to 25% and overestimated the subsequent epoch by up to 31% compared with rolling periods. When the distance decrement between the peak and following period was determined, there was up to a 52% greater reduction in running performance using rolling periods than predefined ones. It is recommended that researchers use rolling as opposed to predefined periods when determining specific match intervals because they provide a more accurate representation of the HiVR distance covered. This will avoid underestimation of both match running distance and the decrement in running performance after an intense period of play. This may have practical implications for not only researchers but also staff involved in a club setting who use this reduction as evidence of transient fatigue during a match.

Relationship Between Running Loads and Soft-Tissue Injury in Elite Team Sport Athletes

Although the potential link between running loads and soft-tissue injury is appealing, the evidence supporting or refuting this relationship in high-performance team sport athletes is nonexistent, with all published studies using subjective measures (e.g., ratings of perceived exertion) to quantify training loads. The purpose of this study was to investigate the risk of low-intensity (e.g., walking, jogging, total distances) and high-intensity (e.g., high acceleration and velocity efforts, repeated high-intensity exercise bouts) movement activities on lower body soft-tissue injury in elite team sport athletes. Thirty-four elite rugby league players participated in this study. Global positioning system data and the incidence of lower body soft-tissue injuries were monitored in 117 skill training sessions during the preseason and in-season periods. The frailty model (an extension of the Cox proportional regression model for recurrent events) was applied to calculate the relative risk of injury after controlling for all other training data. The risk of injury was 2.7 (95% confidence interval 1.2-6.5) times higher when very high-velocity running (i.e., sprinting) exceeded 9 m per session. Greater distances covered in mild, moderate, and maximum accelerations and low- and very low-intensity movement velocities were associated with a reduced risk of injury. These results demonstrate that greater amounts of very high-velocity running (i.e., sprinting) are associated with an increased risk of lower body soft-tissue injury, whereas distances covered at low and moderate speeds offer a protective effect against soft-tissue injury. From an injury prevention perspective, these findings provide empirical support for restricting the amount of sprinting performed in preparation for elite team sport competition. However, coaches should also consider the consequences of reducing training loads on the development of physical qualities and playing performance.

Can application of a pelvic belt change injured hamstring muscle activity?

Hamstring injuries are commonly reported in various sports involving sprinting, high-velocity running and kicking. Aberrant biomechanics and neuromotor control of the lumbopelvic and thigh segments have been reported to play a significant role in hamstring injury incidence and recurrence. Recent evidence suggests that external pelvic compression (EPC) applied with a pelvic belt can augment the stability of the pelvic joints, and alter neuromotor control of the lumbopelvic and thigh muscles in individuals with and without (somatic) lumbopelvic and groin dysfunction. However, the effects of EPC on neuromotor control of injured hamstring muscles remain unknown. We have explored the putative neuromotor link between the lumbopelvic segment and hamstring muscles, and generated hypotheses based on plausible mechanisms through which EPC could affect injured hamstring muscle strength and recruitment. Recent guidelines argue that rehabilitation of hamstring injuries should follow a multi-modal approach and include strategies to improve stability and neuromotor control of the lumbopelvic segment. Further investigations exploring these hypotheses would confirm whether EPC could be recommended as an assessment, intervention and rehabilitation tool for hamstring injury.

The Effect of Proprioceptive Neuromuscular Facilitation and Static Stretch Training on Running Mechanics

Caplan, N, Rogers, R, Parr, MK, and Hayes, PR. The effect of proprioceptive neuromuscular facilitation and static stretch training on running mechanics. J Strength Cond Res 23(4): 1175-1180, 2009-There is a long-standing belief that increased range of movement (RoM) at the hip or knee will improve running mechanics; however, few studies have examined the effect of such an increase in RoM. The aim of this study was to determine the influence of 2 methods of stretch training (static and proprioceptive neuromuscular facilitation [PNF]) on high-velocity running. Eighteen rugby league players were assessed for maximum sprinting velocity. They were randomly allocated into 2 stretch training groups: PNF or static. Each group trained their hamstrings 4 d x w(-1) for 5 weeks. Pre- and posttraining subjects were videoed while running at 80% of maximum velocity. The video was digitized to identify biomechanical changes in hip flexion (HF), knee extension (KE), stride length (SL), stride rate (SR), and contact time (tc). Stretch training resulted in gains (p < 0.05) in HF for the static stretch (SS) (4.9%) and PNF (7.6%) groups. There were reductions in KE (p < 0.05) for SS (1.0%) and PNF (1.6%) groups. Stride mechanics were also altered after training. There were increases in SL (p < 0.05) for SS (7.1%) and PNF (9.1%) and a concomitant reduction in SR (p < 0.05) for SS (1.9%) and PNF (4.3%). No changes were observed in tc in either group. In conclusion, both SS and PNF training improved HF RoM and running mechanics during high-velocity running. These findings suggest that stretch training undertaken at the end of regular training is effective in changing running mechanics.

Effect of altitude on football performance

Altitude will impact football performance through two separate and parallel pathways related to the hypobaric (physical) and hypoxic (physiological) components of terrestrial altitude: (a) the decrease in partial pressure of oxygen reduces maximal oxygen uptake and impairs "aerobic" performance by reducing maximal aerobic power, increasing the relative intensity of any given absolute level of work, and delaying recovery of high-energy phosphates between high-intensity "interval" type efforts; (b) the decrease in air density reduces air resistance which will facilitate high-velocity running, but will also alter drag and lift thereby impairing sensorimotor skills. These effects appear to have their greatest impact very early in the altitude exposure, and their physiological/neurosensory consequences are ameliorated by acclimatization, though the extent of restoration of sea level type performance depends on the absolute magnitude of the competing and living altitudes.