Physical Demands of Elite Women's Ultimate Frisbee Between Halves and Across Matches in an International Tournament.

ABSTRACT: Palmer, JA, Landers, G, Buttfield, A, and Polglaze, T. Physical demands of elite women's Ultimate Frisbee between halves and across matches in an international tournament. J Strength Cond Res 36(3): 838-844, 2022-To quantify the physical match demands of elite women's Ultimate Frisbee across a tournament, elite female Ultimate players (N = 9) from the Australian Under 24 Women's team wore global positioning system units in all 12 matches of the 2018 Under 24 World Championship competition. Temporal, displacement, and energetic parameters were obtained. Distribution of activity above and below a generic speed threshold (12.42 km·h-1) and its equivalent metabolic power value (16.02 W·kg-1) were determined. Players spent 12:44 ± 6:41 min:s on the field, covered 1,559 ± 741 m and expended 8.95 ± 4.21 kJ·kg-1 during a match. The mean stint duration was 2:00 ± 0:48 min:s, mean bench duration was 13:25 ± 7:05 min:s, and work-to-recovery ratio was 0.22 ± 0.11. Players performed 57 ± 27 high-speed runs per match and 45 ± 20 high-accelerations. Mean match speed was 127 ± 18 m·min-1, mean metabolic power was 12.2 ± 1.7 W·kg-1, and mean intermittency index was 1.24 ± 0.04. No differences were found between halves for any parameters. Compared with the first 4 matches, the last 4 matches were shorter and more intense (p < 0.05). At the international level, Ultimate is an intense and highly intermittent sport, characterized by brief playing stints interspersed with long periods of recovery, which allow playing intensity to be maintained throughout a match and elevated in the latter stages of a tournament. The information gained from this research can be used to guide the creation of Ultimate-specific conditioning programs for elite female players.

Reliability and Validity of the Polhemus Liberty System for Upper Body Segment and Joint Angular Kinematics of Elite Golfers.

Golf swing analysis is common in both recreational and professional levels where players are searching for improvements in shot accuracy and distance. The use of motion analysis systems such as the portable Polhemus Liberty system is gaining interest by coaches and players; however, to date, no research has examined the usefulness of the Polhemus Liberty system for golf swing analysis. Therefore, the purpose of this study was to determine the reliability of the Polhemus Liberty system and validity compared to the VICON Nexus motion analysis system when assessing segment (pelvis and thorax) and joint (shoulder, elbow and wrist) angular kinematics during a golf swing at key events (address, top of backswing and impact). Fifteen elite amateur/professional golfers performed ten golf swing trials within specified bounds using their 5-iron club. Reliability was assessed using interclass coefficient, effect size and t-test statistics by all participants completing two separate testing sessions on separate days following the same experimental protocol. Validity was assessed using effect size, Pearson correlation and t-test statistics by comparing swings captured using both Polhemus Liberty and VICON Nexus concurrently. Results demonstrated no difference in ball outcome results using the Trackman launch monitor (P > 0.05) and that the Polhemus Liberty system was reliable across the two sessions for all segment (pelvis and thorax) and joint (lead shoulder (gleno-humeral joint), elbow and wrist) angular kinematics (P > 0.05). Validity analysis showed that the Polhemus Liberty system for the segments (pelvis and thorax) and joints (lead shoulder and wrist) were different compared to the VICON Nexus data at key events during the golf swing. Although validity could not be confirmed against VICON Nexus modeling, the Polhemus Liberty system may still be useful for golf swing analysis across training sessions. However, caution should be applied when comparing data from the system to published research data using different motion analysis methods.

Using the interaction of speed and acceleration to detect repeated-sprint activity in team sports.

PURPOSE: To compare the occurrence and characteristics of repeated-sprint (RS) activity in elite team sport competition when classified according to speed and/or acceleration, and their interaction via metabolic power (Pmet). Methods: Elite male hockey players (N = 16) wore player-tracking devices in six international matches. Sprint efforts were defined using four separate classifications: speed >5.5 m∙s-1, acceleration >1.5 m∙s-2, speed-or-acceleration, and Pmet >25.5 W∙kg-1. RS bouts were defined as ≥3 efforts with mean recovery ≤21 s. For Pmet, RS bouts were also classified using a maximal recovery period ≤21 s. The number of sprint efforts and RS bouts, and the number of efforts, effort durations and recovery periods within RS bouts, were compared across each classification method, and between mean and maximal recovery criteria. Results: More RS bouts were identified via Pmet (8.5 ± 2.8) than either speed and/or acceleration, and comprised more efforts (4.0 ± 0.4) with shorter recovery periods (11.5 ± 1.8 s). Fewer RS bouts (7.3 ± 2.8 vs. 8.5 ± 2.8) were identified with a maximum rather than mean recovery criterion. Conclusions: Definitions of sprint efforts and recovery periods which reflect ATP depletion and replenishment via Pmet suggest that RS activity occurs frequently in team sport competition, and is more demanding than when speed and/or acceleration are used to define RS activity in variable-speed locomotion.

The practical application of a method of analysing the variability of within-step accelerations collected via athlete tracking devices.

Resolving intra-stride accelerations from training and game data routinely collected by athlete tracking devices is rarely attempted, even though these data can provide important insights into the physical condition of athletes. This study describes in detail a novel analysis tool which uses accelerometer-based measures of step variability to assess longitudinal consistency of stride technique. The performance of the analysis tool was examined by combining results from the analysis of data collected over the course of an Australian Football League season with instances of missed or modified training. Results demonstrated increased gait-related trunk acceleration variability when training was modified due to load or accumulated game and training activity (p = 0.02) and reduced trunk acceleration variability in the week following a training modification due to any injury described as "ankle", "heel", or any other description that would loosely refer to a joint or bone in the leg (p = 0.01). These results support the findings of recent research which used a slightly modified version of the same analysis tool to demonstrate an increase in gait-related trunk acceleration variability with the increased acute physical load.

Variability of within-step acceleration and daily wellness monitoring in Collegiate American Football.

OBJECTIVES: It is commonplace to consider accelerometer load and any resultant neuromuscular fatigue in training programs. With these data becoming accepted in sport alongside wellness questionnaires this study aimed to investigate if a deeper analysis of the accelerometry data can provide actionable insight into training-induced disruptions. DESIGN: Accelerometer data from Collegiate American Football athletes (n=63) were collected during training and matches across a regular season. METHODS: These data were processed to: identify instances of high speed running, extract step waveforms from those sections, and determine the variability of those waveforms via a within- and between-section co-efficient of multiple determination. Athletes completed wellness questionnaires prior to sessions that were used to flag areas of muscle soreness as well as fatigue, or disturbed sleep quality. Linear mixed models were used to assess associations between inter stride variability and flags in wellness/soreness markers. RESULTS: An increase in acute (7d) load saw an increased stride variability in these athletes. Feeling less fatigued and/or lower muscle soreness was associated with higher stride variability. CONCLUSIONS: The assessment of variability has the potential to identify athletes who are displaying physical symptoms that would indicate the need to modify training.

Classification of Intensity in Team Sport Activity.

PURPOSE: This study aimed to assess the efficacy of critical metabolic power derived from variable-speed movement for classifying intensity in team sport activity. METHODS: Elite male hockey players (n = 12) completed a series of time trials (100 yards, 400 yards, 1500 yards) and a 3-min all-out test to derive both critical speed (CS) and critical power (CP). Heart rate (HR), blood lactate, and rating of perceived exertion were measured during each protocol. Participants (n = 10) then played two competitive hockey matches. Time spent greater than 85% of maximum HR was compared with time spent above CS (from the time trials) and CP (from the 3-min test). RESULTS: Between protocols, there was a moderate and nonsignificant association for CS (r = 0.359, P = 0.252) and a very large association for CP (r = 0.754, P = 0.005); the association was very large for peak HR (r = 0.866, P < 0.001), large for blood lactate (r = 0.506, P = 0.093), and moderate for rating of perceived exertion (rho = 0.441, P = 0.152). Time trials produced higher CS (4.3 vs 2.0 m·s, P < 0.001) and CP (18.3 vs 10.5 W·kg, P < 0.001) values than did the 3-min test. In matches, there was a very large association between time spent above 85% of maximum HR and time spent above both CS (r = 0.719, P < 0.001) and CP (r = 0.867, P < 0.001). This relationship was stronger for CP compared with CS (Z = 3.29, P = 0.0007). CONCLUSIONS: Speed is not an appropriate parameter for the classification of team sport activity comprising continual changes in speed and direction; however, critical metabolic power derived from variable-speed activity seems useful for this purpose.

Metabolic power and energy expenditure in an international men's hockey tournament.

The purpose of this study was to ascertain the typical metabolic power characteristics of elite men's hockey, and whether changes occur within matches and throughout an international tournament. National team players (n = 16), divided into 3 positional groups (strikers, midfielders, defenders), wore Global Positioning System devices in 6 matches. Energetic (metabolic power, energy expenditure) and displacement (distance, speed, acceleration) variables were determined, and intensity was classified utilising speed, acceleration and metabolic power thresholds. Midfielder's average metabolic power (11.8 ± 1.0 W · kg-1) was similar to strikers (11.1 ± 1.3 W · kg-1) and higher than defenders (10.8 ± 1.2 W · kg-1, P = 0.001). Strikers (29.71 ± 3.39 kJ · kg-1) expended less energy than midfielders (32.18 ± 2.67 kJ · kg-1, P = 0.014) and defenders (33.23 ± 3.96 kJ · kg-1, P < 0.001). Energetic variables did not change between halves or across matches. Across all positions, over 45% of energy expenditure was at high intensity (>20 W · kg-1). International hockey matches are intense and highly intermittent; however, intensity is maintained throughout matches and over a tournament. In isolation, displacement measures underestimate the amount of high-intensity activity, whereas the integration of instantaneous speed and acceleration provides a more comprehensive assessment of the demands for variable-speed activity typically occurring in hockey matches.

Muscle pre-activation strategies play a role in modulating Kvert for change of direction manoeuvres: an observational study.

The aim of the study presented in this paper was to establish if a relationship existed between lower limb muscle pre-activation strategies and vertical stiffness (Kvert). Participants from a professional rugby union club all performed a multidirectional hopping task on a force platform which measured Kvert. Muscle activity was concurrently measured for the gluteus maximus, vastus lateralis, vastus medialis, biceps femoris, semimembranosus, and medial gastrocnemius using electromyography and the activity of those muscles in the 100ms prior to foot contact (pre-activation) was analysed. Moderate to strong positive relationships were typically seen for Kvert and muscle pre-activation for each muscle when normalized to maximum voluntary contraction. Pre-activation cocontraction of the muscles surrounding the knee joint also showed a typically moderate relationship with Kvert and peak muscle activation of antagonist muscles at the knee joint were typically similar. Results suggest that muscle pre-activation strategies play a role in modulating Kvert for change of direction manoeuvre.

Characteristics of anterior cruciate ligament injuries in Australian football.

Anterior cruciate ligament (ACL) injuries are the most costly injuries in football at both professional and amateur levels (Orchard J, Seward H, McGivern J, Hood S. Intrinsic and extrinsic risk factors for anterior cruciate ligament injury in Australian footballers. Am J Sports Med 2001;29:196-200.). In this study video analysis of 34 ACL injuries in Australian football was performed to investigate the causes of these injuries. Factors that may have contributed to the cause of the injury were analysed, rated and reported. The factors analysed were: type of manoeuvre, direction the knee 'gave way', running speed, knee angle, cutting angle and if the player was accelerating or decelerating. The majority of the injuries analysed occurred in non-contact situations (56%). Of these 37% occurred during sidestepping manoeuvres, 32% in landing, 16% land and step, 10% stopping/slowing and 5% crossover cut manoeuvres. Ninety-two percent of the non-contact injuries occurred at extended knee angles of 30 degrees or less, which is also commonly known to place stress on the ACL and reduce the protective role of hamstrings. Over half (54%) of non-contact injuries occurred whilst decelerating. It would be expected that greater speed and angle cut too would increase the frequency of ACL injury. The results could not confirm this with most injuries occurring at running speeds of slow jogging to running and equal number of injuries occurred at cutting to angles of the ranges 15-45 degrees and 45-75 degrees. These results give greater understanding into potential causes or contributors of ACL injury and information to assist in the development of knee injury prevention programs.