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The effects of dormant season burning and flooding on invasive cattail, Typha x glauca, on Rainy Lake and Lake Kabetogama in Northern Minnesota
Get PDFTypha x glauca is one of the most invasive plants in North America. The plant exhibits hybrid vigor and displaces native flora by rapidly forming dense monotypic stands that can break free from the substrate and form floating mat types when established. I tested the effects of prescribed burning, on Typha x glauca in wetlands to adjacent large lakes in Voyageurs National Park in northern Minnesota. My team surveyed four wetlands that were burned in late winter of 2020-21, and six that were unburned controls. Pre-burn data was also collected for all ten wetlands. Pre-flooding data from other wetlands within the Park were used to compare and highlight the impacts of the historic flood of 2022 on Typha x glauca. Changes in percent cover of Typha were not significantly different between burned and unburned wetlands (P=0.85). Typha dropped for both treatments by about 50%. In spring of 2022, the study area was impacted by the greatest flood on historical record, so I took advantage of preflood data to examine how flooding alone affected Typha cover. Mean cover of Typha on floating mats was not significantly different from 2021 to 2022 (P\u3e0.05). However, cover on non-floating mats dropped by 62.4% in 2022 (PTypha x glauca. The 2022 flood only reduced cover on non-floating mats, so manipulating water levels is not likely to eradicate invasive Typha x glauca long term
THE EFFECT OF STEP RATE TRAINING ON RUNNING ECONOMY AND BIOMECHANICS
Get PDFIt is known that running economy is a determinant of running performance. Increased step rate has been correlated with improved running economy, but it is unknown whether these improvements can be maintained with chronic training. The purpose of this study was to determine if a step rate training intervention improves running economy and improves lower body kinetic factors in distance runners. Nine participants were randomly assigned to either an intervention group (n = 7) undergoing a 6-week supplemental training program, or a non-training control group (n = 2). The intervention group trained three times a week, running at a higher percentage, 2-8% of their preferred step rate at their individual submaximal pace. VO2peak, running economy, 5km performance time, peak vertical GRF (Fz), peak braking force (Fy), and loading rates (vertical impact peak, vertical average loading rate, and vertical instantaneous load rate) were measured before and after training. The intervention and the control group resulted in no significant change (p \u3e 0.05) in any variables. There was a positive trend with the intervention group with VO2peak (p = 0.056). This aligns with previous research indicating that step rate manipulation may not significantly impact on running economy; however, no significant change in loading rates contradicted previous research findings. The implications of the findings suggest that step rate training intervention may not lead to significant improvements in running economy or lower limb kinetic factors in distance runners
SIMPLIFYING THE HIGH-PERFORMANCE BIOMECHANICAL ASSESSMENT OF HIGH JUMP TECHNIQUE
Get PDFA multitude of technical performance parameters are used to quantify high jump technique in the Australian high-performance environment, which can be time-consuming to measure and interpret. The purpose of this study was to investigate the efficacy of principal component analysis and stepwise multiple linear regression to simplify high-performance high jump biomechanical reports. Five non-intuitive principal components were derived, and three technical performance parameters (difference in knee angles during take-off contact, lean angle through hip at take-off contact, take-off foot contact time) influenced the height cleared by elite high jump athletes. This study establishes a method for simplifying high jump biomechanical reports and identifies the most important variables that contribute to high jump success
THE ACUTE EFFECTS OF A GRIP-CONSTRAINT TOOL ON UPPER BODY AND RACKET KINEMATICS DURING TENNIS FOREHANDS
Get PDFThe purpose of this study was to compare the acute effect of a grip-constraint tool on upper body and racket kinematics during tennis single-handed forehand strokes. Upper-body and racket kinematics for two grip conditions, Preferred (self-selected) and Grip-constraint tool (fixed semi-western forehand grip) were captured for eleven tennis players using a 22-camera Vicon motion capture system (240 Hz). Using a grip-constraint tool resulted in a more closed racket face tilt (~4°) at ball impact while having variations in joint rotations across the shoulder, elbow and wrist. This possibly demonstrates the participant’s ability to self-organise compensatory angular rotations across the upper limb to achieve similar impact orientations. Collectively, these data demonstrate the acute responses to modifying grip technique using a grip-constraint tool during single-handed down-the-line forehands
IS LATERAL ENTRY BENEFICIAL TO ELITE SWIMMERS? A PRELIMINARY STUDY
Get PDFThe purpose of this study was to improve performance of elite swimmers during the starting phase, by analysing whether the lateral entry technique is beneficial to athletes\u27 starting. Participants’ (N=12) motion data were obtained from a 3D Performance Analysis System (Kistler 9691A1) with three cameras. Extracted 14 parameters were analysed using paired samples t-test. Differences contributing to the lateral entry performance included decrease of both entry angle and maximum depth by 1° and 0.42 m respectively (p\u3c.01), and increase of push force by 0.08 of body weight (p\u3c.01). The preliminary results show that the lateral technique provides a 0.06 s reduction in time to reaching the first 5 m (p\u3c.05) compared to ordinary entry, suggesting performance improvements at start times
THE EFFECTS OF KNEE BRACING ON REACTIVE AGILITY PERFORMANCE AND EMG ACTIVITY IN HEALTHY SOCCER PLAYERS – A PILOT STUDY
Get PDFThis pilot study examined differences between braced and non-braced soccer players on measures of reactive agility time and electromyographic (EMG) activity of the gluteus medius (GM), biceps femoris (BF), and vastus lateralis (VL) muscles during the acceleration and change of direction phases of the Y-shaped reactive agility test. Twenty-four participants completed a Y-shaped reactive agility test under two conditions including wearing no knee brace and wearing a Playmaker II knee brace (DonJoy®, Lewisville, Texas) on their dominant leg. Although higher muscle activation was found in the GM and BF muscles during the change of direction phase compared to the acceleration phase, bracing did not statistically significantly affect agility time and EMG muscle activity. This outcome suggests that preventative bracing does not seem to hinder an athlete’s performance
INTER-JOINT DIFFERENCES EXIST IN KINETIC DEMAND FOR PERFORMANCE IN HIGH JUMP
Get PDFWe aimed to clarify the lower-limb kinetic determinants of inter-individual variability in flight height in the high jump. We hypothesised that although the take-off of the high jump requires great external power, the proximal (hip) joint is required to function as a stabiliser rather than as a power generator for higher performance. We analysed high jump motions by 16 male high jumpers. For the hip joint, only maximum torque significantly correlated with the flight height. Meanwhile, for the knee joint, both peak positive power and peak torque were correlated with the flight height, with a stronger correlation for power than for torque. We found that the kinetic requirement for performance differs between joints, which provides the practical implication that the musculoskeletal functions to be trained differ between joints, such as torque exertion for the hip and power exertion for the knee
EFFECTS OF VIBRATION COMBINED WITH UNSTABLE SURFACE TRAINING ON SOMERSAULT ATHLETIC PERFORMANCE OF ARTISTIC GYMNASTS
Get PDFPurpose: The effect of 4 and 8 weeks of combined training on the somersault performance of artistic gymnasts. Methods: 16 male college gymnasts were randomly paired and divided into combined (CT) and vibration (VT) groups for eight weeks of training. One force plate was used to collect the front and back somersault data before, after four, and eight weeks of training. The significance level was set at α = .05. Results: Back somersault, the take-off force and somersault height of CT were better than pre-test, and the somersault height was better than VT. Front somersault, the take-off force, impulse, and somersault height of CT are better than pre-test, and the somersault height and take-off force are better than VT. Conclusion: The four and eight weeks of vibration combined with unstable surface training can improve the performance of front and back somersaults
IMPULSE GENERATION AND INITIAL VELOCITY DIFFERENCES IN TWO-FOOT RUNNING JUMPS WITH AND WITHOUT A BASKETBALL
Get PDFThis study aimed to (1) identify the roles of each leg in impulse generation and (2) determine differences in impulse generation and initial centre of mass velocities in two-foot running jumps with and without a ball. Eight recreational to collegiate basketball players performed three to ten repetitions of two-foot running jumps with and without a ball. We found that the first leg generated more backward and vertical impulse than the second leg in both two-foot running jumps with and without a basketball. Two-foot running jumps with a ball resulted in lower jump height and less vertical impulse generated by the second leg vs. jumps without a ball. These different impulse generation strategies and jump heights when jumping with a ball prompt further research to uncover why there are differences and which training practices can address the differences and lead to higher jump heights with a ball
PAIN OR NO PAIN – THE KINEMATIC CONSEQUENCES IN OVERHEAD THROWING WITHIN TEAM HANDBALL – A CASE STUDY
Get PDFOveruse injuries are unfortunately common in team handball. Non-optimal throwing kinematic is considered a risk factor in overhead sports, but no investigation has been presented if pain influence throwing kinematics or how it may affect the technique in an overhead throw in team handball players. The aim of the study was to investigate the impact of shoulder pain on throwing kinematics and neuromuscular activity within a female elite handball player – playing with shoulder pain and 4 years later, without shoulder pain. The main findings were that the maximal shoulder extension (8.9°), abduction (5.2°) and internal rotation (27.7°) increased in the no pain condition, while the highest muscular peak was found in the pain period for upper, middle and lower trapezius and in serratus anterior in the no pain condition