Browsing by Author "Jordan, Matthew"

Now showing 1 - 6 of 6
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    An Assessment of Detrended Fluctuation Analysis (Alpha 1) in Demarcating Exercise Intensity, Quantifying Training Load, and Predicting Performance
    (2023-12-21) Ajayi, Oluwatimilehin Olamilekan; MacInnis, Martin; Jordan, Matthew; Holash, John
    The short-term scaling exponent of detrended fluctuation analysis (DFA α1) can be used to measure exercise stress in humans. Based initially on theoretical knowledge, it was suggested that DFA α1 values of 0.75 and 0.5 aligned with the aerobic (i.e., gas exchange threshold (GET)) and anaerobic thresholds (i.e., respiratory compensation point (RCP)), respectively. Regarding constant work rate (CWR) exercise, DFA α1 has been studied while cycling at a fixed intensity with varied cadence. Accordingly, this study aimed to determine the utility and reliability of DFA α1 during ramp incremental (RI; phase one) and CWR exercise (phase two). Twenty (10M, 10F) and fifteen (10M and 5F) healthy recreationally active individuals participated in phases one and two of the project, respectively. Although not different between fast (25 W·min-1; FR) and slow (12.5 W·min-1; SR) RI tests (p=0.192), DFA α1 values at GET (FR: 1.18±0.40; SR: 1.32±0.42) were significantly larger than 0.75 (p<0.001). DFA α1 values at RCP were significantly larger than 0.5 in the slow ramp (0.64±0.24; p=0.020) and were significantly greater compared to the fast ramp (0.54±0.23; p=0.029). DFA α1 values at GET and RCP had moderate (ICC=0.654; p=0.429) and poor reliability (ICC=0.401; p=0.169), respectively. DFA α1 values decreased during 20-min of CWR exercise (p<0.001), with significant differences between the first and last 5 min (0.84±0.23 vs. 0.58±0.22; p=0.003), and DFA α1 was lower in the final 5 min of the second 20-min (0.44±0.14) compared to the final 5 min of the first 20-min (0.57±0.20) of a 40-min CWR bout (p=0.002). DFA α1 at the same relative moderate intensity of exercise (65% GET) declined during each bout, with the lowest values observed after time to task failure tests (p<0.05). This thesis adds to the growing body of work surrounding the use of heart rate variability metrics, specifically DFA α1, during exercise, but these mixed results highlight the need for additional research on DFA α1 values during various exercise protocols.
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    Lower Limb Asymmetry in Mechanical Muscle Function: A Comparison Between Ski Racers With and Without ACL Reconstruction
    (Scandinavian Journal of Medicine and Science in Sports, 2016) Herzog, Walter; Jordan, Matthew; Aagaard, Per
    Due to a high incidence of anterior cruciate ligament (ACL) re-injury in alpine ski racers, the aim was to assess functional asymmetry in the countermovement jump (CMJ), squat jump (SJ) and leg muscle mass in elite ski racers with and without anterior cruciate ligament reconstruction (ACL-R). Elite alpine skiers with ACL-R (n=9; 26.2±11.8 months post-op) and uninjured skiers (n=9) participated in neuromuscular screening. Vertical ground reaction force during the CMJ and SJ was assessed using dual force plate methodology to obtain phase-specific bilateral asymmetry indices (AI) for kinetic impulse (CMJ and SJ phase-specific kinetic impulse AI). Dual X-Ray absorptiometry (DXA) scanning was used to assess asymmetry in lower body muscle mass. Compared to controls, ACL-R skiers had increased AI in muscle mass (P<0.001), kinetic impulse AI in the CMJ concentric phase (P<0.05) and the final phase of the SJ (P<0.05). Positive associations were observed between muscle mass and AI in the CMJ concentric phase (r=0.57, P<0.01) as well as in the late SJ phase (r=0.66, P<0.01). Future research is required to assess the role of the CMJ and SJ phase-specific kinetic impulse asymmetry index as a part of a multi-faceted approach for improving outcome following ACL-R in elite ski racers.
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    Rapid Hamstring/Quadriceps Strength in ACL Reconstructed Elite Alpine Ski Racers
    (Medicine and science in sports and exercise, 2016) Herzog, Walter; Jordan, Matthew; Aagaard, Per
    Due to the importance of hamstrings (HAM) and quadriceps (QUAD) strength for anterior cruciate ligament (ACL) injury prevention, and the high incidence of ACL injury in ski racing, HAM and QUAD maximal and explosive strength was assessed in ski racers with and without ACL reconstruction (ACL-R).
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    A Return to Skiing Envelope of Function for Anterior Cruciate Ligament Reconstructed Elite Alpine Ski Racers
    (Science and Skiing VI, 2016) Herzog, Walter; Jordan, Matthew; Aagaard, Per
    Elite alpine ski racing comprises bidirectional turning with forceful concentric but predominantly eccentric contractions that create large quadriceps muscle loading and hamstrings/quadriceps muscle co-contraction (4, 10). Ski racing also occurs in an unpredictable environment where skiers are at an increased risk for lower body injury, especially to the knee joint and the anterior cruciate ligament (ACL) (2, 3, 8, 15). Unlike field sports, there are no sex-differences in ACL injury rates due to the preclusion of sex-related risk factors resulting from the large forces and unique mechanisms of ACL injury (8, 15).
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    The Influence of Lateral Wedged Insoles on the Performance of Basketball-Specific Movements
    (2023-09-21) Crawford, Reyna Cyan; Stefanyshyn, Darren; Edwards, William Brent; Ferber, Reed; Pasanen, Kati; Jordan, Matthew
    Basketball is a dynamic sport known for its fast-paced and multidirectional nature. The implementation of banking mechanisms has demonstrated performance enhancements and the potential to mitigate ankle and knee injury risks during non-linear movements. However, existing banking mechanisms used in a sport setting are often impractical for basketball. Lateral wedged insoles may be a promising alternative to address this challenge. The aims of this study were to assess the influence of lateral wedged insoles on the performance of basketball-specific movements and to observe any changes at the ankle or knee related to injury risk. Twenty-four collegiate basketball players (twelve females and twelve males) performed a shuffle, forward cutting, backward cutting, and sprinting drills, both with and without a 5° lateral wedged insole in their footwear. Performance times, subjective assessments, medial-lateral sway of the centre of mass, ground reaction forces (GRFs), as well as angles and moments of the left ankle and knee were compared using two tailed paired t-tests. Across all movements, completion time, ankle inversion angles, and knee frontal plane kinetics and kinematics remained unchanged. In the shuffle drill, the lateral wedge condition led to increased ankle plantarflexion moments, higher medial and vertical GRFs, and improved GRF vector alignment, resulting in reduced stance time. An increase in the average ankle eversion moment was observed, with no change in the peak value. While minor kinetic changes were observed in the forward and backward cutting drills with the lateral wedge condition, stance time remained unchanged. The lateral wedged insole had no impact on medial-lateral sway of the centre of mass, or the sagittal plane kinematics and kinetics during the sprint, suggesting that 5° lateral wedged insoles do not influence the performance of linear movements. In subjective assessments, participants expressed greater confidence in non- linear movements and improved stability with the lateral wedge condition, however, they rated the comfort of this condition significantly lower. The results indicate that lateral wedged insoles may induce modifications that could potentially enhance performance without changing the risk of ankle or knee joint injuries during lateral movements.