Electromyograms used to assess neuromuscular demand during high-velocity tasks require normalization to aid interpretation. This paper posits that, to date, methodological approaches to normalization have been ineffective and have limited the application of electromyography (EMG). There is minimal investigation seeking alternative normalization methods, which must be corrected to improve EMG application in sports. It is recognized that differing normalization methods will prevent cross-study comparisons. Users of EMG should aim to identify normalization methods that provide good reliability and a representative measure of muscle activation. The shortcomings of current normalization methods in high-velocity muscle actions assessment are evident. Advances in assessing alternate normalization methods have been done in cycling and sprinting. It is advised that when normalizing high-intensity muscle actions, isometric methods are used with caution and a dynamic alternative, where the muscle action is similar to that of the task is preferred. It is recognized that optimal normalization methods may be muscle and task dependent.
Nick Ball and Joanna Scurr
Peter Ibbott, Nick Ball, Marijke Welvaert and Kevin G. Thompson
Purpose: To assess pacing strategies using prescribed and self-selected interset rest periods and their influence on performance in strength-trained athletes. Methods: A total of 16 strength-trained male athletes completed 3 randomized heavy strength-training sessions (5 sets and 5 repetitions) with different interset rest periods. The interset rest periods were 3 min (3MIN), 5 min (5MIN), and self-selected (SS). Mechanical (power, velocity, work, and displacement), surface electromyography (sEMG), and subjective (rating of perceived exertion) and readiness-to-lift data were recorded for each set. Results: SS-condition interset rest periods increased from sets 1 to 4 (from 207.52 to 277.71 s; P = .01). No differences in mechanical performance were shown between the different interset rest-period conditions. Power output (210 W; 8.03%) and velocity (0.03 m·s−1; 6.73%) decreased as sets progressed for all conditions (P < .001) from set 1 to set 5. No differences in sEMG activity between conditions were shown; however, vastus medialis sEMG decreased as the sets progressed for each condition (1.75%; P = .005). All conditions showed increases in rating of perceived exertion as sets progressed (set 1 = 6.1, set 5 = 7.9; P < .001). Participants reported greater readiness to lift in the 5MIN condition (7.81) than in the 3MIN (7.09) and SS (7.20) conditions (P < .001). Conclusions: Self-selecting interset rest periods does not significantly change performance compared with 3MIN and 5MIN conditions. Given the opportunity, athletes will vary their interset rest periods to complete multiple sets of heavy strength training. Self-selection of interset rest periods may be a feasible alternative to prescribed interset rest periods.
Gina B.D. Sacilotto, Nick Ball and Bruce R. Mason
Resistive or drag forces encountered during free swimming greatly influence the swim performance of elite competitive swimmers. The benefits in understanding the factors which affect the drag encountered will enhance performance within the sport. However, the current techniques used to experimentally measure or estimate drag values are questioned for their consistency, therefore limiting investigations in these factors. This paper aims to further understand how the resistive forces in swimming are measured and calculated. All techniques outlined demonstrate both strengths and weaknesses in the overall assessment of free swimming. By reviewing all techniques in this area, the reader should be able to select which one is best depending on what researchers want to gain from the testing.
Kym J. Williams, Dale W. Chapman, Elissa J. Phillips and Nick Ball
Purpose: To establish the influence of athlete-dependent characteristics on the generation and timing of system and individual joint powers during a countermovement jump (CMJ). Methods: Male national representative athletes from volleyball (n = 7), basketball (n = 6), and rugby (n = 7) performed a set of 3 CMJs at relative barbell loads of 0%, 10%, 20%, 30%, and 40% of absolute back-squat strength. Ground-reaction forces and joint kinematics were captured using a 16-camera motion-capture system integrated with 2 in-ground force plates. Limb lengths and cross-sectional areas were defined using 3-dimensional photonic scans. A repeated-measures analysis of variance determined the interaction between system and joint load–power profiles, whereas a multiregression analysis defined the explained variance of athlete-dependent characteristics on the load that maximized system power. Results: System and isolated hip, knee, and ankle peak powers were maximized across a spectrum of loads between and within sports; power values were not significantly different across loads. A positive shift in the timing of hip and ankle peak powers corresponded to a significant (P < .05) positive shift in the timing of system peak power to occur closer to toe-off. An optimal 3-input combination of athlete-dependent characteristics accounted for 68% (P < .001) of the explained variance in the load that maximized system peak power. Conclusion: The load maximizing system power is athlete-dependent, with a mixture of training and heredity-related characteristics influencing CMJ load–power profiles. The authors recommend that a combination of relative loads be individually prescribed to maximize the generation and translation of system CMJ power.
Jocelyn K. Mara, Kevin G. Thompson, Kate L. Pumpa and Nick B. Ball
To investigate the variation in training demands, physical performance, and player well-being across a women’s soccer season.
Seventeen elite female players wore GPS tracking devices during every training session (N = 90) throughout 1 national-league season. Intermittent high-speed-running capacity and 5-, 15-, and 25-m-sprint testing were conducted at the beginning of preseason, end of preseason, midseason, and end of season. In addition, subjective well-being measures were selfreported daily by players over the course of the season.
Time over 5 m was lowest at the end of preseason (mean 1.148 s, SE 0.017 s) but then progressively deteriorated to the end of the season (P < .001). Sprint performance over 15 m improved by 2.8% (P = .013) after preseason training, while 25-m-sprint performance peaked at midseason, with a 3.1% (P = .05) improvement from the start of preseason, before declining at the end of season (P = .023). Training demands varied between phases, with total distance and high-speed distance greatest during preseason before decreasing (P < .001) during the early- and late-season phases. Endurance capacity and well-being measures did not change across training phases.
Monitoring training demands and subsequent physical performance in elite female soccer players allow coaches to ensure that training periodization goals are being met and related positive training adaptations are being elicited.