Background
Use of Global positioning system (GPS) technology in team sport permits measurement of player position, velocity, and movement patterns. GPS provides scope for better understanding of the specific and positional physiological demands of team sport and can be used to design training programs that adequately prepare athletes for competition with the aim of optimizing on-field performance.

Global Positioning Systems (GPS) and Microtechnology Sensors in Team Sports: A Systematic Review

Sleep and exercise: a reciprocal issue?

Global positioning system (GPS) technology was made possible after the invention of the atomic clock. The first suggestion that GPS could be used to assess the physical activity of humans followed some 40 y later. There was a rapid uptake of GPS technology, with the literature concentrating on validation studies and the measurement of steady-state movement. The first attempts were made to validate GPS for field sport applications in 2006. While GPS has been validated for applications for team sports, some doubts continue to exist on the appropriateness of GPS for measuring short high-velocity movements. Thus, GPS has been applied extensively in Australian football, cricket, hockey, rugby union and league, and soccer. There is extensive information on the activity profile of athletes from field sports in the literature stemming from GPS, and this includes total distance covered by players and distance in velocity bands. Global positioning systems have also been applied to detect fatigue in matches, identify periods of most intense play, different activity profiles by position, competition level, and sport. More recent research has integrated GPS data with the physical capacity or fitness test score of athletes, game-specific tasks, or tactical or strategic information. The future of GPS analysis will involve further miniaturization of devices, longer battery life, and integration of other inertial sensor data to more effectively quantify the effort of athletes.

Applications of GPS Technologies to Field Sports

It is widely accepted that warming-up prior to exercise is vital for the attainment of optimum performance. Both passive and active warm-up can evoke temperature, metabolic, neural and psychology-related effects, including increased anaerobic metabolism, elevated oxygen uptake kinetics and post-activation potentiation. Passive warm-up can increase body temperature without depleting energy substrate stores, as occurs during the physical activity associated with active warm-up. While the use of passive warm-up alone is not commonplace, the idea of utilizing passive warming techniques to maintain elevated core and muscle temperature throughout the transition phase (the period between completion of the warm-up and the start of the event) is gaining in popularity. Active warm-up induces greater metabolic changes, leading to increased preparedness for a subsequent exercise task. Until recently, only modest scientific evidence was available supporting the effectiveness of pre-competition warm-ups, with early studies often containing relatively few participants and focusing mostly on physiological rather than performance-related changes. External issues faced by athletes pre-competition, including access to equipment and the length of the transition/marshalling phase, have also frequently been overlooked. Consequently, warm-up strategies have continued to develop largely on a trial-and-error basis, utilizing coach and athlete experiences rather than scientific evidence. However, over the past decade or so, new research has emerged, providing greater insight into how and why warm-up influences subsequent performance. This review identifies potential physiological mechanisms underpinning warm-ups and how they can affect subsequent exercise performance, and provides recommendations for warm-up strategy design for specific individual and team sports.

Warm-Up Strategies for Sport and Exercise: Mechanisms and Applications.

Background/Aim - To investigate the role of eccentric knee flexor strength, between-limb imbalance and biceps femoris long head (BFlh) fascicle length on the risk of a future hamstring strain injury (HSI). Methods - Elite soccer players (n=152) from eight different teams participated. Eccentric knee flexor strength during the Nordic hamstring exercise and BFlh fascicle length were assessed at the beginning of pre-season. The occurrences of a HSI following this were recorded by the team medical staff. Relative risk (RR) was determined for univariate data, and logistic regression was employed for multivariate data. Results - Twenty-seven new HSIs were reported. Eccentric knee flexor strength below 337N (RR = 4.4; 95% CI = 1.1 to 17.5) and BFlh fascicles shorter than 10.56cm (RR = 4.1; 95% CI=1.9 to 8.7) significantly increased the risk of a subsequent HSI. Multivariate logistic regression revealed significant effects when combinations of age, previous history of HSI, eccentric knee flexor strength and BFlh fascicle length were explored. From these analyses the likelihood of a future HSI in older athletes or those with a previous HSI history was reduced if high levels of eccentric knee flexor strength and longer BFlh fascicles were present. Conclusions - The presence of short BFlh fascicles and low levels of eccentric strength in elite soccer players increase the risk of a future HSI. The greater risk of a future HSI in older players or those with a previous HSI is reduced when they possess longer BFlh fascicles and high levels of eccentric strength.

Short biceps femoris fascicles and eccentric knee flexor weakness increase the risk of hamstring injury in elite football (soccer): A prospective cohort study

This investigation examined physiological and performance effects of cooling on recovery of medium-fast bowlers in the heat. Eight, medium-fast bowlers completed two randomised trials, involving two sessions completed on consecutive days (Session 1: 10-overs and Session 2: 4-overs) in 31 ± 3°C and 55 ± 17% relative humidity. Recovery interventions were administered for 20 min (mixed-method cooling vs. control) after Session 1. Measures included bowling performance (ball speed, accuracy, run-up speeds), physical demands (global positioning system, counter-movement jump), physiological (heart rate, core temperature, skin temperature, sweat loss), biochemical (creatine kinase, C-reactive protein) and perceptual variables (perceived exertion, thermal sensation, muscle soreness). Mean ball speed was higher after cooling in Session 2 (118.9 ± 8.1 vs. 115.5 ± 8.6 km · h−1; P = 0.001; d = 0.67), reducing declines in ball speed between sessions (0.24 vs. −3.18 km · h−1; P = 0.03; d = 1.80). Large effects indicated higher accuracy in Session 2 after cooling (46.0 ± 11.2 vs. 39.4 ± 8.6 arbitrary units [AU]; P = 0.13; d = 0.93) without affecting total run-up speed (19.0 ± 3.1 vs. 19.0 ± 2.5 km · h−1; P = 0.97; d = 0.01). Cooling reduced core temperature, skin temperature and thermal sensation throughout the intervention (P = 0.001–0.05; d = 1.31–5.78) and attenuated creatine kinase (P = 0.04; d = 0.56) and muscle soreness at 24-h (P = 0.03; d = 2.05). Accordingly, mixed-method cooling can reduce thermal strain after a 10-over spell and improve markers of muscular damage and discomfort alongside maintained medium-fast bowling performance on consecutive days in hot conditions.

Effects of mixed-method cooling on recovery of medium-fast bowling performance in hot conditions on consecutive days

Campbell, PG, Stewart, IB, Sirotic, AC, and Minett, GM. Title: The effect of overreaching on neuromuscular performance and wellness responses in Australian rules football athletes. J Strength Cond Res 34(6): 1530-1538, 2020-This study seeks to evaluate the effect of periodized fluctuations in training load on wellness and psychological questionnaires, perceived exertion, performance, and neuromuscular measures in team-sport athletes. Thirteen amateur Australian rules football athletes completed 6 weeks of periodized training, consisting of 2-week normal training (NT), intensified training (IT), and taper training (TT). Training sessions were quantified using global positioning system devices, heart-rate, and session rating of perceived exertion (sRPE), with wellness (general soreness, sleep quality/quantity, readiness to train, fatigue, stress, mood, and motivation) questionnaires collected daily. Psychological (Recovery-Stress Questionnaire for Athletes) and physical performance (countermovement jump, cycle ergometer peak power, 30-m sprint, and 2-km time trial) markers were measured after each training period. Perceived (sRPE) and mechanical loading were higher for IT than NT, and IT than TT (p < 0.03; d = 0.65-25.34). Cycle ergometer peak power, 30-m sprint, 2-km time trial, and countermovement jump height showed reductions in performance after IT compared to initial testing (p < 0.02; d = 0.51-1.46), with subsequent increases in performance after TT (p < 0.04; d = 0.66-2.27). Average wellness was higher during NT compared to IT (p = 0.005; d = 1.11). Readiness to train did not significantly differ from NT to IT or TT (p < 0.55; d = <0.59); however, readiness to train did improve during TT after the IT (p = 0.01; d = 1.05). The disturbances in performance, perceptual, and mood states may indicate a state of functional overreaching. The findings suggest that an averaged wellness score may be useful in potentially identifying overreaching. However, despite the popularity of wellness in monitoring systems, these measures overall demonstrated a limited capacity to differentiate between periodized fluctuations in load.

The Effect of Overreaching on Neuromuscular Performance and Wellness Responses in Australian Rules Football Athletes.

This is a protocol for a Cochrane Review (Intervention). The objectives are as follows:
To assess the effects of heat acclimation interventions aimed at protecting health and performance from exertional heat stress.

/pdf/heat-acclimation-for-protection-from-exertional-heat-stress-agcdjaeaz5.pdf

Heat acclimation for protection from exertional heat stress

This study aimed to identify the predictive capacity of wellness questionnaires on measures of training load using machine learning methods. The distributions of, and dose–response between, wellnes...

Analysing the predictive capacity and dose-response of wellness in load monitoring

In the November issue of Physiology, Sun et al (12) published a review describing the role of lactate as a multi-tissue autocrine regulatory molecule influencing multiple cellular and systemic physiological functions Such functions included transmembrane H+ transport, enzyme regulation, downregulation of multi-tissue lipolysis, anti-inflammation, improved immune tolerance, stimulation of long-term memory, and improved wound healing including ischemic tissue injury, while deleteriously supporting cancer growth and metastasis We acknowledge the detail and quality of the presentation of the contemporary evidence for the involvement of lactate in the regulation of these processes Nevertheless, it is unfortunate that the authors referred to cellular lactate production as lactic acid, repeatedly associated cellular lactic acid production as a cause of acidosis, and used the term lactic acid within their title Such repeated use, totaling 50 occurrences of “lactic acid” throughout the entirety of the manuscript, severely detracts from the scientitic quality of their work

Geoffrey M. Minett

Papers

Effects of mixed-method cooling on recovery of medium-fast bowling performance in hot conditions on consecutive days

The Effect of Overreaching on Neuromuscular Performance and Wellness Responses in Australian Rules Football Athletes.

Heat acclimation for protection from exertional heat stress

Analysing the predictive capacity and dose-response of wellness in load monitoring

Lactate, not lactic acid, is produced by cellular cytosolic energy catabolism (Letter to the Editor)