A Review of the Validity and Reliability of Accelerometer-Based Metrics From Upper Back-Mounted GNSS Player Tracking Systems for Athlete Training Load Monitoring.

ABSTRACT: Dawson, L, Beato, M, Devereux, G, and McErlain-Naylor, SA. A review of the validity and reliability of accelerometer-based metrics from upper back-mounted GNSS player tracking systems for athlete training load monitoring. J Strength Cond Res 38(8): e459-e474, 2024-Athlete load monitoring using upper back-mounted global navigation satellite system (GNSS) player tracking is common within many team sports. However, accelerometer-based load monitoring may provide information that cannot be achieved with GNSS alone. This review focuses on the accelerometer-based metrics quantifying the accumulation of accelerations as an estimation of athlete training load, appraising the validity and reliability of accelerometer use in upper back-mounted GNSS player tracking systems, the accelerometer-based metrics, and their potential for application within athlete monitoring. Reliability of GNSS-housed accelerometers and accelerometer-based metrics are dependent on the equipment model, signal processing methods, and the activity being monitored. Furthermore, GNSS unit placement on the upper back may be suboptimal for accelerometer-based estimation of mechanical load. Because there are currently no feasible gold standard comparisons for field-based whole-body biomechanical load, the validity of accelerometer-based load metrics has largely been considered in relation to other measures of training load and exercise intensity. In terms of convergent validity, accelerometer-based metrics (e.g., PlayerLoad, Dynamic Stress Load, Body Load) have correlated, albeit with varying magnitudes and certainty, with measures of internal physiological load, exercise intensity, total distance, collisions and impacts, fatigue, and injury risk and incidence. Currently, comparisons of these metrics should not be made between athletes because of mass or technique differences or between manufacturers because of processing variations. Notable areas for further study include the associations between accelerometer-based metrics and other parts of biomechanical load-adaptation pathways of interest, such as internal biomechanical loads or methods of manipulating these metrics through effective training design.

Practitioner Usage, Applications, and Understanding of Wearable GPS and Accelerometer Technology in Team Sports.

ABSTRACT: Dawson, L, McErlain-Naylor, SA, Devereux, G, and Beato, M. Practitioner usage, applications, and understanding of wearable GPS and accelerometer technology in team sports. J Strength Cond Res 38(7): e373-e382, 2024-Monitoring training load is essential for optimizing the performance of athletes, allowing practitioners to assess training programs, monitor athlete progress, and minimize the risk of injury and overtraining. However, there is no universal method for training load monitoring, and the adoption of wearable global positioning system (GPS) and accelerometer technology in team sports has increased the volume of data and, therefore, the number of possible approaches. This survey investigated the usage, applications, and understanding of this technology by team sports practitioners. Seventy-two practitioners involved in team and athlete performance monitoring using GPS and accelerometer technology completed the survey. All respondents reported supporting the use of GPS technology in their sport, with 70.8% feeling that GPS technology is important for success. Results showed that 87.5% of respondents use data from wearable technology to inform training prescription, although only 50% use the data to influence decisions in competition. In addition, results showed that GPS metrics are used more than accelerometer-derived metrics; however, both are used regularly. Discrepancies in accelerometer usage highlighted concerns about practitioners' understanding of accelerometer-derived metrics. This survey gained insight into usage, application, understanding, practitioner needs, and concerns and criticisms surrounding the use of GPS and accelerometer metrics for athlete load monitoring. Such information can be used to improve the implementation of this technology in team sport monitoring and highlight gaps in the literature that will help to design future studies to support practitioner needs.

On-field rehabilitation in football: current practice and perceptions. A survey of the English Premier League and Football League.

INTRODUCTION: Return to play related research is increasing rapidly, with two recent competency-based frameworks offering conceptualised support for on-field rehabilitation (OFR) decision-making. It is still unknown, however, who is responsible for OFR and how they typically select, monitor, and progress OFR processes. AIMS: The purpose of this study was to investigate current OFR practice within English professional football to support practitioners with decision-making and highlight opportunities for future research related to the design, monitoring, and progression of OFR. METHODS: Sixty-nine practitioners responsible for the design and implementation of OFR at 69 clubs (75% of the English Premier League and Football League) responded to a survey containing 30 questions (14 open and 16 closed). RESULTS: The main findings were that therapists (physiotherapists/sports therapists) have the largest influence on OFR, followed by physical performance coaches (sports scientists/strength and conditioning coaches), technical coaches and medical doctors. There was more agreement for the ordering of specific OFR drills earlier in the process when activities are easier to control. The most frequently reported objective monitoring tool was global positioning systems (GPS), with functional/clinical experience/expertise remaining subjectively vital. GPS outputs (e.g., sprint metrics and accelerations/decelerations) were most used for between session decision-making, with verbal communication being key for within session decision-making. CONCLUSION: Future research should use evidence of current practice, such as drill design and monitoring techniques, to explore drill-level analysis and give practitioners greater insights into which stage of current OFR frameworks specific drills fall, and how they might be more objectively progressed/regressed.

Effect of a high-intensity short-duration cycling elevation training mask on V̇O2max and anaerobic power. A randomized controlled trial.

This study investigated the effect of high-intensity interval training (HIIT) cycling elevation training mask (ETM) in moderately trained participants on both aerobic (V̇O2max) and anaerobic power performance. Sixteen participants, five females (25.8 ± 7.6 years) and eleven males (22.2 ± 3.5 years) took part in this randomized controlled trial. Participants were assigned to the experimental group (ETM, n = 8 participants) wearing an ETM or the control group (CON, n = 8 participants) without the ETM. V̇O2max was determined during a standardized protocol using Cortex Metalyzer-3B on a cycle ergometer. Peak and average power were calculated a 30-second Wingate test. Participants completed 4-weeks (two sessions a week) of high-intensity cycle training. Each training session consisting of 4 separate bouts of 4-minutes of high-intensity cycling exercise. After the training period, ETM reported an increment in V̇O2max (effect size (d) = 1.19), peak power (d = 0.77), and average power (d = 0.76). CON reported an increment only in V̇O2max (d = 1.00). No-between group differences were found in any parameter (ANCOVA), therefore the two protocols should be considered equally effective. In conclusion, this study reported that both HIIT protocols significantly enhance V̇O2max in a very short training period (4 weeks).

Injury risk and injury incidence rates in CrossFit.

INTRODUCTION: Despite completing complex movements under cardiovascular and muscular fatigued conditions, CrossFit suggested safety of participants is one of the most important factors to consider. Therefore, the aim of this brief review was to provide an overview of the injury incidence and incidence rates reported in the current literature as well as to assess the injury risks associated with CrossFit. EVIDENCE ACQUISITION: Research papers were searched using the following databases: Scopus, SPORTDiscus, Web of Science, PubMed, and MEDLINE. The search identified 718 potential articles across all databases. After the application of inclusion criteria, a total of 14 articles were included in this review. EVIDENCE SYNTHESIS: The shoulder, spine, and knee are the most commonly injured areas in CrossFit. Injury incidence of each study ranges from 12.8-73.5% and reported injury rates ranging from 0.27-3.3/1000 training hours. CONCLUSIONS: Reported findings in the current literature would suggest CrossFit has a relatively low injury risk. The current review highlights three important factors associated with injury incidence and incidence rates in CrossFit: 1) training frequency; 2) duration of CrossFit experience; 3) individuals that compete in CrossFit competitions. Due to recall bias and selection bias further research is warranted over a longitudinal prospective study. Additionally, further research is needed to investigate mechanisms of injury and the relationship between training load and injury risk in CrossFit.

The Ipswich Microbreak Technique to alleviate neck and shoulder discomfort during microscopic procedures.

Neck and shoulder disorders are a considerable health problem amongst frequent microscope users. We aimed to investigate the neck and shoulder discomfort experienced during prolonged microscopic activity and to assess the benefits of minibreaks. A prospective crossover study was performed on 17 healthy volunteers sitting still while looking down a bench with and without the Ipswich Microbreak Technique (IMT). We used a subjective measure of time to fatigue and pain in the neck and shoulder regions as well as objective readings from a surface electromyogram (sEMG). The IMT delayed the sensation of pain in the neck and shoulder region while reducing the overall sEMG muscle activation. In conclusion, IMT is a useful strategy in reducing and delaying the pain in neck and shoulder from prolonged working under the microscope. This technique can be incorporated in other activities that involve a sustained stationary position.

Physical Demands of Exergaming in Healthy Young Adults.

Tietjen, AMJ and Devereux, GR. Physical demands of exergaming in healthy young adults. J Strength Cond Res 33(7): 1978-1986, 2019-The efficacy of whole-body exergaming (WBE) in healthy young adults remains largely unknown. This study aimed to: (a) compare the physical demands of WBE in healthy adults with traditional exercise; (b) determine whether the physical demands of WBE were reproducible. Twenty-five healthy adults (age: 22.9 ± 6.4 years; height: 1.7 ± 0.1 m; mass: 69.1 ± 12.2 kg) completed two 10-minute experimental conditions (WBE on the Xbox Kinect and treadmill walking) in a randomized cross-over design study. Whole-body exergaming produced a significant increase in the peak heart rate (138 ± 23 b·min), oxygen consumption (40 ± 13 ml·kg·min), metabolic equivalents (METs) (11 ± 4) compared with treadmill walking (115 ± 18 b·min, 25 ± 5 ml·kg·min, 7 ± 2 MET) and a modest increase in the mean heart rate (111 ± 19 b·min vs. 104 ± 15 b·min). Whole-body exergaming produced significantly greater vertical (381 ± 118 vs. 127 ± 14 % body mass [%BM]), anterior (70 ± 22 vs. 27 ± 4 %BW), and medial (56 ± 21 vs. 7 ± 2 %BW) ground reaction forces. No difference was present in mean oxygen consumption and MET. The reproducibility of WBE was assessed in a subgroup of 11 participants (age: 24.2 ± 6.7 years; height: 1.8 ± 0.1 m; mass: 75.3 ± 10.0 kg), who completed 2 additional 10-minute WBE sessions. No difference was observed between all outcome measures. These findings indicate that WBE can reliably replicate, or surpass, the physical demands of treadmill walking and may serve as an effective addition to a health-focused exercise program.

Effects of prolonged microscopic work on neck and back strain amongst male ENT clinicians and the benefits of a prototype postural support chair.

Musculoskeletal pain is a common occupational hazard experienced by surgeons. Ear, nose and throat (ENT) surgeons are predisposed to neck and back pain due to regular prolonged microscopic work. We conducted a prospective pilot study to investigate the effects of sustained microscopic work on the neck and back, its correlation to surgical experience and to assess the benefits of a prototype postural support chair (PSC) amongst 10 male, ENT clinicians. We used a subjective measure of time to fatigue and pain for the neck and back as well as objective readings from a surface electromyogram (sEMG). We found that an increase in surgical experience correlated with the time taken to experience fatigue and pain in the neck and back. This was corroborated by our sEMG findings. The PSC significantly delayed the sensations in the neck and also eliminated the difference seen amongst the varying seniority of clinicians.

Validity and Reliability of Global Positioning System Units (STATSports Viper) for Measuring Distance and Peak Speed in Sports.

Beato, M, Devereux, G, and Stiff, A. Validity and reliability of global positioning system units (STATSports Viper) for measuring distance and peak speed in sports. J Strength Cond Res 32(10): 2831-2837, 2018-Previous evidence has proven that large variability exists in the accuracy of different brands of global positioning systems (GPS). Therefore, any GPS model should be validated independently, and the results of a specific brand cannot be extended to others. The aim of this study is to assess the validity and reliability of GPS units (STATSports Viper) for measuring distance and peak speed in sports. Twenty participants were enrolled (age 21 ± 2 years [range 18 to 24 years], body mass 73 ± 5 kg, and height 1.78 ± 0.04 m). Global positioning system validity was evaluated by comparing the instantaneous values of speed (peak speed) determined by GPS (10 Hz, Viper Units; STATSports, Newry, Ireland) with those determined by a radar gun during a 20-m sprint. Data were analyzed using the Stalker (34.7 GHz, USA) ATS Version 5.0.3.0 software as gold standard. Distance recorded by GPS was also compared with a known circuit distance (400-m running, 128.5-m sports-specific circuit, and 20-m linear running). The distance bias in the 400-m trial, 128.5-m circuit, and 20-m trial was 1.99 ± 1.81%, 2.7 ± 1.2%, and 1.26 ± 1.04%, respectively. Peak speed measured by the GPS was 26.3 ± 2.4 km·h, and criterion was 26.1 ± 2.6 km·h, with a bias of 1.80 ± 1.93%. The major finding of this study was that GPS did not underestimate the criterion distance during a 400-m trial, 128.5-m circuit, and 20-m trial, as well as peak speed. Small errors (<5%, good) were found for peak speed and distances. This study supported the validity and reliability of this GPS model.

The Reliability of Technical and Tactical Tagging Analysis Conducted by a Semi-Automatic VTS in Soccer.

The Video Tracking multiple cameras system (VTS) is a technology that records two-dimensional position data (x and y) at high sampling rates (over 25 Hz). The VTS is of great interest because it can record external load variables as well as collect technical and tactical parameters. Performance analysis is mainly focused on physical demands, yet less attention has been afforded to technical and tactical factors. Digital.Stadium® VTS is a performance analysis device widely used at national and international levels (i.e. Italian Serie A, Euro 2016) and the reliability evaluation of its technical tagging analysis (e.g. shots, passes, assists, set pieces) could be paramount for its application at elite level competitions, as well as in research studies. Two professional soccer teams, with 30 male players (age 23 ± 5 years, body mass 78.3 ± 6.9 kg, body height 1.81 ± 0.06 m), were monitored in the 2016 season during a friendly match and data analysis was performed immediately after the game ended. This process was then replicated a week later (4 operators conducted the data analysis in each week). This study reports a near perfect relationship between Match and its Replication. R2 coefficients (relationships between Match and Replication) were highly significant for each of the technical variables considered (p < 0.001). In particular, a high score of interclass correlation and a small coefficient of variation were reported. This study reports meaningless differences between Match and its Replication (intra-day reliability). We concluded that the semi-automatic process behind the Digital.Stadium® VTS was more than capable of recording technical tagging data accurately.

Reliability of internal and external load parameters in recreational football (soccer) for health.

There is limited research focussed around the analysis of internal and external load parameters during football health programmes. The aim of this study was to assess the reliability of internal and external load parameters in this activity. Thrity subjects were enrolled (mean ± SDs; age = 43 ± 3 years, weight = 84 ± 14 kg, height = 176 ± 7 cm, BMI = 27.1 ± 3, VO2max = 40.7 ± 3.4 ml.kg.min-1). The football matches (five a-side) took place on an artificial grass outdoor field (pitch size of 36 × 18.5 m). Participants completed the match (60 min) and replicated the same match a week later. The analysis took into account several parameters: heart rate (HR), total distance (TD), high speed running (HSR), number of accelerations (>2 m.s-2) and metabolic power (MP). We found a good score of reliability in several parameters: TD (ICC = 0.66), accelerations (ICC = 0.62), mean HR (ICC = 0.82), HSR (ICC = 0.77) and MP (ICC = 0.66). The results reported in this study revealed good scores of absolute reliability and small/trivial effect size.

Intensity-dependent reductions in resting blood pressure following short-term isometric exercise training.

To reduce resting blood pressure, a minimum isometric exercise training (IET) intensity has been suggested, but this is not known for short-term IET programmes. We therefore compared the effects of moderate- and low-intensity IET programmes on resting blood pressure. Forty normotensive participants (22.3 ± 3.4 years; 69.5 ± 15.5 kg; 170.2 ± 8.7 cm) were randomly assigned to groups of differing training intensities [20%EMGpeak (~23%MVC, maximum voluntary contraction, or 30%EMGpeak (~34%MVC)] or control group; 3 weeks of IET at 30%EMGpeak resulted in significant reductions in resting mean arterial pressure (e.g. -3.9 ± 1.0 mmHg, P < 0.001), whereas 20%EMGpeak did not (-2.3 ± 2.9 mmHg; P > 0.05). Moreover, after pooling all female versus male participants, IET induced a 6.9-mmHg reduction in systolic blood pressure in female participants, but only a 1.5-mmHg reduction in systolic blood pressure in male participants, although the difference was not significant. An IET intensity between 20%EMGpeak and 30%EMGpeak is sufficient to elicit significant resting blood pressure reductions in a short-term training period (3 weeks). In addition, sexual dimorphism may exist in the magnitude of reductions, but further work is required to confirm this possibility, which could be important in understanding the mechanisms responsible.

Immediate post-isometric exercise cardiovascular responses are associated with training-induced resting systolic blood pressure reductions.

PURPOSE: The purpose of this study was twofold: (1) to investigate the effect of 4 weeks of bilateral-leg isometric exercise training on the immediate isometric post-exercise cardiovascular responses, and (2) to ascertain whether any changes in immediate post-exercise cardiovascular responses may be associated with training-induced adaptations in resting blood pressure. METHODS: Thirteen normotensive males completed both isometric exercise training (IET) and control conditions, which were separated by 6 weeks. Participants performed a total of twelve training sessions; 4 × 2-min bilateral-leg isometric exercise bouts separated by 3-min rest periods, 3 days week(-1). RESULTS: Four weeks of bilateral-leg IET resulted in a reduction in resting SBP (120 ± 12-115 ± 12 mmHg, p = 0.01). The intercept of the 5-min post-exercise systolic blood pressure slope was lower (p = 0.015) following the 4-week training intervention. Individual changes in immediate post-exercise response SBP were also significantly correlated with reductions in resting SBP following 4 weeks of training. There were significant differences in the slopes of the first vs. final post-exercise BRS response (p = 0.009), and the intercepts of the HRR slopes (p = 0.04) recorded during the 5-min post-exercise periods. CONCLUSIONS: Four weeks of IET altered immediate cardiovascular responses to an individual IET session. Altered immediate responses were also associated with training-induced reductions in resting SBP. To our knowledge, this is the first evidence suggesting that very short-term (immediate) cardiovascular responses may be important in defining chronic reductions in resting blood pressure following a period of IET.

Lactate accumulation following isometric exercise training and its relationship with reduced resting blood pressure.

The purpose of this study was (a) to assess lactate accumulation during isometric exercise, and to quantify the shifts in accumulation following isometric training; and (b) to relate any training-induced changes in lactate accumulation to reductions in resting blood pressure. Eleven male participants undertook isometric training for a 4-week period using bilateral-leg exercise. Training caused reductions in systolic, diastolic, and mean arterial resting blood pressure (of -4.9 ± 6.3 mmHg, P = 0.01; -2.6 ± 3.0 mmHg, P = 0.01; and -2.6 ± 2.3 mmHg, P = 0.001 respectively; mean ± s). These were accompanied by changes in muscle activity, taken as electromyographic activity to reach a given lactate concentration (from 114 ± 22 to 131 ± 27 mV and from 136 ± 25 to 155 ± 34 mV for 3 and 4 mmol · L(-1) respectively. Training intensity expressed relative to peak lactate was correlated with reduced resting systolic and mean arterial blood pressure. Training caused significant shifts in lactate accumulation, and reductions in resting blood pressure are strongly related to training intensity, when expressed relative to pre-training peak lactate. This suggests that higher levels of local muscle anaerobiosis may promote the training-induced reductions in resting blood pressure.

Markers of isometric training intensity and reductions in resting blood pressure.

In this study, we examined the correlations between selected markers of isometric training intensity and subsequent reductions in resting blood pressure. Thirteen participants performed a discontinuous incremental isometric exercise test to volitional exhaustion at which point mean torque for the final 2-min stage (2min-torque(peak)) and peak heart rate peak (HR(peak)) were identified. Also, during 4 weeks of training (3 sessions per week, comprising 4 × 2 min bilateral leg isometric exercise at 95% HR(peak)), heart rate (HR(train)), torque (Torque(train)), and changes in EMG amplitude (ΔEMG(amp)) and frequency (ΔEMG(freq)) were determined. The markers of training intensity were: Torque(train) relative to the 2min-torque(peak) (%2min-torque(peak)), EMG relative to EMG(peak) (%EMG(peak)), HR(train) ΔEMG(amp), ΔEMG(freq), and %MVC. Mean systolic (-4.9 mmHg) and arterial blood pressure (-2.7mmHg) reductions correlated with %2min-torque(peak) (r = -0.65, P = 0.02 and r = -0.59, P = 0.03), ΔEMG(amp) (r = 0.66, P = 0.01 and r = 0.59, P = 0.03), ΔEMG(freq) (r = -0.67, P = 0.01 and r = -0.64, P = 0.02), and %EMG(peak) (systolic blood pressure only; r = -0.63, P = 0.02). These markers best reflect the association between isometric training intensity and reduction in resting blood pressure observed after bilateral leg isometric exercise training.

Reductions in resting blood pressure after 4 weeks of isometric exercise training.

There is some evidence to suggest isometric training can reduce resting blood pressure in a shorter period than the typical 8 weeks, reported most commonly. The purpose of the present study was to explore whether 4 weeks of bilateral-leg isometric training can reduce resting blood pressure, and whether these changes are associated with altered cardiac output or total peripheral resistance. Thirteen participants volunteered for a 4-week crossover training study, involving three sessions per week (each session involving 4 x 2 min bilateral-leg isometric exercise). The training intensity used (95% peak HR) was equivalent to 24% MVC. In addition to blood pressure, resting heart rate, cardiac output, stroke volume, and total peripheral resistance were measured. Results demonstrated that bilateral-leg isometric exercise training for 4 weeks caused significant reductions in systolic, diastolic, and mean arterial pressure. Changes were -4.9 +/- 5.8, -2.8 +/- 3.2, and -2.7 +/- 2.4 mmHg, respectively. No differences were observed in the other resting measures. In conclusion, this study has shown that it is possible to induce reductions in arterial blood pressure after 4 weeks of bilateral-leg isometric exercise.