Examination of the ZXY Arena Tracking System for Association Football Pitches.

Modern analyses of football games require precise recordings of positions and movements. The ZXY arena tracking system reports the position of players wearing a dedicated chip (transponder) at high time resolution. The main issue addressed here is the quality of the system's output data. Filtering the data to reduce noise may affect the outcome adversely. Therefore, we have examined the precision of the data given, possible influence by sources of noise, the effect of the filtering, and the accuracy of the built-in calculations. The system's reported positions of the transponders at rest and during different types of movements, including accelerations, were recorded and compared with the true positions, speeds, and accelerations. The reported position has a random error of ≈0.2 m, defining the system's upper spatial resolution. The error in signals interrupted by a human body was of that magnitude or less. There was no significant influence of nearby transponders. Filtering the data delayed the time resolution. Consequently, accelerations were dampened and delayed, causing an error of 1 m for sudden changes in position. Moreover, fluctuations of the foot speed of a running person were not accurately reproduced, but rather, averaged over time periods >1 s. Results calculated from measured values appeared accurate and were readily reproduced in a spreadsheet output. In conclusion, the ZXY system reports the position with little random error. Its main limitation is caused by averaging of the signals.

Effect of Computational Method on Accumulated O2 Deficit.

The aim of this study was to examine how relationships between exercise intensity and the rate of energy release established in different ways, affect the calculated O2 deficit accumulated during strenuous exercise. Aerobic energy release is readily measured by the O2 uptake, while anaerobic energy release is by definition independent of O2. The latter is not easily measured during strenuous exercise, but it can be estimated using the accumulated O2 deficit principle. We have calculated it using nine different approaches. Thirteen moderately trained persons (three women) volunteered to serve as subjects for cycle ergometry. Their maximal O2 uptake was 2.9 ± 0.6 mmol s-1 (x̄ ± s; 3.9 ± 0.8 LSTPD min-1). Our reference method (M0) is based on measuring the steady state O2 uptake at the end of at least ten bouts of 10 min of exercise at constant intensity, varying between 30 and 40% of that corresponding to the maximal O2 uptake and up to a power >90% of the maximal O2 uptake, which is a rather time-consuming method. The outcomes of eight different simpler approaches have been compared with those of the reference method. The main result is that the accumulated O2 deficit calculated depends a great deal on the relationship used to calculate it. A protocol of stepwise increases in exercise intensity every 4 min appeared to work well. A gross efficiency method showed the poorest performance. Another important result is that at constant power the O2 uptake continued to increase beyond 4 min of exercise at all powers examined, also at powers well-below those corresponding to the lactate threshold. Finally, the O2 uptake during loadless pedaling was considerably higher than resting O2 uptake, and it appeared to follow a cubic function of the pedaling frequency. In conclusion, to obtain reliable values of the anaerobic energy release using the accumulated O2 deficit principle, reliable relationships between exercise intensity and O2 demand must be established.

Examination of a new functional firefighter fitness test.

Firefighters must meet certain physical requirements. This study compares the demands of a new firefighting-specific tasks test with an existing laboratory test. Thirty-five male subjects were tested. In both tests, the subjects wore a complete firefighting outfit including breathing apparatus, but not the usual facemask. Test durations were 8 min (existing test) vs ≈10 min (new test). Peak oxygen uptake was similar in the tests, ≈45 ml · kg-1 min-1. The time with an oxygen uptake above 35 ml kg-1 min-1 was longer in the new test, 6.4 vs 4.7 min. The results suggest that the new test is as demanding as the traditional test and offers the advantages of being more specific. The new test could therefore serve as an alternative to the existing test. Based on regression analysis of the two tests, a pass/fail time of 10 min 30 s is suggested.

The steady-state load of five firefighting tasks.

Purpose. Physiologic demands of five common tasks in firefighting have been examined. Methods. Eight male volunteers, dressed up as smoke divers (+21 kg extra load), carried out the following tasks at constant pace for 5 min: walking at 1.4 m·s-1, walking (all walks at the same speed) while carrying a 10-kg ladder, walking carrying two hose packs of 16 kg together, walking carrying a 32-kg spreader tool and, finally, climbing up and down a ladder at a preset pace. A 5-min break separated each exercise. The heart rate, oxygen uptake and lung ventilation were measured continuously, and the blood lactate concentration was recorded after each task. Results. The end-exercise heart rate rose from 108 to 180 bpm from the first to last task, blood lactate concentration rose from 1 to 7 mmol·L-1, oxygen uptake rose from 19 to 48 ml·kg-1 min-1 and lung ventilation rose from 38 to 124 L·min-1. Discussion. Walking was an easy task even when dressed up as a smoke diver. Adding loads increased demands; ladder climbing taxed >90% of the subjects' aerobic power. Conclusions. The physiologic demands varied considerably between different tasks.

Are elderly construction workers sufficiently fit for heavy manual labour?

This study analysed the work ability of elderly construction workers. Forty male construction workers, 20 young (age < 33 yrs) and 20 senior (age>44 yrs) workers, were tested regarding aerobic power (VO2max) and muscle strength. The aerobic demand of a number of tasks in construction work was measured and compared with the workers' aerobic power. VO2max was higher for the young, and they performed better on most muscle strength tests. The measurements showed that about half of the senior workers had to use more than 30% of their maximum oxygen uptake on some tasks. In conclusion, because elderly construction workers decline in physical fitness, they are more exposed to overload when performing heavy manual work than are their younger peers. Increasing their individual fitness or adjusting their workload may be important for staying in the workforce for such workers. PRACTITIONER SUMMARY: Construction workers must occasionally perform strenuous work tasks that may endanger their safety. This was more often the case for elderly workers investigated here. Elderly workers should therefore be particularly observant of their physical fitness, and should possibly train during leisure time to improve their fitness.

A comparison of two physical ability tests for firefighters.

Smoke diving is physically demanding, and firefighters must therefore meet certain minimum physical requirements. The aim of this study was to compare the physiological demands of two fire fitness tests: a test of 8-min treadmill walking approved by the Norwegian Labour Inspection Authority (NLIA) (a laboratory test) and a Canadian test consisting of 10 firefighting specific tasks carried out in sequence (an applied field test). If the Canadian field test is as physically demanding as the NLIA-approved laboratory test, it may be suitable for testing Norwegian firefighters. Twenty-two male professional firefighters were tested on separate days. In both tests, the subjects wore a complete firefighting outfit including a breathing apparatus. The test durations were 8 min (NLIA test) versus approximately 6 min (Canadian test). Neither the peak O2 uptake (VO2) of approximately 45 ml kg⁻¹ min⁻¹ nor the blood lactate concentration (BLC) at test termination ( ≈ 9 mmol L⁻¹) differed between the two tests. Rating of perceived exertion (RPE(CR-10)) was lower for the Canadian test than for the Norwegian test (5.2 ± 1.5 vs. 7.0 ± 2.0, respectively), and the exercise time at a high VO2 was also shorter. In conclusion, the Canadian test appeared to be almost as physically demanding as the NLIA-approved test, having equal peak VO2 and BLC, but shorter time at a high VO2 and shorter duration. It might thus be a suitable alternative to the NLIA test with some modifications. The advantage of the Canadian field test is the inclusion of specific firefighting-like tasks that are not part of the NLIA test. PRACTITIONER SUMMARY: The physiological load from two firefighter fitness tests was compared. The demands were found to be similar, but the field test was of a shorter duration. With some modifications, the field test may be sufficiently demanding to be used as a fire fitness test for smoke divers in Norway.

Energy cost of the Trondheim firefighter test for experienced firefighters.

AIM: The aim of this study was to measure aerobic demands of fire fighting activities including exercise in the heat. METHODS: Twenty-two experienced firefighters performed the Trondheim test simulating fire fighting tasks including work in the heat. Maximal oxygen uptake (VO2 max), heart rate (HR) and ventilation were recorded continuously. Data were compared with results obtained during a treadmill test during which the participants were dressed as smoke divers. RESULTS: The participants completed physical parts of the Trondheim test in ˜12 min (range: 7.5-17.4). Time to complete the test was closely related to the participant's VO2 max. HR of ˜170 beats/min and pulmonary ventilation of ˜100 L/min were higher than at lactate threshold (LT) during laboratory tests. VO2 averaged over the test's physical part was 35 ± 7 ml/min/kg, which was at the same or below the level corresponding to the participants' LT. Physically fit participants completed the test faster than less fit participants. Slower and physically less fit participants consumed more air and used more oxygen than faster and physically more fit participants. CONCLUSION: The Trondheim test is physically demanding; it distinguishes physically fit and less fit participants.

Performance on a work-simulating firefighter test versus approved laboratory tests for firefighters and applicants.

AIM: Firefighters must meet minimum physical demands. The Norwegian Labour Inspection Authority (NLIA) has approved a standardised treadmill walking test and 3 simple strength tests for smoke divers. The results of the Trondheim test were compared with those of the NLIA tests taking into account possible effects of age, experience level and gender. METHODS: Four groups of participants took part in the tests: 19 young experienced firefighters, 24 senior male firefighters and inexperienced applicants, 12 male and 8 female. RESULTS: Oxygen uptake (VO2) at exhaustion rose linearly by the duration of the treadmill test. Time spent on the Trondheim test was closely related to performance time and peak VO2 on the treadmill test. Senior experienced firefighters did not perform better than equally fit young applicants. However, female applicants performed poorer on the Trondheim test than on the treadmill test. Performance on the Trondheim test was not closely related to muscle strength beyond a minimum. CONCLUSION. Firefighters completing the Trondheim test in under 19 min fit the requirements of the NLIA treadmill test. The Trondheim test can be used as an alternative to the NLIA tests for testing aerobic fitness but not for muscular strength. Women's result of the Trondheim test were poorer than the results of the NLIA treadmill test, probably because of their lower body mass.

Examination of the Moxus Modular Metabolic System by the Douglas-bag technique.

The purpose of this study was to examine the performance of the Moxus Modular Metabolic System from AEI Technologies, Inc. using the Douglas-bag method as reference. To achieve this, eight moderately trained subjects cycled for 5 min at constant powers from 50 to 300 W in increments of 50 W. The O2 uptake was measured simultaneously by both systems during the last minute of each stage. The O2 uptake reported by the Moxus system was 83 ± 78 mL·min⁻¹ higher (mean ± SD; ≈3%, +62 µmol·s⁻¹, P < 0.001) than that reported by the Douglas-bag method; the bias varied by ≈2% between the subjects. The higher O2 uptake of the Moxus system was a consequence of 1.4% ± 3.0% higher reported ventilation and 2% ± 3% higher reported O2 extraction per volume of air breathed. The respiratory exchange ratio (R value) reported by the Moxus system rose proportionally to that of the Douglas-bag method and was 1% ± 2% higher for the range examined (0.75-1.10). Repeated tests of the maximal O2 uptake showed a variability (coefficient of variation) of 2.5%. The study concluded that measurements by the Moxus system showed some bias and residual variation and, in addition, some systematic differences between the subjects in the O2 uptake. The R value was reported quite accurately with moderate random error. Although there were some computer software and hardware instability problems that need to be solved, the Moxus system worked quite well and provided data more reliable than those of most commercial instruments.

Blood flow in the brachial artery increases after intense cycling exercise.

During cycling blood flow is redistributed from physically inactive tissues to working leg muscles. It is unknown how long this situation persists after very intense exercise or whether it differs between intense exhausting and non-exhausting exercise. It is also not known to what extent the redistribution differs between different types of non-active tissues. Therefore nine healthy young men cycled first for 2 min at 328 W (non-exhausting exercise, mean). Blood velocity in thigh and arm (ultrasound-doppler), perfusion of forearm skin (non-acral skin) and finger tip (acral skin, with arterio-venous anastomoses) were measured for 30 min after exercise (laser-doppler). To be able to study vascular resistance and central circulation, blood pressure (Finometer), heart rate (ECG), and stroke volume (ultrasound-doppler) were measured. Thereafter the subjects cycled at the same power to exhaustion (4 min), and the measurements were repeated. After both exercises mean blood pressure was unchanged (< or = 80 mm Hg) despite increased cardiac output (> or = + 30% vs. pre-exercise). Blood velocity in the brachial artery was higher during the whole recovery period than at rest (p< or =0.02; no differences between exercises). Blood perfusion of non-acral skin was unchanged from pre-exercise level after 2 min of non-exhausting exercise, but it was twice as high after 4 min cycling to exhaustion as at rest (p=0.02). Blood perfusion of acral skin rose after both exercises and did not differ between exhausting and non-exhausting exercise. In conclusion, arm blood flow increases above the pre-exercise level in the recovery period after short-lasting, strenuous exercise.

Examination of blood haemoglobin concentration measured using the OSM2.

Blood haemoglobin concentration is regularly measured automatically by instruments reporting the value in around 1 min. The OSM2 from Radiometer is an example. Results from this instrument have been compared with those of a reference method using the hemiglobincyanide principle. Four healthy, moderately trained, young men (non-smokers) cycled for 2 min to exhaustion. Blood samples were drawn from indwelling catheters in the femoral artery and vein before exercise, during exercise and in the 1 h recovery. Blood haemoglobin concentration was analysed using both methods. The results of the OSM2 were linearly related to those of the control method, with a random variation of 0.14 mmol L(-1) (1.5%). For arterial blood, the OSM2 showed a systematic bias of -0.36 mmol L(-1) (-4%). For femoral venous samples the bias varied depending on the haemoglobin concentration, being negative at low concentrations and positive at high values (-3 to +2%). Consequently, the arteriovenous (a-v) difference differed systematically between the two methods. The varying bias in the results of the OSM2 for femoral-venous samples correlated with pH, pCO(2), O(2) saturation of haemoglobin (sO(2)) and with the haemoglobin concentration itself (cHb). Partial correlation analyses suggest that only the latter two correlations were independent, while correlations of the bias with pH and pCO(2) were removed when correcting for the effect of sO(2) and cHb. In conclusion, the OSM2 measures the blood haemoglobin concentration fairly precisely, but there is a variable bias of up to 4% in absolute value. Finally, the instrument does not report a-v differences reliably.

Muscular performance after concentric and eccentric exercise in trained men.

PURPOSE: We studied previously resistance-trained men and compared the effects of concentric and eccentric training on performance and structural muscle parameters. METHODS: Seventeen trained individuals (age 26.9 +/- 3.4 yr) participated in 12 wk of either maximum concentric (N = 8) or eccentric (N = 9) resistance training of the elbow flexors. The functional performance was measured as the maximum concentric and eccentric strength and angular velocity at standard loads. Muscle cross-sectional area and cross-sectional area of single cells were used as measures of muscular hypertrophy. Fiber-type proportions were assessed by staining cells for myofibrillar ATPase. RESULTS: Both eccentric and concentric training increased concentric strength to a similar extent (14 vs 18%), whereas eccentric training led to greater increases in eccentric strength than concentric training did (26 vs 9%). The maximum angular velocity at all loads was enhanced equally in both training groups. The cross-sectional area of both the elbow flexors (+11%) and of the type I and type IIA fibers increased only after the eccentric training. In addition, the relative cross-sectional area occupied by the type II fibers increased from 64 to 73% after the eccentric training. There were only minor changes in the fiber-type proportions. CONCLUSION: The present data suggest that for resistance-trained men, increases in concentric strength and velocity performance after eccentric training are largely mediated by changes in fiber and muscle cross-sectional area. However, hypertrophy alone could not explain the increase in eccentric strength. Because the increases in strength and velocity performance after concentric training could not be ascribed to muscular adaptations alone, we suggest that they may be attributable to additional neural factors.

Physiological responses of firefighters and performance predictors during a simulated rescue of hospital patients.

There is incomplete information about how physically demanding rescue work may be. The aim therefore of this paper was to examine the physiological responses of firefighters during a simulated rescue of hospital patients and to relate the firefighters' performance to their endurance, strength and working technique. Fourteen part-time male firefighters with a maximal oxygen uptake (VO(2max)) of 4.4 +/- 0.3 l/min (mean +/- SD) served as subjects in this study. First, each firefighter ascended six floors (a 20.5 m vertical ascent) carrying tools, wearing protective clothing and a breathing apparatus, an extra mass of 37 kg. He thereafter 'rescued' six persons by dragging each person on a fire-sheet on a flat floor. The technique used was recorded and the O(2) uptake and the heart rate were measured continuously during the whole operation. The blood lactate concentration and the subjective rating of perceived exertion were measured during and just after the rescue. The VO(2max) and the muscle strength were measured in the laboratory. The whole operation was carried out in the course of 5-9 min. The operation was a virtual all-out effort and the peak blood lactate concentration was 13 +/- 3 mmol/l. The peak oxygen uptake was 3.7 +/- 0.5 l/min (84% of the VO(2max)) during the operation. Large and heavy firefighters carried out the task faster than smaller ones. The VO(2max) in absolute terms and the dragging technique used were both related to the rescue performance. Rescuing patients at a hospital was physically very demanding and the time needed to complete the task depended on the VO(2max) in absolute values and the working technique used. A minimum VO(2max) of 4 l/min for firefighters was recommended.

Effect of intensive acupuncture on pain-related social and psychological variables for women with chronic neck and shoulder pain--an RCT with six month and three year follow up.

OBJECTIVES: This study examines whether intensive acupuncture treatment can improve several social and psychological variables for women with chronic pain in the neck and shoulders, and whether possible effects are long-lasting. The effects on pain have been reported elsewhere. METHODS: Twenty-four female office workers (47 +/- 9 years old, mean +/- SD) who had had neck and shoulder pain for 12 +/- 9 years, were randomly assigned to a test group or a control group. Acupuncture was applied 10 times during three to four weeks either at presumed acupuncture points for pain (test group) or at sham points (control group). In addition, acupressure was given to patients between treatments, at either real or sham points. Questionnaires for social and psychological variables were completed before each treatment, just after the course, and six months and three years later. RESULTS: The pain-related activity impairment at work was significantly less in the test group than the controls by the end of treatment (P < 0.04). Also there were significant differences between the groups for quality of sleep, anxiety, depression and satisfaction with life (P < 0.05). At six months and three years follow ups the acupuncture group showed further improvements in most variables and was again significantly different from the control group. CONCLUSION: Intensive acupuncture treatment may improve activity at work and several relevant social and psychological variables for women with chronic pain in the neck and shoulders. The effect may last for at least three years.