Stroke Count Research Articles

Physiological, Perceptual, and Technical Responses to On-Court Tennis Training on Hard and Clay Courts

The aim of this study was to investigate the effect of court surface (clay vs. hard court) on technical, physiological, and perceptual responses to on-court tennis training. Four high-performance junior male players performed 2 identical training sessions on hard and clay courts, respectively. Sessions included both physical conditioning and technical elements as led by the coach. Each session was filmed for later notational analysis of stroke count and error rates. Furthermore, players wore a global positioning satellite device to measure distance covered during each session, while heart rate, countermovement jump distance, and capillary blood measures of metabolites were measured before, during, and after each session. Additionally, a respective coach and athlete rating of perceived exertion (RPE) were measured after each session. Total duration and distance covered during each session were comparable (p > 0.05; d < 0.20). Although forehand and backhands stroke volume did not differ between sessions (p > 0.05; d < 0.30), large effects for increased unforced and forced errors were present on the hard court (p > 0.05; d > 0.90). Furthermore, large effects for increased heart rate, blood lactate, and RPE values were evident on clay compared with hard courts (p > 0.05; d > 0.90). Additionally, although player and coach RPE on hard courts were similar, there were large effects for coaches to underrate the RPE of players on clay courts (p > 0.05; d > 0.90). In conclusion, training on clay courts results in trends for increased heart rate, lactate, and RPE values, suggesting that sessions on clay courts tend towards higher physiological and perceptual loads than hard courts. Furthermore, coaches seem effective at rating player RPE on hard courts but may underrate the perceived exertion of sessions on clay courts.

Validation of GPS and accelerometer technology in swimming

To evaluate the validity of an integrated accelerometer and Global Positioning System (GPS) device to quantify swimming kinematics variables in swimming. Criterion validation study. Twenty-one sub-elite swimmers completed three 100 m efforts (one butterfly, breaststroke and freestyle) in an outdoor 50 m Olympic pool. A GPS device with an integrated tri-axial accelerometer was used to obtain mid-pool velocity and stroke count of each effort. This data was compared to velocity and stroke count data obtained from concurrently recorded digital video of the performance. A strong relationship was detected between the accelerometer stroke count and the video criterion measure for both breaststroke (r>0.98) and butterfly (r>0.99). Also, no significant differences were detected between the GPS velocity and video obtained velocity for both freestyle and breaststroke. There was a significant difference between the GPS velocity and criterion measure for butterfly. Acceptable standard error and 95% limits of agreement were obtained for freestyle (0.13 m s(-1), 0.36 m s(-1)) and breaststroke (0.12 m s(-1), 0.33 m s(-1)) compared to butterfly (0.18 m s(-1), 0.50 m s(-1)). Relative error measurements ranged between 10.2 and 13.4% across the three strokes. The integrated accelerometer and GPS device offers a valid and accurate tool for stroke count quantification in breaststroke and butterfly as well as measuring mid-pool swimming velocity in freestyle and breaststroke. The application of GPS technology in the outdoor training environment suggests advantageous practical benefits for swimmers, coaches and sports scientists.

Applied Force as a Determining Factor in Lithic Use-Wear Accrual: An Experimental Investigation of its Validity as a Method with which to Infer Hominin Upper Limb Biomechanics

The advent of flake technology represented a fundamental shift in the capability of hominins to effectively access and process animal food sources. As such, the efficiency with which these tools were utilized is often widely implicated in palaeoanthropological debate, most pertinently, with regards to the evolution of upper limb biomechanics. Hence, it would then be of significance if the force, and by association efficiency, with which these tools were used is able to be determined. Presented here is the first attempt to correlate the force with which flaked tools are used to the associated microwear polish accrued on the lithics worked edge. This would potentially allow biomechanical inferences to be taken from stone artifacts and subsequently be applied to the populations that were using them. Twenty five participants of varying strength carried out a simple cutting task using small, unhafted flakes made from English chalk flint. Both maximum and mean applied force was recorded during these tasks by a sensor placed under the worked material while all other variables, including stroke count and flake size, were controlled for. Lithic polish was quantified through seven textural analyses of SEM micrographs. Results indicated that there were no statistically significant relationships between lithic polish and both maximum and mean applied force at low levels of variation. It is, however, suggested that given more archaeologically inferable experimental conditions then polish accrual may have displayed higher developmental distinctions, thus allowing lithic wear to differentiate between applied forces.

Abstract 141: Stroke Trends in Mexican Americans and non Hispanic Whites

Objective: As a primary, pre-specified objective of the population-based Brain Attack Surveillance in Corpus Christi (BASIC) project we studied trends in stroke occurrence among Mexican Americans (MAs) and non Hispanic whites (NHWs) in Corpus Christi, Texas. Previous work suggested higher stroke rates in MAs compared with NHWs. Methods: We performed active and passive surveillance, and using source documentation, validated all stroke cases from January, 2000-December, 2010 in this community. Yearly population counts were obtained from the 2000, 2010 US Census and intercensal estimates. Incidence rates of total stroke (completed ischemic and intracerebral hemorrhage) were calculated per 10,000 population. Poisson regression models using the stroke counts within categories of race/ethnicity, age (45-59; 60-74, and 75+) and sex as the outcome and (log) population counts as the offset were used to estimate adjusted rates, rate ratios and time trends. Time trends were modeled as a linear term of years since 2000. The models used data from the entire study period to estimate incidence rates in 2000 and 2010. Results: There were 3,086 strokes in MAs and 2,328 in NHWs. Between 2000 and 2010 stroke incidence declined by 3.8% per year (95%CI: 3.0%, 4.6%) (see Figure). In 2000 the incidence rate was 54.2/10,000, it was 35.9/10,000 in 2010. For those aged 45-59; 60-74, and 75+, the yearly declines were 0.6% (95%CI: 1.2%, 2.3%); 6.1% (95%CI: 4.8%, 7.5%); and 3.9% (95%CI: 2.6%, 5.1%) per year, respectively. The decline in stroke incidence was not significantly different by ethnicity in any age group. Within each age category, the ethnicity rate ratios in 2000 vs. 2010 were: 45-59, 2.23 vs 2.15 (p=0.87); 60-74, 1.58 vs 1.77 (p=0.45); and 75 or older, 1.17 vs 1.02 (p=0.29). Conclusions: Stroke occurrence rates have declined dramatically in the last decade in both MAs and NHWs, particularly in those 60 and older. However, the disparity between MA and NHW stroke rates persists among those &lt;75.

Effects of Different Types of Warm-Up on Swimming Performance, Reaction Time, and Dive Distance

The purpose of this study was to evaluate the effects of 3 types of warm-up (WU) on swimming performance, reaction time, and dive distance. In repeated-measures counterbalanced design, National Collegiate Athletic Association Division I swimmers (n = 16) used 3 WUs before performing 50-yd (45.7-m) freestyle swim trials. The WU consisted of (a) no WU, (b) short WU (50-yd at 40% of swimmers' maximal effort and 50-yd at 90%), and (c) regular WU (usual precompetition WU). The mean 50-yd time was significantly faster (p = 0.01) after the regular WU (24.95 ± 1.53 seconds) when compared with that of the short WU (25.26 ± 1.61 seconds). However, individual data indicated that 19% of the participants performed their best in the 50-yd category after short, 37% after no, and 44% after regular WU. Heart rate was significantly higher (p = 0.01) after regular WU (100 ± 13 b·min(-1)) when compared with that of the no WU category (88 ± 18 b·min(-1)). However, no significant differences among WUs were found for reaction time (p = 0.96), rating of perceived exertion post 50-yd time trial (p = 0.11), dive distance (p = 0.67), or stroke count (p = 0.23). In conclusion, the average regular WU was better than short or noWU to achieve the fastest mean time in the 50-yd freestyle; however, some individual performances were faster after WUs different from their regular approach.

Development of a wireless sensor network for use as an automated system for monitoring swimming starts

A wireless sensor network has been developed and used to monitor the important performance parameters pertaining to a swimmer’s start. The variables identified as important include time to back foot leaving the block, time to hip entry into the water, time to first kick, time to first stroke, number and rate of the underwater kick and stroke count and rate. These parameters were specified by the users (coaches, biomechanists and swimmers) of the system. The measurements were validated against the vision analysis system currently used during in-water training with the national swimming team. From the results, it can be suggested that the wireless sensor network can be used as an automated system for monitoring performance parameters considered of importance to the user during the swimming start.

Decreased chewing activity during mouth breathing

This study examined the effect of mouth breathing on the strength and duration of vertical effect on the posterior teeth using related functional parameters during 3 min of gum chewing in 39 nasal breathers. A CO(2) sensor was placed over the mouth to detect expiratory airflow. When no airflow was detected from the mouth throughout the recording period, the subject was considered a nasal breather and enrolled in the study. Electromyographic (EMG) activity was recorded during 3 min of gum chewing. The protocol was repeated with the nostrils occluded. The strength of the vertical effect was obtained as integrated masseter muscle EMG activity, and the duration of vertical effect was also obtained as chewing stroke count, chewing cycle variation and EMG activity duration above baseline. Baseline activity was obtained from the isotonic EMG activity during jaw movement at 1.6 Hz without making tooth contact. The duration represented the percentage of the active period above baseline relative to the 3-min chewing period. Paired t-test and repeated analysis of variance were used to compare variables between nasal and mouth breathing. The integrated EMG activity and the duration of EMG activity above baseline, chewing stroke count and chewing cycle significantly decreased during mouth breathing compared with nasal breathing (P<0.05). Chewing cycle variance during mouth breathing was significantly greater than nasal breathing (P<0.05). Mouth breathing reduces the vertical effect on the posterior teeth, which can affect the vertical position of posterior teeth negatively, leading to malocclusion.

Using image processing for biomechanics measures in swimming

Underwater video analysis is common in elite level swimming for stroke correction, technique analysis and as a visual aid to support coaches and athletes. Because of the challenges of the underwater visual environment and ambulatory camera work, video can be degraded and considered non ideal, additionally the athletes movement can lead to blurred vision and bubbles from cavitation effects. In this paper we use image analysis techniques to enhance images for improved clarity and automated detection of limb segments related to metrics of interest at the elite level. Thus we address the problems of detection, segmentation and estimation of body configuration using several image processing algorithms. These classic image processing problems are even more complicated with video footage of poor quality as described above. Our approach is to use adaptive algorithms like the global probability for boundary detection to detect the swimmer's boundaries and deformable models arranged in a pictorial structure to recognize body and limbs plus their configuration. Our results show that it is possible to detect the athlete and relevant body segments. Identification and estimation of the body configuration in every frame is demonstrated to be feasible. From this analysis, common metrics can also be extracted such as stroke counts, stroke rate and primary phases of an arm stroke. The goal of this work is to support the training of athletes and help them improve their technique.

2P1-O03 ひらがなのキネクトを用いた空中手書きインタフェース(VRとインタフェース)

This paper discussed the input interface of aerial hand written characters using Kinect which is the sensor device for Xbox 360. The proposed recognition algorithm of hiragana is based on simplified glyph data composed of a stroke count and a series of writing direction. The effectiveness of our approach is demonstrated by some experiments.

Inspiratory Muscle Fatigue Significantly Affects Breathing Frequency, Stroke Rate, and Stroke Length during 200-m Front-Crawl Swimming

The aim of the current study was to assess the impact of inspiratory muscle fatigue (IMF) on total breaths taken (f(tot)), breaths per minute (f(b)), stroke count (SC), stroke rate (SR), and stroke length (SL) during constant velocity front-crawl swimming. Eight collegiate swimmers undertook a 200-m front-crawl swim on 2 separate occasions. On 1 occasion, IMF was induced immediately before the swim (IMF trial), and on the other occasion, the swim was undertaken in the absence of IMF (control trial). Trials were administered using a randomized crossover design and at a swimming velocity equivalent to 85% of race pace: Pilot testing identified this as being the fastest pace, which did not induce IMF. Maximal inspiratory mouth pressure, which was measured at the mouth and from residual volume, fell by 17% (p < 0.05) in response to IMF but was unchanged in response to the swim itself (p < 0.05). When compared to the control trial, f(tot), f(b), SC, and SR increased (p < 0.05) and SL decreased (p < 0.05) in response to IMF. These data suggest that the increase in f(tot) and f(b) in the presence of IMF occurred, in part, in an attempt to alleviate dyspnea. As a result, SL decreased and SR and SC increased, although variability in the SR and SC response did occur. However, as a number of identical muscles are recruited during deep inspirations and the front-crawl arm stroke, the possibility that arm coordination was changed, in part, to compensate for a reduced force-generating capacity per arm stroke should not be overlooked.

Weather, season, and daily stroke admissions in Hong Kong

Previous studies examining daily temperature and stroke incidence have given conflicting results. We undertook this retrospective study of all stroke admissions in those aged 35 years old and above to Hong Kong public hospitals from 1999 through 2006 in order to better understand the effects of meteorological conditions on stroke risk in a subtropical setting. We used Poisson Generalized Additive Models with daily hemorrhagic (HS) and ischemic stroke (IS) counts separately as outcomes, and daily mean temperature, humidity, solar radiation, rainfall, air pressure, pollutants, flu consultation rates, day of week, holidays, time trend and seasonality as predictors. Lagged effects of temperature, humidity and pollutants were also considered. A total of 23,457 HS and 107,505 IS admissions were analyzed. Mean daily temperature had a strong, consistent, negative linear association with HS admissions over the range (8.2-31.8°C) observed. A 1°C lower average temperature over the same day and previous 4 days (lags 0-4) being associated with a 2.7% (95% CI: 2.0-3.4%, P < .0.0001) higher admission rate after controlling for other variables. This association was stronger among older subjects and females. Higher lag 0-4 average change in air pressure from previous day was modestly associated with higher HS risk. The association between IS and temperature was weaker and apparent only below 22°C, with a 1°C lower average temperature (lags 0-13) below this threshold being associated with a 1.6% (95% CI:1.0-2.2%, P < 0.0001) higher IS admission rate. Pollutant levels were not associated with HS or IS. Future studies should examine HS and IS risk separately.

Physiological demands of match-play in elite tennis: A case study

The physiological and perceptual demands together with match notation of a four-set tennis match were studied in two elite professional players during the preparation for the 2008 Davis Cup. The design of this case report is unique in that it is the first to describe the demands of prolonged match-play (197 min) over four sets in ecologically valid conditions. The variables measured before and after each set included blood lactate and glucose concentrations, body mass, and perception of effort. Stroke count for each rally and heart rate were recorded during each set while salivary cortisol concentration was determined before and after the match. The rally length decreased as the match progressed. The results showed significant physiological stress, with each player losing greater than 2.5% of body mass (as fluid) and having elevated salivary cortisol concentrations after the match. Heart rate and perception of effort were also increased following each set indicating increasing stress. However, blood lactate decreased following the fourth set while blood glucose was maintained. The results also suggest that elite players may adjust work rates or tactics to cope with the increased perception of effort. This report shows that four sets of tennis are associated with increasing stress and fatigue.

B23 Integration of multiple data sources for swimming biomechanics

Assessment of swimming biomechanics is challenging because the activity is water based and is not stationary, nor can easily be simulated as such. This paper introduces sensors fusion tools to combine several technologies to enable a more robust investigation into the movements of swimmers. Swimming assessment is traditionally a labour intensive process where even the primary measures of stroke phase, stroke rates, stroke counts, and lap times have to be manually recorded or extracted from video data. While more detailed stroke information can be gathered from inertial sensor and video data it is time consuming and manually based. Recent advances in microsensors have demonstrated the validity of using wearable sensors to replace these manual methods in an automated way [1] and the potential to further extend the capability to detailed biomechanics measures [2] though the use of multiple sensors per swimmer. The use of microsensors however introduces new complexity through the collection of large amounts of data that need to be collected, saved, synchronized, and appropriately conditioned prior to analysis. Analysis techniques include filtering, event detection and display in a form useful for a range of audiences including athletes, coaches, sports scientists and researchers. This paper describes tools developed that facilitate the use of microsensor technology and its fusion with other data sources.

An unobtrusive swimming monitoring system for recreational and elite performance monitoring

Swimming is one of Australia's most successful sports at international competition. This success is due to the elite level support provided at Australia's sports academies and institutes, together with strong recreational and developmental programmes. In recent years Australia's approach to elite level sport has been somewhat eroded as other countries adopt our processes, coupled with a shrinking talent pool nationally. Since early 2000 a technology initiative has been undertaken to help address this by offering a way to provide elite level support at the local level. Swimming assessment is traditionally a labour intensive process where stroke phase, stroke rates, stroke counts, and lap times are often manually recorded or extracted from video data. This manual process is dependent on high staffing levels and is generally unavailable for routine training activities or remote areas. Beyond the basic measures above the coordination of key body segments in swimming is of growing interest for swimmers and coaches though it is difficult to obtain. Understanding these movements can identify whether the action is enhancing swimming performance, or potentially harmful. The use of wearable sensors, and in particular inertial sensors, is an emerging field in sports monitoring and a promising tool for swimming assessment. This paper describes the scaling of wearable sensor technology from single device/single user to multiple devices/ multiple users together with a framework that allows near real time data analysis as well as post session and multi session. Results demonstrate the usefulness and feasibility for such devices in the preparation of athletes. The developed system demonstrates how analysis will facilitate the primary goals of developing athlete performance to be realised, both through poolside interventions and long term developmental planning.

Myanmar Printed Portable Document Format Recognition and Transformation with Formatting

This paper proposed Myanmar Printed Character Recognition with their related format. The system consists of two parts; recognition and formatting. It recognizes for Myanmar Portable Document Format (.pdf) such as font size, font style, alignment and table, and it converts the existing document to Machine Editable Word Document (.doc). Table classification can also be performed for table recognition and formatting. The extraction of text format, paragraph format and table format can be done efficiently. The system is based on MICR (Myanmar Intelligent Character Recognition) which is one kind of ICR (Intelligent Character Recognition). MICR used statistical and semantic information which includes width and height ratio, black stroke counts, number of loops, open directions and histogram value, etc. MICR has become successful in character recognition area recent years. MICR can produce character recognition with high accuracy rate and faster speed. The final decision is made by the voting system. The system use image processing and Matlab programming. General Terms Character recognition and formatting, image processing, ICR Keywords Hough Transformation, Statistical and Semantic, table and paragraph formatting, pali character recognition

Thunderstorm Electrical Parameters vis-a-vis Rainfall and Surface Air Temperatures over a Tropical Inland Station, Pune, India

The relationship of lightning with rainfall and temperature is investigated on the basis of a four-year (2004-2007) data set over the Pune region. It is found that the annual variations of stroke count and rainfall both are bimodal with the first peak value of rainfall showing a one month time lag from the first peak value of stroke count. This is attributed to the prime period of the onset phase of summer monsoon rainfall over the Pune region. Lightning is found to be highly correlated with rainfall (r = 0.792, significant at 0.4%), but by excluding the data for the month of July. The annual variation in the monthly mean surface wet bulb temperature and stroke count for the period under study over the Pune region shows similar peaks in June and September. These two parameters are well-correlated and show a positive correlation coefficient of 0.59, which is significant at the 5% level. A massive reduction in the lightning stroke count during July and August is attributed to low ground temperature that gives rise to lower updraft velocities and shallower cloud depth. There is good parallelism in the variation of surface air temperature and Point Discharge Current (PDC). The correlation coefficient between these two parameters is 0.934, and it is highly significant.

Lightning-produced NO&amp;lt;sub&amp;gt;x&amp;lt;/sub&amp;gt; during the Northern Australian monsoon; results from the ACTIVE campaign

Abstract. Measurements of nitrogen oxides onboard a high altitude aircraft were carried out for the first time during the Northern Australian monsoon in the framework of the Aerosol and Chemical Transport in Tropical Convection (ACTIVE) campaign, in the area around Darwin, Australia. During one flight on 22 January 2006, average NOx volume mixing ratios (vmr) of 984 and 723 parts per trillion (ppt) were recorded for both in and out of cloud conditions, respectively. The in-cloud measurements were made in the convective outflow region of a storm 56 km south-west of Darwin, whereas those out of cloud were made due south of Darwin and upwind from the storm sampled. This storm produced a total of only 8 lightning strokes, as detected by an in-situ lightning detection network, ruling out significant lightning-NOx production. 5-day backward trajectories suggest that the sampled airmasses had travelled over convectively-active land in Northern Australia during that period. The low stroke count of the sampled storm, along with the high out-of-cloud NOx concentration, suggest that, in the absence of other major NOx sources during the monsoon season, a combination of processes including regional transport patterns, convective vertical transport and entrainment may lead to accumulation of lightning-produced NOx, a situation that contrasts with the pre-monsoon period in Northern Australia, where the high NOx values occur mainly in or in the vicinity of storms. These high NOx concentrations may help start ozone photochemistry and OH radical production in an otherwise NOx-limited environment.

Validity and reliability of kick count and rate in freestyle using inertial sensor technology

In freestyle swimming the arm action is routinely quantified by stroke count and rate, yet no method is currently available for quantifying kick. In this study, we assessed the validity and reliability of inertial sensor technology (gyroscope) to assess kick count and rate. Twelve Paralympic swimmers completed a 100-m freestyle-swimming time-trial and freestyle kicking-only time-trial three times each in a season. An algorithm was developed to detect the up and down beat of individual kicks from the gyroscope trace. For comparative purposes, underwater video analysis provided the criterion measure. The standard error of the estimate (validity) for kick count, expressed as a coefficient of variation, was 5.9% (90% confidence interval 5.5 to 6.4) for swimming, and 0.6% (0.5 to 0.6) for kicking-only trials. The mean bias for kick count was −1.7% (−2.4 to −1.1) for swimming, and −0.1% (−0.2 to −0.1) for kicking-only trials. Correlations between the sensor and video for kick count were 0.96 (0.95 to 0.97) for swimming, and 1.00 (1.00 to 1.00) for kicking-only trials. The typical error of the measurement (reliability) between trials was approximately 4% for kick count and rate. The inertial sensors and associated software used generated sufficient validity and reliability estimates to quantify moderate to large changes in kick count and rate in freestyle swimming.

Comparison of Identification of Chinese versus English Words with Brief Exposures

The orthographic differences between Chinese and English should influence the identification of words in the two languages. This study compared the identification of 50 Chinese and 50 comparable English words by 17 Chinese and 17 English participants, respectively. For English words, correlation and analysis of variance indicated significant effects for frequency and letter count. For Chinese words, the same statistical analyses yielded a significant frequency effect. Both analyses also showed stroke count of the first Chinese character was not related to accuracy of identification, while the two analyses yielded inconsistent results concerning relationships between the stroke count of the second character and accuracy of identification. These studies did not employ a masking stimulus, and 5 msec. were enough to activate sensory memory of most Chinese words, while 10 msec. were needed for most English words. These differences were significant by Wilcoxon rank-sum tests.

On predictive models and user-drawn graphical passwords

In commonplace text-based password schemes, users typically choose passwords that are easy to recall, exhibit patterns, and are thus vulnerable to brute-force dictionary attacks. This leads us to ask whether other types of passwords (e.g., graphical) are also vulnerable to dictionary attack because of users tending to choose memorable passwords. We suggest a method to predict and model a number of such classes for systems where passwords are created solely from a user's memory. We hypothesize that these classes define weak password subspaces suitable for an attack dictionary. For user-drawn graphical passwords, we apply this method with cognitive studies on visual recall. These cognitive studies motivate us to define a set of password complexity factors (e.g., reflective symmetry and stroke count), which define a set of classes. To better understand the size of these classes and, thus, how weak the password subspaces they define might be, we use the “Draw-A-Secret” (DAS) graphical password scheme of Jermyn et al. [1999] as an example. We analyze the size of these classes for DAS under convenient parameter choices and show that they can be combined to define apparently popular subspaces that have bit sizes ranging from 31 to 41—a surprisingly small proportion of the full password space (58 bits). Our results quantitatively support suggestions that user-drawn graphical password systems employ measures, such as graphical password rules or guidelines and proactive password checking.