EXPLOSIVE PLANTAR FLEXOR PERFORMANCE: A COMPARISON OF ELITE SPRINTERS VERSUS PHYSICALLY ACTIVE INDIVIDUALS

This study examined differences in explosive muscular torque production of the plantar flexors of participants with differing training backgrounds. Explosive performance of a group of elite sprinters (n = 14) and physically active individuals (n = 14) were examined during explosive and maximal isometric contractions across different muscle-tendon unit (MTU) lengths. The rate of torque development (RTD) across time windows (0-50, 50-100, 100-150 ms) and maximal voluntary torque (MVT) was measured. Sprinters exhibited greater early phase RTD (0-50, 50-100 ms) across MTU lengths. Relative MVT was greater for sprinters at the dorsiflexed MTU length only. The results suggest sprint-specific training contributes to the improved explosive performance of the plantar flexors across MTU lengths, particularly in the early phase of muscular contraction

VISUAL DETECTION OF RESPONSE TIME IN ATHLETICS: A “GOLD STANDARD”?

The response time (RT) in the sprint start in athletics is determined automatically from sensors on the blocks but the final decision on whether an athlete is disqualified is determined by visual inspection of the sensor data. This study explored the level of uncertainty of the visual detection of athletes’ RT in the sprint start. Fifteen sprinters performed six sprint starts while forces from the front block, rear block and hands were recorded. Two experimenters performed visual RT detection on two consecutive occasions using two sizes for the analysis window. Intra- and inter-reliability analysis indicated that the mean level of uncertainty of the visual detection was approximately 20 ms for the starting block data. More research is needed to formally assess the precision of the visual detection, which may result in changes in the current false start regulation

MAPPING OUT THE RESPONSE SEQUENCE OF THE SPRINT START

Establishing the limits of sprint start response time (SSRT) requires the mapping of the muscular sequence of activation and mechanical response delays and was the aim of the current study. Sprint start performance of 15 sprinters was examined with kinematic, EMG, and block force data collected. A general muscle activation sequence was identified, with both deltoid muscles, the rear leg rectus femoris, and the rear leg tibialis anterior the first muscles to increase activation from the set position. With ankle dorsiflexion the initial motion during the block push, examining the period between tibialis anterior muscle onset and block force onset is critical for quantifying mechanical response delays . Estimates of this delay period were as low as 7 ms which has implications for our understanding of the minimum SSRT a sprinter can legally produce

Patient-To-Physician Messaging: Volume Nearly Tripled As More Patients Joined System, But Per Capita Rate Plateaued

Patients want to be able to communicate with their physicians by e-mail. However, physicians are often concerned about the impact that such communications will have on their time, productivity, and reimbursement. Typically, physicians are not reimbursed for time spent communicating with patients electronically. But under federal meaningful-use criteria for information technology, physicians can receive a modest incentive for such communications. Little is known about trends in secure e-mail messaging between physicians and patients. To understand these trends, we analyzed the volume of messages in a large academic health care system’s patient portal in the period 2001–10. At the end of 2010, 49,778 patients (22.7 percent of all patients seen within the system) had enrolled in the portal, and 36.9 percent of enrolled patients (8.4 percent of all patients) had sent at least one message to a physician. Physicians in the aggregate saw a near tripling of e-mail messages during the study period. However, the number of messages per hundred patients per month stabilized between 2005 and 2010, at an average of 18.9 messages. As physician reimbursement moves toward global payments, physicians’ and patients’ participation in secure messaging will likely increase, and electronic communication should be considered part of physicians’ job descriptions

Neuromuscular performance of the plantar flexors in sprinters and the contribution to the sprint start response time sequence

The sprint start is an important phase of maximal sprinting, with various muscle-tendon units  (MTU) and joints contributing toward performance in this phase. The ankle joint and plantar flexor MTU are of particular importance. Ankle joint and plantar flexor MTU performance in explosive  tasks is dependent on neural, morphological, and mechanical factors and may contribute to  mechanical delays in sprint start response time (SSRT). Despite the importance of the ankle joint  and plantar flexor MTU, their precise contribution to sprint start performance remains unclear.  The aim of this thesis is to investigate the influence of ankle joint mechanical delays and plantar  flexor musculoskeletal factors on sprint start performance. This research has been implemented  by conducting a literature review, and a series of experiments examining: i) the relationship  between plantar flexor mechanical delays and SSRT, ii) the accuracy of EMG onset detection  methods, iii) the reliability of neuromuscular measures of plantar flexor function across ankle joint  angles, muscle activation modes, and sex, iv) the differences in plantar flexor neuromuscular and  mechanical function due to training background, and v) the influence of the neuromuscular system  on sprint start performance variables and SSRT. Examination of sprinters’ electromechanical  delay (EMD) during a heel-lift experiment, and SSRT during competitive sprint starts found the  combined influences of signal processing time (SPT) and EMD accounted for a significant  proportion of the variability in an athlete’s SSRT (37%). This provided initial suggestions that  certain athletes may gain a performance advantage due to reduced EMD. The accuracy of  automatic detection methods compared to visual detection in EMG onset detection was examined  across various contraction types. To attain the accuracy needed, visual detection is recommended.  The inclusion of the Teager-Kaiser energy operator (TKEO) as a conditioning step prior to visual detection improved inter and intra-rater reliability. A reliability analysis highlighted that maximal  voluntary torque (MVT), early-phase rate of torque development (RTD) measures (involuntary,  and voluntary explosive), late-phase RTD measures (involuntary only), involuntary force  development time (FDT), and tendon stiffness (DF angle only) can be reliably interpreted across  the measured ankle angles when assessing between-group differences in these parameters. A  comparison of the neuromuscular function of the plantar flexor MTU of sprinters and physically  active individuals revealed explosive RTD production was greater in sprinters across ankle angles  (10° plantarflexion (PF), 0°(anatomical zero (AZ)), 10° dorsiflexion (DF)) for early-phase RTD  and at 10° DF only for late-phase RTD. Improved synchrony in neural activation of the  predominantly fast-twitch gastrocnemii muscles and the intrinsic contractile properties of the  sprinters appears to explain the greater early-phase RTD compared to physically active  individuals. Sprinters’ higher late-phase RTD at the DF angle is consistent with increased plantar  flexor neuromuscular activation and relative MVT at this angle, which are key determinants of  late-phase RTD. This work has implications for practitioners, suggesting that practice of explosive  movements can improve early and late-phase RTD of the plantar flexor MTU, mainly through  neural adaptations. During the sprint start, ankle joint muscle activation onsets and mechanical  delay parameters were related to sprint start performance variables of block clearance time (BCT)  and center of mass velocity (COMV) at block exit as well as SSRT. Improved rapid muscle  activation appears to be more important for sprint start performance than maximal muscular  strength or tendon stiffness, which aligns with previous research on the determinants of explosive  force production. Furthermore, reduced mechanical delay periods of the ankle joint were related  to a decreased SSRT. </p

Preparing residents for future practice: report of a curriculum for electronic patient–doctor communication

Objectives Patients frequently use secure web portals to access their medical record and communicate with their doctors, though few institutions currently train residents for electronic communication. We sought to develop a curriculum for secure messaging between patients and resident physicians, and to assess resident attitudes before and after the curriculum. Methods In 2011, we developed a curriculum for patient–doctor secure messaging using a web-based patient portal within an internal medicine residency programme. We asked all residents to perform a self- assessment of skills, and report attitudes toward electronic communication at the beginning and end of the experience (9 months apart). We enrolled residents who practiced at the hospital-based clinic site into the patient portal, and recorded usage statistics. Results The completed survey response rate was 108/159 (68%). At baseline, 57% of residents had used traditional email with patients, and most residents felt that the portal would increase work for providers but benefit patients. Postintervention questionnaires demonstrated no significant changes among all respondents, but residents who used the portal perceived improvements in care. Most residents were concerned about professional liability. More residents felt comfortable writing electronic messages to patients after the curriculum (80% to 91%, p=0.01). Conclusions Implementing a patient web portal and secure messaging in a residency clinic is feasible and may improve the work and educational experience of trainees. Residents were initially sceptical of secure messaging being an additional burden to their work, but this was not realised among residents who used the portal

Influence of triceps surae electromechanical delay on movement responses in the sprint start event

This study examined the delay in sprint start performance related to electromechanical delay (EMD) in the triceps surae muscle and aimed to determine whether sprinters may gain an advantage in sprint start response time (SSRT). SSRT’s of nineteen sprinters were measured using an International Association of Athletics Federations approved SSRT detection system. EMD times were also obtained from the triceps surae muscle during a simple heel-lift experiment. Using Brosnan et al. (2016) response time limits, the results demonstrated that EMD produced a significant moderate correlation with SSRT (r = 0.572, P = 0.01). Initial results suggest EMD influences SSRT. However greater specificity in the EMD measurement to the sprint start action is required to determine the true effects of EMD on SSRT

Sprint start performance: the potential influence of triceps surae electromechanical delay

In the sprint start, a defined sequence of distinct response delays occurs before the athlete produces a movement response. Excitation of lower limb muscles occurs prior to force production against the blocks, culminating in a movement response. The time delay between muscle excitation and movement, electromechanical delay (EMD), is considered to influence sprint start response time (SSRT). This study examined the delay in sprint start performance from EMD of the triceps surae muscle and examined whether certain sprinters gain an advantage in SSRT. Nineteen experienced sprinters performed sprint starts from blocks, with SSRT measured by an International Association of Athletics Federations (IAAF)-approved starting block system. EMD times were detected during a heel-lift experiment. Using revised SSRT limits, based on concerns over the validity of the IAAF 100 ms false start limit, EMD produced a significant moderate correlation with SSRT (r = 0.572, p = 0.011). Regression analysis determined that together, EMD and signal processing time (the delay between the auditory signal and muscle excitation) accounted for 37% of the variance in SSRT. Initial results suggest EMD is part of the response time process and that certain athletes may gain a performance advantage due to reduced EMD

Reliability of mechanical properties of the plantar flexor muscle tendon unit with consideration to joint angle and sex

The reliability of mechanical measures can be impacted by the protocol used, including factors such as joint angle and the sex of participants. This study aimed to determine the interday reliability of plantar flexor mechanical measures across ankle joint angles and contraction types and consider potential sex-specific effects. 14 physically-active individuals participated in two identical measurement sessions involving involuntary and voluntary plantar flexor contractions, at three ankle angles (10˚ plantarflexion (PF), 0˚ (anatomical zero (AZ)), and 10˚ dorsiflexion (DF)), while torque and surface EMG were recorded. The reliability of mechanical parameters of maximal voluntary torque (MVT), rate of torque development (RTD), electromechanical delay, and tendon stiffness were assessed using absolute and relative reliability measures. MVT measures were reliable across ankle angles. RTD measures showed good group level reliability and moderate reliability for an individual during the early phase of contraction across ankle angles. Explosive voluntary torque measures tended to be less reliable from 50 ms onward, with varied reliability across angles for late-phase RTD. Tendon stiffness demonstrated the best reliability at the DF angle. Sex-based differences in the reliability of tendon measures found that females had significantly different initial tendon length between testing sessions. Despite this, tendon excursion, force, and stiffness measures demonstrated similar reliability compared to males. Ankle angle changes influence the reliability of plantar flexor mechanical measurements across contraction types, particularly for voluntary contractions. These results highlight the importance of establishing potential protocol effects on measurement reliability prior to quantifying plantar flexor mechanical measures.</p

Onset detection in surface electromyographic signals across isometric explosive and ramped contractions: a comparison of computer-based methods

Objective. Accurate identification of surface electromyography (EMG) muscle onset is vital when examining short temporal parameters such as electromechanical delay. The visual method is considered the ‘gold standard’ in onset detection. Automatic detection methods are commonly employed to increase objectivity and reduce analysis time, but it is unclear if they are sensitive enough to accurately detect EMG onset when relating them to short-duration motor events. Approach. This study aimed to determine: (1)if automatic detection methods could be used interchangeably with visual methods in detecting EMG onsets(2)if the Teager–Kaiser energy operator(TKEO) as a conditioning step would improve the accuracy of popular EMG onset detection methods. The accuracy of three automatic onset detection methods: approximated generalized likelihood ratio (AGLR), TKEO, and threshold-based method were examined against the visual method. EMG signals from fast, explosive, and slow, ramped isometric plantarflexor contractions were evaluated using each technique. Main results. For fast, explosive contractions, the TKEO was the best-performing automatic detection method, with a low bias level(4.7 ± 5.6 ms) and excellent intraclass correlation coefficient (ICC) of 0.993, however with wide limits of agreement (LoA) (−6.2 to +15.7 ms). For slow, ramped contractions, the AGLR with TKEO conditioning was the best-performing automatic detection method with the smallest bias(11.3 ± 32.9 ms) and excellent ICC(0.983) but produced wide LoA (−53.2 to +75.8 ms). For visual detection, the inclusion of TKEO conditioning improved inter-rater and intra-rater reliability across contraction types compared with visual detection without TKEO conditioning. Significance. In conclusion, the examined automatic detection methods are not sensitive enough to be applied when relating EMG onset to a motor event of short duration. To attain the accuracy needed, visual detection is recommended. The inclusion of TKEO as a conditioning step before visual detection of EMG onsets is recommended to improve visual detection reliability