Physiological and Perceptual Responses to a Single Session of Resisted Sled Sprint Training at Light or Heavy Sled Loads.

ABSTRACT: Monahan, M, Petrakos, G, and Egan, B. Physiological and perceptual responses to a single session of resisted sled sprint training at light or heavy sled loads. J Strength Cond Res 36(10): 2733-2740, 2022-The acute physiological and perceptual responses to a single session of resisted sled sprint (RSS) training are largely unexplored, nor have differences, if any, between male and female athletes been compared. Team field sport athletes (n = 27; male/female, 15/12; 21.1 ± 2.7 years) were assessed for Maximal Resisted Sled Load (MRSL) from which light (L-RSS, 30%MRSL) and heavy (H-RSS, 80%MRSL) sled loads were prescribed. On separate occasions in random order, 2 training sessions of 12 × 20 m RSS repetitions at either L- or H-RSS were performed, and assessments of physiological and perceptual responses were performed before (PRE), during, after (POST) and 24 hours after (+24 hours POST) each session. Compared to unresisted sprints, velocity decrements of 7.5 ± 2.2 and 22.7 ± 8.1% were produced by L-RSS and H-RSS, respectively. Heart rate, blood lactate, and ratings of perceived exertion were higher in H-RSS compared to L-RSS. Decrements in 20 m sprint and countermovement jump performance observed at POST had returned to PRE values at +24 hours POST. Except for a higher heart rate (∼7-12 b·min-1) in females during the respective sessions, responses to L- and H-RSS were generally similar between males and females. A single session of heavy RSS training is more demanding than light RSS training when matched for sprint number and distance, but measures of lower limb power and sprint performance return to pre-training levels within 24 hours regardless of sled load. Males and females respond similarly to a single session of RSS training when individualized, relative intensity sled loads are prescribed.

Influence of lightness difference of single anterior tooth to smile attractiveness.

OBJECTIVES: To evaluate the influence of lightness difference of a single anterior maxillary tooth on difference smile attractiveness. METHODS: A frontal view full-portrait image of a smiling male Caucasian, was digitally modified altering a single tooth, creating a series of images with varying lightness (ΔL) for the maxillary central, lateral and canine. A total of 160 participants (80 dentists, 80 laypersons) were asked to fill out a Visual Analog Scale questionnaire for every image recording smile attractiveness. RESULTS: For central incisors ΔL≥1 negatively affected attractiveness. There was a higher tolerance for lightness mismatch when one lateral incisor is lighter and the same applies when the canine was darker. Difference in lightness affected smile attractiveness both for dentists and laypersons. No difference between males and females was observed for the dentists. For laypersons, females perceived smiles with lightness difference as significantly less attractive compared to males. Dentist's age did not affect smile attractiveness perception. Younger laypersons perceived darker color, as less attractive. CONCLUSIONS: Changes in lightness of a single anterior tooth significantly affected smile attractiveness in a different way for the central vs lateral vs canine. For the dentists, age and gender did not significantly affect smile perception, in contrast to laypeople. CLINICAL SIGNIFICANCE: Lightness differences of a single anterior tooth affects smile attractiveness.

Reliability of the Maximal Resisted Sprint Load Test and Relationships With Performance Measures and Anthropometric Profile in Female Field Sport Athletes.

Petrakos, G, Tynan, NC, Vallely-Farrell, AM, Kiely, C, Boudhar, A, and Egan, B. Reliability of the maximal resisted sprint load test and relationships with performance measures and anthropometric profile in female field sport athletes. J Strength Cond Res 33(6): 1704-1714, 2019-Resisted sled sprint (RSS) training is an effective modality for the improvement of linear sprint speed. Previous methods of RSS load prescription, e.g., an absolute load or as a percentage of body mass (%BM), do not account for interindividual differences in strength, power, or speed characteristics, although the "maximum resisted sled load" (MRSL) method of RSS load prescription may provide a solution. Maximum resisted sled load is defined as the final RSS load before an athlete can no longer accelerate between 2 phases (10-15 and 15-20 m) of a 20-m linear sprint. However, the MRSL test has not been analyzed for reliability. In addition, MRSL performance has not been compared with the outcome of other performance tests. The primary aim of this study was to investigate the reliability of the MRSL testing protocol in female field sport athletes. Participants (age, 20.8 ± 1.9 years; body mass, 64.3 ± 8.4 kg; height, 1.66 ± 0.65 m) tested for anthropometric measurements, strength and power performance testing, and twice for MRSL. Maximum resisted sled load values ranged from 20.7 to 58.9% BM. Maximum resisted sled load test-retest reliability intraclass correlation coefficient, confidence intervals, and coefficient of variations were 0.95, 0.85-0.98, and 7.6%, respectively. Maximum resisted sled load was"moderately" and "strongly" correlated with a number of anthropometric and performance tests (p ≤ 0.05), including percentage fat free mass, countermovement jump, loaded countermovement jump, rate of force development, horizontal jump, and horizontal bound performance. Maximum resisted sled load is a reliable measure for determining the RSS load at which an individual can no longer accelerate during a single RSS effort over 0-20 m. Maximum resisted sled load also accounts for interindividual variation in body composition, power, and speed characteristics of female field sport players.

Physical and Physiological Demands of Elite International Female Field Hockey Players During Competitive Match Play.

McGuinness, A, Malone, S, Petrakos, G, and Collins, K. The physical and physiological demands of elite international female field hockey players during competitive match play. J Strength Cond Res 33(11): 3105-3113, 2019-The aim of the current investigation was to quantify the physical and physiological demands of elite international female field hockey match play across halves of play. Thirty-eight participants (24 ± 5 years; 173 ± 5 cm; 72 ± 5 kg) took part in 19 competitive matches during the 2014-2015 season. Participants were monitored with global positioning system technology and heart rate monitors. Players were categorized based on 3 different playing positions. Activity was categorized into total (m), high-speed running distance (m; >16 km·h), and relative distance (RD) (m·min) due to the use of rolling substitutions. Heart rate was classified based on the percentage of players' individual peak heart rate (HRpeak) determined by a Yo-Yo intermittent recovery level 1 test. Players spent on average 44 ± 7 minutes in match play. The total distance (TD) covered was 5,558 ± 527 m (125 ± 23 m·min) with 589 ± 160 m (13 ± 4 m·min) completed at high speed. Defenders covered a greater TD compared with other positions of play (p ≤ 0.001). Midfield players covered a greater distance at high speed (p ≤ 0.001) with the forwards having a higher relative distance (p ≤ 0.001). The HRpeak of the players was 199 ± 1 b·min with a mean exercise intensity of 86 ± 7.8% of HRpeak. The time spent >85% HRpeak decreased significantly across the halves (p = 0.04, η = 0.09, small). Defenders were found to spend more time >85% HRpeak when compared with forwards (p ≤ 0.001). The current investigation provides normative data that coaches should consider when constructing training regimen.

Very-Heavy Sled Training for Improving Horizontal-Force Output in Soccer Players.

BACKGROUND: Sprint running acceleration is a key feature of physical performance in team sports, and recent literature shows that the ability to generate large magnitudes of horizontal ground-reaction force and mechanical effectiveness of force application are paramount. The authors tested the hypothesis that very-heavy loaded sled sprint training would induce an improvement in horizontal-force production, via an increased effectiveness of application. METHODS: Training-induced changes in sprint performance and mechanical outputs were computed using a field method based on velocity-time data, before and after an 8-wk protocol (16 sessions of 10- × 20-m sprints). Sixteen male amateur soccer players were assigned to either a very-heavy sled (80% body mass sled load) or a control group (unresisted sprints). RESULTS: The main outcome of this pilot study is that very-heavy sled-resisted sprint training, using much greater loads than traditionally recommended, clearly increased maximal horizontal-force production compared with standard unloaded sprint training (effect size of 0.80 vs 0.20 for controls, unclear between-groups difference) and mechanical effectiveness (ie, more horizontally applied force; effect size of 0.95 vs -0.11, moderate between-groups difference). In addition, 5-m and 20-m sprint performance improvements were moderate and small for the very-heavy sled group and small and trivial for the control group, respectively. Practical Applications: This brief report highlights the usefulness of very-heavy sled (80% body mass) training, which may suggest value for practical improvement of mechanical effectiveness and maximal horizontal-force capabilities in soccer players and other team-sport athletes. RESULTS: This study may encourage further research to confirm the usefulness of very-heavy sled in this context.

Pregnancy in women with thalassemia: challenges and solutions.

Advances in treatment of thalassemia have led to the aging of thalassemic patients, and consequently concern about successful reproductive outcome is augmented. Although women with thalassemia intermedia only were considered competent of achieving pregnancy, case series reveal the willingness of both thalassemia major and thalassemia intermedia women to have a family. Pregnancy in general is characterized by dynamic multiple-system changes and increased susceptibility to oxidative stress, while homozygous, transfusion-dependent, ß-thalassemia patients manifest cardiac, hepatic, endocrine, and metabolic disorders attributable to chronic anoxia and iron overload and thalassemia intermedia, usually nontransfused, is associated with augmented risk of thromboembolic events. Pregnancy in thalassemia should be considered a high risk for both mother and fetus, and favorable outcomes are the result of continuous preconception, antenatal, and postpartum assessment and management by a team of thalassemia experts.

Resisted Sled Sprint Training to Improve Sprint Performance: A Systematic Review.

BACKGROUND: Based on recent findings regarding the mechanical determinants of sprint performance, resisted sled sprint (RSS) training may provide an effective tool for the improvement of sprint acceleration and maximal velocity. However, the volume and intensity for effective RSS training in different populations is unclear. OBJECTIVES: The primary objective was to evaluate the effectiveness of RSS training compared with unresisted sprint (URS) training, and the differential effects of sled load on RSS training outcomes. DATA SOURCES: STUDY ELIGIBILITY AND APPRAISAL: A systematic review was performed primarily using PubMed and SPORTDiscus databases. Peer-reviewed studies were accepted only if the participants used a sled towing device for a longitudinal intervention of resisted sprint training, and if RSS training was the primary difference in training intervention between groups. Effect size (ES) reported using Cohen's d was presented to compare the magnitude of effect between both dependent and independent groups. RESULTS: A total of 11 studies fulfilled the eligibility criteria. Sled loads were prescribed either as a percentage of body mass (%BM), a targeted reduction in velocity compared with unresisted sprint velocity (%V(dec)) or as an absolute load (kg). RSS training with 'light' (<10 %BM or <10 %V(dec)) loads provide 'small' decrements in acceleration (-1.5%, ES = 0.50) to 'moderate' improvements in maximal sprint velocity (2.4%, ES = 0.80) in sprint-trained individuals. 'Moderate' (10-19.9%BM or 10-14.9%V(dec)) to 'very heavy' (>30%BM or >30%V(dec)) sled loads provide 'trivial' to 'extremely large' improvements in acceleration performance (0.5-9.1%, ES = 0.14-4.00) in strength-trained or team sport individuals. Whether RSS training is more effective than URS training in the improvement of acceleration or maximal sprint velocity remains equivocal. CONCLUSIONS: RSS training is a novel training method with potential for the improvement of sprint performance, but its performance benefits over URS training remain to be conclusively demonstrated. Between-study comparisons are limited primarily by discrepancies in the training status and phase of the participants, and sled load prescription. Future work is required to define the optimal load and volume for RSS depending on the specific components of sprint performance to be enhanced.

Trichinella spiralis: differential effect of host bile on the in vitro invasion of infective larvae into epithelial cells.

The differential effect of fox and pig bile and its corresponding low molecular weight fraction (LMW) was investigated on the in vitro invasion of MDCK-AA7 epithelial cell monolayers by Trichinella spiralis muscle larvae. Seven invasion experiments were performed and a total of 274 cell monolayers were examined. Fox and pig raw bile at 1:10 and 1:20 dilution and their LMW fractions at 1:10 dilution activated T. spiralis larvae to invade the cell monolayers. In addition, fox raw bile caused significantly larger cell damage than pig raw bile at both dilutions. The area of cell damage was larger at 1:10 than at 1:20 dilution for both fox and pig raw bile (p<0.05). On the other hand, there was no significant difference between the areas of cell damage caused by the LMW fractions of fox and pig bile. It is concluded that differences between host bile actions may account for differences in host susceptibility to T. spiralis.