Breathing through a diving snorkel; theory and experiment of air flow resistance and cost of breathing.

The snorkel allows a surface swimmer to observe the underwater world through the face mask without being disturbed by inhaling. The effect of a snorkel on breathing resistance and cost is widely held to be substantial. This study aims to model these parameters and to measure indirectly the actual increases. Further, resistances of differing designs and dimensions were assessed and recommendations were made concerning use and choice. Maximal voluntary ventilation in 12 seconds (MVV12) was measured in 19 volunteers seated on dry land with and without a classic J-type snorkel (inner diameter 20.5 mm). The extra and total resistances and costs were calculated using the MVV12 data and using estimated airways resistance extrapolated from subject's demography and spirometric literature data. MVV12 measurements with snorkel showed a minute volume of 152 ±38 L∙min-1, 6.0 ±3.7% lower than without snorkel (p = 7.0x10-6). The theoretical MVV12, calculated from snorkel and airways resistances, decreased by 3.2%. Experimental total breathing resistance (457±83 Pa∙s∙L-1) was 6.5 ± 3.2% higher than without snorkel (p = 2.6x10-7), but the total mechanical breathing cost was unaffected by the snorkel (13.58 Watts with; 13.64 Watts without). Divers' estimations of resistance increase were exaggerated (8.8% at rest, 23% swimming). Classical J-type snorkels with an inner diameter ≥19.5 mm add 3-16% resistance . There is no risk of hypercapnia. Scuba divers are recommended to use their snorkel to breathe more comfortably on the surface. It is recommended the snorkel be made a mandatory safety accessory. The best multipurpose snorkel (19-21 mm) has no top appendages and no water release valve.

Women Are at Higher Risk for Concussions Due to Ball or Equipment Contact in Soccer and Lacrosse.

BACKGROUND: There is ample evidence to suggest sex- and gender-based differences in the incidence of sports-related concussions. The mechanisms of concussion may vary between male and female athletes and contribute to this observed difference. Understanding the underlying etiology by pooling data from primary studies across different settings and sport types will inform interventions that can reduce concussion rates. QUESTIONS/PURPOSES: Specifically, we asked: (1) In which sports are female athletes less likely to experience concussions from player contact? (2) In which sports are female athletes more likely to experience concussions because of ball or equipment contact? METHODS: PubMed, EMBASE, and Cochrane Library databases were searched to identify articles published from January 2000 to December 2018. Ten studies met the inclusion criteria, which were studies that reported concussion incidence by mechanism for both male and female athletes. Exclusion criteria included non-English studies, conference abstracts, and studies on non-sports related concussions. The sports represented by the 10 studies included ice hockey (n = 4), soccer (n = 5), basketball (n = 4), baseball/softball (n = 4), and lacrosse (n = 5). The rate ratio was calculated as the incidence rate in female athletes/male athletes for each concussion mechanism or activity. Data were pooled using the DerSimonian-Laird random-effects model. Study quality was assessed with the Newcastle-Ottawa Scale. RESULTS: Female athletes were at lower risk of player-contact-induced concussions in lacrosse (pooled rate ratio 0.33 [95% CI 0.25 to 0.43]; p < 0.001), basketball (pooled rate ratio 0.86 [95% CI 0.76 to 0.97]; p = 0.01), ice hockey (pooled rate ratio 0.64 [95% CI 0.56 to 0.73]; p < 0.001), soccer (pooled rate ratio 0.70 [95% CI 0.66 to 0.75]; p < 0.001), and soccer heading (pooled rate ratio 0.80 [95% CI 0.72 to 0.90]; p < 0.001); in these sports, men were at higher risk of concussions from player contact. Female athletes were more likely to experience concussions because of ball or equipment contact in lacrosse (pooled rate ratio 3.24 [95% CI 2.10 to 4.99]; p < 0.001), soccer (pooled rate ratio 2.04 [95% CI 1.67 to 2.49]; p < 0.001), and soccer heading (pooled rate ratio 2.63 [95% CI 1.84 to 3.77]; p < 0.001). CONCLUSIONS: The mechanism or activity underlying concussions differs between male and female athletes across different sports. This finding remains the same regardless of whether there are rule differences between the men's and women's games. The implementation of other interventions are required to further ensure player safety, including protective head equipment, concussion prevention training, or rules limiting player contact in the men's game. LEVEL OF EVIDENCE: Level III, retrospective study.

Is ski boot sole abrasion a potential ACL injury risk factor for male and female recreational skiers?

OBJECTIVES: To evaluate the potential impact of ski boot sole abrasion on the ACL injury risk of recreational skiers. METHODS: During the past two winter seasons 2016/17 and 2017/18, this retrospective case-control study was conducted in one Austrian ski area. Among a cohort of 148 ACL-injured (51.4% females) and 455 uninjured recreational skiers (43.3% females), age, sex, height, weight, and self-reported skill level were collected by questionnaire, ski length and sidecut radius were notated and sole abrasion of the toe and heel piece of the ski boot was measured using a digital caliper. RESULTS: ACL-injured skiers showed a higher proportion of female (51.4% vs 43.3%, P < 0.001) and less skilled skiers (48.6% vs 20.9%, P < 0.001), and ski length to height ratio was higher (94.7 ± 3.7 vs 93.8 ± 5.0%, P = 0.019) compared to uninjured skiers. ACL-injured skiers used ski boots of greater abrasion at the toe (4.8 ± 1.8 vs 2.4 ± 2.5 mm, P < 0.001) and heel piece (5.4 ± 1.8 vs 3.3 ± 2.3 mm, P < 0.001) compared to controls. Multivariate regression analysis revealed, beside female sex (OR 6.0, 95% CI, 3.1-11.5, P < 0.001), lower skill level (OR 3.2, 95% CI, 1.9-5.4, P < 0.001) and ski length to height ratio (OR 1.1, 95% CI, 1.0-1.2, P < 0.001), sole abrasion at the toe (OR 1.8, 95% CI, 1.5-2.1, P < 0.001) and heel piece (OR 1.4, 95% CI, 1.2-1.6, P < 0.001) to be independently associated with an ACL injury among recreational alpine skiers. CONCLUSIONS: Based on the underlying findings, ski boot sole abrasion was found to be an independent risk factor and may contribute to an increased ACL injury risk.

Friction Blister by Climbing Harness: A Case Report.

An experienced 24-y-old climber on Mount Everest presented to the Base Camp medical clinic with a friction blister on his right flank. The blister was filled with clear fluid and was located about 3 cm posterior and 3 cm superior to the highest point of the right iliac crest, the site where a climbing harness would support the climber while hanging. A diagnosis of friction blister caused by a climbing harness used while traversing between Camp 2 and Camp 3 of Mount Everest was made. The blister was managed with hydrocolloid dressing, and the patient resumed climbing after 1 wk. The lesion healed with scarring at 2 wk. Friction blisters of the feet are common in climbers wearing ill-fitting shoes, but friction blisters caused by climbing harnesses are unusual and have not been reported in the literature as far as the authors are aware. All existing guidelines for blister management pertain to blisters of the feet, and there are inconsistencies in recommendations made by various authors. This unusual case in an extreme environment provides a good learning opportunity.

Wearing body armour and backpack loads increase the likelihood of expiratory flow limitation and respiratory muscle fatigue during marching.

The effect of load carriage on pulmonary function was investigated during a treadmill march of increasing intensity. 24 male infantry soldiers marched on six occasions wearing either: no load, 15 kg, 30 kg, 40 kg or 50 kg. Each loaded configuration included body armour which was worn as battle-fit or loose-fit (40 kg only). FVC and FEV1 were reduced by 6 to 15% with load. Maximal mouth pressures were reduced post load carriage by up to 11% (inspiratory) and 17% (expiratory). Increased ventilatory demands associated with carrying increased mass were met by increases in breathing frequency (from 3 to 26 breaths·min-1) with minimal changes to tidal volume. 72% of participants experienced expiratory flow limitation whilst wearing the heaviest load. Loosening the armour had minimal effects on pulmonary function. It was concluded that as mass and exercise intensity are increased, the degree of expiratory flow limitation also increases. Practitioner Summary: This study investigated the effect of soldier load carriage on pulmonary function, to inform the trade-off between protection and burden. Load carriage caused an inefficient breathing pattern, respiratory muscle fatigue and expiratory flow limitation during marching. These effects were exacerbated by increases in mass carried and march intensity.

Is Helmet and Faceguard Modification Common in Hurling and Camogie and Why Is It Done?

Aims Despite no previous research, it is anecdotally reported that hurling and camogie players modify their helmet and faceguard, which is against GAA regulations and can potentially increase injury risk. This study aimed to establish the prevalence and rationale behind modifications in hurling and camogie. Methods An online questionnaire was completed by 304 players aged over 18 (62% hurlers, 38% camogie players) which consisted of 27 questions. Results Appearance (43%) was the primary reasons for helmet brand choice, with just 1.6% citing safety as a main reason for choice. Surprisingly, 8% of helmets were already modified when purchased and 31% of participants made further modifications, primarily switching faceguards and removal of bars. Restricted vision, comfort and perceived poor quality of the helmet/faceguard were the most common reasons for modification. Players predominantly (75.8%) agreed that further education on modifications is required. Conclusion Future research on the relationship between helmet/faceguard modification and injury risk is required.

Paediatric injury from indoor trampoline centres.

Indoor trampoline parks are increasing as a source of injuries among children. We conducted a prospective cohort study, with semi-structured interview and medical record review, of children aged <17 years presenting to a paediatric emergency department following an injury at an indoor trampoline park. In a 6-month period in 2014, 40 such children (55% female) presented to the department. Common mechanisms were individual jumpers falling while attempting a somersault or trick, landing awkwardly on an obstacle such as a ball or protective padding, and multiple users on a single trampoline. Most sustained soft tissue injuries (n=22, 55%) and fractured bones (n=15, 37.5%). One child sustained an unstable cervical fracture/dislocation. Unlike domestic trampolines, where the majority of injuries occur from falling off, most trampoline-park injuries occur on the trampoline surface. These differences require injury prevention strategies that engage children, carers and businesses to meet best practice design and management standards.

Effect of bike-fit in the perception of comfort, fatigue and pain.

The aim of this study was to assess the influence of different bike positions on the perception of fatigue, pain and comfort. Twenty cyclists underwent three tests that involved cycling for 45 min at their individual 50% peak aerobic power output while adopting different positions on the bike. Participants performed the cycling tests adopting three positions defined by two parameters (knee flexion angle [20°, 30°, 40°] and trunk flexion angle [35°, 45°, 55°]) in random order. Angles were measured using a 2D motion analysis system during cycling and applying Fonda's correction factor. Perceptions of comfort, fatigue and pain were reported before the end of each test. The combination of 40° knee flexion and 35° trunk flexion was perceived as the most uncomfortable position. Moreover, greater knee flexion had a negative effect on trunk comfort, accompanied by greater levels of fatigue and pain perception in the anterior part of the thigh and knee. In conclusion, cyclists perceived the most comfortable position to be when the saddle height was within the recommended knee angle (30° calculated from the offset position or 40 ± 4.0° of absolute value). Upright trunk was found to be the most comfortable position for recreational cyclists, where aerodynamics is not so important. Cyclists' bike perceptions should be taken into account when it comes to choosing the most beneficial position, since this can play a role in injury prevention and enhance cycling performance.

Contact Dermatitis to Personal Sporting Equipment in Youth.

BACKGROUND: Contact dermatitis to personal sporting equipment in youth is poorly studied. OBJECTIVE: To review the results of patch testing 6 youth to their sporting equipment in a dermatology general private practice from 2006 to 2011. METHODS: A retrospective analysis of 6 youth aged 11 to 14 who were evaluated for chronic and persistent dermatitis occurring in relation to sports equipment was conducted. All patients were subjected to epicutaneous (patch) testing, which included some or all of the following: North American Contact Dermatitis Group (NACGD) series, textile series, rubber series, corticosteroid series, and raw material from the patients' own personal equipment. RESULTS: All cases had 1 or more positive patch test reactions to an allergen within the aforementioned series, and 3 subjects tested positive to their personal equipment in raw form. CONCLUSIONS: Allergic contact dermatitis, not irritant, was deemed the relevant cause of chronic dermatitis in 4 of the 6 patients due to positive reactions to epicutaneous tests and/or personal equipment. The utility of testing to patients' own sporting equipment was shown to be of additional value and should be considered when patch testing for contact allergy to sporting equipment.

Etiological Foundation for Practical Strategies to Prevent Exercise-Related Foot Blisters.

This work outlines the etiological factors for exercise-related foot blisters and the pertinent prevention strategies related to these causes. Blisters result from shear forces within the epidermis causing cell necrosis. The extent of skin shear is influenced by friction at the skin and other interfaces, various skin characteristics, bony movement, and the shear modulus of the foot ware. The number of shear cycles is another factor in the development of blisters. Key preventative strategies include limiting the number of shear cycles, avoiding moisture and particulate accumulation next to the skin, frequent use of skin lubricants, elimination of pressure points through proper fitting and broken in shoes and callous removal, use of low shear modulus insoles, and induction of skin adaptations through proper training. Other methods requiring further research, but with theoretical support, include the use of taping and low friction patches over high-friction areas, and double-layered or toe socks.

Influence of voluntary standards and design modifications on trampoline injury in Victoria, Australia.

PURPOSE: To examine the influence of the voluntary Australian trampoline standard (AS 4989-2006) and market-driven design modifications on relevant trampoline injuries. METHODS: Trend and intervention analysis on frequencies and proportions of hospital-treated trampoline-related injury in Victoria, Australia, extracted from the Victorian Emergency Minimum Dataset from 1 July 1999 to 30 June 2013. The injuries relevant to the AS were contact with spring and frame, and multiple-user injury. Falls from trampolines were relevant for netted trampolines, a market-driven modification. RESULTS: Frequency of all trampoline injuries increased by 11.4% (95% CI 10.0% to 11.7%) on average each year. Spring and frame, and fall injuries increased to a lesser extent (8.7%, 95% CI 6.9% to 9.8% and 7.3%, 95% CI 5.8% to 8.3%, respectively). Multiple-user injuries increased by 21.0% (95% CI 16.3% to 21.9%). As a proportion of all trampoline injuries, spring and frame injury and falls injury decreased, while multiple-user injuries increased. The intervention analysis showed no significant change in spring and frame injuries associated with the AS (p=0.17). A significant increase was found for multiple-user injuries (p=0.01), in particular for the 0-year to 4-year age group (p<0.0001), post 2007. CONCLUSIONS: There was little evidence for an effect of the voluntary standard on spring and frame injury and none for multiple-user injury. Netted trampolines appear to be associated with a decrease in falls from trampolines but an increase in injuries to multiple users. A mandated trampoline safety standard and a safety campaign including warnings about multiple users is recommended. Continued monitoring of injury data will be required.

The influence of sport goggles on visual target detection in female intercollegiate athletes.

The aim of this study was to examine the effects of sport goggles on visual target detection in female intercollegiate athletes. Participants were randomly divided into three groups that varied in goggle use (G) or no goggle use (NG) over a total of three 1-min trials during a visual target detection task. The NG-NG-NG group did not wear goggles for any of the trials, whereas the NG-G-NG group wore goggles for the second trial only, and the G-NG-G group wore goggles for the first and third trials. The task consisted of illuminated targets arranged in five concentric rings from central to peripheral visual angles. The effects of sport goggles on response time to detect targets were most evident in the peripheral rings. Those who did not wear sport goggles showed improved performance from the first to second trials. This improvement was impaired, however, in those who wore sport goggles. Moreover, there was a reversal of the performance improvements achieved without goggles in those who wore goggles on the third trial. Together, these findings suggest the sport goggles not only impaired the expected initial performance but also impaired visual target detection after performance improvements were seen. These findings suggest sport goggles may impair detection of peripheral visual stimuli in athletes.

[Bilateral carotid artery dissection in a kite surfer by strangulation with the kite lines]. / Bilaterale Karotisdissektion eines Kitesurfers durch Strangulation mit Kiteleinen.

While a kite surfer was preparing the kite it was caught by a gust of wind, which blew it 10 m into the air and the cords became entangled around the neck of the kite surfer causing strangulation. After admittance to hospital, the diagnostics revealed multiple injuries including a bilateral dissection of the internal carotid arteries, cerebral edema and multiple fractures. As kitesurfing is gaining popularity severe injuries are becoming more frequent. Safety precautions, such as preparing the kite with two persons, wearing safety equipment and using bars with a safety leash can prevent severe injuries.

A systematic video analysis of 69 injury cases in World Cup alpine skiing.

We have limited insight into how injuries occur in professional ski racing. The aim of this study was to describe the injury situations in World Cup alpine skiing. Injuries reported through the International Ski Federation Injury Surveillance System for three consecutive World Cup seasons (2006-2009) were obtained on video. In total, 69 injuries and 124 runs of matched controls were analysed by five experts to evaluate the skiing situation, skier behavior, as well as piste-related factors. A chi-square test (95% CI, P ≤ 0.05) was used to examine whether there was a difference between course sections regarding where the injury situation occurred. The skier was most frequently turning (n = 55) or landing from a jump (n = 13) at the time of injury. Most of the injuries to the head and upper body (96%) resulted from crashes, while the majority of knee injuries (83%) occurred while the skier was still skiing. Gate contact contributed to 30% of the injuries, while 9% occurred at contact with safety nets/material. Almost half of the injuries (46%) occurred in the final fourth of the course. A particular concern was the high contribution of inappropriate gate contact and the high-energy impacts to the body when crashing.

A 1-year prospective analysis of injuries in amateur and elite fistball.

The purpose of this study was to examine the incidence and mechanisms of acute injuries in the sport of fistball. No scientific studies on injury characteristics have yet been conducted in this traditional sport game. The study was conducted prospectively over the course of 12 months. During a total of 40.308 h of sport-specific exposure, 240 players reported 492 injuries, representing an overall injury rate of 12.2 injuries/1000 h of exposure. Most injuries were classified as bagatelle injuries (67.8%). The majority of the injuries were located in the knee (23.5%) followed by the elbow (11.9%) and the hip (11.5%). Ankle injuries resulted in the longest impairment from sports participation. The most common types of injury were abrasions (38.2%), contusions (21.1%), distortions (7.5%) and muscle strains (6.9%). Wrong or insufficient equipment (15.0%) was the most commonly mentioned causes of injury. The data indicate that the injury risk in fistball is rather high; however, the sport should not be considered a high-risk sport because most of the injuries are slight and do not prevent the players from training or competition. Injury prevention strategies should include the development of fistball-specific protective equipment with focus on the knee and elbow joint.