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PubMed1983

Some technical, physiological and anthropometrical aspects of speed skating.

Five elite speed skaters and fourteen well trained skaters of a lower performance level performed three maximal tests: a 3,000 m race from which the skating position and the stroke frequency were derived, an oxygen consumption test both during skating and during a bicycle ergometer test. From all subjects anthropometric measures were taken. The elite group showed a VO2 during cycling of 64.4 +/- 3.5 ml . kg-1 . min-1 and 59.4 +/- 3.7 ml . kg-1 . min-1 during skating. The elite skaters showed: a shorter upper leg length with respect to total leg length, higher aerobic power during cycling, higher stroke frequency, smaller pre-extension knee angle coupled to higher work per stroke, higher "efficiency" during skating and higher external power during skating and during cycling when compared with the group of lower performance level. It is concluded that an important pre-requisite for speed skating appears to be the possibility to skate at a small pre-extension knee angle without an excessive claim to anaerobic metabolism.

Aerobiosis↗
PubMed1997

A population-based survey of in-line skaters' injuries and skating practices.

OBJECTIVE: To describe in-line skating interests and practices, protective gear usage, and injury patterns in a population-based group of in-line skaters. DESIGN: A two-page questionnaire with multiple choice questions and one write-in response question. PARTICIPANTS: The survey was sent to 1,000 members of an in-line skating club in Detroit, MI and 45 other states. MAIN OUTCOME MEASURES: The study was designed to profile skater injury patterns. The effects of protective gear and skater lessons on injury were examined. RESULTS: Of the 435 skaters returning questionnaires, 56.7% were men. The mean age was 35 years. The frequency of in-line skating lessons was 31.7%. Of respondents, 72.5% wear some kind of protective gear while skating, and 79.8% reported that they had been injured while skating. Of those who had skated for 5 or more years, 93.7% had been injured. Upper extremity injuries were reported by 58.8% of skaters and lower extremity injuries by 66.7%. The majority suffered abrasions and bruises only. More serious injuries were reported by very few skaters: fractures by 5.5% and concussions by 2.1%. Only 3% of respondents required orthopedic surgery. CONCLUSION: Lessons and protective gear decrease the risk of injury. However, risk of incurring minor injury exists even if full protective gear is used. Those who have skated for more than 5 years are almost certain to report having been injured.

Adolescent↗
PubMed1997

Molecular cloning of a rod opsin cDNA from the skate retina.

Skates (Raja erinacea and R. ocellata) are among the few animals that have an exclusively rod retina. However, skate rods are unusual in that they are capable of adapting to extremely high levels of illumination that initially saturate the rod photocurrent. This adaptive process restores the ability of the visual cells to respond to incremental photic stimuli and enables them to function under ambient conditions that are subserved by the cone mechanism in mixed (rod/cone) retinae. As a first step towards exploring the molecular basis of visual adaptation in the skate retina, we have cloned and analyzed the opsin cDNA from a skate retina library. The cDNA codes for a protein 354 amino acids (aa) long and 39.7 kDa predicted molecular mass, and labels a single abundant transcript of 1.7 kb in retinal RNA. Amino acid alignments and a parsimony analysis of nucleotide alignments show the skate opsin to be homologous to other rod opsins. An analysis of the aa sequence reveals a high degree of conservation of those residues thought to be important for most aspects of rhodopsin function. However, a few critical aa replacements may indicate alterations in the interactions of skate rhodopsin with other proteins in the phototransduction cascade. In particular, replacements of Glu150 with serine and Cys323 with leucine are in cytoplasmic domains thought to interact with transducin and rhodopsin kinase. The latter change eliminates one of the conserved acylation sites in the carboxyl terminal tail. These substitutions increase the similarity of the cytoplasmic domains of skate opsin to those of blue-sensitive visual pigments.

Amino Acid Sequence↗
PubMed2001

Ice friction in speed skating: can klapskates reduce ice frictional loss?

PURPOSE: Reducing ice friction was one of the motives for developing the klapskate. However, the magnitude of power dissipation that occurs with conventional skates when a skater plantar flexes his ankle and the tip of the blade is pressed into the ice has not been quantified previously. In this study, we examine how ice friction varies during a single stroke with conventional skates and estimate the reduction in ice friction that might be obtained with klapskates. METHODS: Five elite speed skaters performed a series of trials at constant velocity and a series of maximal accelerations. Energy dissipated to ice friction during a stroke with conventional skates was analyzed using an instrumented skate and high-speed 3D kinematic analysis. The energy that would be dissipated when klapskates were used was estimated from the collected data with conventional skates. RESULTS: The estimated difference in power loss between conventional and klapskates was less dramatic than has been suggested frequently. Pressing the tip of the blade into the ice comprises only 0.84 W of the total power dissipated by ice friction (54 W) during constant velocity speed skating. During an all-out acceleration, this power loss reached 4.55 W. CONCLUSION: We conclude that only a minor part of the benefit of klapskates can be attributed to a reduction in ice friction. It is shown that this relatively small increase in ice friction is related to the large length of the skate blade.

Adult↗
PubMed1997

In-line skating: a deadly pediatric activity?

OBJECTIVES: To report pediatric injuries requiring hospitalization and deaths related to in-line skating in a children's hospital and to review the trend and description of in-line skating-related pediatric deaths reported by the National Electronic Injury Surveillance System (NEISS) from 1991 to 1995. DESIGN: The medical records of patients admitted or pronounced dead at Miami Children's Hospital (MCH) related to in-line skating injuries and the NEISS national database pediatric death reports were reviewed and analyzed. SETTING: Tertiary trauma center at a children's hospital in southern Florida and emergency departments that participated in NEISS. PATIENTS: Pediatric patients who required admission or were pronounced dead for injuries related to in-line skating during a two-year study period at MCH. Pediatric deaths reported to NEISS related to in-line skating from 1991 to 1995. RESULTS: Eight admissions and one death occurred at MCH and are discussed separately. The median age was 13 years with a range of four, 77% were male. NEISS had 28 cases of pediatric death reported, 96.4% were due to motor vehicle collision with the skater. The median age was 12 years, 81.5% were male. The 0- to 14-year age group represented 57.9% of all injuries in 1994, an increase of 136% from 1993. CONCLUSION: We report a pediatric death related to in-line skating and the data from NEISS of pediatric deaths to emphasize the morbidities related to sports involving wheels. In-line skating-related injuries are increasing in the pediatric population in frequency as well as severity. The population at risk is becoming younger and thus education for injury prevention is needed.

Accidents, Traffic↗
PubMed1984

Ice-skating and roller disco injuries in Dublin.

A comparative study was carried out on a series of 72 ice-skating and 57 roller skating injuries over a sixteen month period. The average patient age was 20.5 years in the ice-skating group and 16.5 years in the roller skating group. Females predominated in both groups accounting for 72% of ice-skaters injured and 77% of roller skaters injured. Ice-skaters sustained more serious injuries than roller skaters as was evident from the significant difference in fracture numbers in the two groups. Ice-skating fractures accounted for 40% of all injuries while roller skating fractures were only 14% of their total injuries. The majority of ice-skating fractures occurred in females. As a result of our study we recommended several preventative measures.

Adolescent↗
PubMed2002

Molecular characterization of a multidrug resistance-associated protein, Mrp2, from the little skate.

Multidrug resistance protein Mrp2 (symbol Abcc2) in liver plays a significant role in the biliary excretion of organic anionic conjugates. Mutations in human MRP2 result in defects in excretion of conjugated bilirubin and other cholephiles known as the Dubin-Johnson syndrome. Previous studies indicate that transporters with Mrp2-like functions are present in ancient vertebrates. We have now characterized an Mrp2 ortholog at the molecular level from the liver of the small skate, Raja erinacea, a marine vertebrate that evolved approximately 200 million years ago. The full-length skate Mrp2 cDNA is 6 kb and encodes for a 1,564-amino acid peptide with 56% identity to human Mrp2. Northern blot analysis demonstrated that skate Mrp2 is abundantly expressed in skate liver, intestine, and kidney. Immunoblots reveal a 180-kDa protein in skate liver. Immunofluorescence studies locate skate Mrp2 to the apical membrane of hepatocytes, renal tubules, and intestine. A PDZ-interacting motif is also found at its COOH terminus. Further sequence analysis indicates that transmembrane domains 1, 9, 11, 16, and 17 are the most highly conserved transmembrane domains between skate Mrp2 and mammalian MRP2/Mrp2s. This analysis indicates that Mrp2 orthologs evolved early in vertebrate evolution and that conserved domains may be important determinants of Mrp2 substrate specificity.

Amino Acid Sequence↗
PubMed2005

Experimental evaluation of the power balance model of speed skating.

Prediction of speed skating performance with a power balance model requires assumptions about the kinetics of energy production, skating efficiency, and skating technique. The purpose of this study was to evaluate these parameters during competitive imitations for the purpose of improving model predictions. Elite speed skaters (n = 8) performed races and submaximal efficiency tests. External power output (P(o)) was calculated from movement analysis and aerodynamic models and ice friction measurements. Aerobic kinetics was calculated from breath-by-breath oxygen uptake (Vo(2)). Aerobic power (P(aer)) was calculated from measured skating efficiency. Anaerobic power (P(an)) kinetics was determined by subtracting P(aer) from P(o). We found gross skating efficiency to be 15.8% (1.8%). In the 1,500-m event, the kinetics of P(an) was characterized by a first-order system as P(an) = 88 + 556e(-0.0494t) (in W, where t is time). The rate constant for the increase in P(aer) was -0.153 s(-1), the time delay was 8.7 s, and the peak P(aer) was 234 W; P(aer) was equal to 234[1 - e(-0.153(t-8.7))] (in W). Skating position changed with preextension knee angle increasing and trunk angle decreasing throughout the event. We concluded the pattern of P(aer) to be quite similar to that reported during other competitive imitations, with the exception that the increase in P(aer) was more rapid. The pattern of P(an) does not appear to fit an "all-out" pattern, with near zero values during the last portion of the event, as assumed in our previous model (De Koning JJ, de Groot G, and van Ingen Schenau GJ. J Biomech 25: 573-580, 1992). Skating position changed in ways different from those assumed in our previous model. In addition to allowing improved predictions, the results demonstrate the importance of observations in unique subjects to the process of model construction.

Adolescent↗
PubMed1997

GABA receptors of bipolar cells from the skate retina: actions of zinc on GABA-mediated membrane currents.

GABA receptors of bipolar cells from the skate retina: actions of zinc on GABA-mediated membrane currents. J. Neurophysiol. 78: 2402-2412, 1997. gamma-Aminobutyric acid (GABA)-induced currents were recorded from isolated bipolar cells of the skate retina using perforated patch-clamp methodology. Pharmacological analysis of the responses, using selective agonists and antagonists of the major classes of GABA receptor, revealed the presence of both GABAA and GABAC receptors at both the dendrites and axon terminals of the bipolar cells. The two receptor types showed very different reactions to zinc, a divalent metallic cation that was detected in the synaptic terminal region of skate photoreceptors. Currents mediated by the activation of GABAC receptors were down-regulated by zinc, a feature that is typical of the action of zinc on GABAC receptors. On the other hand, the effects of zinc on GABAA receptor-mediated activity was highly dependent on zinc concentration. Unlike the GABAA receptors on other neurons, responses mediated by activation of the GABAA receptor of skate bipolar cells were significantly enhanced by zinc concentrations in the range of 0. 1-100 mu M; at higher concentrations of zinc (>100 mu M), response amplitudes were suppressed below control levels. The enhancement of GABAA receptor activity on skate bipolar cells showed little voltage dependence, suggesting that zinc is acting on the extracellular domain of the GABAA receptor. In the presence of 10 mu M zinc, the dose-response curve for 4,5,6, 7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol (THIP; a GABAA agonist that suppresses GABAC-activated currents) was shifted to the left of the curve obtained in the absence of zinc, but without a significant change in the response maximum. This finding indicates that the enhancing effect of zinc is due primarily to its ability to increase the sensitivity of the GABAA receptor. The novel enhancement of neuronal GABAA receptor activity by zinc, observed previously in the GABAA-mediated responses of skate Müller (glial) cells, may reflect the presence of a unique subtype of GABAA receptor on the bipolar and Müller cells of the skate retina.

Animals↗
PubMed2005

Pediatric fractures during skateboarding, roller skating, and scooter riding.

BACKGROUND: Skateboarding, roller skating, and scooter riding are popular recreational and sporting activities for children and adolescents but can be associated with skeletal injury. The purpose of this study is to describe the frequency and characteristics of fractures resulting from these activities. PURPOSE: Fractures from skateboarding, roller skating, and scooter riding compose a considerable proportion of pediatric musculoskeletal injuries. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: Demographic data and injury characteristics were analyzed for all patients who presented to the pediatric fracture clinic of the level I trauma center from January 2001 to May 2002 after sustaining fractures due to skateboarding, roller skating, and scooter riding. RESULTS: Among a total of 2371 fractures, the authors identified 325 fractures (13.7%) that occurred during one of these activities. There were 187 patients (mean age, 13 years; 95% male) who sustained 191 skateboard-related fractures, 64 patients (mean age, 10.8 years; 54% male) who sustained 65 fractures while roller skating, and 66 patients (mean age, 9.7 years; 64% male) who sustained 69 fractures while riding a scooter. The forearm was fractured most often, composing 48.2% of skate-boarding fractures, 63.1% of roller-skating fractures, and 50.7% of fractures due to scooter riding. Of the forearm fractures, 94% were located in the distal third. In the skateboarding group, 10 of 191 (5.2%) fractures were open injuries of the forearm, compared to 6 of 2046 (0.3%) fractures caused by other mechanisms of injury (significant odds ratio, 18.8). CONCLUSIONS: Skateboarding, roller-skating, and scooter-riding accidents result in a large proportion of pediatric fractures. An open fracture, especially of the forearm, was more likely to be caused by skateboarding than by other mechanisms of injury. Use of wrist and forearm protective equipment should be considered in all children who ride a skateboard.

Adolescent↗
PubMed2001

In-line skating injuries.

In-line skating has remained a popular recreational activity all over the world. The number of injuries seemingly reached a plateau in the late 1990s. However, there are still more injuries caused by in-line skating than from skateboarding, hockey or lacrosse and rugby. In 1997, the estimated annual cost of medical treatment for these injuries in the US was over $US4 billion. Adolescence still represents the largest group of skaters, both in participation and injury. Although 10- to 14-year-olds account for 60% of injuries, in 1996 the US Consumer Product Safety Commission reported nearly 1500 injuries in individuals 65 years and over. Risk factors for injury include inexperience, aggressive skating and amount of time spent skating. There are also more recent data to suggest that self-reported expert skaters are more likely to sustain an injury. Reluctance to use personal protective equipment (PPE) by in-line skaters remains high. The general consensus is that PPE is effective in reducing the incidence and severity of in-line skating injuries. Therefore, efforts should be made to increase awareness of risk factors for injury in all skaters; to increase use of safety equipment; to provide safe environments for skating; and to legislate skating laws that will protect skaters from injuries.

Accidental Falls↗
PubMed2000

[Epidemiology of in-line skate injuries: state of the art].

During the last decade, in-line skating has become an increasingly popular activity. Along with the number of reports, highlighting the number of injuries and their degree of severity, in-line skating injuries have to be considered a growing public health issue. The objective of this work is to report epidemiological knowledge about in-line skate injuries and ways of prevention. A thorough search of all reports and publications on the subject was performed through the Medline database and in references of selected publications. There are numerous case series studies and several observational ones, most of them undertaken in North America. In-line skates are used for recreation, sports, and transportation, in a variety of settings (parks, streets, bike path, etc.) and by most of age groups (5 to 71 years, median generally about 15). The most common site of injury is the wrist and forearm, although other parts of the body can be severely injured. Age, sex, physical training level, formal instruction level, lack of wearing of protective gear, skating location, may be risk factors for injury. Some preventive measures were proposed by a number of research workers (information campaigns, wearing of protective gear, instruction, laws, etc.). Several preventive attempts were undertaken but no one was appraised. In-line skates are used by all age groups and for a variety of activities. In-line skating is related to a great number of factors, such as cultural, social, geographic, urban and behavioural factors. Therefore, groups at risk for injury are very different. Emergence of an important type of injury should lead to the development of analytic epidemiological studies, based on particular groups of in-line skaters, in order to describe them, to identify and quantify risk factors and to design preventive measures, and then to appraise their efficiency.

Accidents, Traffic↗
PubMed1985

Ontogenic studies on the appearance of two classes of immunoglobulin-forming cells in the spleen of the Aleutian skate, Bathyraja aleutica, a cartilaginous fish.

We identified the presence in the Aleutian skate, Bathyraja aleutica, of two classes of immunoglobulins (Ig), a high molecular weight Ig analogous to mammalian IgM and a low molecular weight Ig, similarly to the spiny rasp skate, Raja kenojei, (Kobayashi, K. et al., Mol. Immunol. 1984. 21: 397), using an immunological cross-reaction with the specific antisera to the spiny rasp skate Ig components. The antigenic similarity of the heavy chains of the Ig of the Aleutian skate and those of the spiny rasp skate was less than that between their light chains. Two types of Ig-producing cells, one producing the high molecular weight and the other forming the low molecular weight Ig, were present in the spleen of embryos and adults in the Aleutian skate at a ratio of 5-6:4-5. The number of these Ig-producing cells increased with advancing development of the embryos but was 1/20 to 1/50 of those of adults. Cells, each of which were capable of forming both classes of Ig, were found in the spleen of embryos but not in that of adults. These results suggested that the spleen of the Aleutian skate is the primary lymphoid organ for B lymphocyte differentiation and proliferation, possibly equivalent to the bursa of birds.

Animals↗
PubMed1996

Pharmacology of the skate electroretinogram indicates independent ON and OFF bipolar cell pathways.

Organization of afferent information into parallel ON and OFF pathways is a critical feature of the vertebrate visual system. All afferent visual information in the vertebrate retina reaches the inner plexiform layer (IPL) via bipolar cells. It is at the bipolar cell level that separation of ON and OFF information first appears for afferent information from cones. This may also hold true for the rod pathway of cold-blooded vertebrates, but not for mammals. The all-rod retina of the skate presents an opportunity to examine such pathways in a retina having but a single class of photoreceptor. Immunocytochemical evidence suggests that both ON and OFF bipolar cells are present in the skate retina. We examined the pharmacology of the skate electroretinogram (ERG) to test the hypothesis that independent ON and OFF bipolar cell pathways are functional as rod afferent pathways from outer to inner plexiform layer in the skate. 100 microM 2-amino-4-phosphonobutyric acid (APB) reversibly blocked the skate ERG b-wave. A small d-wave-like OFF component of the ERG revealed by DC recording of response to a prolonged (10 s) flash of light was reduced or blocked by 5 mM kynurenic acid (KYN). We found that addition of 200 microM picrotoxin to the Ringer's solution revealed prominent ON and OFF components of the skate ERG while reducing the c-wave. These ON and OFF components were reversibly blocked by 100 microM APB and 5 mM KYN, respectively. Reversible block of the OFF component by KYN was also accomplished in the presence of 500 microM N-methyl-DL-aspartate. From these findings, we conclude that ON and OFF bipolar cells are likely to be functional as parallel afferent interplexiform pathways in the all-rod retina of the skate.

Afferent Pathways↗
PubMedDate not supplied

Anterior compartment pressures in cross-country skiers. A comparison of classic and skating skis.

This paper compares the pressure changes in the anterior compartment of the leg when cross-country skiing using the skating method on either skating skis or classic skis. Intracompartmental pressures of the right leg were recorded from the tibialis anterior muscle of 10 subjects at rest and 15 seconds after 10 to 12 minutes of cross-country skiing on a designated course. All subjects completed two trials on different days. In one trial, subjects used skating skis and for the other trial, classic skis were used for the skating technique. Although the average pressure increase was higher for the classic ski trials than for the skating ski trials, the difference was not significant. This finding indicates that cross-country skiers who skate on a classic ski as opposed to a shorter skating ski do not experience a significantly greater increase in their anterior compartment pressure. Thus, it appears that the type of ski used is not the most significant factor contributing to chronic compartment syndrome.

Adult↗
PubMed2005

[Injury patterns and prophylaxis in inline skating].

Inline skating has become one of the fastest growing sports since its appearance in 1980. The increasing number of inline skaters has also led to a rising incidence of injuries. The most common injury is the distal fracture of the radius, which occurs in 50% of all fractures. There are several reasons for increasing serious injuries in inline skating. The majority of skaters do not wear proper protective equipment (helmet, elbow, knee and wrist protectors), however, many users can not handle their inline skates in dangerous situations. All skaters should take care by buying industrially tested inline skates and appropriate protective equipment; novice skaters should additionally attend special skating schools to learn skating, braking and the the correct falling techniques.

Humans↗
PubMed2002

An investigation of carbonic anhydrase activity in the gills and blood plasma of brown bullhead (Ameiurus nebulosus), longnose skate (Raja rhina), and spotted raffish (Hydrolagus colliei).

Separated plasma and whole blood non-bicarbonate buffering capacities, together with plasma and gill carbonic anhydrase activities and endogenous plasma carbonic anhydrase inhibitor activity were investigated in three species of fish: the brown bullhead (Ameirus nebulosus), a teleost; the longnose skate (Raja rhina), an elasmobranch; and the spotted ratfish (Hydrolagus colliei), a chimaeran. The objective was to test the hypothesis that species possessing gill membrane-bound carbonic anhydrase and/or plasma carbonic anhydrase activity would also exhibit high plasma nonbicarbonate buffering capacity relative to whole blood non-bicarbonate buffering capacity and would lack an endogenous plasma carbonic anhydrase inhibitor. Separated plasma non-bicarbonate buffering capacity constituted > or = 40% of whole-blood buffering in all three species. In addition, all species lacked an endogenous plasma carbonic anhydrase inhibitor. Separated plasma from skate and ratfish contained carbonic anhydrase activity, whereas bullhead plasma did not. Examination of the subcellular distribution and characteristics of branchial carbonic anhydrase activity revealed that the majority of branchial carbonic anhydrase activity originated from the cytoplasmic fraction in all species, with only 3-5% being associated with a microsomal fraction. The microsomal carbonic anhydrase activity of bullhead and ratfish was significantly reduced by washing, indicating the presence of carbonic anhydrase activity that was not integrally associated with the membrane pellet, microsomal carbonic anhydrase activity in skate was unaffected by washing. In addition, microsomal carbonic anhydrase activity from skate and ratfish but not bullhead gills was released to a significant extent from its membrane association by treatment with phosphatidylinositol-specific phospholipase C. The results obtained for skate are consistent with published data for dogfish, suggesting that the possession of branchial membrane-bound carbonic anhydrase activity may be a generalised elasmobranch characteristic. Ratfish, which also belong to the class Chondrichthyes, exhibited a similar pattern. Unlike skate and ratfish, bullhead exhibited high plasma non-bicarbonate buffering capacity and lacked an endogenous carbonic anhydrase inhibitor in the absence of plasma and gill membrane-bound carbonic anhydrase activities.

Acetazolamide↗
PubMed2006

cDNA cloning and characterization of Type I procollagen alpha1 chain in the skate Raja kenojei.

A full-length cDNA of the Type I procollagen alpha1 [pro-alpha1(I)] chain (4388 bp), coding for 1463 amino acid residues in the total length, was determined by RACE PCR using a cDNA library constructed from 4-week embryo of the skate Raja kenojei. The helical region of the skate pro-alpha1(I) chain consisted of 1014 amino acid residues - the same as other fibrillar collagen alpha chains from higher vertebrates. Comparison on denaturation temperatures of Type I collagens from the skate, rainbow trout (Oncorhynchus mykiss) and rat (Rattus norvegicus) revealed that the number of Gly-Pro-Pro and Gly-Gly in the alpha1(I) chains could be directly related to the thermal stability of the helix. The expression property of the skate pro-alpha1(I) chain mRNA and phylogenetic analysis with other vertebrate pro-alpha1(I) chains suggested that skate pro-alpha1(I) chain could be a precursor form of the skate Type I collagen alpha1 chain. The present study is the first evidence for the primary structure of full-length pro-alpha1(I) chain in an elasmobranch.

Amino Acid Sequence↗