Mechanisms of submaximal (quasi-)isometric knee extension exercise related to dinghy sailing performance

Dinghy sailing performance is related to hiking endurance (Blackburn & Hubinger, 1995; Tan et al., 2006; Vangelakoudi et al., 2007). However, there is no clear understanding of the underlying physiological mechanisms of hiking. Previous studies established during upwind sailing a significant disproportionate increase in heart rate (up to 75 % HRpeak) and oxygen uptake (up to 40 % VO2peak), reflecting the isometric tension on the anterior body muscles (Vogiatzis et al., 1995). Furthermore, significant increases in both systolic and diastolic blood pressure indicate the isometric nature of this exercise (Blackburn, 1994). However, lactate concentration ([La]) during upwind sailing does not exceed 4 mmol·l-1 which suggests only a small oxygen and energy deficit during upwind sailing (Vogiatzis et al., 2008). Consensus was reached to use the term quasi-isometric to categorise the hiking exercise (Spurway, 2007). In the mean time, the cardiorespiratory, -vascular and metabolic demands during upwind sailing have been thoroughly investigated whereas the muscular mechanisms have only been superficially studied. This research enhances our understanding of dinghy sailing performance by pursuing 3 research aims, that is: (1) investigating the determinants of dinghy sailing performance, (2) developing a sailing ergometer which accurately represents the physiological responses during on-water upwind sailing, and (3) exploring the physiological mechanisms during submaximal (quasi-)isometric knee extension exercise (as a part of upwind sailing exercise) with a distinct focus on the muscle level. To achieve these goals, five studies with each their own purpose and design have been conducted. The illustration (A) above demonstrates the different study populations, designs, methods and aims. Results and conclusions: The determinants of dinghy sailing performance include motor coordination skills and incremental knee extension strength. Motor coordination skills for Optimist sailors (i.e. ≤ 15 years) were highly related to sailing level, whereas incremental knee extension strength endurance (i.e. measured by bucket test) for dynamic hikers (i.e. > 15 years) was related to sailing level. The contribution of incremental knee extension strength endurance to performance for Optimist and Laser sailors was related to a delay in muscle fatigue. The muscle fatigue for Laser sailors was clearly related to maximal quadriceps strength. This result emphasizes the importance of implementing dry-land motor coordination skill training for Optimist sailors and dry-land maximal strength training for Laser sailors. In addition, an innovative biologically validated upwind sailing emulation ergometer was developed by applying a biofeedback system to measure the hiking moment. As such, the researcher can impose a certain quasi-isometric upwind sailing protocol to several subjects or to one subject on different occasions. The emulation ergometer can be implemented as tool for sailing performance diagnostics and training follow-up. Optimist and Laser sailors’ quadriceps muscle fatigue (as indicated by a decrease in mean power frequency an increase in root mean square) increased throughout submaximal (quasi-)isometric knee extension exercise (as a part of upwind sailing exercise). However, after an initial increase, a steady state phase was observed, presumably due to compensation strategies (e.g. tacking, fore and aft movements, and alternate-legs-strategy) conducted by the sailors to delay exhaustion. This results in a momentary relaxation of the quadriceps muscle causing a rapid outflow of deoxygenated blood and inflow of fresh oxygenated blood. Optimist sailors possess other fiber recruitment or O2 extraction patterns, probably to postpone exhaustion and increase knee extension strength endurance, than untrained controls

Development of an upwind sailing ergometer

Purpose: To develop a sailing ergometer that accurately simulates upwind sailing exercise. Methods: A sailing ergometer that measures roll moment accompanied by a biofeedback system that allows imposing a certain quasi-isometric upwind sailing protocol (ie, 18 bouts of 90-s hiking at constantly varying hiking intensity interspersed with 10 s to tack) was developed. Ten male high-level Laser sailors performed an incremental cycling test (ICT; ie, step protocol at 80W + 40 W/3 min) and an upwind sailing test (UST). During both, heart rate (HR), oxygen uptake (VO2), ventilation (V-E), respiratory-exchange ratio, and rating of perceived exertion were measured. During UST, also the difference between the required and produced hiking moment (HM) was calculated as error score (ES). HR, VO2, and V-E were calculated relative to their peak values determined during ICT. After UST, the subjects were questioned about their opinion on the resemblance between this UST and real-time upwind sailing. Results: An average HM of 89.0% +/- 2.2% HMmax and an average ES of 4.1% +/- 1.8% HMmax were found. Mean HR, VO2, and V-E were, respectively, 80% +/- 4% HRpeak, 39.5% +/- 4.5% VO2peak, and 30.3% +/- 3.7% V-Epeak. Both HM and cardiorespiratory values appear to be largely comparable to literature reports during on-water upwind sailing. Moreover, the subjects gave the upwind sailing ergometer a positive resemblance score. Conclusions: Results suggest that this ergometer accurately simulates on-water upwind sailing exercise. As such, this ergometer could be a great help in performance diagnostics and training follow-up

Defining the genotypic and phenotypic spectrum of X-linked MSL3-related disorder

PURPOSE: We sought to delineate the genotypic and phenotypic spectrum of female and male individuals with X-linked, MSL3-related disorder (Basilicata-Akhtar syndrome). METHODS: Twenty-five individuals (15 males, 10 females) with causative variants in MSL3 were ascertained through exome or genome sequencing at ten different sequencing centers. RESULTS: We identified multiple variant types in MSL3 (ten nonsense, six frameshift, four splice site, three missense, one in-frame-deletion, one multi-exon deletion), most proven to be de novo, and clustering in the terminal eight exons suggesting that truncating variants in the first five exons might be compensated by an alternative MSL3 transcript. Three-dimensional modeling of missense and splice variants indicated that these have a deleterious effect. The main clinical findings comprised developmental delay and intellectual disability ranging from mild to severe. Autism spectrum disorder, muscle tone abnormalities, and macrocephaly were common as well as hearing impairment and gastrointestinal problems. Hypoplasia of the cerebellar vermis emerged as a consistent magnetic resonance image (MRI) finding. Females and males were equally affected. Using facial analysis technology, a recognizable facial gestalt was determined. CONCLUSION: Our aggregated data illustrate the genotypic and phenotypic spectrum of X-linked, MSL3-related disorder (Basilicata-Akhtar syndrome). Our cohort improves the understanding of disease related morbidity and allows us to propose detailed surveillance guidelines for affected individuals

Does Cicero\u27s Decision stand the test of time?

The question of the circumstances under which an individual has a duty to disclose valuable information unknown to the person with whom she bargains represents one of the most puzzling and extensively debated legal issues. Does the party have the right to remain silent and profit from her secret knowledge? These questions have fascinated scholars in philosophy, law and history from ancient times and have produced an impressive amount of literature, decisions and comments. Most recently, it has also gained extensive attention in many prominent laws and among economics scholars. In addition, the pre-contractual duty to disclose information is, among many comparative legal scholars, widely used as an illustration of the current deep, sharp common/civil law division. This paper overcomes an old legal and moral crux and critically examines the disclosure duties of ancient Roman law and in particularly the famous Cicero decision on the famine at Rhodes

Quadriceps Reoxygenation And Muscle Fatigue During Sailing-specific Isometric Bilateral Knee Extension Exercise

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Reliability Of A New Handgrip Exercise Protocol Measuring Forearm Oxygenation With Near Infrared Spectroscopy (nirs)

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Quadriceps reoxygenation and muscle fatigue during sailing-specific isometric bilateral knee extension exercise

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Physical profile of Flemish youth Olympic-class sailors

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Physical profile of Flemish youth Olympic-class sailors

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