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Jan Wright and R.C. King

An analysis of the teacher language used in physical education lessons reveals the influence of many discourses that are current in our culture, including those related to gender. The subtle meanings carried in the linguistic choices made by teachers provide one framework through which girls and boys come to form particular relationships with their bodies. These relationships are culturally constructed and influence the desire to be active and the choice of activities. The process of gender production can be made visible by a comparative analysis of the lexico-grammatical structure of texts from two gymnastic lessons using the systemic functional model of linguistics developed by Michael Halliday (1978, 1985). The most distinctive features that have emerged from the analysis have been the different linguistic choices made by male and female teachers in the grammatical realization of interpersonal meanings. These differences contribute to the construction of a social order for the participants in physical education lessons that mirrors the gender relations in the culture of the larger society. Revealing the way the language works provides for the possibility of different linguistic choices—choices that may constitute a different social reality.

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Deborah R. Smith, Ben Jones, Louise Sutton, Roderick F.G.J. King, and Lauren C. Duckworth

Good nutrition is essential for the physical development of adolescent athletes, however data on dietary intakes of adolescent rugby players are lacking. This study quantified and evaluated dietary intake in 87 elite male English academy rugby league (RL) and rugby union (RU) players by age (under 16 (U16) and under 19 (U19) years old) and code (RL and RU). Relationships of intakes with body mass and composition (sum of 8 skinfolds) were also investigated. Using 4-day diet and physical activity diaries, dietary intake was compared with adolescent sports nutrition recommendations and the UK national food guide. Dietary intake did not differ by code, whereas U19s consumed greater energy (3366 ± 658 vs. 2995 ± 774 kcal·day-1), protein (207 ± 49 vs. 150 ± 53 g·day-1) and fluid (4221 ± 1323 vs. 3137 ± 1015 ml·day-1) than U16s. U19s consumed a better quality diet than U16s (greater intakes of fruit and vegetables; 4.4 ± 1.9 vs. 2.8 ± 1.5 servings·day-1; nondairy proteins; 3.9 ± 1.1 vs. 2.9 ± 1.1 servings·day-1) and less fats and sugars (2.0 ± 1. vs. 3.6 ± 2.1 servings·day-1). Protein intake vs. body mass was moderate (r = .46, p < .001), and other relationships were weak. The findings of this study suggest adolescent rugby players consume adequate dietary intakes in relation to current guidelines for energy, macronutrient and fluid intake. Players should improve the quality of their diet by replacing intakes from the fats and sugars food group with healthier choices, while maintaining current energy, and macronutrient intakes.

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Filipe Conceição, Mark A. King, Maurice R. Yeadon, Martin G.C. Lewis, and Stephanie E. Forrester

This study aimed to determine whether subject-specific individual muscle models for the ankle plantar flexors could be obtained from single joint isometric and isovelocity maximum torque measurements in combination with a model of plantar flexion. Maximum plantar flexion torque measurements were taken on one subject at six knee angles spanning full flexion to full extension. A planar three-segment (foot, shank and thigh), two-muscle (soleus and gastrocnemius) model of plantar flexion was developed. Seven parameters per muscle were determined by minimizing a weighted root mean square difference (wRMSD) between the model output and the experimental torque data. Valid individual muscle models were obtained using experimental data from only two knee angles giving a wRMSD score of 16 N m, with values ranging from 11 to 17 N m for each of the six knee angles. The robustness of the methodology was confirmed through repeating the optimization with perturbed experimental torques (±20%) and segment lengths (±10%) resulting in wRMSD scores of between 13 and 20 N m. Hence, good representations of maximum torque can be achieved from subject-specific individual muscle models determined from single joint maximum torque measurements. The proposed methodology could be applied to muscle-driven models of human movement with the potential to improve their validity.

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Marta D. Van Loan, Barbara Sutherland, Nicola M. Lowe, Judith R. Turnlund, and Janet C. King

In this study we tested the effect of zinc (Zn) on muscle function in humans. After receiving 12 mg Zn/day for 17 days. 8 male subjects received 0.3 mg Zn/day tor either 33 or 41 days. Subjects were divided into two groups for repletion. Group A subjects received overnight infusions of 66 mg Zn on Days 1 and 10 and then were fed 12 mg Zn/day for another 16 days. Group B subjects were fed 12 mg Zn/day for 3 weeks. Peak force and total work capacity of the knee and shoulder extensor and flexor muscle groups were assessed using an isokinetic dynamometer at baseline, at two points during depletion, and at repletion. Plasma Zn declined significantly during depletion and remained below baseline levels after repletion. The peak force of the muscle groups tesied was not affected by acute Zn depletion: however, total work capacity for the knee extensor muscles and shoulder extensor and flexor muscles declined significantly. The data suggest that acute Zn depletion alters the total work capacity of skeletal muscle.

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Martin G.C. Lewis, Mark A. King, Maurice R. Yeadon, and Filipe Conceição

This study determines whether maximal voluntary ankle plantar flexor torque could be more accurately represented using a torque generator that is a function of both knee and ankle kinematics. Isovelocity and isometric ankle plantar flexor torques were measured on a single participant for knee joint angles of 111° to 169° (approximately full extension) using a Contrex MJ dynamometer. Maximal voluntary torque was represented by a 19-parameter two-joint function of ankle and knee joint angles and angular velocities with the parameters determined by minimizing a weighted root mean square difference between measured torques and the two-joint function. The weighted root mean square difference between the two-joint function and the measured torques was 10 N-m or 3% of maximum torque. The two-joint function was a more accurate representation of maximal voluntary ankle plantar flexor torques than an existing single-joint function where differences of 19% of maximum torque were found. It is concluded that when the knee is flexed by more than 40°, a two-joint representation is necessary.

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Jason D. Stone, Adam C. King, Shiho Goto, John D. Mata, Joseph Hannon, James C. Garrison, James Bothwell, Andrew R. Jagim, Margaret T. Jones, and Jonathan M. Oliver

Purpose: To provide a joint-level analysis of traditional (TS) and cluster (CS) set structure during the back-squat exercise. Methods: Eight men (24 [3] y, 177.3 [7.9] cm, 82.7 [11.0] kg, 11.9 [3.5] % body fat, and 150.3 [23.0] kg 1-repetition maximum [1RM]) performed the back-squat exercise (80%1RM) using TS (4 × 6, 2-min interset rest) and CS (4 × [2 × 3], 30-s intraset rest, 90-s interset rest), randomly. Lower-limb kinematics were collected by motion capture, as well as kinetic data by bilateral force platforms. Results: CS attenuated the loss in mean power (TS −21.6% [3.9%]; CS −12.4% [7.5%]; P = .042), although no differences in gross movement pattern (sagittal-plane joint angles) within and between conditions were observed (P ≥ .05). However, joint power produced at the hip increased from repetition (REP) 1 through REP 6 during TS, while a decrease was noted at the knee. A similar pattern was observed in the CS condition but was limited to the hip. Joint power produced at the hip increased from REP 1 through REP 3 but returned to REP 1 values before a similar increase through REP 6, resulting in differences between conditions (REP 4, P = .018; REP 5, P = .022). Conclusions: Sagittal-plane joint angles did not change in either condition, although CS elicited greater power. Differing joint power contributions (hip and knee) suggest potential central mechanism that may contribute to enhanced power output during CS and warrant further study. Practitioners should consider incorporating CS into training to promote greater power adaptations and to mitigate fatigue.

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Jeremy A. Steeves, Catrine Tudor-Locke, Rachel A. Murphy, George A. King, Eugene C. Fitzhugh, David R. Bassett, Dane Van Domelen, John M. Schuna Jr, and Tamara B. Harris

Background: Little is known about the daily physical activity (PA) levels of people employed in different occupational categories. Methods: Nine ActiGraph accelerometer-derived daily PA variables are presented and ranked for adults (N = 1465, 20–60 y) working in the 22 occupational categories assessed by NHANES 2005–2006. A composite score was generated for each occupational category by summing the rankings of 3 accelerometer-derived daily PA variables known to have strong associations with health outcomes (total activity counts [TAC], moderate to vigorous PA minutes per week in modified 10-minute bouts [MVPA 10], and percentage of time spent in sedentary activity [SB%]). Results: Classified as high-activity occupational categories, “farming, fishing, forestry,” and “building & grounds cleaning, maintenance” occupations had the greatest TAC (461 996 and 449 452), most MVPA 10 (149.6 and 97.8), most steps per day (10 464 and 11 602), and near the lowest SB% (45.2% and 45.4%). “Community, social services” occupations, classified as low-activity occupational categories, had the second lowest TAC (242 085), least MVPA 10 (12.1), fewest steps per day (5684), and near the highest SB% (64.2%). Conclusions: There is a strong association between occupational category and daily activity levels. Objectively measured daily PA permitted the classification of the 22 different occupational categories into 3 activity groupings.

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Mika R. Moran, Perla Werner, Israel Doron, Neta HaGani, Yael Benvenisti, Abby C. King, Sandra J. Winter, Jylana L. Sheats, Randi Garber, Hadas Motro, and Shlomit Ergon

Walking is a central form of physical activity among older adults that is associated with the physical environment at various scales. This mixed-methods study employs a concurrent nested design to explore objective and perceived environmental characteristics of older adults’ local walking routes. This was achieved by integrating quantitative Geographic Information System (GIS) data with qualitative data obtained using the Stanford Discovery Tool (DT). Fifty-nine community-dwelling middle-aged and older adults (14 men and 45 women aged 50+) were recruited in a snowball approach through community centers in the city of Haifa (Israel). Four neighborhood environment themes were identified: pedestrian infrastructure, access to destinations, aesthetics, and environmental quality. Both geometrical traits (i.e., distance, slope) and urban features (i.e., land-uses, greenery) of the route may impact the experience of walking. The findings thus highlight the importance of micro-scale environmental elements in shaping environmental perceptions, which may consequently influence the choice of being active.

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Kenneth E. Powell, Abby C. King, David M. Buchner, Wayne W. Campbell, Loretta DiPietro, Kirk I. Erickson, Charles H. Hillman, John M. Jakicic, Kathleen F. Janz, Peter T. Katzmarzyk, William E. Kraus, Richard F. Macko, David X. Marquez, Anne McTiernan, Russell R. Pate, Linda S. Pescatello, and Melicia C. Whitt-Glover

Background: The 2018 Physical Activity Guidelines Advisory Committee Scientific Report provides the evidence base for the Physical Activity Guidelines for Americans, 2nd Edition. Methods: The 2018 Physical Activity Guidelines Advisory Committee addressed 38 questions and 104 subquestions selected for their public health relevance, potential to inform public policies and programs, maturity of the relevant science, and applicability to the general US population. Rigorous systematic literature searches and literature reviews were performed using standardized methods. Results: Newly described benefits of physical activity include reduced risk of excessive weight gain in children and adults, incidence of 6 types of cancer, and fall-related injuries in older people. Physical activity is associated with enhanced cognitive function and mental health across the life span, plus improved mental health and physical function. There is no threshold that must be exceeded before benefits begin to accrue; the accrual is most rapid for the least active individuals. Sedentary time is directly associated with elevated risk of all-cause and cardiovascular mortality, incident cardiovascular disease and type 2 diabetes, and selected cancer sites. A wide range of intervention strategies have demonstrated success in increasing physical activity. Conclusion: The 2018 Physical Activity Guidelines Advisory Committee Scientific Report provides compelling new evidence to inform physical activity recommendations, practice, and policy.