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Paul D. Loprinzi

Objective:

Examine the association between objectively-measured moderate-to-vigorous physical activity (MVPA) and engagement in self-reported muscle strengthening activities (MSA) with alanine aminotransferase (ALT) and gamma-glutamyltransferase (GGT), and in turn, how each of these parameters associate with of all-cause mortality.

Methods:

Data from the 2003–2006 NHANES were employed, with follow-up through December 31, 2011 (N = 5030; 20+ yrs). Physical activity was assessed via accelerometry; MSA was assessed via survey; and ALT and GGT were assessed via a blood sample. Linear regression and Cox proportional hazard models were used.

Results:

MVPA (βadjusted = 0.15; 95% CI: –0.45 to 0.76; P = .60) was not associated with ALT, but MSA was (β adjusted = –0.31; 95% CI: –0.56 to –0.05; P = .02). With regard to GGT, MSA was not significant (β adjusted = –0.12; 95% CI: –0.71 to 0.47; P = .67), nor was MVPA (β adjusted = –1.10; 95% CI: –2.20 to 0.06; P = .06). Higher ALT levels were associated with increased allcause mortality risk (HRadjusted = 1.05; 95% CI: 1.02 to 1.06; P < .001).

Conclusion:

Physical activity is favorably associated with markers of hepatic inflammation, and higher levels of markers of hepatic inflammation are associated with increased mortality risk. These findings suggest that physical activity may help protect against premature mortality through its influence on liver pathology.

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Oscar Mac Ananey, Brendan McLoughlin, Ann Leonard, Lewena Maher, Peter Gaffney, Gerard Boran and Vincent Maher

Background:

Several obesity related factors are reported to exacerbate premature arterial stiffening, including inactivity and metabolic disarray. The aim of the current study was to investigate the relationship between physical activity, arterial stiffness and adiposity using objective methods. To further explore the role of adiposity in this complex process, obesity associated anthropometric and humoral biomarkers were measured.

Methods:

Seventy-nine healthy, lifelong nonsmoking subjects were recruited. Habitual physical activity was measured using accelerometry. Arterial stiffness [augmentation index (AIx) and pulse wave velocity (PWV)] was measured using tonometry. Body composition was estimated using bioimpedence. Adipose associated biomarkers, leptin and adiponectin, were also measured.

Results:

Sedentary time was significantly associated with AIx (r = 0.38, P < .001), PWV (r = 0.33, P < .01), body fat composition (r = 0.40, P < .001) and age (r = 0.30, P < .01). Moderate-to-vigorous physical activity (MVPA) was inversely correlated with AIx (r = –0.28, P < .05), body fat composition (r = –0.30, P < .01), postprandial insulin (r = –0.35, P < .01), and leptin/adiponectin ratio (r = –0.28, P < .05). MVPA, body fat composition, and postprandial insulin remained independent predictors of AIx but not PWV.

Conclusion:

The more time healthy individuals spend being sedentary, the greater their body fat and arterial stiffness. Conversely higher activity levels are associated with reduced body fat and less arterial stiffness.

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Wendy J. Brown and Toby Pavey

The Australian Longitudinal Study on Women’s Health (ALSWH) commenced in Australia in 1996 when researchers recruited approximately 40,000 women in three birth cohorts: 1973–1978, 1946–1951, and 1921–1926. Since then participants have completed surveys on a wide range of health issues, at approximately three-year intervals. This overview describes changes in physical activity (PA) over time in the mid-age and older ALSWH cohorts, and summarizes the findings of studies published to date on the determinants of PA, and its associated health outcomes in Australian women. The ALSWH data show a significant increase in PA during mid-age, and a rapid decline in activity levels when women are in their 80s. The study has demonstrated the importance of life stages and key life events as determinants of activity, the additional benefits of vigorous activity for mid-age women, and the health benefits of ‘only walking’ for older women. ALSWH researchers have also drawn attention to the benefits of activity in terms of a wide range of physical and mental health outcomes, as well as overall vitality and well-being. The data indicate that maintaining a high level of PA throughout mid and older age will not only reduce the risk of premature death, but also significantly extend the number of years of healthy life.

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Steven J. Elmer, John McDaniel and James C. Martin

One-legged cycling has served as a valuable research tool and as a training and rehabilitation modality. Biomechanics of onelegged cycling are unnatural because the individual must actively lift the leg during flexion, which can be difficult to coordinate and cause premature fatigue. We compared ankle, knee, and hip biomechanics between two-legged, one-legged, and counterweighted (11.64 kg) one-legged cycling. Ten cyclists performed two-legged (240 W), one-legged (120 W), and counterweighted one-legged (120 W) cycling (80 rpm). Pedal forces and limb kinematics were recorded to determine work during extension and flexion. During counterweighted one-legged cycling relative ankle dorsiflexion, knee flexion, and hip flexion work were less than one-legged but greater than two-legged cycling (all P < .05). Relative ankle plantar flexion and hip extension work for counterweighted one-legged cycling were greater than one-legged but less than two-legged cycling (all P < .05). Relative knee extension work did not differ across conditions. Counterweighted one-legged cycling reduced but did not eliminate differences in joint flexion and extension actions between one- and two-legged cycling. Even with these differences, counterweighted one-legged cycling seemed to have advantages over one-legged cycling. These results, along with previous work highlighting physiological characteristics and training adaptations to counterweighted one-legged cycling, demonstrate that this exercise is a viable alternative to one-legged cycling.

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Lynne Halley Johnston and Douglas Carroll

This study used grounded theory to describe the emotional responses of athletes following injury and their situational and temporal contexts. Sixteen seriously injured athletes were interviewed. The NUD*IST (Nonnumerical Unstructured Data Indexing Searching and Theorizing) computer program was used to search, store, explore, and organize the qualitative material. The main emotional responses, appraisals, events, and behaviors that emerged from the analysis were represented diagrammatically. Frustration and depression were the prevalent emotional responses throughout rehabilitation, although the situational corollaries differed as recovery progressed. In the early phase of rehabilitation, frustration and depression resulted from disruption to normal function, in the middle phase they were provoked by a negative appraisal of rehabilitation progress, and. at the end of rehabilitation the main instigator was impatience to return to sport. Whether to risk returning prematurely to sport emerged as a key theme, as did the confounding effects of exercise withdrawal. symptoms in extremely committed athletes. The results were considered in terms of both cognitive appraisal and risk models.

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Tania Pereira, John Durocher and Jamie Burr

Background: Insufficient physical activity (PA) is associated with numerous chronic diseases and premature mortality, and the challenge of meeting recommended PA guidelines is exacerbated in the winter. Snowmobiling can potentially contribute to PA accumulation, but the objective metabolic and physical demands are unclear. The purpose of this study was to assess the physical demands of riding a snowmobile. Methods: Habitual snowmobile riders responded to a survey describing a typical ride (n = 4015). Using this data, terrain-specific testing courses were created, and recreational snowmobile riders (n = 40) participated in a scaled representative ride (21 [8] min) while aerobic metabolism (VO2) and muscular fatigue were quantified. Results: The mean VO2 while riding, irrespective of terrain, was 18.5 (8.4) mL·kg−1·min−1, with significant differences based on geographic location (13.4 [5.2] vs 25.7 [6.6] mL·kg−1·min−1, P < .001). Muscular fatigue was apparent in maximal handgrip (−7% [8%], P < .001) across both riding terrains, but not lower body power, suggesting a greater influence of an upper body strength component. Conclusions: Snowmobiling is an activity that generally falls within the moderate-intensity activity range and involves both aerobic fitness and muscular strength. There were substantial differences in demand between terrains, suggesting that additional benefits may be conferred from mountain riding as it was more metabolically demanding.

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Philip F. Skiba, David Clarke, Anni Vanhatalo and Andrew M. Jones

Recently, an adaptation to the critical-power (CP) model was published, which permits the calculation of the balance of the work capacity available above the CP remaining (Wbal) at any time during intermittent exercise. As the model is now in use in both amateur and elite sport, the purpose of this investigation was to assess the validity of the Wbal model in the field. Data were collected from the bicycle power meters of 8 trained triathletes. Wbal was calculated and compared between files where subjects reported becoming prematurely exhausted during training or competition and files where the athletes successfully completed a difficult assigned task or race without becoming exhausted. Calculated Wbal was significantly different between the 2 conditions (P < .0001). The mean Wbal at exhaustion was 0.5 ± 1.3 kJ (95% CI = 0–0.9 kJ), whereas the minimum Wbal in the nonexhausted condition was 3.6 ± 2.0 kJ (95% CI = 2.1–4.0 kJ). Receiver-operator-characteristic (ROC) curve analysis indicated that the Wbal model is useful for identifying the point at which athletes are in danger of becoming exhausted (area under the ROC curve = .914, SE .05, 95% CI .82–1.0, P < .0001). The Wbal model may therefore represent a useful new development in assessing athlete fatigue state during training and racing.

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Dan Benardot, Wes Zimmermann, Gregory R. Cox and Saul Marks

Competitive diving involves grace, power, balance, and flexibility, which all require satisfying daily energy and nutrient needs. Divers are short, well-muscled, and lean, giving them a distinct biomechanical advantage. Although little diving-specific nutrition research on performance and health outcomes exists, there is concern that divers are excessively focused on body weight and composition, which may result in reduced dietary intake to achieve desired physique goals. This will result in low energy availability, which may have a negative impact on their power-to-weight ratio and health risks. Evidence is increasing that restrictive dietary practices leading to low energy availability also result in micronutrient deficiencies, premature fatigue, frequent injuries, and poor athletic performance. On the basis of daily training demands, estimated energy requirements for male and female divers are 3,500 kcal and 2,650 kcal, respectively. Divers should consume a diet that provides 3–8 g/kg/day of carbohydrate, with the higher values accommodating growth and development. Total daily protein intake (1.2–1.7 g/kg) should be spread evenly throughout the day in 20 to 30 g amounts and timed appropriately after training sessions. Divers should consume nutrient-dense foods and fluids and, with medical supervision, certain dietary supplements (i.e., calcium and iron) may be advisable. Although sweat loss during indoor training is relatively low, divers should follow appropriate fluid-intake strategies to accommodate anticipated sweat losses in hot and humid outdoor settings. A multidisciplinary sports medicine team should be integral to the daily training environment, and suitable foods and fluids should be made available during prolonged practices and competitions.

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Enda F. Whyte, Nicola Gibbons, Grainne Kerr and Kieran A. Moran

Context: Determination of return to play (RTP) after sport-related concussion (SRC) is critical given the potential consequences of premature RTP. Current RTP guidelines may not identify persistent exercise-induced neurocognitive deficits in asymptomatic athletes after SRC. Therefore, postexercise neurocognitive testing has been recommended to further inform RTP determination. To implement this recommendation, the effect of exercise on neurocognitive function in healthy athletes should be understood. Objective: To examine the acute effects of a high-intensity intermittent-exercise protocol (HIIP) on neurocognitive function assessed by the Symbol Digits Modality Test (SDMT) and Stroop Interference Test. Design: Cohort study. Setting: University laboratory. Participants 40 healthy male athletes (age 21.25 ± 1.29 y, education 16.95 ± 1.37 y). Intervention: Each participant completed the SDMT and Stroop Interference Test at baseline and after random allocation to a condition (HIIP vs control). A mixed between-within-subjects ANOVA assessed time- (pre- vs postcondition) -by-condition interaction effects. Main Outcome Measures: SDMT and Stroop Interference Test scores. Results: There was a significant time-by-condition interaction effect (P < .001, η 2 = .364) for the Stroop Interference Test scores, indicating that the HIIP group scored significantly lower (56.05 ± 9.34) postcondition than the control group (66.39 ± 19.6). There was no significant time-by-condition effect (P = .997, η 2 < .001) for the SDMT, indicating that there was no difference between SDMT scores for the HIIP and control groups (59.95 ± 10.7 vs 58.56 ± 14.02). Conclusions: In healthy athletes, the HIIP results in a reduction in neurocognitive function as assessed by the Stroop Interference Test, with no effect on function as assessed by the SDMT. Testing should also be considered after high-intensity exercise in determining RTP decisions for athletes after SRC in conjunction with the existing recommended RTP protocol. These results may provide an initial reference point for future research investigating the effects of an HIIP on the neurocognitive function of athletes recovering from SRC.

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Nicole Reams, Rodney A. Hayward, Jeffrey S. Kutcher and James F. Burke

Purpose:

Lingering neurologic injury after concussion may expose athletes to increased risk if return to play is premature. The authors explored whether on-field performance after concussion is a marker of lingering neurologic injury.

Design:

Retrospective cohort study on 1882 skill-position players who played in the National Football League (NFL) during 2007–2010.

Methods:

Players with concussion based on the weekly injury report were compared with players with other head and neck injuries (controls) on measures of on-field performance using Football Outsiders’ calculation of defense-adjusted yards above replacement (DYAR), a measure of a player’s contribution controlling for game context. Changes in performance, relative to a player’s baseline level of performance, were estimated before and after injury using fixed-effects models.

Results:

The study included 140 concussed players and 57 controls. Players with concussion performed no better or worse than their baseline on return to play. However, a decline in DYAR relative to their prior performance was noted 2 wk and 1 wk before appearing on the injury report. Concussed players performed slightly better than controls in situations where they returned to play the same week as appearing on the injury report.

Conclusions:

On return, concussed NFL players performed at their baseline level of performance, suggesting that players have recovered from concussion. Decline in performance noted 2 wk and 1 wk before appearing on the injury report may suggest that concussion diagnosis was delayed or that concussion can be a multihit phenomenon. Athletic performance may be a novel tool for assessing concussion injury and recovery.