You are looking at 211 - 220 of 25,287 items

Restricted access

Akihiro Tamura, Kiyokazu Akasaka and Takahiro Otsudo

Context: Excessive knee valgus on landing can cause anterior cruciate ligament injury. Therefore, knee valgus alignment may show characteristic energy absorption patterns during landings with lateral movement that impose greater impact forces on the knee joint compared with landings in other alignments. Objective: To investigate the energy absorption strategy in lower-extremities during side steps in females with knee valgus alignment. Design: Controlled laboratory study. Setting: University research laboratory. Participants: A total of 34 female college students participated in this experiment. Interventions: Participants performed single-leg drop vertical jump and side steps. All participants were divided into valgus (n = 13), neutral (n = 9), and varus (n = 12) groups according to knee position during landing in single-leg drop vertical jumps. Main Outcome Measures: Lower-extremity joint angles, moments, and negative works were calculated during landing in side steps, and 1-way analysis of variance and post hoc tests were used to determine between-group differences. Results: Negative works of hip extensors, knee abductors, and ankle plantar flexors during landing in side steps were significantly smaller in the valgus than in the varus group; however, negative work of the knee extensors was significantly greater in the valgus group than in varus group. Conclusions: The findings of this study indicated that landing with knee valgus induced the characteristic energy absorption strategy in the lower-extremity. Knee extensors contributed more to energy absorption when landing in knee valgus than in knee varus alignment. Learning to land in knee varus alignment might reduce the impact on the knee joint by increasing the energy absorption capacities of hip extensors, knee abductors, and ankle plantar flexors.

Full access

Paul J. Collings, Diane Farrar, Joanna Gibson, Jane West, Sally E. Barber and John Wright

Background: Physical activity performed while pregnant is beneficially associated with maternal cardiovascular health. It is unknown if benefits extend to neonatal cardiovascular health. This study investigated associations of maternal physical activity with neonatal cord blood lipid and lipoprotein concentrations. Methods: Cord blood lipids were measured at birth in a pseudorandomly selected subgroup of Born in Bradford birth cohort participants (N = 1634). Pregnant women were grouped into 4 activity categories (inactive/somewhat active/moderately active/active) based on their self-reported physical activity at 26- to 28-weeks gestation. Regression was used to calculate adjusted mean differences in neonatal cord blood lipid concentrations among the 4 groups of physical activity. Results: Maternal physical activity was associated with higher neonatal cord blood high-density lipoprotein cholesterol. Cord blood high-density lipoprotein cholesterol was higher in neonates of women who were somewhat and moderately active compared with neonates of women who were inactive. There were no associations of pregnancy physical activity with triglycerides, low-density lipoprotein, very low-density lipoprotein cholesterol, or adiponectin levels. Conclusions: Maternal physical activity is favorably associated with neonatal cord blood high-density lipoprotein cholesterol levels. This novel beneficial finding highlights the potential for physical activity in pregnancy to aid the early prevention of cardiovascular disease.

Restricted access

Sarah C. Moudy, Neale A. Tillin, Amy R. Sibley and Siobhán Strike

Individuals with unilateral transtibial amputations experience greater work demand and loading on the intact limb compared with the prosthetic limb, placing this limb at a greater risk of knee joint degenerative conditions. It is possible that increased loading on the intact side may occur due to strength deficits and joint absorption mechanics. This study investigated the intact limb mechanics utilized to attenuate load, independent of prosthetic limb contributions and requirements for forward progression, which could provide an indication of deficiencies in the intact limb. Amputee and healthy control participants completed 3 unilateral drop landings from a 30-cm drop height. Joint angles at touchdown; range of motion; coupling angles; peak powers; and negative work of the ankle, knee, and hip were extracted together with isometric quadriceps strength measures. No significant differences were found in the load or movement mechanics (P ≥ .31, g ≤ 0.42), despite deficits in isometric maximum (20%) and explosive (25%) strength (P ≤ .13, g ≥ 0.61) in the intact limb. These results demonstrate that, when the influence from the prosthetic limb and task demand are absent, and despite deficits in strength, the intact limb adopts joint mechanics similar to able-bodied controls to attenuate limb loading.

Full access

Chia-Yuan Yu and Biyuan Wang

Background: This study explored the percentage change of walking to/from public transit to work from 2009 to 2017 in general and for specific sociodemographic characteristics. Furthermore, this study also examined the sociodemographic characteristics of those who walked to/from transit to work and those who walked 30 minutes or more per day to/from transit to work and compared the difference between 2009 and 2017. Methods: 2009 and 2017 National Household Travel Survey were used. This study used weighted logistic regressions to explore the sociodemographic characteristics of those who walked to/from transit to work and those who walked 30 minutes or more per day to/from transit to work in both 2009 and 2017. Results: The percentage of trips achieving the recommended level of physical activity (30 min or more per day) by walking to/from transit work solely has a slightly increase from 9 in 2009 to 9.5 in 2017. However, the weighted percentages of walking to/from transit to work decreased for low-education, low-income, and minority populations. High population density areas were related to more transit-related walking trips to work in both 2009 and 2017. Conclusions: Policymakers in terms of transit location and service should consider low-education, low-income, and minority populations to address potential equity issues.

Restricted access

Margaret C. Morrissey, Michael R. Szymanski, Andrew J. Grundstein and Douglas J. Casa

Intense exercise in extreme heat can increase the risk of developing exertional heat stroke (EHS). EHS is 100% survivable with appropriate care, and it is imperative that health care professionals recognize predisposing factors that may increase susceptibility to EHS. Understanding risk factors for EHS will enable clinicians to create effective prevention strategies to improve exercise heat tolerance and mitigate EHS risk. This review addresses new perspectives on risk factors for EHS that focus on hydration, heat acclimatization, medical conditions, climate change and policies, medications, and strength and conditioning sessions.

Restricted access

James Dimmock, David Simich, Timothy Budden, Leslie Podlog, Mark Beauchamp and Ben Jackson

Across 2 studies, the authors explored reactance effects to overexaggerated claims and controlling language in exercise messaging. In Study 1, participants received either a message exaggerating the benefits of an upcoming exercise session or no message. They subsequently undertook a mundane exercise session led by an instructor, which was either need supportive or “realistically controlling.” Relative to no-message participants, those who had read the message reported less positive evaluations of the session. These results were observed despite participants in the message condition holding more positive presession expectations, and the effect was apparent even for those who received need-supportive instruction. In Study 2, participants read an advertisement that was written in either autonomy-supportive language or controlling language. Despite reporting comparable expectations, participants who received a controlling-language message reported significantly greater anger and freedom threat—factors commonly linked to contrast effects. These studies highlight the operation of message-driven contrast effects in exercise.

Open access

Bradley D. Hatfield, Calvin M. Lu and Jo B. Zimmerman

Restricted access

Mark S. Dyreson

Since the origins of Homo sapiens 300,000 years ago, the quest to optimize human performance has shaped historical development. A macrohistorical perspective reveals that for 290,000 years the necessities of survival pushed hunter-forager cultures toward mass improvement of endurance capabilities and weapons skills. The agricultural revolution that began about 10,000 years ago changed those dynamics, focusing on enhancement for elite warriors while simultaneously diminishing the necessity of mass optimization. The multiple revolutions of modernity that began 500 years ago reanimated mass optimization while paradoxically removing physical enhancement from the realm of necessity through the increasing power of human-made motors rather than human locomotion. Microhistorical perspectives reveal that beyond the general patterns that shaped human cultures across time and place, the historical particularities vastly complicated optimization strategies. Employing macro- and microhistorical perspectives can enhance scientific understandings of optimal performance.

Restricted access

Aaron Sciascia, Jacob Waldecker and Cale Jacobs

Background: Pain is the most common patient-reported symptom but the perception of pain is complex, differs between individuals and is not directly proportional to the extent of injury. The relationship between aberrant pain coping strategies such as pain catastrophizing and the presence of pain in competitive athletes should be further established to employ the most optimal treatment. Hypothesis: The hypotheses were that numeric pain rating and pain catastrophizing (Pain Catastrophizing Scale, PCS) scores would have a moderate to strong relationship in college athletes, and athletes with either a current injury or previous injury, or playing with pain, would have significantly higher pain catastrophizing scores compared with noninjured/nonpainful athletes. Study Design: Cross-sectional study. Level of Evidence: III. Methods: College athletes completed a demographic form, injury questionnaire, numeric pain rating, and the PCS. All athletes were medically cleared for sports participation at the time of survey completion. A total PCS score was calculated in addition to a rumination, magnification, and helplessness score. Spearman rank was utilized to measure the strength of relationship between the PCS score and pain rating. Results: A total of 291 athletes from 15 different sports completed the questionnaires (males: 156, females: 135; age: 19 [2] y). Negligible correlations existed between the PCS score and pain (r = .27). Athletes who were currently injured or previously injured had significantly higher PCS scores compared with uninjured athletes (P < .01). Conclusions: Approximately one-third of college athletes reported playing injured and/or with pain, but the relationship between pain rating and PCS score was negligible. The individualistic nature of pain perception and coping strategies would suggest that clinicians may want to consider screening for pain catastrophizing either prior to athletic participation or for athletes not following an expected recovery after injury in an effort to enhance individualized patient care.

Restricted access

Bruno G.G. da Costa, Kelly S. da Silva, Rafael M. da Costa, Edio L. Petroski, Isabela C. Back, Paulo H.A. Guerra and Luiz R.A. de Lima

Purpose: Sedentary behavior (SB) has been shown to be associated with unhealthy outcomes in children, and it is not clear whether children living with human immunodeficiency virus (HIV) engage in different patterns of SB compared with healthy children. This cross-sectional study aimed to compare patterns of SB between children living with HIV and a healthy control group. Methods: A group of children with HIV and a paired control group wore accelerometers for 1 week and answered a questionnaire with items related to television viewing habits and computer usage. Accelerometer-derived and self-reported SB were compared between children living with HIV and controls and between treatment-based and viral load subgroups. Results: A total of 130 children (of which 53% are girls with a mean age of 12.1 y) participated in the study with 65 in each group. Children in the control group exhibited significantly more objectively measured SB daily when compared with the HIV group (515 vs 490 min/d, respectively), but no differences were found between the treatment-based and viral load subgroups. Children with HIV watched more television on weekdays, compared with the control group (P < .05). No other differences were found in comparisons of self-reported SB between the control and HIV and the treatment-based or viral load subgroups. Conclusion: Children living with HIV spend less time being sedentary than those in the healthy control group. Future studies are important for clarifying the causes and consequences of these differences.