Impact of range-of-motion during ecologically validresistance training protocols, on muscle size, subcutaneous fat and strength
- Journal of strength and conditioning research / National Strength & Conditioning Association
- Published over 6 years ago
The impact of using different resistance training (RT) kinematics, which therefore alters RT mechanics, and their subsequent effect on adaptations remain largely unreported. The aim of this study was to identify differences to training at a longer (LR) compared with a shorter (SR) range of motion, as well as the time-course of any changes during detraining. Recreationally active participants in LR (aged 19 ± 2.6 years; n=8) and SR (aged 19 ± 3.4 years; n=8) groups undertook 8 weeks of RT and 4 weeks detraining. Muscle size, architecture, subcutaneous fat and strength were measured at weeks 0, 8, 10 and 12 (repeated measures). A control group (aged 23 ± 2.4 years; n=10) was also monitored during this period. Significant (p>0.05) post-training differences existed in strength (on average 4±2% vs. 18±2%), distal anatomical cross-sectional area (59±15% vs. 16±10%), fascicle length (23±5% vs. 10±2%) and subcutaneous fat (22±8% vs. 5±2%), with LR exhibiting greater adaptations than SR. Detraining resulted in significant (p>0.05) deteriorations in all muscle parameters measured in both groups, with the SR group experiencing a more rapid relative loss of post-exercise increases in strength than LR (p>0.05). Greater morphological and architectural RT adaptations in LR (owing to higher mechanical stress) result in a more significant increase in strength compared to SR. The practical implications for this body of work follow that LR should be observed in resistance training where increased muscle strength and size are the objective, since we demonstrate here that ROM should not be compromised for greater external loading.
Background. Although the association between attention-deficit/hyperactivity disorder (ADHD) and drug use disorder (DUD) is well documented, it is unclear whether it is causal or results from familial confounding. Method. In this study we included all 551 164 individuals born in Sweden between 1991 and 1995 and used linked data from multiple nationwide registries to identify those with ADHD prior to age 15 years (1.71%). We used Cox proportional hazards models to investigate the future risk for DUD as a function of an ADHD registration and then compared the results from the entire population with the results from a co-relative design. Using the Swedish Multi-Generation Register, we identified all full-sibling, half-sibling and first-cousin pairs discordant for ADHD. Results. In the population sample, ADHD had a substantially increased risk for future DUD with a hazard ratio (HR) of 3.34 after accounting for gender and parental education. Examining discordant cousin pairs, discordant half-siblings and discordant siblings, those with ADHD had HRs for DUD of 3.09, 2.10 and 2.38 respectively. Controlling for the number of ADHD registrations, ADHD patients with and without stimulant treatment were similarly associated with later DUD risk. Conclusions. ADHD diagnosed before 15 years of age was strongly related to future risk for DUD. The magnitude of this association was modestly reduced in relative pairs discordant for ADHD, suggesting that the ADHD-DUD association is partly causal and partly a result of familial confounding. We found no evidence to suggest that this association resulted from stimulant treatment.
- Journal of strength and conditioning research / National Strength & Conditioning Association
- Published almost 4 years ago
Researchers have demonstrated that increases in strength result in increases in athletic performance, although the development of strength is still neglected in some sports. Our aim was to determine whether a simple in-season strength training program would result in increases in maximal squat strength and short sprint performance, in professional soccer players. Professional soccer players (n=17, age = 18.3 ± 1.2 years, height = 1.79 ± 0.06 m, body mass (BM) = 75.5 ± 6.1 kg) completed one repetition maximum (1RM) back squat and sprint tests (5-, 10-, 20 m) before and after a six-week (2 x week) in-season strength training (85-90% 1RM) intervention. Strength training resulted in significant improvements in absolute and relative strength (pre: 125.4 ± 13.8 kg, post 149.3 ± 16.2 kg, p < 0.001, Cohen's d = 0.62; 1RM/BM pre: 1.66 ± 0.24 kg.kg-1, post 1.96 ± 0.29 kg.kg-1, p < 0.001, Cohen's d = 0.45; respectively). Similarly, there were small yet significant improvements in sprint performance over 5 m (pre 1.11 ± 0.04 s, post 1.05 ± 0.05 s, p < 0.001, Cohen's d = 0.55) 10 m (pre 1.83 ± 0.05 s, post 1.78 ± 0.05 s, p < 0.001, Cohen's d = 0.45) and 20 m (pre 3.09 ± 0.07 s, post 3.05 ± 0.05 s, p < 0.001, Cohen's d = 0.31). Changes in maximal squat strength appear to be reflected in improvements in short sprint performance highlighting the importance of developing maximal strength to improve short sprint performance. Moreover this demonstrates that these improvements can be achieved during the competitive season in professional soccer players.
Aquatic exercises are widely used for rehabilitation or preventive therapies in order to enable mobilization and muscle strengthening while minimizing joint loading of the lower limb. The load reducing effect of water due to buoyancy is a main advantage compared to exercises on land. However, also drag forces have to be considered that act opposite to the relative motion of the body segments and require higher muscle activity. Due to these opposing effects on joint loading, the load-reducing effect during aquatic exercises remains unknown. The aim of this study was to quantify the joint loads during various aquatic exercises and to determine the load reducing effect of water. Instrumented knee and hip implants with telemetric data transfer were used to measure the resultant joint contact forces in 12 elderly subjects (6x hip, 6x knee) in vivo. Different dynamic, weight-bearing and non-weight-bearing activities were performed by the subjects on land and in chest-high water. Non-weight-bearing hip and knee flexion/extension was performed at different velocities and with additional Aquafins. Joint forces during aquatic exercises ranged between 32 and 396% body weight (BW). Highest forces occurred during dynamic activities, followed by weight-bearing and slow non-weight-bearing activities. Compared to the same activities on land, joint forces were reduced by 36-55% in water with absolute reductions being greater than 100%BW during weight-bearing and dynamic activities. During non-weight-bearing activities, high movement velocities and additional Aquafins increased the joint forces by up to 59% and resulted in joint forces of up to 301%BW. This study confirms the load reducing effect of water during weight-bearing and dynamic exercises. Nevertheless, high drag forces result in increased joint contact forces and indicate greater muscle activity. By the choice of activity, movement velocity and additional resistive devices joint forces can be modulated individually in the course of rehabilitation or preventive therapies.
Investigating the association between consumption of sweetened beverages and dietary quality is challenging because issues such as reverse causality and unmeasured confounding might result in biased and inconsistent estimates. Using a dynamic panel model with instrumental variables to address those issues, we examined the independent associations of beverages sweetened with caloric and low-calorie sweeteners with dietary quality and food-purchasing patterns. We analyzed purchase data from the Homescan survey, an ongoing, longitudinal, nationally representative US survey, from 2000 to 2010 (n = 34,294). Our model included lagged measures of dietary quality and beverage purchases (servings/day in the previous year) as exposures to predict the outcomes (macronutrient (kilocalories per capita per day; %), total energy, and food purchases) in the next year after adjustment for other sociodemographic covariates. Despite secular declines in purchases (kilocalories per capita per day) from all sources, each 1-serving/day increase in consumption of either beverage type resulted in higher purchases of total daily kilocalories and kilocalories from food, carbohydrates, total sugar, and total fat. Each 1-serving/day increase in consumption of either beverage was associated with more purchases of caloric-sweetened desserts or sweeteners, which accounted for a substantial proportion of the increase in total kilocalories. We concluded that consumers of both beverages sweetened with low-calorie sweeteners and beverages sweetened with caloric sweeteners had poorer dietary quality, exhibited higher energy from all purchases, sugar, and fat, and purchased more caloric-sweetened desserts/caloric sweeteners compared with nonconsumers.
A burgeoning literature has established that exposure to atrocities committed by in-group members triggers moral-disengagement strategies. There is little research, however, on how such moral disengagement affects the degree to which conversations shape people’s memories of the atrocities and subsequent justifications for those atrocities. We built on the finding that a speaker’s selective recounting of past events can result in retrieval-induced forgetting of related, unretrieved memories for both the speaker and the listener. In the present study, we investigated whether American participants listening to the selective remembering of atrocities committed by American soldiers (in-group condition) or Afghan soldiers (out-group condition) resulted in the retrieval-induced forgetting of unmentioned justifications. Consistent with a motivated-recall account, results showed that the way people’s memories are shaped by selective discussions of atrocities depends on group-membership status.
- The Australian and New Zealand journal of psychiatry
- Published over 5 years ago
Objectives:This paper systematically reviews all outcome studies of patients with mood disorders treated prior to the widespread use of antidepressants, mood stabilizers, and major tranquillizers. The aim is to estimate recovery and sustained recovery rates and to provide some evidence about the efficacy of modern drug treatments in changing the long-term outcome of mood disorders.Methods:MEDLINE and PSYCHINFO searches for studies on mood disorders published prior to 1970 were performed. Most studies were obtained by hand searching and extensive cross referencing. Information was independently extracted by the two authors.Results:A total of 29 relevant articles were obtained. The studies reviewed over 14,000 patients in total. Patients were mainly inpatients with a predominance of females. The majority of patients suffered from depression. The cohorts were followed up for 1-30 years. The median rate of recovery was 69% (range 17-91%). The time to recovery was generally several months. The median rate of recovering and remaining well was 51% (range 21-67%).Conclusions:The median rate of recovery is less than modern cohorts and the time to recovery longer. However, the rate of recovering and remaining well appears high compared to modern cohorts, although this result may reflect methodological issues. This review provides no support to the belief that pharmacological treatments have resulted in an improvement in the long-term outcome of patients with mood disorders.
Several studies have shown that early cannabis use is correlated with poor educational performance including high school drop-out. The predominant explanation for this relationship is that cannabis use causes disengagement from education. Another explanation is that the association between early cannabis use and educational attainment is not causal, but the result of overlapping risk factors that increase the likelihood of both early cannabis use and disengagement from education. These confounding factors could be of genetic and/or environmental origin.
Implant loosening - commonly linked with elevated initial micromotion - is the primary indication for total ankle replacement (TAR) revision. Finite element modelling has not been used to assess micromotion of TAR implants; additionally, the biomechanical consequences of TAR malpositioning - previously linked with higher failure rates - remain unexplored. The aim of this study was to estimate implant-bone micromotion and peri-implant bone strains for optimally positioned and malpositioned TAR prostheses, and thereby identify fixation features and malpositioning scenarios increasing the risk of loosening. Finite element models simulating three of the most commonly used TAR devices (BOX(®), Mobility(®) and Salto(®)) implanted into the tibia/talus and subjected to physiological loads were developed. Mobility and Salto demonstrated the largest micromotion of all tibial and talar components, respectively. Any malpositioning of the implant creating a gap between it and the bone resulted in a considerable increase in micromotion and bone strains. It was concluded that better primary stability can be achieved through fixation nearer to the joint line and/or while relying on more than a single peg. Incomplete seating on the bone may result in considerably elevated implant-bone micromotion and bone strains, thereby increasing the risk for TAR failure.
Experimentally induced sensorimotor conflicts can result in a loss of the feeling of control over a movement (sense of agency). These findings are typically interpreted in terms of a forward model in which the predicted sensory consequences of the movement are compared with the observed sensory consequences. In the present study we investigated whether a mismatch between movements and their observed sensory consequences does not only result in a reduced feeling of agency, but may affect motor perception as well. Visual feedback of participants' finger movements was manipulated using virtual reality to be anatomically congruent or incongruent to the performed movement. Participants made a motor perception judgment (i.e. which finger did you move?) or a visual perceptual judgment (i.e. which finger did you see moving?). Subjective measures of agency and body ownership were also collected. Seeing movements that were visually incongruent to the performed movement resulted in a lower accuracy for motor perception judgments, but not visual perceptual judgments. This effect was modified by rotating the virtual hand (Exp.2), but not by passively induced movements (Exp.3). Hence, sensorimotor conflicts can modulate the perception of one’s motor actions, causing viewed “alien actions” to be felt as one’s own.