Impact of COVID-19 Confinement on Physical Activity and Sedentary Behaviour in Spanish University Students: Role of Gender.

During the COVID-19 pandemic, entire populations were instructed to live in home-confinement to prevent the expansion of the disease. Spain was one of the countries with the strictest conditions, as outdoor physical activity was banned for nearly two months. This study aimed to analyse the changes in physical activity and sedentary behaviours in Spanish university students before and during the confinement by COVID-19 with special focus on gender. We also analysed enjoyment, the tools used and motivation and impediments for doing physical activity. An online questionnaire, which included the International Physical Activity Questionnaire Short Form and certain "ad hoc" questions, was designed. Students were recruited by distributing an invitation through the administrative channels of 16 universities and a total of 13,754 valid surveys were collected. Overall, university students reduced moderate (-29.5%) and vigorous (-18.3%) physical activity during the confinement and increased sedentary time (+52.7%). However, they spent more time on high intensity interval training (HIIT) (+18.2%) and mind-body activities (e.g., yoga) (+80.0%). Adaptation to the confinement, in terms of physical activity, was handled better by women than by men. These results will help design strategies for each gender to promote physical activity and reduce sedentary behaviour during confinement periods.

Progressions of core stabilization exercises based on postural control challenge assessment.

PURPOSE: The intensity progression of core stabilization exercises (CSEs) is usually based on personal criteria rather than on objective parameters. To develop exercise progressions for four of the most common CSEs based on the postural control challenge imposed on the participants, and to analyze the effect of participants' sex and postural control level on these progressions. METHODS: Seventy-six males and females performed five variations of front bridge, back bridge, side bridge and bird-dog exercises on two force platforms. The mean velocity of the center of pressure displacement was calculated to assess exercise intensity through the measurement of the participants' body sway (PBS). RESULTS: In general, long bridges produced higher PBS than short bridges, bridging with single leg support produced higher PBS than bridging with double leg support and bridging on a hemisphere ball produced higher PBS than bridging on the floor. The most difficult bridging variations were those performed on a hemisphere ball with single leg support. Regarding the bird-dog, two-point positions produced higher PBS than three-point positions and the positions performed on a hemisphere ball produced higher PBS than those performed on the floor. CONCLUSION: The CSE progressions obtained by males and females were very similar. However, the participants with high trunk control showed less significant differences between exercise variations than the participants with low trunk control, which shows the need to individualize the progressions according to the participants' training level. Overall, this study provides useful information to guide the prescription of CSE progressions in young physically active individuals.

Trunk Stability, Trunk Strength and Sport Performance Level in Judo.

Although trunk muscle function has been suggested to be a determinant of judo performance, its contribution to high-level performance in this sport has been poorly studied. Therefore, several tests were used to assess the differences in trunk muscle function between 11 international and 14 national level judo practitioners (judokas). Trunk strength and endurance were assessed using isokinetic tests and core stability was assessed using two protocols: 1) sudden loading, to assess trunk responses to unexpected external perturbations; 2) stable and unstable sitting, to assess the participants' ability to control trunk balance. No differences between groups were found for trunk flexor isokinetic strength, trunk responses against lateral and posterior loading and trunk control while sitting. However, international level judokas showed significantly higher trunk extensor isokinetic strength (p <0.05) and lower trunk angular displacement after anterior trunk loading (p <0.05) than national level judokas. Few and low (r < 0.512) significant correlations were found between strength, endurance and stability parameters, which suggests that trunk strength and endurance are not limiting factors for trunk stability in competitive judokas. These results support the importance of trunk extensor strength and trunk stability against forward perturbations in elite judo performance.

Electromyographic studies in abdominal exercises: a literature synthesis.

OBJECTIVE: The purpose of this article is to synthesize the literature on studies that investigate electromyographic activity of abdominal muscles during abdominal exercises performance. METHODS: MEDLINE and Sportdiscus databases were searched, as well as the Web pages of electronic journals access, ScienceDirect, and Swetswise, from 1950 to 2008. The terms used to search the literature were abdominal muscle and the specific names for the abdominal muscles and their combination with electromyography, and/or strengthening, and/or exercise, and/or spine stability, and/or low back pain. The related topics included the influence of the different exercises, modification of exercise positions, involvement of different joints, the position with supported or unsupported segments, plane variation to modify loads, and the use of equipment. Studies related to abdominal conditioning exercises and core stabilization were also reviewed. RESULTS: Eighty-seven studies were identified as relevant for this literature synthesis. Overall, the studies retrieved lacked consistency, which made it impossible to extract aggregate estimates and did not allow for a rigorous meta-analysis. The most important factors for the selection of abdominal strengthening exercises are (a) spine flexion and rotation without hip flexion, (b) arm support, (c) lower body segments involvement controlling the correct performance, (d) inclined planes or additional loads to increase the contraction intensity significantly, and (e) when the goal is to challenge spine stability, exercises such as abdominal bracing or abdominal hollowing are preferable depending on the participants' objectives and characteristics. Pertaining to safety criteria, the most important factors are (a) avoid active hip flexion and fixed feet, (b) do not pull with the hands behind the head, and (c) a position of knees and hips flexion during upper body exercises. CONCLUSIONS: Further replicable studies are needed to address and clarify the methodological doubts expressed in this article and to provide more consistent and reliable results that might help us build a body of knowledge on this topic. Future electromyographic studies should consider addressing the limitations described in this review.

Effects of abdominal muscle coactivation on the externally preloaded trunk: variations in motor control and its effect on spine stability.

STUDY DESIGN: A repeated measures biomechanical analysis of the effects of abdominal bracing in preparation for a quick release of the loaded trunk. OBJECTIVES: To quantify the ability of individuals to abdominally brace the externally loaded trunk, and assess their success in achieving and enhancing appropriate spine stability. SUMMARY OF BACKGROUND DATA: Spine stability requires trunk muscle coactivation, which demands motor control skill that differs across people and situations. The quick release protocol may offer insight into the motor control scheme and subsequent effect on spine stability. METHODS: There were 10 individuals who sat, torso upright, in an apparatus designed to foster a neutral spine position. They were instructed to support a posteriorly directed load to the trunk in either their naturally chosen manner, or by activating the abdominal muscles to 10%, 20%, or 30% of maximum ability. The externally applied load was then quickly released, thereby unloading the participant. Muscle pre-activation patterns, spine stability, and kinematic measures of trunk stiffness were quantified. RESULTS: Participants were able to stabilize their spine effectively by supporting the load in a naturally selected manner. Conscious, voluntary overdriving of this natural pattern often resulted in unbalanced muscular activation schemes and corresponding decreases in stability levels. CONCLUSIONS: Individuals in an externally loaded state appear to select a natural muscular activation pattern appropriate to maintain spine stability sufficiently. Conscious adjustments in individual muscles around this natural level may actually decrease the stability margin of safety.