Nature’s hierarchical materials

https://www.healio.com/psychiatry/journals/psycann/1976-12-6-12/{806b8887-c02e-40c8-a228-57f1cdb2bdba}/the-stress-of-life.pdf

The stress of life

The International Physical Activity Questionnaire - Short Form (IPAQ-SF) has been recommended as a cost-effective method to assess physical activity. Several studies validating the IPAQ-SF have been conducted with differing results, but no systematic review of these studies has been reported. The keywords "IPAQ", "validation", and "validity" were searched in PubMed and Scopus. Studies published in English that validated the IPAQ-SF against an objective physical activity measuring device, doubly labeled water, or an objective fitness measure were included. Twenty-three validation studies were included in this review. There was a great deal of variability in the methods used across studies, but the results were largely similar. Correlations between the total physical activity level measured by the IPAQ-SF and objective standards ranged from 0.09 to 0.39; none reached the minimal acceptable standard in the literature (0.50 for objective activity measuring devices, 0.40 for fitness measures). Correlations between sections of the IPAQ-SF for vigorous activity or moderate activity level/walking and an objective standard showed even greater variability (-0.18 to 0.76), yet several reached the minimal acceptable standard. Only six studies provided comparisons between physical activity levels derived from the IPAQ-SF and those obtained from objective criterion. In most studies the IPAQ-SF overestimated physical activity level by 36 to 173 percent; one study underestimated by 28 percent. The correlation between the IPAQ-SF and objective measures of activity or fitness in the large majority of studies was lower than the acceptable standard. Furthermore, the IPAQ-SF typically overestimated physical activity as measured by objective criterion by an average of 84 percent. Hence, the evidence to support the use of the IPAQ-SF as an indicator of relative or absolute physical activity is weak.

/pdf/validity-of-the-international-physical-activity-2bakdgm0sa.pdf

Validity of the international physical activity questionnaire short form (IPAQ-SF): A systematic review

Quasi-experimentation - design and analysis issues for field settings - cook,td, campbell,dt

Exercise Physiology: Energy, Nutrition and Human Performance

Purpose: This study was conducted to criterion-validate the short format of International Physical Activity Questionnaire (IPAQ) against health-related fitness.

Methods: Participants included 951 men, aged 21-43 yr. V?O2max by ergometer was used to measure cardiorespiratory fitness. Muscular fitness tests included the number of sit-ups, push-ups, and squats performed during 60 s. Physical activity was assessed from IPAQ by categories for health (health-enhancing physical activity (HEPA)) and by calculating total and vigorous MET-hours per week. The participants were classified in five groups of almost equal size by the IPAQ outcomes. Moreover, the frequency of vigorous activity was assessed by one precoded question (single-item question on leisure-time vigorous physical activity (SIVAQ)).

Results: The mean fitness improved from the first through the fourth IPAQ group. V?O2max in the most active IPAQ group, however, was lower than in the fourth group (P < 0.05), both with HEPA categories and vigorous METs as the outcome. In contrast, the weekly frequency of vigorous physical activity showed a positive association with fitness through all six categories. The 65 sedentary (according to SIVAQ) and unfit individuals who belonged to the highest 20% (by IPAQ total METs) were older (30.6 ± 5.1 vs 28.9 ± 3.8, P = 0.02), more obese (waist 93 ± 12 vs 89 ± 10 cm), more often current smokers (59.4 vs 42.0%; P = 0.03), and less educated (<12 yr of education 70.8 vs 52.0%; P = 0.02), compared with the others in the highest IPAQ group.

Conclusions: Almost 10% of young men had poor fitness and apparently low physical activity, but they reported very high physical activity by IPAQ. An evident need therefore exists to develop IPAQ further to solve the apparent overreporting by a considerable proportion of sedentary individuals.

International Physical Activity Questionnaire: Validity against fitness.

Experiments were carried out to test the effect of prolonged and repeated passive stretching (RPS) of the triceps surae muscle on reflex sensitivity. The results demonstrated a clear deterioration ...

/pdf/altered-reflex-sensitivity-after-repeated-and-prolonged-4k90wr1dlz.pdf

Altered reflex sensitivity after repeated and prolonged passive muscle stretching

KUITUNEN, S., P. V. KOMI, and H. KYROLAINEN. Knee and ankle joint stiffness in sprint running. Med. Sci. Sports Exerc., Vol. 34, No. 1, 2002, pp. 166–173.IntroductionStiffness has often been considered as a regulated property of the neuromuscular system. The purpose of this study was to examine the

Knee and ankle joint stiffness in sprint running.

The spring-mass model, representing a runner as a point mass supported by a single linear leg spring, has been a widely used concept in studies on running and bouncing mechanics However, the measurement of leg and vertical stiffness has previously required force platforms and high-speed kinematic measurement systems that are costly and difficult to handle in field conditions We propose a new "sine-wave" method for measuring stiffness during running Based on the modeling of the force-time curve by a sine function,this method allows leg and vertical stiffness to be estimated from just a few simple mechanical parameters: body mass, forward velocity, leg length, flight time, and contact time We compared this method to force-platform-derived stiffness measurements for treadmill dynamometer and overground running conditions, at velocities ranging from 333 ms-1 to maximal running velocity in both recreational and highly trained runners Stiffness values calculated with the proposed method ranged from 067 % to 693 % less than the force platform method, and thus were judged to be acceptable Furthermore, significant linear regressions (p < 001) close to the identity line were obtained between force platform and sine-wave model values of stiffness Given the limits inherent in the use of the spring-mass model, it was concluded that this sine-wave method allows leg and stiffness estimates in running on the basis of a few mechanical parameters, and could be useful in further field measurements

A simple method for measuring stiffness during running.

KYROLAINEN, H., A. BELLI, and P. V. KOMI. Biomechanical factors affecting running economy. Med. Sci. Sports Exerc., Vol. 33, No. 8, 2001, pp. 1330 -1337. Purpose: The present study was designed to investigate kinematics, kinetics, and muscle activity for explaining running economy at different running speeds. Methods: A total of 17 young endurance runners ran at 12-13 different running speeds. Respiratory gases were collected. Kinematic records were obtained by a high-speed video camera, and 3-D ground reaction forces (GRF) were measured simultaneously with telemetric EMG recordings of the selected leg muscles. In the analysis, joint moments and power were calculated by inverse dynamic methods. Results: The oxygen consumption and energy expenditure increased quite linearly with increasing running speed. However, already at the slowest speed, interindividual differences in running economy were noticed, and they increased with increasing running speed. Simultaneously, the instantaneous joint moment-angular velocity curves of the ankle and knee joints shifted to the right and upward, thus increasing joint power in the push-off phase of contact. Most definitive was the increase in EMG-activity of the BF muscle and its correlation with energy expenditure (r 5 0.48, P , 0.05). This two-joint muscle seems to be very active during the maximal running: its amplitude increased (P , 0.05) both in the swinging and contact phases with increasing running speed. Conclusions: The increased EMG of working muscles and the associated increase in power output may partly explain the increased energy expenditure with increasing running speed. Lower performances in running economy by some of the athletes may also be explained by poor running technique, such as unusually high braking and mediolateral forces, which may be caused by limited action of the hamstring muscles. However, no exclusive biomechanical parameters could be

Heikki Kyröläinen

Papers

International Physical Activity Questionnaire: Validity against fitness.

Altered reflex sensitivity after repeated and prolonged passive muscle stretching

Knee and ankle joint stiffness in sprint running.

A simple method for measuring stiffness during running.

Biomechanical factors affecting running economy.