Duration Of Rest Period Research Articles

The Role of Resting Duration in the Kinematic Pattern of Two Consecutive Bench Press Sets to Failure in Elite Sprint Kayakers

This study aimed to investigate the role of rest period duration (RP) on the time course of the acceleration portion (AP) and mean velocity of the concentric phase across two bench press sets to failure with a submaximal load (60% of the 1RM) using different RP. Ten elite junior kayakers performed, on four different days, two consecutive bench press sets to failure, allowing randomly 1-, 2-, 3- and 4-min RP between sets. AP reached a maximal value of 66% of the concentric movement time. This maximal AP was observed in repetition number 2 or 3, and then AP declined during the set, with a significant decrease when the number of repetitions was over 80% of the total number of repetitions performed. AP and lifting velocity patterns of the concentric phase were not altered during a second set to failure, regardless of RP. However, when velocity was expressed in absolute terms, 1-min RP was insufficient to maintain the average lifting velocity during the second set, compared to the first one. These results may be of use in selecting number of repetitions and resting duration in order to ensure optimal maintenance of the accelerative portion of concentric movement time with different resting-period durations.

The Combined Acute Effects of Massage, Rest Periods, and Body Part Elevation on Resistance Exercise Performance

Although massage administered between workouts has been suggested to improve recovery and subsequent performance, its application between bouts of repetitive supramaximal anaerobic efforts within a given workout has received little attention. The purpose of the study compared different forms of very short rest periods administered between resistance exercise sets of individual workouts on subsequent performance. With a within-subjects design methodology, subjects (n = 30) performed three workouts that were identical in terms of the exercises (45 degrees leg press, prone leg curl, seated shoulder press, standing barbell curl), number of sets, and the resistance employed. For each workout, subjects received one of the following treatments between sets: 1 minute of rest as they stood upright, 30 seconds of rest as they stood upright, or 30 seconds of concurrent massage and body part elevation (MBPE), which entailed petrassage of the exercised limbs in a raised and supported position in an attempt to abate fatigue and enhance recovery from the previous set. Subjects were instructed to perform as many repetitions as possible for each set. For each exercise, two dependent variables were calculated: a total work/elapsed time ratio and the cumulative number of repetitions performed. For each exercise, one-way repeated-measures analysis of variance and Tukey's post hoc test revealed the following total work/elapsed time results: 1 minute rest <30 seconds' rest, 30 seconds' MBPE. For each exercise, cumulative repetition results were as follows: 1 minute rest >30 seconds' rest, 30 seconds' MBPE. Results imply that rest period duration exerts more influence on resistance exercise performance than MBPE. Those who seek improved resistance exercise performance should pay particular attention to rest period durations.

Universal Scaling Law in Human Behavioral Organization

We describe the nature of human behavioral organization, specifically how resting and active periods are interwoven throughout daily life. Active period durations with physical activity count successively above a predefined threshold, when rescaled with individual means, follow a universal stretched exponential (gamma-type) cumulative distribution with characteristic time, both in healthy individuals and in patients with major depressive disorder. On the other hand, resting period durations below the threshold for both groups obey a scale-free power-law cumulative distribution over two decades, with significantly lower scaling exponents in the patients. We thus find universal distribution laws governing human behavioral organization, with a parameter altered in depression.

Influence of rest periods on fatigue characteristics of SBS polymer modified bituminous concrete mixtures

In the present study the laboratory investigations were carried out to study the effect of rest periods on the fatigue life of polymer modified bituminous concrete (BC) mix with Styrene–Butadiene–Styrene (SBS) tri block co-polymer (PMBC) and to compare with control mix of 80/100 neat BC. PMBC mix shows higher fatigue lives when compared to BC mix at different loading ratios, i (ratio of duration of rest period to that of loading). When loading ratios were increased for PMBC as well as BC mixes fatigue lives have been increased. The beneficial effect of loading ratio is higher in case of BC mixes when compared to PMBC mixes. With increase in strain level BC mixes have undergone higher reduction in life ratio (the ratio of fatigue life obtained from fatigue tests conducted with and without rest periods) when compared to PMBC mixes. Increase in life ratio with increase in loading ratio is higher in case of BC mixes when compared to PMBC mixes.

Influence of rest period duration between successive muscular strength sets on acute modifications of blood pressure and heart rate in the healthy subject

Objective. To measure the impact of different recovery periods on systolic blood pressure (SBP) and heart rate (HR) during classical resistance training (RT) modalities Background. Resistance training was introduced into rehabilitation programs to improve the efficiency of traditional training. The impact of different RT modalities on muscular performance is well known but the recovery periods between successive RT sets recommended in the literature varied between 30 s and 5 min. Method. Twenty one healthy subjects were tested while performing a classical RT paradigm: 3 sets of 10 repetitions at 75% of 1-RM, with recovery periods of 30, 60, 90 and 120 s. Results. A recovery period of 30 or 60 s did not allow a return of SBP and HR to resting values. A progressive drift of the values was observed in the successive rests as well as in the successive efforts. A recovery period longer than 60 s (90 and 120 s) allowed a return of SBP and HR to resting values. Conclusions. A recovery period of 90 s or more between successive classical RT sets is recommended in order to avoid excessive SBP and HR elevation.

Coronary MR Imaging: Breath-hold Capability and Patterns, Coronary Artery Rest Periods, and β-Blocker Use

To prospectively evaluate breath-hold capability and patterns, coronary artery rest periods, and beta-blocker use in coronary magnetic resonance (MR) imaging. Ethics committee approval and informed consent were obtained. In 210 consecutive patients (mean age, 61.8 years +/- 10.3 [standard deviation]; 146 men, 64 women), breath-hold patterns and maximal capability were assessed at expiration with dynamic navigator MR imaging (temporal resolution, 1 second). Left coronary artery (LCA) and right coronary artery (RCA) rest periods were determined at transverse cine imaging (steady-state free precession, retrospective gating, 40 phases per cycle). Before and after beta-blockade, rest periods were assessed in 25 additional patients (mean age, 61.4 years +/- 7.1; 20 men, five women). Differences were tested within groups with paired Student t test and between groups with unpaired Student t test (continuous variables) and chi(2) test (categoric variables). Pearson correlation was used to test the relationship between rest period and heart rate. Four distinct breath-hold patterns, characterized by diaphragmatic motion, were identified: pattern 1, steady plateau (55% of patients); 2, initial drift followed by plateau (12%); 3, continuous drift (19%); and 4, irregular, unsteady behavior (14%). Mean breath-hold capability with patterns 1 and 2 was 29 seconds +/- 13 (range, 10-64 seconds). The rest period of LCA was longer than that of RCA (163 msec +/- 75 vs 123 msec +/- 60; P < .01) and began earlier in the cardiac cycle (521 msec +/- 149 vs 540 msec +/- 160; P < .01); In a minority of patients, LCA rest period began later (21%) or was shorter (14%). With no pharmacologic intervention, correlation between rest period duration and heart rate was weak (LCA, r = -0.52; RCA, r = -0.38; P < .01). However, beta-blockade significantly lowered heart rate (61.3 beats/min +/- 7.2 vs 82.6 beats/min +/- 12.5, P < .001) and increased rest duration (LCA, 201.8 msec +/- 83.6 vs 111.8 msec +/- 44.55; RCA, 134.8 msec +/- 57.3 vs 83.1 msec +/- 35.8; P < .001). In 33% of patients (patterns 3 and 4), breath-hold pattern was unsuitable for high-spatial-resolution breath-hold MR imaging. LCA and RCA rest periods showed large variability in starting point and duration, with no correlation to heart rate.

Long‐term side‐effects of intermittent androgen suppression therapy in prostate cancer: results of a phase II study

To assess the feasibility and tolerability of intermittent androgen suppression therapy (IAS) in prostate cancer. Patients with recurrent or metastic prostate cancer received cyclical periods of treatment with leuprolide acetate and nilutamide for 8 months, and rest periods. Cycles were repeated at progression until the treatment failed to achieve normal prostate-specific antigen (PSA) levels. Patients were followed with PSA level, testosterone level, haemoglobin level, weight and bone mineral density evaluations. The median time to treatment failure, recovery from anaemia, or normalization of testosterone level was estimated by the Kaplan-Meier method. In all, 95 patients received 245 cycles; the median duration of rest periods was 8 months and median time to treatment failure 47 months. Testosterone recovery during rest periods was documented in 117 (61%) of cycles. Anaemia was mild and reported in 33%, 44% and 67% of cycles 1, 2 and 3, respectively. Sexual function recovered during the rest periods in 47% of cycles. There was no significant overall change in body mass index at the end of the treatment period. Osteoporosis was documented in at least one site evaluated in 41 patients (37%). IAS has the potential to reduce side-effects, including recovery of haemoglobin level, return of sexual function and absence of weight gain at the end of the study period.

Rest period duration of the coronary arteries: Implications for magnetic resonance coronary angiography

Magnetic resonance (MR) and computed tomography coronary imaging is susceptible to artifacts caused by motion of the heart. The presence of rest periods during the cardiac and respiratory cycles suggests that images free of motion artifacts could be acquired. In this paper, we studied the rest period (RP) duration of the coronary arteries during a cardiac contraction and a tidal respiratory cycle. We also studied whether three MR motion correction methods could be used to increase the respiratory RP duration. Free breathing x-ray coronary angiograms were acquired in ten patients. The three-dimensional (3D) structure of the coronary arteries was reconstructed from a biplane acquisition using stereo reconstruction methods. The 3D motion of the arterial model was then recovered using an automatic motion tracking algorithm. The motion field was then decomposed into separate cardiac and respiratory components using a cardiac respiratory parametric model. For the proximal-to-middle segments of the right coronary artery (RCA), a cardiac RP (<1 mm 3D displacement) of 76+/-34 ms was measured at end systole (ES), and 65+/-42 ms in mid-diastole (MD). The cardiac RP was 80+/-25 ms at ES and 112+/-42 ms at MD for the proximal 5 cm of the left coronary tree. At end expiration, the respiratory RP (in percent of the respiratory period) was 26+/-8% for the RCA and 27+/-17% for the left coronary tree. Left coronary respiratory RP (<0.5 mm 3D displacement) increased with translation (32% of the respiratory period), rigid body (51%), and affine (79%) motion correction. The RCA respiratory RP using translational (27%) and rigid body (33%) motion correction were not statistically different from each other. Measurements of the cardiac and respiratory rest periods will improve our understanding of the temporal and spatial resolution constraints for coronary imaging.

Intermittent sand filtration for wastewater treatment in rural areas of the Middle East - a pilot study

This paper concentrates on Intermittent Sand Filtration (ISF) as a polishing stage for effluent from a facultative pond. During the three-year research program, the system operated with an influent flow-rate of 500-1,000 L/day and an average BOD concentration of 200-400 hydraulic and BOD loadings of 110-200 L/m2/day and 20-40 gBOD/m2/day, respectively. Flow to the ISF was applied intermittently with a different number of doses in each run. In addition, the effects of the frequency and the duration of rest periods (no feeding) were studied. Removal of 90-95% of BOD and 75-90% of COD and TSS was achieved consistently throughout the study period. Elevated levels of nitrification were observed with 95-100% removal of NH3. The ISF performed best when fed with 5-10 doses/day. Reducing the daily number of doses to 3/day at the same hydraulic loading rate resulted in a 20-30% reduction in removal efficiency. The 2-4 week rest period had no effect on the biological activity in the subsequent run. However, rest periods of more than 30 days were found to negatively affect removal efficiency.

Artificial neural networks as a tool of modeling of training loads

This paper shows that extremely important element of forming speed capabilities is proper (quantitative) structure of exercise loads. This means that training means should be chosen from point of view of energy production in metabolic processes, which depends on the structure of training means from the information area and energy area, therefore on the character of work made, its intensity, duration of exercise, number of repetitions and duration of rest periods. From the training process effectiveness point of view, it is extremely important to find the correct tool for choosing means in given training cycle. The investigation results confirm the experiences of coaches and theorists of sport, that the structure of volume and intensity of exercise loads should be individually chosen with consideration of predispositions of separate athletes. Individualization of training is condition for its optimization.

Herzfrequenz, Aktivitäts- und Ruhezeiten sowie Wachstumsleistung von in Gruppen mit Tränkeautomatenfütterung gehaltenen Milchrindkälbern während der Aufzucht im Winter und Frühjahr

Abstract. Title of the paper: Heart rate, activity and resting times and growth in group reared feeder-fed dairy calves reared at transition from winter to spring To characterize the food entrainable oscillator and/or light entrainable oscillator determined rhythmicity of physiological variables of feeder-fed dairy calves reared at transition from winter to spring (35 German Holstein Friesian, 2 German Red Pied, 17 male and 20 female) long term heart rate recordings were taken at 5 , 15, 40 and 60 days of age using Polar Sport Tester, from which the number and duration of activity (ZDA) and rest periods (ZDR) and the total activity (GZA) and rest times (GZR) could be established. For these periods characteristic heart rate values were calculated (HFA and HFR) and they were analysed for daytime periods of three hours duration at different life ages. HF of feeder-fed dairy calves showed substantial interindividual variation and a high individual specificity. Mean HFA and HFR were significantly smaller at 15 and 40 days then at 5 and 60 days of age. HFA and HFR showed a high correlation and the mean values of HFA and HFR were allways significantly different. More profound increases of HF (HFA-HFR) could be observed at feeding and service times. Individual level of HFA and HFR changed regularly with daytime, but mean values were significantly different between daytime periods only at some age points. Deviation of HFA and HFR from the mean of the individual daytime heart rate recording followed a circadian rhythm that became more obvious with advanced development and adaptation of the animals in case of HFA and HFR. For the means of the deviations of HFA and HFR significant differences between the daytime periods could be found. The mean ZDA and the quotient GZA/GZR were greater at 40 and 60 days of age then at 5 and 15 days of age. ZDA and ZDR showed great variation and presented rhythmic changes during the course of the day. The means of ZDA and ZDR were significantly different between the daytime periods of three hours duration at the age points excluding that of ZDA for 15 days of age. Results show the establishment and the prevalence of a circadian rhythm of heart rate at the early growth period in feeder-fed dairy calves reared at transition from winter to spring and how this was superimposed by feeding activity around the programmed daytimes of feed access at the start of rearing.

Work-time profile, blood lactate concentration and rating of perceived exertion in the 1998 Greco-Roman wrestling World Championship

The aim of this study was to examine work-time profiles, blood lactate concentrations and perceived exertion among Greco-Roman wrestlers in the 1998 World Championship. Forty-two senior wrestlers from nine nations were studied in 94 matches. Each match was recorded with a video camera (Panasonic AG 455, film rate: 25 Hz) and analysed for duration of work (wrestling) and rest (interrupt) periods. Blood lactate concentration was determined with an electrochemical device (Analox P-LM5) and a rating of perceived exertion scale (Borg) was used to estimate general exertion and exertion in the extremity and trunk muscles. The mean duration of the matches was 427 s (range 324-535 s), with mean durations of work and rest of 317 and 110 s, respectively. The mean periods of work and rest were 37.2 and 13.8 s, respectively. Mean blood lactate concentration was 14.8 mmol · l -1 (range 6.9-20.6). The difference in mean blood lactate concentration between the first- and final-round matches was not significant ( P > 0.05). Blood lactate concentration was significantly higher ( P ≪ 0.04) in matches of long duration than in those of short duration. The mean general rating of perceived exertion for all matches was 13.8 according to the scale used. Most of the wrestlers (53.3%) perceived exertion to be highest in the flexors of the forearm, followed by the deltoids (17.4%) and the biceps brachii muscles (12.0%). In addition to a relatively high rating of perceived exertion in the arm muscles, this indicates a high specific load on the flexor muscles of the forearm.

Effects of space allowance and duration of rest periods during the transport of calves

Grigor, P. N., Cockram, M. S., Steele, W. B., Le Sueur, C. J., Forsyth, R. E., Guthrie, J. A., Johnson, A. K., Sandilands, V., Reid, H. W., Sinclair, C. &...

Posterior Lumbar Interbody Fusion in the Pyogenic Discitis

Study design : To present preliminary results of PLIF (Posterior lumbar interbody fusion) and pedicle screw fixation in the lumbar pyogenic discitis. Objectives : To evaluate the advantages and effects of PLIF and posterior instrumentation over recurrence of infection in lumbar pyogenic discitis which are resistant to antibiotics. Summary of Literature Review : To the date, anterior removal of the focus followed by interposing autogenous bone graft without additional instrumentation and postoperative long-term immobilization has been the standard operative procedure. Materials and Methods : 10 consecutive patients who had lumbar pyogenic discitis were treated by posterior approach from October 1997 to March 1999. Results : Based on MRI or CT finding, 9 solid union at 3~4 months after operation and 1 suspicious union at 1 year after operation were observed. The mean preoperative lordotic angle of the affected segments was 9°, compared to 20°after postoperation and 17°at last follow up. As for functional result of Kirkaldy-Willis, outcome was excellent in 3, good in 5, fair in 2, none poor case. The duration of postoperative bed rest period was an average of 3 days. Conclusions : PLIF with instrumentation in lumbar pyogenic discitis is a useful treatment in posterior epidural abscess,coexistent spinal stenosis and lower lumbar level where anterior fixation is impossible. It is especially indicated in the case of scanty antevertebral abscess with minimal bone destruction. Its main advantage is early ambulation.

Alterations in shoulder muscle activity due to changes in data entry organisation

The aim of the present study was to investigate how changed work organisation and different work tasks influence shoulder muscular load and to quantify the magnitude, duration and frequency of rest periods from shoulder muscular load during a working day. Shoulder muscular load was measured in 22 females working at their data entry workplaces, during a whole working day. The activity from both trapezius muscles was measured with EMG before (1991) and after (1992) a reorganisation programme intended to redistribute repetitive work and provide new work tasks. The change in work organisation did not change the magnitude of muscular load or the duration and frequency of rest periods, but decreased musculoskeletal problems. The subjects' increased desk work involved greater muscular load than the data entry did, but also allowed more movement. The changes in work tasks seemed to be important, although small. In repetitive work, organisational changes aimed at reducing musculoskeletal disorders should focus on providing employees with tasks that afford variation in muscular load. Relevance to industry The paper discusses the need of physical work task variation in repetitive work in order to minimise the risk of musculoskeletal disorders. It seems more important to vary the tasks than to minimise the shoulder muscular load.

Movement of solute through a porous medium under intermittent leaching

SummaryExcess salts may be removed from soil by leaching, but ponding water on the soil's surface and allowing infiltration requires large quantities of water. During such leaching water flows preferentially through macropores between aggregates, while the flow within aggregates is much less. Consequently, solute within aggregates is removed much more slowly, thus decreasing overall leaching efficiency. For this reason intermittent ponding can be more efficient because it allows time for solute to diffuse to the surfaces of aggregates during the rest period and subsequently be removed in macropore flow. We explored solute transport in aggregated soils under intermittent leaching in three ways: theoretically, by laboratory experiments on columns of porous ceramic spheres as analogues of aggregates, and by simulation. Solute movement during displacement is described by the mobile‐immobile convection‐dispersion equation. During the rest period flow ceases, and solute redistributes within the aggregates by diffusion, the key variable being the effective diffusion coefficient, De of the solute in the aggregates, and longitudinally by diffusion within macropores (though this was ignored in the simulation). We estimated De for our porous spheres from observations of solute outflow into finite volumes of stirred distilled water. The theory was validated against experiments on saturated columns for different aggregate‐size distributions, flow velocities, and displacement and rest periods, with most parameters estimated independently. Experiments and simulations showed that water savings of 25% were possible under our laboratory conditions, increasing as aggregate size, flow velocity and duration of rest period increased. The potential of intermittent leaching in the field is considered.

Kinetics of fatigue failure of polystyrene

AbstractTo study the mechanism of crack initiation in the fatigue of amorphous polymers, flexural fatigue tests have been performed on injection molded samples (ISO 1 standard 4 mm thick 10 mm large) of polystyrene homopolymer (PS), at a frequency of 10 Hz. Two types of fatigue tests were performed: (i) Monosequential Fatigue Test (MFT) in which cycling loading is not interrupted: (ii) Polysequential Fatigue Test (PFT) during which fatigue periods alternate with rest periods. The number of cycles to rupture has been determined for various values of the strain amplitude, temperature and duration of rest periods. Two kinetics regimes were observed: (i) at temperature higher than 75°C, the thermal regime is quasi adiabatic and failure results from polymer softening. In this regime, rest periods have a strong stabilizing effect, since they limit self heating; (ii) At temperatures lower than 75°C, the thermal regime is quasi isothermal and fracture results from crazing followed by brittle rupture. Rest periods (on the order of half fatigue lifetime) have no effect on the number of cycles to rupture. The influence of temperature here is considerably lower than in the “adiabatic” regime. The endurance limit values ϵ∞ are close to the critical strains for crazing ϵC in static conditions. A kinetic model based on the above observations is proposed for strain amplitudes close to the endurance limit (2ϵ∞ ≥ ϵ ≥ ϵ∞). This model reasonably fits the experimental data.

Séchage intermittent de maïs en lit fluidisé à flottation : étude expérimentale et modélisation

This work concerns the drying of maize in a flotation fluidized bed by intermittent blowing of hot air. The aim of the study was on the one hand to determine the effect of this drying technique not only on the energy consumption, but also on the grain quality, and on the other hand to develop a mathematical model which simulates the observed phenomena. The effect of the conditions of intermittent drying as the duration of aeration and rest periods, respectively, t a and t r has been examined. The ratio t r t a does not affect the drying kinetics for values greater than 2. Besides, intermittent drying consumes less energy than drying with a continuous air flow because it reduces the actual drying duration by 50%. However, for the operating conditions of this study, this technique did not allow an improvement in the wet-milling quality. A mathematical model adapted to intermittent drying has been developed. This model leads to very good predictions on the evolution of air humidity, dryer temperature, grain moisture content and temperature, but also the variation of maize wet-milling and proteic qualities. This model can be used for the control of drying process under optimal conditions.

Deadhead Selection for the Long-Haul Crew Pairing Problem

The long-haul crew pairing problem involves the assignment of crews to scheduled flights such that overall costs are minimized and crew availability and work rule restrictions are satisfied. These problems are characterized by international flights that typically do not operate on a daily schedule, resulting in a sparsity of flights and extended periods of inactivity for crews at some stations. To eliminate these extended rest periods and reduce overall costs, it is advantageous in some cases to deadhead crews, that is, to assign crews to flights as passengers for repositioning and better utilization. In this paper, a heuristic methodology is developed to improve crew pairing solutions through the efficient selection and utilization of deadhead flights. The methodology uses the dual solutions determined in solving the linear programming relaxation of the crew pairing problem to build arrival and departure profiles at each station. These profiles provide a mechanism to price-out potential deadhead flights. Flights that price-out favorably may be used to build improved solutions to the crew pairing problem. The Deadhead Selection Procedure is tested using data provided by a long-haul airline and is shown to achieve significant improvement in crew costs by reducing the total number of deadhead hours flown and by reducing the total duration of rest periods.

Behavioural response of three nereid polychaetes to injection of sulfide inside burrows

The behavioural response (ventilation rate, duration of ventilation bursts, length of pauses between ventilation bursts) of 3 closely related nereid polychaetes (Nereis virens, N. diversicolor and N. succinea) to various levels of sulfide exposure was investigated during spring and summer of 1992. The response to HSwas species specific. N. virens reacted strongly to HSby increasing the duration of ventilation bursts. Duration of rest periods was affected less severely while ventilation fa~led to show any significant vanation. The behavioural response of N. diversicolor did not show much variation under HSexposure. The only significant response was a decreased duration of rest periods at high HSconcentration. The type of reaction displayed by N. succinea was similar to the response of N. virens, although less pronounced. N. diversicolor removed most HSfrom the burrow in less than 10 rnin due to the generally high ventilation rate of this species. The slow removal of H S by the other 2 species is caused by a slower response and lower ventilation rate. The shape of the H S efflux curve indicated that changes in the response during exposure are important in N. virens and substantiate a possible toxic effect of HSN. diversicolor displayed the fastest recuperation following HSexposure (restored ventilation behaviour). For all species, time of recuperation increased with increasing sulfide concentration.