Dark matter and stable bound states of primordial black holes

We present three reasons for the formation of gravitational bound states of primordial black holes,called holeums,in the early universe.Using Newtonian gravity and nonrelativistic quantum mechanics we find a purely quantum mechanical mass-dependant exclusion property for the nonoverlap of the constituent black holes in a holeum.This ensures that the holeum occupies space just like ordinary matter.A holeum emits only gravitational radiation whose spectrum is an exact analogue of that of a hydrogen atom. A part of this spectrum lies in the region accessible to the detectors being built.The holeums would form haloes around the galaxies and would be an important component of the dark matter in the universe today.They may also be the constituents of the invisible domain walls in the universe.Comment: 13 pages,2tables,for wider circulation,PD

Intra- and inter-day reliability of typical and alternative weightlifting variables during heavy cleans

The pull in weightlifting has previously been categorized into 3 phases: weighting 1 (W1), unweighting (UW), and weighting 2 (W2) (Enoka 1979). Research into the examination of weightlifting has typically utilized pulling derivatives initiated at or above the knee (Suchomel et al 2015; Haff et al 2012), which excludes a detailed examination of W1 and UW phases. Weightlifting is a sport initiated from floor level, which would imply that performance of W1 and UW may impact overall performance outcomes and therefore this study aimed to examine which variables can be collected throughout the entire duration of the pull, which of those are reliable within and between days, and which can be monitored for performance

Exercise technique: the push press

The push press exercise has been used for years by coaches as one of many tools to enhance an athletes’ physical development. Recent research has further validated this exercise to augment power development. Thus, the aim of this paper is to outline the benefits this exercise has for strength and conditioning coaches

The acute effects of heavy sled towing on subsequent sprint acceleration performance

Objectives: The purpose of this study was to assess the practical use of heavy sled towing and its acute implications on subsequent sprint acceleration performance. Design and Methods: Eight healthy male varsity team sport athletes (age: 21.8±1.8years, height: 185.5±5.0cm, weight: 88.8±15.7kg, 15m sprint time: 2.66±0.13s) performed sprints under three separate weighted sled towing conditions in a randomized order. Each condition consisted of one baseline unweighted sprint (4-min pre), the sled towing sprint protocol: (1) 1x50% body mass, (2) 2x50% body mass, (3) 3x50% body mass (multiple sprints interspersed with 90s recovery), and 3 post-testing unweighted sprints thereafter (4, 8, 12-min post). All sprints were conducted over a 15m distance. Results: Significantly faster sprint times for the 3x sled towing protocol were identified following 8-min of rest (p=0.025, d=0.46, 2.64±0.15s to 2.57±0.17s). When individual best sprint times were analyzed against baseline data, significantly faster sprint times were identified following both 1x (p=0.007, d=0.69, 2.69±0.07s to 2.64±0.07s) and 3x (p=0.001, d=0.62, 2.64±0.15s to 2.55±0.14s) sled towing protocols. Within the 3x condition, all athletes achieved fastest sprint times following 8–12 min of rest. Conclusions: The findings from the present study indicate that a repeated bout of sled towing (3x50% body mass) leads to the enhancement in subsequent sprint acceleration performance, following adequate, and individualized recovery periods

Asymmetries of the lower limb: the calculation conundrum in strength training and conditioning

Asymmetry detection has been a topic of interest in the strength and conditioning (S&C) literature with numerous studies proposing many different equations for calculating between-limb differences. However, there does not appear to be a clear delineation as to which equation should be used when quantifying asymmetries. Consequently, the authors have uncovered nine different equations which pose confusion as to which method the S&C specialist should employ during data interpretation. This article aims to identify the different equations currently being used to calculate asymmetries and offer practitioners a guide as to which method may be most appropriate when measuring asymmetries

Intra- and inter-day reliability of weightlifting variables and correlation to performance during cleans

The purpose of this investigation was to examine intra- and inter-day reliability of kinetic and kinematic variables assessed during the clean, assess their relationship to clean performance, and determine their suitability in weightlifting performance analysis. Eight competitive weightlifters performed 3 sets of single repetition cleans with 90% of their one-repetition maximum. Force-time data were collected via dual force plates with displacement-time data collected via 3-dimensional motion capture, on three separate occasions under the same testing conditions. Seventy kinetic and kinematic variables were analyzed for intra- and inter-day reliability using intraclass correlation coefficients (ICC) and the coefficient of variation (CV). Pearson’s correlation coefficients were calculated to determine relationships between barbell and body kinematics and ground reaction forces and for correlations to be deemed as statistically significant, an alpha-level of p ≤ 0.005 was set. Eleven variables were found to have ‘good’ to ‘excellent’ intra- and inter-day ICC (0.779-0.994 and 0.974-0.996, respectively) and CV (0.64-6.89% and 1.14-6.37%, respectively), with strong correlations (r = 0.880-0.988) to cleans performed at 90% 1RM. Average resultant force of the weighting 1 (W1) phase demonstrated the best intra- and inter-day reliability (ICC = 0.994 and 0.996 respectively), and very strong correlation (r = 0.981) to clean performance. Average bar power from point of lift off to peak bar height exhibited the highest correlation (r = 0.988) to clean performance. Additional reliable variables with strong correlations to clean performance were found, many of these occurred during or included the W1 phase, which suggests coaches should pay particular attention to the performance of the W1 phase

Alternative jump variables as surrogate measures of weightlifting performance in national weightlifters

Surrogate measures of weightlifting performance (WLp) have previously been monitored using loaded and unloaded squat jumps (SJ) (Bazyler et al 2018; Travis et al 2018; Carlock et al 2004) and countermovement jumps (CMJ) (Carlock et al 2004). Typically measures of jump height (JH) (Travis et al 2018; Carlock et al 2004) and peak power (PP) (Carlock et al 2004), and their associated scaled counterparts (Travis et al 2018; Carlock et al 2004) have been used to identify relationships between them and WLp. While these variables have been shown to have moderate to strong relationships (r = 0.60-0.93) (Carlock et al 2004), further information into the underpinning mechanisms that contribute to such outcome measures has not yet been investigated and may provide insight into variables more sensitive to change; thus, owing to the continued monitoring process

Considerations for selecting field-based strength and power fitness tests to measure asymmetries

The prevalence of lower limb asymmetries has been reported in numerous studies; however, methodological differences exist in the way they can be detected. Strength and jumping-based tasks have been most commonly used to examine these differences across both athlete and non-athlete populations. The aim of this review was to critically analyze the utility of strength and jumping tests that are frequently used to measure asymmetry. Reliability, validity, and considerations for assessment are examined to enhance test accuracy and effectiveness in the quantification of asymmetries during strength and jumping-based tasks. Medline and SPORT Discus databases were used with specific search terms to identify relevant articles in both athlete and non-athlete populations. The findings of the current review indicate that assessing inter-limb differences during strength and jumping-based tasks may result in different levels of asymmetry; thus, inter-limb differences appear to be task-dependent. Consequently, quantification during both types of assessment is warranted and a selection of tests has been suggested to measure asymmetries in both strength and jumping-based tasks

Using unilateral strength, power and reactive strength tests to detect the magnitude and direction of asymmetry: A test-retest design

The aims of the present study were to determine test-retest reliability for unilateral strength and power tests used to quantify asymmetry and determine the consistency of both the magnitude and direction of asymmetry between test sessions. Twenty-eight recreational trained sport athletes performed unilateral isometric squat, countermovement jump (CMJ) and drop jump (DJ) tests over two test sessions. Inter-limb asymmetry was calculated from both the best trial and as an average of three trials for each test. Test reliability was computed using the intraclass correlation coefficient (ICC), coefficient of variation (CV) and standard error of measurement (SEM). In addition, paired samples t-tests were used to determine systematic bias between test sessions and Kappa coefficients to report how consistently asymmetry favoured the same side. Within and between-session reliability ranged from moderate to excellent (ICC range = 0.70⁻0.96) and CV values ranged from 3.7⁻13.7% across tests. Significant differences in asymmetry between test sessions were seen for impulse during the isometric squat (p = 0.04; effect size = ⁻0.60) but only when calculating from the best trial. When computing the direction of asymmetry across test sessions, levels of agreement were fair to substantial for the isometric squat (Kappa = 0.29⁻0.64), substantial for the CMJ (Kappa = 0.64⁻0.66) and fair to moderate for the DJ (Kappa = 0.36⁻0.56). These results show that when asymmetry is computed between test sessions, the group mean is generally devoid of systematic bias; however, the direction of asymmetry shows greater variability and is often inter-changeable. Thus, practitioners should consider both the direction and magnitude of asymmetry when monitoring inter-limb differences in healthy athlete populations