The acute effects of different high-intensity conditioning activities on sprint performance differ between sprinters of different strength and power characteristics

The purpose of the present study was to examine the effect of different conditioning activities (CAs) on short-term increase in sprint performance. In twelve male sprinters (21.1±2.6 years, 100 m performance: 11.5±0.6 s) their body composition, half squat maximum strength, 100 m sprinting and countermovement jump performances were evaluated. The performance of a 50 m sprint (splits at 10 m, 30 m and 50 m) was evaluated before and 5, 10 and 15 min after four postactivation performance enhancement CAs on different occasions: [1] 3 sets x 4 s maximum isometric half squat (IHF), [2] 3 sets x 3 consecutive countermovement jumps (cCMJs), [3] 3 repetitions x 30 m overspeed sprinting (OVSP) and [4] dynamic submaximal half squat (2 sets x 2 reps x 90% of 1-RM half squat; HSQ). Significant improvements of sprinting performance were found 10 and 15 min following the cCMJs, OVSP and HSQ’s interventions, in all distances (p.05). Significant inter-individual differences were found in the magnitude of sprint performance improvements as well as in the optimal time window (p<.05), with the stronger sprinters responding better after HSQs, while the more powerful sprinters after cCMJs and OVSPs. In conclusion, it seems that cCMJs, OVSP and HSQ can acutely increase sprinting performance after 10 min, but CA’s induced increases in sprinting performance are highly related to the strength and power characteristics of each sprinter

Improvement of long-jump performance during competition using a plyometric exercise

Purpose: To examine the acute effects of a conditioning plyometric exercise on long-jump performance during a simulated long-jump competition. Methods: Eight national-level track and feld decathletes performed 6 long-jump attempts with a full approach run separated by 10-min recoveries. In the experimental condition subjects performed 3 rebound vertical jumps with maximal effort 3 min before the last 5 attempts, while the 1st attempt served as baseline. In the control condition the participants performed 6 long jumps without executing the conditioning exercise. Results: Compared with baseline, long-jump performance progressively increased only in the experimental condition, from 3.0%, or 17.5 cm, in the 3rd attempt (P =.046, d = 0.56), to 4.8%, or 28.2 cm, in the 6th attempt (P =.0001, d = 0.84). The improvement in long-jump performance was due to a gradual increase in vertical takeoff velocity from the 3rd (by 8.7%, P =.0001, d = 1.82) to the 6th jump (by 17.7%, P =.0001, d = 4.38). Horizontal-approach velocity, takeoff duration, and horizontal velocity at takeoff were similar at all long-jump attempts in both conditions (P =.80, P =.36, and P =.15, respectively). Conclusions: Long-jump performance progressively improved during a simulated competition when a plyometric conditioning exercise was executed 3 min before each attempt. This improvement was due to a progressive increase in vertical velocity of takeoff, while there was no effect on the horizontal velocity. © 2017 Human Kinetics, Inc

How Effectively Can Students&apos; Personal Smartphones be Used as Tools in Physics Labs?

This study seeks to answer the question of how effectively students can use their smartphones as tools for measuring and processing data when they perform physics experiments. The research was conducted in a local secondary school in Athens, Greece. The sample consisted of fifty-two 16-year-old students (10th grade), who were divided into 26 pairs and asked to perform an experiment using their smartphones for measuring, processing and saving data, and then to email the data file to the researchers. During the implementation, each pair completed the steps on a worksheet. Two researchers monitored each pair individually, and recorded scores and comments on evaluation sheets. The worksheets, the evaluation sheets, and the experimental data emailed by each pair constituted the data of the present study. The findings of the study show that the integration of students&apos; smart mobile devices in the performance of physics experiments in the classroom or in the school lab is possible without posing particular problems. However, this integration presupposes the proper planning by the teacher and the dedication of appropriate time both for the preparation of students for the activity, and for the installation of the necessary applications in the devices. © 2021. All Rights Reserved

Acute Improvement of Vertical Jump Performance after Isometric Squats Depends on Knee Angle and Vertical Jumping Ability

Tsoukos, A, Bogdanis, GC, Terzis, G, and Veligekas, P. Acute improvement of vertical jump performance after isometric squats depends on knee angle and vertical jumping ability. J Strength Cond Res 30(8): 2250-2257, 2016 - This study examined the acute effects of maximum isometric squats at 2 different knee angles (90 or 140°) on countermovement jump (CMJ) performance in power athletes. Fourteen national-level male track and field power athletes completed 3 main trials (2 experimental and 1 control) in a randomized and counterbalanced order 1 week apart. Countermovement jump performance was evaluated using a force-plate before and 15 seconds, 3, 6, 9, and 12 minutes after 3 sets of 3 seconds maximum isometric contractions with 1-minute rest in between, from a squat position with knee angle set at 90 or 140°. Countermovement jump performance was improved compared with baseline only in the 140° condition by 3.8 ± 1.2% on the 12th minute of recovery (p 0.027), whereas there was no change in CMJ height in the 90° condition. In the control condition, there was a decrease in CMJ performance over time, reaching -3.6 ± 1.2% (p 0.049) after 12 minutes of recovery. To determine the possible effects of baseline jump performance on subsequent CMJ performance, subjects were divided into 2 groups (&quot;high jumpers&quot; and &quot;low jumpers&quot;). The baseline CMJ values of &quot;high jumpers&quot; and &quot;low jumpers&quot; differed significantly (CMJ: 45.1 ± 2.2 vs. 37.1 ± 3.9 cm, respectively, p 0.001). Countermovement jump was increased only in the &quot;high jumpers&quot; group by 5.4 ± 1.4% (p 0.001) and 7.4 ± 1.2% (p 0.001) at the knee angles of 90 and 140°, respectively. This improvement was larger at the 140° angle (p 0.049). Knee angle during isometric squats and vertical jumping ability are important determinants of the acute CMJ performance increase observed after a conditioning activity. © 2016 National Strength and Conditioning Association

An educational proposal for students&apos; experimentation in a distance learning environment

The social distancing rules during the Covid-19 quarantine period posed new challenges in the teaching of physics especially for the laboratory sessions. One solution, that permitted students to carry on the experimental work during this period, was the &apos;do it at home&apos; activities using simple materials for setting up the experiment and a smartphone as a measuring device. In this line of reasoning an educational intervention was designed and carried out in a junior high school of Athens. After discussing the criteria for selecting the &apos;do it at home&apos; activities assigned to the students the chosen experiments are presented, and the distance education tools that were used for carrying out the intervention are described. The findings and the conclusions were drawn both by the papers submitted by pupils and from a questionnaire that students answered online a few days after the completion of the whole action. Students enjoyed the experimental work and they managed to carry out quite successfully all the required steps despite a few difficulties they had encountered. It is worth mentioning that such &apos;do it at home&apos; experiments could also be possibly used at periods when there is a normal access to a school physics lab and not only in the context of a distance learning environment. © 2021 IOP Publishing Ltd

Postactivation potentiation of bench press throw performance using velocity-based conditioning protocols with low and moderate loads

This study examined the acute effects of the bench press exercise with low and moderate loads as well as with two predetermined movement velocity loss percentages on bench press throw performance and surface electromyographic (sEMG) activity. Ten trained men completed 5 main trials in randomized and counterbalanced order one week apart. Mean propulsive velocity (MPV), peak velocity (PV) and sEMG activity of prime movers were evaluated before and periodically for 12 minutes of recovery under five conditions: Using loads of 40 or 60% of 1 RM, until mean velocity dropped to 90 or 70%, as well as a control condition (CTRL). MPV and PV were increased 4-12 min into recovery by 4.5-6.8% only after the 60%1RM condition during which velocity dropped to 90% and total exercise volume was the lowest of all conditions (p &lt; 0.01, Hedges&apos; g = 0.8-1.7). When peak individual responses were calculated irrespective of time, MPV was increased by 9.2 ± 4.4 (p &lt; 0.001, Hedges&apos; g = 1.0) and 6.1 ± 3.6% (p &lt; 0.001, Hedges&apos; g = 0.7) under the two conditions with the lowest total exercise volume irrespective of the load, i.e. under the conditions of 40 and 60% 1RM where velocity was allowed to drop to 90%. sEMG activity of the triceps was significantly greater when peak individual responses were taken into account only under the 60%1RM condition when velocity dropped to 90% (p &lt; 0.05, Hedges&apos; g = 0.4). This study showed that potentiation may be maximized by taking into account individual fatigue profiles using velocity-based training. © 2019 Athanasios Tsoukos, Lee E. Brown, Panagiotis Veligekas, Gerasimos Terzis, Gregory C. Bogdanis, published by Sciendo

Changes in EMG and movement velocity during a set to failure against different loads in the bench press exercise

This study examined changes in movement velocity and surface electromyographic (sEMG) activity of the pectoralis major (PM) and triceps brachii (TB) muscles during the bench press exercise to failure against different loads. Fourteen men performed a set to failure with maximum intended velocity, against low (40%-1 repetition maximum-RM), moderate (60%-1RM), and heavy loads (80%-1RM). Number of repetitions, volume load, mean and peak velocity, and total time increased with decreasing load (40% &gt; 60% &gt; 80%, p &lt; 0.01). sEMG comparisons between different loads were performed by matching time under tension at the initial, middle, and last part of the set. sEMG was higher in the middle and last repetitions, compared with the initial, for all loads in both muscles (p &lt; 0.001). sEMG activity of both muscles was higher in the 60% and 80%-1RM conditions compared with the 40%1-RM (p &lt; 0.007). Also, sEMG of both muscles was similar for the 60%-1RM and 80%-1RM loads at the initial, middle, and last repetitions, with the exception of the last repetitions for the TB muscle. In contrast, sEMG integrated activity was higher for the 40% 1-RM and 60% 1-RM (p &lt; 0.01) compared with the 80% 1-RM load. Mean velocity loss at exhaustion and drop in sEMG median frequency were greater in the 40% and 60%-1RM compared with the 80%-1RM condition (p &lt; 0.05). It was concluded that performing a set to exhaustion with maximum intended velocity using a load of 60% 1-RM combines the characteristics of the high average sEMG activity of heavier loads, and the high total integrated sEMG observed at lighter loads. © 2021 John Wiley &amp; Sons A/S. Published by John Wiley &amp; Sons Lt

Delayed effects of a low-volume, power-type resistance exercise session on explosive performance

This study examined the delayed effects of a power-type training session on explosive performance. Seventeen well-trained male power and team sport athletes (age: 22.7 ± 5.5 years, height: 181 ± 8 cm, body mass: 80.7 ± 8. ± kg, body fat: 9.2 ± 1.7%, 1 repetition maximum (1RM) half-squat: 163 6 29 kg) performed 4 sessions (2 experimental and 2 control) 1 week apart in a randomized and counterbalanced order. Explosive performance was assessed before, 24 and 48 hours after a low-volume, power-type training session (5 3 4 jump squats at 40% 1RM with 3 minutes rest), as well as before and after 24 and 48 hours of rest (control). Dependent variables were as follows: countermovement jump (CMJ), reactive strength index (RSI) during a drop jump, leg press maximum isometric force, and rate of force development (RFD) at 3 time windows: 0–100, 0–200, and 0–300 milliseconds. Analysis of variance revealed no changes in the control conditions. In contrast after training, CMJ was improved by 5.1 ± 1.0% and 3.0 ± 1.0% at 24 and 48 hours, respectively, compared with baseline. The RSI improved by 10.7 ± 2.1% only at 24 hours. The RFD increased at all time windows at 24 hours (range of improvement: 9.7 ± 3.4% to 18.3 ± 4.1%, p&amp;lt; 0.01). However, at 48 hours, improvement was only seen in RFD0–100 (9.8 ± 3.1%, p &amp;lt; 0.01). These findings suggest that a low-volume, power-type training session results in delayed enhancement of explosive muscle performance, which is greatest at 24 hours after the activity. Athletes are advised to perform power-type training 1 day before competition or a high-quality training session to improve their performances. © 2017 National Strength and Conditioning Association

Changes in Body Composition and Strength after 12 Weeks of High-Intensity Functional Training with Two Different Loads in Physically Active Men and Women: A Randomized Controlled Study

This study examined the effects of two different resistance loads during high-intensity Functional Training (HIFT) on body composition and maximal strength. Thirty-one healthy young individuals were randomly assigned into three groups: moderate load (ML: 70% 1-RM), low load-(LL: 30% 1-RM), and control (CON). Each experimental group performed HIFT three times per week for 12 weeks with a similar total volume load. Body fat decreased equally in both experimental groups after 6 weeks of training (p &lt; 0.001), but at the end of training it further decreased only in LL compared to ML (−3.19 ± 1.59 vs. −1.64 ± 1.44 kg, p &lt; 0.001), with no change in CON (0.29 ± 1.08 kg, p = 0.998). Lean body mass (LBM) increased after 6 weeks of training (p = 0.019) in ML only, while after 12 weeks a similar increase was observed in LL and ML (1.11 ± 0.65 vs. ML: 1.25 ± 1.59 kg, p = 0.034 and 0.013, respectively), with no change in CON (0.34 ± 0.67 kg, p = 0.991). Maximal strength increased similarly in four out of five exercises for both experimental groups by between 9.5% and 16.9% (p &lt; 0.01) at the end of training, with no change in CON (−0.6 to 4.9%, p &gt; 0.465). In conclusion, twelve weeks of HIFT training with either low or moderate resistance and equal volume load resulted in an equal increase in LBM and maximal strength, but different fat loss. © 2022 by the authors. Licensee MDPI, Basel, Switzerland