Validating two systems for estimating force and power

Validity and between-unit agreement of commercially-available linear position transducer and inertial sensor devices during loaded countermovement jumps

To assess the validity and between-unit agreement of velocity monitoring devices during incrementally-loaded countermovement jumps (CMJ), 16 males (24.0 ± 3.5 yr) completed 12 CMJs on a force plate (FP). Performance variables were collected through two linear position transducers (GymAware [GA]) and four accelerometer-based devices (two PUSH units, two Bar Sensei units). Pearson correlations (r) and coefficients of variation (CV) demonstrated strong to very-strong relationships (r = 0.60-0.88) and poor agreement (CV = 11.7-25.3%) between FP and GA, and moderate to very-strong relationships (r = 0.31-0.81) and poor agreement (CV = 10.1-24.2%) between FP and PUSH. Between-unit comparisons demonstrated moderate to very-strong relationships (r = 0.50-0.88) with poor agreement (CV = 10.8-26.6%) for GA, and very weak to very-strong relationships (r = 0.01-0.87) with moderate to poor agreement (CV = 9.1-24.1%) for PUSH. Bar Sensei units were excluded from analyses. Loaded CMJ data collected with either device displayed poor agreement with a FP. Velocity monitoring devices demonstrate poor validity across all loads; however, GA demonstrated strong between-unit agreement. A FP should be utilised to accurately assess CMJ performance at all times.

Does a linear position transducer placed on a stick and belt provide sufficient validity and reliability of countermovement jump performance outcomes?

Manufacturers recommend that linear position transducers (LPTs) should be placed on the side of a barbell (or wooden dowel) to measure countermovement jump (CMJ) height, but the validity and reliability of this placement have not been compared to other attachment sites. Since this recommended attachment site is far from the centre of mass, a belt attachment where the LPT is placed between the feet may increase the validity and reliability of CMJ data. Thirty-six physical education students participated in the study (24.6 ± 4.3 years; 177.0 ± 7.7 cm; 77.2 ± 9.0 kg). Parameters from the two LPT attachments (barbell and belt) were simultaneously validated to force plate data, where the nature of bias was analysed (systematic vs random). The within-session and between-session reliability of both attachment sites were compared to force plate data using a test-retest protocol of two sets of 5 CMJs separated by 7 days. The LPT provided highly reliable and valid measures of peak force, mean force, mean power, and jump height, where the bias was mostly systematic (r² > 0.7; ICC > 0.9). Peak velocity, mean velocity, and peak power were in very good agreement with the force plate and were highly reliable (r² > 0.5; ICC > 0.7). Therefore, both attachment sites produced similar results with a systematic bias compared to force plate data. Thus, both attachment sites seem to be valid for assessing CMJs when the measuring tool and site remain consistent across measurements. However, if LPT data are to be compared to force plate data, recalculation equations should be used.

Validity and reliability of linear position transducers and linear velocity transducers: a systematic review

This systematic review aimed to summarise and analyse the evidence on the reliability and validity of linear tranducers (LTs) in exercises of different nature and different modes of execution. This systematic review was carried out under PRISMA guidelines, and was carried out using three databases (PubMed, Web of Sciences, and Scopus). Of the 351 initially found, 21 were included in the qualitative synthesis. The results reflected that linear position transducers (LPTs) were valid and reliable in monitoring movement velocity in non-plyometric exercises. However, precision and reliability were lower in execution protocols without isometric phase and in the execution of exercises in multiple planes of movement, with greater measurement errors at higher sampling frequencies. On the other hand, linear velocity transducers (LVTs) proved to be valid and reliable in measuring velocity during plyometric and non-plyometric exercises performed on the Smith machine, with less variation in measurement in the latter. Finally, the use of peak values is recommended, since they are less dependent on the technological errors of LTs. Therefore, the performance of non-plyometric exercises, carried out in the Smith machine and with an isometric phase in the execution of the movement, will help to minimise the technological error of the LTs.

Impaired Isometric, Concentric, and Eccentric Rate of Torque Development at the Hip and Knee in Patellofemoral Pain

ABSTRACT

Ferreira, AS, de Oliveira Silva, D, Barton, CJ, Briani, RV, Taborda, B, Pazzinatto, MF, and de Azevedo, FM. Impaired isometric, concentric, and eccentric rate of torque development at the hip and knee in patellofemoral pain. J Strength Cond Res 35(9): 2492-2497, 2021-The aims of this study were to compare maximal muscle strength and rate of torque development (RTD) of knee extensor and hip abductor during isometric, concentric, and eccentric contractions between women with and without patellofemoral pain (PFP). Thirty-eight women with PFP (PFPG) and 38 pain-free women (CG) participated in this study. Isometric, concentric, and eccentric maximal torque and RTD of knee extensor and hip abductor were assessed using an isokinetic dynamometer. Rate of torque development was calculated as the change in torque over the change in time from torque onset to 30, 60, and 90% of the maximal torque (RTD30%, RTD60%, and RTD90%) during isometric, concentric, and eccentric contractions. PFPG had lower isometric, concentric, and eccentric knee extensor maximal torque (29.9, 28.3, and 26.7%) compared with the CG. For knee extensor RTD, PFPG had slower isometric RTD30% (17.8%), RTD60% (21.5%), and RTD90% (23.4%); slower concentric RTD30% (35.7%), RTD60% (29.3%), and RTD90% (28.2%); and slower eccentric RTD30% (20.5%), RTD60% (25.2%), and RTD90% (22.5%) compared with the CG. PFPG had lower isometric, concentric, and eccentric hip abductor maximal torque (28.3, 21.8, and 17%) compared with the CG. For hip abductor RTD, PFPG had slower isometric RTD30% (32.6%), RTD60% (31.1%), and RTD90% (25.4%); slower concentric RTD90% (11.5%); and slower eccentric RTD30% (19.8%), RTD60% (26.4%), and RTD90% (24%) compared with the CG. In conclusion, women with PFP presented deficits in both maximal strength and RTD of knee extensor and hip abductor during isometric, concentric, and eccentric contractions, which highlight the potential importance of addressing different aspects of muscle function through exercise therapy.

Concurrent validity of barbell force measured from video-based barbell kinematics during the snatch in male elite weightlifters

This study examined the concurrent validity of an inverse dynamic (force computed from barbell acceleration [reference method]) and a work-energy (force computed from work at the barbell [alternative method]) approach to measure the mean vertical barbell force during the snatch using kinematic data from video analysis. For this purpose, the acceleration phase of the snatch was analyzed in thirty male medal winners of the 2018 weightlifting World Championships (age: 25.2±3.1 years; body mass: 88.9±28.6 kg). Vertical barbell kinematics were measured using a custom-made 2D real-time video analysis software. Agreement between the two computational approaches was assessed using Bland-Altman analysis, Deming regression, and Pearson product-moment correlation. Further, principal component analysis in conjunction with multiple linear regression was used to assess whether individual differences related to the two approaches are due to the waveforms of the acceleration time-series data. Results indicated no mean difference (p > 0.05; d = −0.04) and an extremely large correlation (r = 0.99) between the two approaches. Despite the high agreement, the total error of individual differences was 8.2% (163.0 N). The individual differences can be explained by a multiple linear regression model (R²_adj = 0.86) on principal component scores from the principal component analysis of vertical barbell acceleration time-series waveforms. Findings from this study indicate that the individual errors of force measures can be associated with the inverse dynamic approach. This approach uses vertical barbell acceleration data from video analysis that is prone to error. Therefore, it is recommended to use the work-energy approach to compute mean vertical barbell force as this approach did not rely on vertical barbell acceleration.

Comparison of the FitroDyne and GymAware Rotary Encoders for Quantifying Peak and Mean Velocity During Traditional Multijointed Exercises

ABSTRACT

Fernandes, JFT, Lamb, KL, Clark, CCT, Moran, J, Drury, B, Garcia-Ramos, A, and Twist, C. Comparison of the FitroDyne and GymAware rotary encoders for quantifying peak and mean velocity during traditional multijointed exercises. J Strength Cond Res 35(6): 1760-1765, 2021-The FitroDyne and GymAware rotary encoders are being increasingly used in resistance training to monitor movement velocity, but how closely their velocity outcomes agree is unknown. Consequently, this study aimed to determine the level of agreement between the FitroDyne and GymAware for the assessment of movement velocity in 3 resistance training exercises. Fifteen men performed 3 repetitions of bench press, back squat, and bent-over-row exercises at 10% 1 repetition maximum increments (from 20 to 80%). For each repetition, the FitroDyne and GymAware recorded peak and mean barbell velocity (cm·s-1). Although strongly correlated (r = 0.79-1.00), peak velocity values for the GymAware were significantly lower than the FitroDyne for all exercises and loads. Importantly, the random errors between the devices, quantified through Bland and Altman's 95% limits of agreement, were unacceptable, ranging from ±3.8 to 25.9 cm·s-1. Differences in mean velocity were smaller (and nonsignificant for most comparisons) and highly correlated (r = 0.86-1.00) between devices. Notwithstanding smaller random errors than for the peak values, mean values still reflected poor agreement (random errors between ±2.1 and 12.0 cm·s-1). These findings suggest that the FitroDyne and GymAware cannot record peak or mean velocity with acceptable agreement and should neither be used interchangeably nor their data compared.

Validity and Reliability of the Inertial Measurement Unit for Barbell Velocity Assessments: A Systematic Review

The use of inertial measurement unit (IMU) has become popular in sports assessment. In the case of velocity-based training (VBT), there is a need to measure barbell velocity in each repetition. The use of IMUs may make the monitoring process easier; however, its validity and reliability should be established. Thus, this systematic review aimed to (1) identify and summarize studies that have examined the validity of wearable wireless IMUs for measuring barbell velocity and (2) identify and summarize studies that have examined the reliability of IMUs for measuring barbell velocity. A systematic review of Cochrane Library, EBSCO, PubMed, Scielo, Scopus, SPORTDiscus, and Web of Science databases was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. From the 161 studies initially identified, 22 were fully reviewed, and their outcome measures were extracted and analyzed. Among the eight different IMU models, seven can be considered valid and reliable for measuring barbell velocity. The great majority of IMUs used for measuring barbell velocity in linear trajectories are valid and reliable, and thus can be used by coaches for external load monitoring.

The Validity and Reliability of Commercially Available Resistance Training Monitoring Devices: A Systematic Review

Background

Monitoring resistance training has a range of unique difficulties due to differences in physical characteristics and capacity between athletes, and the indoor environment in which it often occurs. Traditionally, methods such as volume load have been used, but these have inherent flaws. In recent times, numerous portable and affordable devices have been made available that purport to accurately and reliably measure kinetic and kinematic outputs, potentially offering practitioners a means of measuring resistance training loads with confidence. However, a thorough and systematic review of the literature describing the reliability and validity of these devices has yet to be undertaken, which may lead to uncertainty from practitioners on the utility of these devices.

Objective

A systematic review of studies that investigate the validity and/or reliability of commercially available devices that quantify kinetic and kinematic outputs during resistance training.

Methods

Following PRISMA guidelines, a systematic search of SPORTDiscus, Web of Science, and Medline was performed; studies included were (1) original research investigations; (2) full-text articles written in English; (3) published in a peer-reviewed academic journal; and (4) assessed the validity and/or reliability of commercially available portable devices that quantify resistance training exercises.

Results

A total of 129 studies were retrieved, of which 47 were duplicates. The titles and abstracts of 82 studies were screened and the full text of 40 manuscripts were assessed. A total of 31 studies met the inclusion criteria. Additional 13 studies, identified via reference list assessment, were included. Therefore, a total of 44 studies were included in this review.

Conclusion

Most of the studies within this review did not utilise a gold-standard criterion measure when assessing validity. This has likely led to under or overreporting of error for certain devices. Furthermore, studies that have quantified intra-device reliability have often failed to distinguish between technological and biological variability which has likely altered the true precision of each device. However, it appears linear transducers which have greater accuracy and reliability compared to other forms of device. Future research should endeavour to utilise gold-standard criterion measures across a broader range of exercises (including weightlifting movements) and relative loads.

Electronic supplementary material

The online version of this article (10.1007/s40279-020-01382-w) contains supplementary material, which is available to authorized users.

Validity and Reliability of Methods to Determine Barbell Displacement in Heavy Back Squats: Implications for Velocity-Based Training

Appleby, BB, Banyard, H, Cormack, SJ, and Newton, RU. Validity and reliability of methods to determine barbell displacement in heavy back squats: Implications for velocity-based training. J Strength Cond Res 34(11): 3118-3123, 2020-The purpose of this study was to investigate the validity and reliability of methods for determining barbell displacement during heavy back squats. Twelve well-trained rugby union players (mean ± SD 1 repetition maximum [1RM] 90° squat = 196.3 ± 29.2 kg) completed 2 sets of 2 repetitions at 70, 80, and 90% of 1RM squats. Barbell displacement was derived from 3 methods across 4 load categories (120-129, 140-149, 160-169, and 180-189 kg) including: a (a) linear position transducer (LPT) attached 65 cm left of barbell center, (b) 3D motion analysis tracking of markers attached to either end of a barbell, and (c) cervical marker (C7) (criterion measurement). Validity was calculated using the typical error of the estimate as a coefficient of variation (CV%) ±90% confidence interval (CI), mean bias as a percentage, and the Pearson product moment correlation (r). Intraday reliability was calculated using the intraclass correlation coefficient and the typical error expressed as a percentage of CV% ±90% (CI). Mean displacement for C7, LPT, and the barbell ends was 520, 529, and 550-564 mm, respectively. Validity of the LPT compared with the criterion was acceptable (CV% = 2.1-3.0; bias = 0.9-1.5%; r = 0.96-0.98), whereas that of the barbell ends was less (CV% = 2.7-7.5; bias = 4.9-11.2%; r = 0.71-0.97). The CV% reliability of the C7 marker across the load categories was 6.6%, the LPT 6.6%, and the barbell ends between 5.9 and 7.2%. Despite reliable measures, overestimation of displacement occurs as the tracking location moves to the barbell ends in weighted back squats. The LPT demonstrated high validity to the criterion and high trial-to-trial reliability.

Seasonal Variations in Game Activity Profiles and Players' Neuromuscular Performance in Collegiate Division I Basketball: Non-conference vs. Conference Tournament

Basketball has a high demand on a player's neuromuscular system due to a high volume of explosive high-intensity actions. This study aimed to examine the seasonal variations on game demands and players' neuromuscular performance during the Non-Conference (NON-CONF) and Conference (CONF) seasons in NCAA Division I Men's Basketball. Seven NCAA Division I Basketball players' (20 ± 1.2 years, 1.95 ± 0.1 m, and 94 ± 15 kg) match activity profiles were tracked in 17 home games (7 NON-CONF; 10 CONF); furthermore, players performed a repeat hop test on a force platform the day before competition to assess neuromuscular performance. A t-test for paired samples was used to analyze the differences between NON-CONF and CONF. Results indicated no significant differences in Total Distance, Peak Speed, Acceleration, and Deceleration loads when comparing NON-CONF and CONF match-play. Regarding neuromuscular performance, Jump Height (p = 0.03; ES = 0.43) was negatively affected during CONF. Moreover, a trend toward a decline in Peak Force (p = 0.06; ES = 0.38) was found in CONF. Conversely, no differences were obtained regarding Reactive Strength Index and Contact Time. In conclusion, match-play demands remained constant across the season whilst neuromuscular outputs were inhibited during the CONF season.

Weightlifting Overhead Pressing Derivatives: A Review of the Literature

This review examines the literature on weightlifting overhead pressing derivatives (WOPDs) and provides information regarding historical, technical, kinetic and kinematic mechanisms as well as potential benefits and guidelines to implement the use of WOPDs as training tools for sports populations. Only 13 articles were found in a search of electronic databases, which was employed to gather empirical evidence to provide an insight into the kinetic and kinematic mechanisms underpinning WOPDs. Practitioners may implement WOPDs such as push press, push jerk or split jerk from the back as well as the front rack position to provide an adequate stimulus to improve not only weightlifting performance but also sports performance as: (1) the use of WOPDs is an additional strategy to improve weightlifting performance; (2) WOPDs require the ability to develop high forces rapidly by an impulsive triple extension of the hips, knees and ankles, which is mechanically similar to many sporting tasks; (3) WOPDs may be beneficial for enhancing power development and maximal strength in the sport population; and, finally, (4) WOPDs may provide a variation in training stimulus for the sports population due to the technical demands, need for balance and coordination. The potential benefits highlighted in the literature provide a justification for the implementation of WOPDs in sports training. However, there is a lack of information regarding the longitudinal training effects that may result from implementing WOPDs.

Validity and Reliability of a Wearable Inertial Sensor to Measure Velocity and Power in the Back Squat and Bench Press

Orange, ST, Metcalfe, JW, Liefeith, A, Marshall, P, Madden, LA, Fewster, CR, and Vince, RV. Validity and reliability of a wearable inertial sensor to measure velocity and power in the back squat and bench press. J Strength Cond Res 33(9): 2398-2408, 2019-This study examined the validity and reliability of a wearable inertial sensor to measure velocity and power in the free-weight back squat and bench press. Twenty-nine youth rugby league players (18 ± 1 years) completed 2 test-retest sessions for the back squat followed by 2 test-retest sessions for the bench press. Repetitions were performed at 20, 40, 60, 80, and 90% of 1 repetition maximum (1RM) with mean velocity, peak velocity, mean power (MP), and peak power (PP) simultaneously measured using an inertial sensor (PUSH) and a linear position transducer (GymAware PowerTool). The PUSH demonstrated good validity (Pearson's product-moment correlation coefficient [r]) and reliability (intraclass correlation coefficient [ICC]) only for measurements of MP (r = 0.91; ICC = 0.83) and PP (r = 0.90; ICC = 0.80) at 20% of 1RM in the back squat. However, it may be more appropriate for athletes to jump off the ground with this load to optimize power output. Further research should therefore evaluate the usability of inertial sensors in the jump squat exercise. In the bench press, good validity and reliability were evident only for the measurement of MP at 40% of 1RM (r = 0.89; ICC = 0.83). The PUSH was unable to provide a valid and reliable estimate of any other criterion variable in either exercise. Practitioners must be cognizant of the measurement error when using inertial sensor technology to quantify velocity and power during resistance training, particularly with loads other than 20% of 1RM in the back squat and 40% of 1RM in the bench press.

Reliability and Criterion Validity of the Assess2Perform Bar Sensei

The Assess2Perform Bar Sensei is a device used to measure barbell velocity for velocity-based training that has not yet been validated. The purpose of this study was to determine criterion validity and reliability of the Assess2Perform Bar Sensei in barbell back squats by comparing it against the GymAware PowerTool, a previously validated instrument. Sixteen injury-free, resistance-trained subjects (eleven males and five females) were recruited. Subjects were tested for their back squat one repetition maximum (1RM). Then, on two separate days, subjects performed two sets of three repetitions at loads of 45%, 60% and 75% 1RM. The GymAware PowerTool and Bar Sensei were attached to the barbell in similar locations for concurrent collection of mean concentric velocity (MCV) and peak concentric velocity (PCV). The Bar Sensei and PowerTool showed generally fair to poor agreement for MCV and PCV when subjects lifted 45% of 1RM (intraclass correlation;ICC 0.4–0.59), and they showed poor agreement when subjects lifted 60% and 75% of 1RM (ICC 0.3–0.4). Inter-repetition/within-set reliability for the Bar Sensei ranged between ICC = 0.273–0.451 for MCV and PCV compared to the far more reliable PowerTool (ICC = 0.651–0.793). Currently, the Bar Sensei is not a reliable or valid tool for measuring barbell velocity in back squats.

Force-Velocity Relationship in the Countermovement Jump Exercise Assessed by Different Measurement Methods

This study aimed to compare force, velocity, and power output collected under different loads, as well as the force-velocity (F-V) relationship between three measurement methods. Thirteen male judokas were tested under four loading conditions (20, 40, 60, and 80 kg) in the countermovement jump (CMJ) exercise, while mechanical output data were collected by three measurement methods: the Samozino's method (SAM), a force platform (FP), and a linear velocity transducer (LVT). The variables of the linear F-V relationship (maximum force [F0], maximum velocity [V0], F-V slope, and maximum power [P0]) were determined. The results revealed that (1) the LVT overestimated the mechanical output as compared to the SAM and FP methods, especially under light loading conditions, (2) the SAM provided the lowest magnitude for all mechanical output, (3) the F-V relationships were highly linear either for the SAM (r = 0.99), FP (r = 0.97), and LVT (r = 0.96) methods, (4) the F-V slope obtained by the LVT differed with respect to the other methods due to a larger V0 (5.28 ± 1.48 m·s-1) compared to the SAM (2.98 ± 0.64 m·s-1) and FP (3.06 ± 0.42 m·s-1), and (5) the methods were significantly correlated for F0 and P0, but not for V0 or F-V slope. These results only support the accuracy of the SAM and FP to determine the F-V relationship during the CMJ exercise. The very large correlations of the SAM and LVT methods with respect to the FP (presumed gold-standard) for the mean values of force, velocity and power support their concurrent validity for the assessment of mechanical output under individual loads.

Validity and reliability assessment of 3-D camera-based capture barbell velocity tracking device

Velocity-based training (VBT) requires the monitoring of lift velocity plus the prescribed resistance weight. A validated and reliable device is needed to capture the velocity and power of several exercises.

OBJECTIVES

The study objectives were to examine the validity and reliability of the Elite Form Training System® (EFTS) for measures of peak velocity (PV), average velocity (AV), peak power (PP), and average power (AP).

DESIGN

Validity of the EFTS was assessed by comparing measurements simultaneously obtained via the Qualisys Track Manager software (C-motion, version 3.90.21, Gothenburg, Sweden) utilizing 6 motion capture cameras (Oqus 400, 240 Hz, Gothenburg, Sweden).

METHODS

Six participants performed 6 resistance exercises in 2 sessions: power clean, dead lift, bench press, back squat, front squat, and jump squat.

RESULTS

Simple Pearson correlations indicated the validity of the device (0.982, 0.971, 0.973, and 0.982 for PV, AV, PP, and AP respectively) and ranged from 0.868 to 0.998 for the 6 exercises. The test-retest reliability of the EFTS was shown by lack of significant change in the Pearson correlation (<0.3% for each variable) between the 2 sessions. The multiple count error rate was 2.0% and the missed count error rate was 2.1%.

CONCLUSIONS

The validity and reliability of the EFTS were classified as excellent across all variables and exercises with only one exercise showing a slight influence by the velocity of the movement.

Validity of the iLOAD® app for resistance training monitoring

Background

This study aimed (I) to assess the inter-rater agreement for measuring the mean velocity (MV) of the barbell with the iLOAD® app, and (II) to compare the magnitude of the MV and total work of a training session between the iLOAD® app and a linear encoder (reference method).

Method

Sixteen young healthy individuals (four women and 12 men) were tested in two sessions separated by 48 h. The 10 repetition maximum (RM) load was determined in the first testing session in the half squat exercise. The second testing session consisted of 3 sets of 10 repetitions during the half squat exercise performed against the 10RM load. Both the iLOAD® app and a linear encoder were used to calculate the MV and total work of each training set. MV was recorded with the iLOAD® app by two independent researchers to evaluate the inter-rater agreement.

Results

Trivial differences and nearly perfect correlations were observed between raters for the MV values collected under individual sets (effect size [ES] ≤ 0.02, r ≥ 0.987), as well as for the whole training session (ES = 0.01, r = 0.997). Trivial-small differences and nearly perfect correlations were observed between the iLOAD® app and the linear encoder (Chronojump, Barcelona, Spain) for MV (EV ≤ 0.25, r ≥ 0.903) and total work (ES ≤ 0.05, r ≥ 0.973). Bland-Altman plots did not reveal heteroscedasticity of the errors between the iLOAD® app and the linear encoder for MV (r² = 0.010) and total work (r² < 0.001).

Conclusions

iLOAD® is a valid smartphone app which can provide real-time feedback of the MV and total work completed in a set of multiple repetitions in the half squat exercise.

Repeated Linear and Quadrangular Sprint as a Function of Anaerobic Power

Almansba, R, Boucher, VG, Parent, AA, and Comtois, AS. Repeated linear and quadrangular sprint as a function of anaerobic power. J Strength Cond Res 33(8): 2177-2184, 2019-This investigation aims to study in U17 soccer players the relationships among performance indices of linear or quadrangular (square shape) repeated-sprint bouts (RSBs) and leg muscular power measured with the Wingate test and the squat jump. Seventeen athletes were recruited. Participants were 16 ± 0.35 years old and had a body mass of 66.5 ± 8.69 kg and a height of 175 ± 0.05 cm. All participants performed linear or quadrangular RSBs, the Wingate test, and a vertical jump test. The mean fast linear sprint time was strongly correlated (p < 0.01) with the force and power measured with the vertical jump test (r = -0.68 and -0.75, respectively), whereas the mean linear RSB was weakly correlated with the peak power and fatigue index measured by the Wingate test (r = -0.54 and -0.56, respectively). There was a correlation between quadrangular RSBs performance indices and both Wingate and vertical jump parameters. In addition, there were no correlations (p > 0.05) between indices of the linear RSBs (decrement index, average, and fastest times) and quadrangular RSBs. Moreover, physiological and perceptual responses were significantly higher (p < 0.01) with quadrangular RSBs compared with linear RSBs. These results indicate that the Wingate test and the vertical jump test can be used as a substitute for repeated-sprint performance time. Finally, however, the repeated sprints with or without direction changes are 2 different motor abilities that should be trained independently of one another.

Validation of an opto-electronic instrument for the measurement of execution velocity in squat exercise

The purpose of this study was to analyse the reliability and validity of an opto-electronic sensor system (Velowin) for assessment of the bar-velocity in the deep squat exercise. Mean velocity, mean propulsive velocity and peak velocity generated in the deep squat exercise performed in the Smith machine bar were analysed compared to a linear velocity transducer considered as the gold standard. The study was conducted with a sample of 26 men with experience in resistance training. Six measurements were analysed for squat exercise in concentric phase using a progressive loading increase. Three consecutive repetitions were performed per load with a 3-4 min recovery between loads. Analysis of variance confirmed that there were no significant differences (p > 0.05) for the velocity variables between Velowin and T-Force for each of the loads. The reliability analysis showed high values of the intraclass correlation coefficient (ICC = 0.94-0.99), an 'almost perfect' Lin's concordance coefficient (CCC = 0.99) and a low coefficient of variation (CV <3.4%) for each of the loads and velocities. These results confirm the reliability and validity of the Velowin device for measuring the execution velocity in deep squat exercise.

Assessment of the loaded squat jump and countermovement jump exercises with a linear velocity transducer: which velocity variable provides the highest reliability?

This study aimed to compare the between-session reliability of three typically measured velocity variables (mean velocity [MV], mean propulsive velocity [MPV], and maximum velocity [Vmax]) to assess vertical jump performance. Totally, 23 men had their squat jump (SJ) and countermovement jump (CMJ) tested against five different loading conditions (17, 30, 45, 60 and 75 kg) during two consecutive weeks. The two sessions of each jump type were performed within the same week separated by 48-72 h. The main finding was a significant difference in reliability between the variables, which were ranked from the highest to the lowest reliable as follows (median coefficient of variation [CV] and range): Vmax (CV = 2.35% [1.85%-3.23%]) >MV (CV = 3.29% [2.18%-4.40%]) >MPV (CV = 3.69% [2.08%-5.17%]). A significant variable × exercise interaction was also observed showing that the differences in reliability between the variables were meaningful during the SJ (MV: CV = 3.93% [3.06%-4.40%], MPV: CV = 4.61% [4.07%-5.17%], and Vmax: CV = 2.14% [1.85%-2.71%]), while no significant differences were observed for the CMJ (MV: CV = 2.43% [2.18%-3.70%], MPV: CV = 2.71% [2.08%-3.63%], and Vmax: CV = 2.40% [1.97%-3.23%]). These results suggest that the Vmax should be the recommended variable for obtaining a reproducible measure of lower-body ballistic performance, especially during the SJ exercise.

Validity and Reliability of the GymAware Linear Position Transducer for Squat Jump and Counter-Movement Jump Height

The purpose of this study was to assess the concurrent validity and test-retest reliability of a linear position transducer (LPT) for the squat jump (SJ) and counter-movement jump (CMJ) height. Twenty-eight subjects (25.18 ± 7.1 years) performed three SJs followed by three CMJs using a force plate concurrently with the LPT to test validity. Subjects returned on a separate day, at least 48 h apart, to measure test-retest reliability. A t-test showed a significant difference between the two devices for both SJ (p < 0.001) and CMJ (p < 0.001) while Bland–Altman analysis for validity revealed that the LPT overestimated jump height for both SJ (mean difference (MD) = 8.01 ± 2.93 cm) and CMJ (MD = 8.68 ± 2.99 cm). With regards to reliability of the LPT, mean intraclass correlation (ICC) for both SJ (ICC = 0.84) and CMJ (ICC = 0.95) were high, and Bland–Altman analysis showed mean differences lower than minimal detectable change (MDC) between the days for both SJ (MD = 1.89 ± 4.16 cm vs. MDC = 2.72 cm) and CMJ (MD = 0.47 ± 3.23 cm vs. MDC = 2.11 cm). Additionally, there was a low coefficient of variation (CV) between days for both SJ (CV = 3.25%) and CMJ (CV = 0.74%). Therefore, while the LPT overestimates jump height, it is a reliable tool for tracking changes in jump height to measure performance improvement and monitor fatigue.

Validity and Reliability of a Commercially-Available Velocity and Power Testing Device

Given the relationship between explosive-type training and power adaptation, tracking movement velocity has become popular. However, unlike previous variables, tracking velocity necessitates the use of a valid and reliable tool to monitor adaptation over time. Therefore, the primary purpose of this research was to assess the validity and reliability of a commercially-available linear position transducer (LPT). Nine resistance-trained men completed four sessions consisting of a single set of barbell back squat to volitional failure at 75% or 90% one-repetition maximum. Kinetic and kinematic data were captured for each repetition by the LPT and a 3-dimensional motion capture system and bipedal force platforms. In total, 357 instances of data from both systems were analyzed using intraclass correlations (ICC), effect size estimates, and standard error of measurement. Overall, the LPT yielded excellent ICCs (all ≥0.94) and small/trivial differences (d < 0.60). When categorized by median values, ICCs remained high (all ≥0.89) and differences remained small or trivial with the exception of high peak velocities (d = −1.46). Together, these data indicate that the commercially-available LPT is a valid and reliable measure for kinetic and kinematic variables of interest with the exception of high peak velocities.

Validity and Reliability of the Load-Velocity Relationship to Predict the One-Repetition Maximum in Deadlift

Ruf, L, Chéry, C, Taylor, KL. Validity and reliability of the load-velocity relationship to predict the 1RM in deadlift. J Strength Cond Res 32(3): 681-689, 2018-The aim of this study was to verify the reliability and validity of using submaximal loads from the load-velocity relationship to predict the actual 1 repetition maximum (1RM) in the deadlift. Data from 11 resistance-trained athletes were analyzed performing three 1RM assessments separated by at least 3 days. Reliability was assessed by comparing predicted 1RMs of sessions 2 and 3, whereas for validity purposes, predicted 1RMs of session 3 were compared with actual 1RMs of session 2. Mean concentric velocity at 1RM (v at 1RM) was entered in individualized linear regression equations, derived from the load-velocity relationship for 3 (20-60%, 40-80%, and 60-90% of 1RM), 4 (20-80% and 40-90% of 1RM), and 5 (20-90% of 1RM) incremental loads to predict 1RMs. There were trivial changes for all predicted 1RMs between sessions with 20-90% of 1RM being the most reliable model. Similarly, the actual 1RM was very stable (effect size [ES] = 0.04, 90% confidence limit [CL] [-0.03 to 0.12], typical error of measurement [TE] = 3.4 kg [2.5-5.4], intraclass coefficient [ICC] = 0.99 [0.96-0.996], and coefficient of variation [CV] = 1.9% [1.4-3.0]), whereas the v at 1RM was unreliable between trials (ES = -0.30, 90% CL [-0.78 to 0.17], TE = 0.029 m·s [0.022-0.047], ICC = 0.63 [0.19-0.86], and CV = 15.7% [11.7-26.1]). However, predicted 1RMs computed from all submaximal load ranges substantially overestimated the actual 1RM with considerable differences between athletes. Although 1RM predictions showed high reliability, they all overestimated the actual 1RM, which was stable between sessions. Therefore, it is not recommended to apply the prediction models used in this study to compute daily 1RMs.

Validity and reliability of a linear positional transducer across commonly practised resistance training exercises

This study investigated the validity and reliability of the GymAware PowerTool (GPT). Thirteen resistance trained participants completed three visits, consisting of three repetitions of free-weight back squat, bench press, deadlift (80% one repetition maximum), and countermovement jump. Bar displacement, peak and mean velocity, peak and mean force, and jump height were calculated using the GPT, a three-dimensional motion capture system (Motion Analysis Corporation; 150 Hz), and a force plate (Kistler; 1500 Hz). Least products regression were used to compare agreeability between devices. A within-trial one-way ANOVA, typical error (TE; %), and smallest worthwhile change (SWC) were used to assess reliability. Regression analysis resulted in R² values of >0.85 for all variables excluding deadlift mean velocity (R² = 0.54-0.69). Significant differences were observed between visits 3-2 for bench press bar displacement (0.395 ± 0.055 m; 0.383 ± 0.053 m), and deadlift bar displacement (0.557 ± 0.034 m; 0.568 ± 0.034 m). No other significant differences were found. Low to moderate TE (0.6-8.8%) were found for all variables, with SWC ranging 1.7-7.4%. The data provides evidence that the GPT can be used to measure kinetic and kinematic outputs, however, care should be taken when monitoring deadlift performance.

Trends Supporting the In-Field Use of Wearable Inertial Sensors for Sport Performance Evaluation: A Systematic Review

Recent technological developments have led to the production of inexpensive, non-invasive, miniature magneto-inertial sensors, ideal for obtaining sport performance measures during training or competition. This systematic review evaluates current evidence and the future potential of their use in sport performance evaluation. Articles published in English (April 2017) were searched in Web-of-Science, Scopus, Pubmed, and Sport-Discus databases. A keyword search of titles, abstracts and keywords which included studies using accelerometers, gyroscopes and/or magnetometers to analyse sport motor-tasks performed by athletes (excluding risk of injury, physical activity, and energy expenditure) resulted in 2040 papers. Papers and reference list screening led to the selection of 286 studies and 23 reviews. Information on sport, motor-tasks, participants, device characteristics, sensor position and fixing, experimental setting and performance indicators was extracted. The selected papers dealt with motor capacity assessment (51 papers), technique analysis (163), activity classification (19), and physical demands assessment (61). Focus was placed mainly on elite and sub-elite athletes (59%) performing their sport in-field during training (62%) and competition (7%). Measuring movement outdoors created opportunities in winter sports (8%), water sports (16%), team sports (25%), and other outdoor activities (27%). Indications on the reliability of sensor-based performance indicators are provided, together with critical considerations and future trends.

Using Perceptual and Neuromuscular Responses to Estimate Mechanical Changes During Continuous Sets in the Bench Press

Chapman, M, Larumbe-Zabala, E, Gosss-Sampson, M, Triplett, NT, and Naclerio, F. Using perceptual and neuromuscular responses to estimate mechanical changes during continuous sets in the bench press. J Strength Cond Res 33(10): 2722-2732, 2019-This study analyzed the effectiveness of the OMNI-RES (0-10) and the electromyographic signal for monitoring changes in the movement velocity during a set to muscular failure performed with different relative loads in the bench press (BP) exercise. Ten males (30.8 ± 5.7 years) were evaluated on 8 separate days with 48 hours of rest between sessions. After determining the 1 repetition maximum value, participants performed 7 sets to failure with the following relative loads ranges: 30 < 40%, 40 < 50%, 50 < 60%, 60 < 70%, 70 < 80%, 80 < 90%, and >90%. The mean accelerative velocity (MAV), the rating of perceived exertion (RPE), and the normalized root-mean-square (N-RMS) signal from the anterior deltoids were measured for every repetition of each set. The RPE expressed after the first repetition and when the maximum value of MAV was achieved over the sets was lower (p < 0.001, d > 0.80) than the RPE associated with a 10% drop in MAV and at failure. Furthermore, the initial RPE was useful to distinguish different loading zones between the light relative loads (30 < 40% vs. 40 < 50% vs. 50 < 60%) and from these 3 zones to the higher relative load ranges (60 to >90%). Similar, but less clear, differences were observed for the N-RMS. In conclusion, apart from differentiating between relative loads, the RPE and in some cases N-RMS can both reflect changes associated with the initial, maximal, 10% drop in movement velocity, and muscular failure during a continuous set in the BP.

Comparison between traditional strength training and complex contrast training on soccer players

BACKGROUND

The purpose of this study was to compare traditional strength training (TST) versus complex and contrast training (CCT) on sprint, change of direction speed (COD) and squat jump (SJ) in young male soccer players.

METHODS

Twenty-two soccer players (age: 18.4±0.4 years, body mass: 70.2±9.1 kg, height: 179.9±7.5 cm), were randomly assigned to one of two groups: TST (N.=12) and CCT (N.=10). The study was conducted using a randomized experimental design over an eight-week period. The participants assigned to the CCT group performed high-power exercises paired with high-velocity exercises. The participants assigned to the TST group performed resistance exercises in a straight-set forma. During the study period, sprint tests for 5, 10, 20 and 30 m split times, COD and SJ were applied. A two-way ANOVA was applied, and the alpha level was P<0.05.

RESULTS

The results demonstrated that the CCT regimen elicited significant within-group differences in 5 m sprint time (1.032 s to 0.997 s, pre- and postintervention, respectively, effect size (ES) = -0.5, medium; P=0.04), COD (5.963 s to 5.639 s, pre- and postintervention, respectively, ES -2.7, large; P<0.001) and SJ (30.9 cm to 34.4 cm, pre- and postintervention, respectively, ES =0.8, large; P<0.001). Conversely, the TST did not elicit significant within-group differences for any of the dependent variables. No differences were found between groups at the post-test time point.

CONCLUSIONS

In conclusion, the CCT protocol could be used to improve sprint, COD and SJ in male soccer players.

Comparison Between Power Off-Ice Test and Performance On-Ice Anaerobic Testing

Boucher, VG, Parent, AA, Miron, FSJ, Leone, M, and Comtois, AS. Comparison between power off-ice test and performance on-ice anaerobic testing. J Strength Cond Res 34(12): 3498-3505, 2020-The importance of specific testing has been shown in ice hockey performance, and the understanding and connection between them may lead to adapting training and follow-up in elite athletes. The aim of this study was to compare 2 off-ice power tests with performances on ice with National Hockey League (NHL) players. The vertical jump and broad jump tests were used for the off-ice evaluations, whereas a modified SAS-40 and a repeated-sprint skate (RSSm) test were used on-ice as performance variables. Thirty-one players (3 goalkeepers, 10 defense players, and 18 forward players) from the NHL performed before preseason training camp. Four evaluation sessions were performed with 48-hour time intervals between them. The results show that the 2 jump types were correlated (r = 0.45 p < 0.01), and there was a significant correlation between the vertical jump and the best SAS-40 time trial for defense players, but not for forward players (r = 0.76 p = 0.02; r = 0.21 p = 0.16, respectively). By contrast, there was a significant correlation between broad jump and best SAS-40 time trial for forward players but not for defensive players (r = 0.75 p < 0.01; r = 0.19 p = 0.28, respectively). In conclusion, results show that specific player ability needs to be taken into consideration when choosing off-ice tests.

Concurrent Validity and Reliability of a Linear Positional Transducer and an Accelerometer to Measure Punch Characteristics

Lambert, C, Beck, BR, and Weeks, BK. Concurrent validity and reliability of a linear positional transducer and an accelerometer to measure punch characteristics. J Strength Cond Res 32(3): 675-680, 2018-Punch speed is an important factor in the sport of boxing, and its measurement has important implications for monitoring training progression and outcomes. The aim of the current study was to establish the concurrent validity and reliability of a linear positional transducer and an accelerometer for the quantification of punch characteristics in untrained adults. Men and women aged 18-30 years with no previous boxing experience and no upper-limb musculoskeletal injuries were recruited. Participants performed 6 straight right punches; 3 at a self-determined 50% effort; and 3 at maximum effort. An accelerometer (Crossbow) and a linear positional transducer (GymAware) were used to examine peak velocity and acceleration of each punch. Validity was examined using Pearson's correlation analyses and by calculating mean bias and limits of agreement between measures from each device, whereas reliability was established using intraclass correlation coefficients (ICCs). Forty-four healthy young adults (28M and 16F; age 22.2 ± 2.9 years) participated. Moderate-to-strong positive associations were observed for both devices at 50% effort for velocity (r = 0.572-0.696) and acceleration (r = 0.867-0.921) and at maximum effort for velocity (r = 0.748-0.781) and acceleration (r = 0.897-0.946). High levels of reliability were observed with maximum punches for both devices (ICC = 0.922-0.981). Overall, moderate-strong measurement validity and reliability for punch speed was observed between the accelerometer and GymAware. Thus, the GymAware linear positional transducer is an acceptable measurement tool for the quantification of punch speed for straight punches in untrained adults.

Variability of Jump Kinetics Related to Training Load in Elite Female Basketball

The purpose of this study was to quantify changes in jump performance and variability in elite female basketballers. Junior and senior female representative basketball players (n = 10) aged 18 ± 2 years participated in this study. Countermovement jump (CMJ) data was collected with a Gymaware™ optical encoder at pre-, mid-, and post-season time points across 10 weeks. Jump performance was maintained across the course of the full season (from pre to post). Concentric peak velocity, jump height, and dip showed the most stability from pre- to post-season, with the %CV ranging from 5.6⁻8.9%. In the period of the highest training load (mid-season), the variability of within-subject performance was reduced by approximately 2⁻4% in all measures except for jump height. Altered jump mechanics through a small (0.26 effect size) increase in dip were evident at mid-season, suggesting that CMJ analysis is useful for coaches to use as an in-season monitoring tool. The highest coefficient of variation (8⁻22%CV) in inter-set scores in all measures except eccentric peak velocity also occurred mid-season. It appears that in-season load not only impairs jump performance, but also movement variability in basketball players.

Validity of a Linear Velocity Transducer for Testing Maximum Vertical Jumps

This study aimed to examine the validity of mechanical variables obtained by a linear velocity transducer from the unconstrained and constrained squat jump (SJ). Twenty-three men were tested on the unconstrained SJ and the SJ constrained by a Smith machine. Maximum values of force, velocity, and power were simultaneously recorded both by a linear velocity transducer attached to a bar of mass of 17, 30, 45, 60, and 75 kg and by a force plate. Linear velocity transducer generally overestimated the outcomes measured as compared to the force plate, particularly in unconstrained SJ. Bland-Altman plots revealed that heteroscedasticity of errors was mainly observed for velocity variables (r 2 = .26–.58) where the differences were negatively associated with the load magnitude. However, exceptionally high correlations were observed between the same outcomes recorded with the 2 methods in both unconstrained (median r = .89 [.71–.95]) and constrained SJ (r = .90 [.65–.95]). Although the systematic and proportional bias needs to be acknowledged, the high correlations between the variables obtained by 2 methods suggest that the linear velocity transducer could provide valid values of the force, velocity, and power outputs from both unconstrained and constrained SJ.

Validity and reliability of a novel iPhone app for the measurement of barbell velocity and 1RM on the bench-press exercise

The purpose of this study was to analyse the validity and reliability of a novel iPhone app (named: PowerLift) for the measurement of mean velocity on the bench-press exercise. Additionally, the accuracy of the estimation of the 1-Repetition maximum (1RM) using the load-velocity relationship was tested. To do this, 10 powerlifters (Mean (SD): age = 26.5 ± 6.5 years; bench press 1RM · kg^-1 = 1.34 ± 0.25) completed an incremental test on the bench-press exercise with 5 different loads (75-100% 1RM), while the mean velocity of the barbell was registered using a linear transducer (LT) and Powerlift. Results showed a very high correlation between the LT and the app (r = 0.94, SEE = 0.028 m · s^-1) for the measurement of mean velocity. Bland-Altman plots (R² = 0.011) and intraclass correlation coefficient (ICC = 0.965) revealed a very high agreement between both devices. A systematic bias by which the app registered slightly higher values than the LT (P < 0.05; mean difference (SD) between instruments = 0.008 ± 0.03 m · s^-1). Finally, actual and estimated 1RM using the app were highly correlated (r = 0.98, mean difference (SD) = 5.5 ± 9.6 kg, P < 0.05). The app was found to be highly valid and reliable in comparison with a LT. These findings could have valuable practical applications for strength and conditioning coaches who wish to measure barbell velocity in the bench-press exercise.

Acute Effects of Loaded Half-Squat Jumps on Sprint Running Speed in Track and Field Athletes and Soccer Players

The purpose of the study was to determine the acute responses to a jump squat protocol designed to induce postactivation potentiation on sprint running performance in experienced track and field athletes and soccer players. Twenty-five regional level athletes (12 track and field: ∼17 years; ∼177 cm; ∼73 kg and 13 soccer: ∼18 years; ∼175 cm; ∼72 kg) performed 2 test sessions assessing 40-m sprint running performance in a balanced, crossover design. Dual-beam light timing gates measured 0-20 and 20-40 m sprint times before and after either 9 minutes of sitting (control) or 2 sets of 6 repetition half-squat jump with the load eliciting maximum power (experimental) conditions. Sprint performance was significantly enhanced over both 0-20 m (3.09 ± 0.07 to 3.04 ± 0.08 seconds; Δ ∼1.5%; p ≤ 0.05) and 20-40 m (2.42 ± 0.09 to 2.39 ± 0.09 seconds; Δ ∼1%; p ≤ 0.05) in track and field athletes only. Also, the magnitude of enhanced sprint performance was related to baseline 0-20 m sprint performance (r = 0.44; p = 0.028; n = 25). It seems that using loaded half-squat jumps to enhance sprint performance could be used in training of high-level young athletes.

Validation of a Video Analysis Software Package for Quantifying Movement Velocity in Resistance Exercises

Sañudo, B, Rueda, D, del Pozo-Cruz, B, de Hoyo, M, and Carrasco, L. Validation of a video analysis software package for quantifying movement velocity in resistance exercises. J Strength Cond Res 30(10): 2934-2941, 2016-The aim of this study was to establish the validity of a video analysis software package in measuring mean propulsive velocity (MPV) and the maximal velocity during bench press. Twenty-one healthy males (21 ± 1 year) with weight training experience were recruited, and the MPV and the maximal velocity of the concentric phase (Vmax) were compared with a linear position transducer system during a standard bench press exercise. Participants performed a 1 repetition maximum test using the supine bench press exercise. The testing procedures involved the simultaneous assessment of bench press propulsive velocity using 2 kinematic (linear position transducer and semi-automated tracking software) systems. High Pearson's correlation coefficients for MPV and Vmax between both devices (r = 0.473 to 0.993) were observed. The intraclass correlation coefficients for barbell velocity data and the kinematic data obtained from video analysis were high (>0.79). In addition, the low coefficients of variation indicate that measurements had low variability. Finally, Bland-Altman plots with the limits of agreement of the MPV and Vmax with different loads showed a negative trend, which indicated that the video analysis had higher values than the linear transducer. In conclusion, this study has demonstrated that the software used for the video analysis was an easy to use and cost-effective tool with a very high degree of concurrent validity. This software can be used to evaluate changes in velocity of training load in resistance training, which may be important for the prescription and monitoring of training programmes.

Validity and Reliability of the PUSH Wearable Device to Measure Movement Velocity During the Back Squat Exercise

Balsalobre-Fernández, C, Kuzdub, M, Poveda-Ortiz, P, and Campo-Vecino, Jd. Validity and reliability of the PUSH wearable device to measure movement velocity during the back squat exercise. J Strength Cond Res 30(7): 1968-1974, 2016-The purpose of this study was to analyze the validity and reliability of a wearable device to measure movement velocity during the back squat exercise. To do this, 10 recreationally active healthy men (age = 23.4 ± 5.2 years; back squat 1 repetition maximum [1RM] = 83 ± 8.2 kg) performed 3 repetitions of the back squat exercise with 5 different loads ranging from 25 to 85% 1RM on a Smith Machine. Movement velocity for each of the total 150 repetitions was simultaneously recorded using the T-Force linear transducer (LT) and the PUSH wearable band. Results showed a high correlation between the LT and the wearable device mean (r = 0.85; standard error of estimate [SEE] = 0.08 m·s) and peak velocity (r = 0.91, SEE = 0.1 m·s). Moreover, there was a very high agreement between these 2 devices for the measurement of mean (intraclass correlation coefficient [ICC] = 0.907) and peak velocity (ICC = 0.944), although a systematic bias between devices was observed (PUSH peak velocity being -0.07 ± 0.1 m·s lower, p ≤ 0.05). When measuring the 3 repetitions with each load, both devices displayed almost equal reliability (Test-retest reliability: LT [r = 0.98], PUSH [r = 0.956]; ICC: LT [ICC = 0.989], PUSH [ICC = 0.981]; coefficient of variation [CV]: LT [CV = 4.2%], PUSH [CV = 5.0%]). Finally, individual load-velocity relationships measured with both the LT (R = 0.96) and the PUSH wearable device (R = 0.94) showed similar, very high coefficients of determination. In conclusion, these results support the use of an affordable wearable device to track velocity during back squat training. Wearable devices, such as the one in this study, could have valuable practical applications for strength and conditioning coaches.

Impact of traditional Greek dancing on jumping ability, muscular strength and lower limb endurance in cardiac rehabilitation programmes

AIMS

The objective of this study was to evaluate the effect of a training programme based on traditional Greek dance on the jumping ability, muscle strength and lower limb endurance in patients with chronic heart failure (CHF).

PATIENTS AND METHODS

Forty Greek patients with CHF graded as NYHA ⩽ II and aged 73.2±4.7 years were randomly divided into two groups. Group A ( n=20) participated in a three-month physical rehabilitation programme based on Greek traditional dances, whereas group B ( n=20) remained untrained and served as the control group. All patients were studied before and after the 12-week exercise training programme. At baseline and follow-up the exercise capacity of the patients was evaluated by the six-minute walking test, their lower extremity muscle strength was evaluated by an isokinetic dynamometer and their jumping ability by the Myotest-Pro test, which includes three types of jumps (plyometric, countermovement and squat jumps).

RESULTS

No significant difference was observed between the two groups at the baseline evaluation. At follow-up, group A showed significant improvements in walking distance calculated from the six-minute walking test (10.0% improvement; p<0.05), in lower limb strength (10.32% improvement; p<0.05), and in countermovement jump speed (6.9%; p<0.05) and squat jump speed (5.8%; p<0.05). Group A also increased their jump plyometry height by 13.86% ( p<0.05), their counter jump height by 10.68% ( p<0.05) and their squat jump height by 10.45% ( p<0.05). Group A had a 6.85% ( p<0.05) increased force of counter jump compared with group B.

CONCLUSION

The design and implementation of cardiac rehabilitation programmes using Greek traditional dances in patients with CHF are both safe and effective in improving lower limb function.

The effect of an acute antioxidant supplementation compared with placebo on performance and hormonal response during a high volume resistance training session

Antioxidant supplementation is known to increase human endogenous antioxidant (AOX) capacity providing a means of blunting exercise induced reactive oxygen species (ROS). The purpose of this study was to compare the effects of a single acute dose of an AOX (vs blinded placebo) on muscle contractile performance and hormonal responses to a single bout of lower limb ‘hypertrophic’ resistance training (RT). Fifteen resistance trained subjects (age 23 ± 4 years: body mass 86 ± 6 kg) volunteered to participate in the study. Each subject attended the laboratory on three occasions, firstly to determine three repetition maximum (3-RM) isotonic strength in the back squat and perform a familiarisation of the experimental task. On the second/third visits subjects completed the hypertrophic training session (HTS) which consisted of six sets of 10 repetitions of 70% of a predicted 1 RM load (kg). Four hours prior to the HTS the subjects consumed 2 ml#x2219;kg⁻¹ total body mass of either the placebo mixture or AOX supplement in a randomised order. Work completed during the strength training session was completed with equipment that had an integrated linear force transducer (Gymaware system, Kinetic Performance Technology, Canberra, Australia). During the placebo trials concentric mean power significantly (p < 0.05) decreased from sets 1–6. Accumulated power output during the AOX HTS was 6746 ± 5.9 W which was significantly greater compared to the placebo HTS of 6493 ± 17.1 W (p < 0.05, ES’r = 0.99). Plasma growth hormone (GH) concentration was significantly less immediately following AOX supplementation (6.65 ± 1.84 vs 16.08 ± 2.78 ng#x2219;ml⁻¹; p < 0.05, ES’r = 0.89). This study demonstrates ingestion of an AOX cocktail prior to a single bout of resistance training improved muscle contractile performance and modulated the GH response following completion of the resistance exercise. Future studies should explore the mechanisms associated with the performance modification and specific muscle adaptations to AOX supplementation in conjunction with heavy RT.