Linear Position Transducer Research Articles

A PILOT ANALYSIS: CAN THE BULGARIAN SPLIT-SQUAT POTENTIATE SPRINT ACCELERATION IN STRENGTH-TRAINED MEN?

This study determined whether a five repetition-maximum Bulgarian split-squat (5RM BSS) could potentiate a 0-5, 0-10, and 0-20 m (meter) sprint performance. Seven men were assessed in the 5RM BSS (a linear position transducer measured peak power [PP] and force [PF] for each leg), and completed two post activation potentiation (PAP) sessions. One session involved a control condition (CC) of 4 minutes (min) rest; the other the 5RM BSS. Participants were assessed in baseline sprints, and sprints of 15 seconds, 2, 4, 8, 12, and 16 min post-PAP intervention. A repeated measures ANOVA (p < 0.05) calculated significant changes in sprint times. The best potentiated time for each interval was also compared to the baseline. Spearman’s correlations (r; p < 0.05) calculated relationships between absolute and relative strength, PP and PF, with percent potentiation in sprint times. The BSS did not potentiate speed at any time, although there was great individual variation. The best 0-5 m time was significantly different from the baseline (p = 0.022), with no differences between PAP conditions. Significant correlations were found between strength and sprint potentiation at 16 min for the 0-5 m interval, and at 8 min and the best times for the 0-20 m interval (r = -0.786 to -0.893). There were correlations between PP and PF for each leg with sprint potentiation from 2-12 min across all intervals (r = -0.786 to -0.964). Stronger individuals who generate greater PP and PF in a 5RM BSS will be more likely to potentiate 20-m sprint performance.

Relationship Between Maximum Pull-up Repetitions and First Repetition Mean Concentric Velocity.

Beckham, GK, Olmeda, JJ, Flores, AJ, Echeverry, JA, Campos, AF, and Kim, SB. Relationship between maximum pull-up repetitions and first repetition mean concentric velocity. J Strength Cond Res 32(7): 1831-1837, 2018-Mean concentric velocity (MCV) of exercise execution has been used by strength and conditioning professionals to improve exercise technique, provide accurate feedback, and predict exercise 1 repetition maximum. There is still limited research on velocity-based training and currently only one research study on the pull-up exercise. The primary purpose of this research was to determine whether the maximum number of pull-ups an individual can perform can be predicted by the MCV of a single pull-up repetition. Forty-nine healthy men and women were recruited who reported they could do at least 2 pull-ups. Each subject performed a standardized warm-up, then a single pull-up repetition, followed by one set of pull-up repetitions to failure. The GymAware PowerTool, a linear position transducer, was used to measure the MCV of each pull-up repetition. Both the MCV of the single repetition and first repetition of the set to failure were recorded, and the greater of the 2 was used in later analysis. Weighted least squares linear regression was used to estimate the relationship between the single-repetition MCV and maximum amount of pull-up repetitions. We observed a statistically significant linear relationship between the maximum number of pull-ups and the MCV of a single pull-up repetition (y = -6.661 + 25.556x, R = 0.841). Prediction of the maximum pull-up number by a single repetition rather than testing the maximal pull-up number may improve efficiency and effectiveness of exercise testing batteries for military, police, and other populations.

Relationships between Mechanical Variables in the Traditional and Close-Grip Bench Press.

The study aim was to determine relationships between mechanical variables in the one-repetition maximum (1RM) traditional bench press (TBP) and close-grip bench press (CGBP). Twenty resistance-trained men completed a TBP and CGBP 1RM. The TBP was performed with the preferred grip; the CGBP with a grip width of 95% biacromial distance. A linear position transducer measured: lift distance and duration; work; and peak and mean power, velocity, and force. Paired samples t-tests (p < 0.05) compared the 1RM and mechanical variables for the TBP and CGBP; effect sizes (d) were also calculated. Pearson’s correlations (r; p < 0.05) computed relationships between the TBP and CGBP. 1RM, lift duration, and mean force were greater in the TBP (d = 0.30-3.20). Peak power and velocity was greater for the CGBP (d = 0.50-1.29). The 1RM TBP correlated with CGBP 1RM, power, and force (r = 0.685-0.982). TBP work correlated with CGBP 1RM, lift distance, power, force, and work (r = 0.542-0.931). TBP power correlated with CGBP 1RM, power, force, velocity, and work (r = 0.484-0.704). TBP peak and mean force related to CGBP 1RM, power, and force (r = 0.596-0.980). Due to relationships between the load, work, power, and force for the TBP and CGBP, the CGBP could provide similar strength adaptations to the TBP with long-term use. The velocity profile for the CGBP was different to that of the TBP. The CGBP could be used specifically to improve high-velocity, upper-body pushing movements.

The validity and reliability of the GymAware linear position transducer for measuring counter-movement jump performance in female athletes

ABSTRACTThe current study aimed to assess the validity and test–retest reliability of a linear position transducer when compared to a force plate through a counter-movement jump in female participants. Twenty-seven female recreational athletes (19 ± 2 years) performed three counter-movement jumps simultaneously using the linear position transducer and force plate for validity. In addition, 11 elite female athletes (23 ± 6 years) performed 3 counter-movement jumps with the linear position transducer on three separate days for test–retest reliability. Pearson correlations for jump height between the devices were at a high level (r = .90), with the linear position transducer overestimating jump height by 7.0 ± 2.8 cm. The reliability measured by the linear position transducer resulted in a mean intraclass correlation of .70 for jump height, .90 for peak velocity, and .91 for mean velocity. The linear position transducer was reliable for measuring counter-movement jumps in elite female athletes; however, caution should be taken for one-off jump measures as it may over-estimate jump height.

Comparison of Different Minimal Velocity Thresholds to Establish Deadlift One Repetition Maximum.

The aim of this study was to compare the actual deadlift one repetition maximum (1RM) and the deadlift 1RM predicted from individualised load-velocity profiles. Twelve moderately resistance-trained men participated in three deadlift sessions. During the first, 1RM was assessed; during the second, load-velocity profiles were recorded with six loads (65% to 90% 1RM) using a linear position transducer recording at 1000 Hz; and during the third, minimal velocity thresholds (MVT) were recorded from the velocity of the last repetition during sets to volitional fatigue with 70% and 80% 1RM with a linear position transducer recording at 1000 Hz. Regression was then used to generate individualised load-velocity profiles and the MVT was used as a cut-off value from which to predict deadlift 1RM. In general, velocity reliability was poor to moderate. More importantly, predicted deadlift 1RMs were significantly and meaningfully less than actual deadlift 1RMs (p < 0.05, d = 1.03–1.75). The main practical application that should be taken from the results of this study is that individualized load-velocity profiles should not be used to predict deadlift 1RM. Practitioners should not use this method in combination with the application of MVT obtained from the last repetition of sets to volitional fatigue.

Between-Leg Mechanical Differences as Measured by the Bulgarian Split-Squat: Exploring Asymmetries and Relationships with Sprint Acceleration.

Between-leg strength differences can negatively influence sprint acceleration. The challenge is to find a method to measure this within a unilateral exercise. This study analyzed a five repetition-maximum (5RM) Bulgarian split-squat (BSS) to identify between-leg differences for the dominant and non-dominant legs in peak and mean power, force, and velocity as measured by a linear position transducer. Between-leg differences in these variables were correlated with 20-m (0–5, 0–10, 0–20 m intervals) sprint velocity. Eight men were assessed in the 5RM BSS and 20-m sprint. T-tests calculated between-leg differences in power, force, and velocity. Spearman’s correlations calculated relationships between the between-leg differences in the mechanical variables with velocity over each interval. When comparing the dominant and non-dominant legs, there were significant (p = 0.002–0.056) differences in 11 of 12 variables. However, percentage differences were low (~0.3–12%). There was one large, non-significant correlation (best repetition mean force between-leg difference and 0–5 m velocity; ρ = −0.810) out of 36 relationships. The BSS can provide a profile of between-leg differences in power, force, and velocity. There were limited relationships between the BSS between-leg differences and 20-m sprint velocities. Smaller between-leg differences in BSS power, force, and velocity could ensure minimal impact on acceleration.

Increases in Variation of Barbell Kinematics Are Observed with Increasing Intensity in a Graded Back Squat Test.

The purpose of the current study was two-fold: (1) To examine the variation in velocity and power with increasing intensity in the back squat among subjects; and (2) To explore individual subject characteristics as possible explanations for variations of velocity in the back squat. Fourteen recreationally trained male subjects with experience in the back squat agreed to participate in the study (age = 25.0 ± 2.6 years, height = 178.9 ± 8.1 cm, body mass = 88.2 ± 15.8 kg). One-repetition maximums (1RM) were performed for each subject on force platforms with four linear position transducers attached to the barbell. The 1RM assessment was immediately preceded by warm-up sets at 65%, 75%, 85%, and 95% of estimated 1RM for 5, 3, 2, and 1 repetitions, respectively. Mean concentric velocity (MCV) and mean power were recorded for each intensity condition and were analyzed using Pearson correlation to determine the relationship between each variable and relative intensity (%1RM). Statistically significant negative relationships existed between %1RM and MCV (r = −0.892) and mean power (r = −0.604). Between-subject coefficient of variation tended to increase as %1RM increased for both MCV and mean power. These results suggest that MCV is superior to mean power as an indicator of relative intensity in the back squat. Additionally, the between-subject variation observed at higher intensities for MCV and mean power support the use of velocity ranges by strength and conditioning coaches.

An Investigation of the Mechanics and Sticking Region of a One-Repetition Maximum Close-Grip Bench Press versus the Traditional Bench Press.

The close-grip bench press (CGBP) is a variation of the traditional bench press (TBP) that uses a narrower grip (~95% of biacromial distance (BAD)) and has potential application for athletes performing explosive arm actions from positions where the hands are held close to the torso. Limited research has investigated CGBP mechanics compared to the TBP. Twenty-seven resistance-trained individuals completed a one-repetition maximum TBP and CGBP. The TBP was performed with the preferred grip; the CGBP with a grip width of 95% BAD. A linear position transducer measured lift distance and duration; peak and mean power, velocity, and force; distance and time when peak power occurred; and work. Pre-sticking region (PrSR), sticking region, and post-sticking region distance and duration for each lift was measured. A repeated measures ANOVA was used to derive differences between TBP and CGBP mechanics (p < 0.01); effect sizes (d) were also calculated. A greater load was lifted in the TBP, thus mean force was greater (d = 0.16–0.17). Peak power and velocity were higher in the CGBP, which had a longer PrSR distance (d = 0.49–1.32). The CGBP could emphasize power for athletes that initiate explosive upper-body actions with the hands positioned close to the torso.

Velocity-based Training

Although training intensity is commonly adapted by modifying the relative load (e.g. %1RM), absolute velocities are also targeted to facilitate speed- and power-oriented training objectives. PURPOSE: Examine the variation in relative loads and relative velocities used to perform a bench press at 6 absolute velocities. METHODS: Thirty men completed three bench press tests: 1RM, max velocity with 2.5kg bar, and 6 sets of 4 reps with loads of 15-90% 1RM. Participants were instructed to lower and lift the bar as fast as possible. Mean and peak concentric barbell velocity was computed via a linear position transducer. The average mean velocity of each 4-rep set and the relative load lifted were used to create participant-specific regression equations that would capture each individual’s load-velocity relationship. These equations were then used to estimate the %1RM that would have been used to move the bar with the group’s mean velocity with loads of 15-90% 1RM). These “target” velocities were also expressed as a relative percentage of the maximum velocity (%Vmax) achieved by each participant during the 2.5kg test. The variation in %1RM for each velocity was described by the standard deviation and range amongst participants. A similar approach was used to estimate the %Vmax that would have been achieved using a range of loads (15-100% 1RM). RESULTS: Lower %1RM and higher mean velocities were associated with the largest variation in training intensity across participants (Table 1). CONCLUSION: Using specific absolute mean velocities as “targets” could result in substantial variation to the corresponding %1RM and %Vmax across a group of athletes. To accommodate the abilities of each performer, it may be important to use relative velocity targets.Table 1: Participants’ estimated %1RM and estimated %Vmax for 7 absolute velocities and relative loads, respectively. Data were computed using the participant-specific regression equations, and are expressed as a mean, standard deviation (SD) and range.

Validity of Linear Position Transducers Versus the Optotrak 3D Motion Capture System

Validity of Linear Position Transducers Versus the Optotrak 3D Motion Capture System

Validity of Various Methods for Determining Velocity, Force, and Power in the Back Squat.

To examine the validity of 2 kinematic systems for assessing mean velocity (MV), peak velocity (PV), mean force (MF), peak force (PF), mean power (MP), and peak power (PP) during the full-depth free-weight back squat performed with maximal concentric effort. Ten strength-trained men (26.1 ± 3.0 y, 1.81 ± 0.07 m, 82.0 ± 10.6 kg) performed three 1-repetition-maximum (1RM) trials on 3 separate days, encompassing lifts performed at 6 relative intensities including 20%, 40%, 60%, 80%, 90%, and 100% of 1RM. Each repetition was simultaneously recorded by a PUSH band and commercial linear position transducer (LPT) (GymAware [GYM]) and compared with measurements collected by a laboratory-based testing device consisting of 4 LPTs and a force plate. Trials 2 and 3 were used for validity analyses. Combining all 120 repetitions indicated that the GYM was highly valid for assessing all criterion variables while the PUSH was only highly valid for estimations of PF (r = .94, CV = 5.4%, ES = 0.28, SEE = 135.5 N). At each relative intensity, the GYM was highly valid for assessing all criterion variables except for PP at 20% (ES = 0.81) and 40% (ES = 0.67) of 1RM. Moreover, the PUSH was only able to accurately estimate PF across all relative intensities (r = .92-.98, CV = 4.0-8.3%, ES = 0.04-0.26, SEE = 79.8-213.1 N). PUSH accuracy for determining MV, PV, MF, MP, and PP across all 6 relative intensities was questionable for the back squat, yet the GYM was highly valid at assessing all criterion variables, with some caution given to estimations of MP and PP performed at lighter loads.

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.

Two Consecutive Days of Extreme Conditioning Program Training Affects Pro and Anti-inflammatory Cytokines and Osteoprotegerin without Impairments in Muscle Power

The aim of this study was to investigate the effects of two consecutive extreme conditioning program training sessions (24 h apart) designed to enhance work-capacity that involved both cardiovascular and muscular exercises on cytokines, muscle power, blood lactate and glucose. Nine male members of the extreme conditioning community (age 26.7 ± 6.6 years; body mass 78.8 ± 13.2 kg; body fat 13.5 ± 6.2%; training experience 2.5 ± 1.2 years) completed two experimental protocols (24 h apart): (1) strength and power exercises, (2) gymnastic movements, and (3) metabolic conditioning as follows: 10 min of as many rounds as possible (AMRAP) of 30 double-unders and 15 power snatches (34 kg). The same sequence as repeated on session 2 with the following metabolic conditioning: 12 min AMRAP of: row 250 m and 25 target burpees. Serum interleukin-6 (IL-6), IL-10, and osteoprotegerin were measured before, immediately post and 24 h after workout of the day (WOD) 1, immediately post, 24 and 48 h after WOD 2. Peak and mean power were obtained for each repetition (back squat with 50% of 1 repetition maximum) using a linear position transducer measured before, immediately post and 24 h after WOD 1, immediately post and 24 h after WOD 2. Blood lactate and glucose were measured pre and immediately post WOD 1 and 2. Although both sessions of exercise elicited an significant increase in blood lactate (1.20 ± 0.41 to 11.84 ± 1.34 vs. 0.94 ± 0.34 to 9.05 ± 2.56 mmol/l) and glucose concentration (81.59 ± 10.27 to 114.99 ± 12.52 vs. 69.47 ± 6.97 to 89.95 ± 19.26 mg/dL), WOD 1 induced a significantly greater increase than WOD 2 (p ≤ 0.05). The training sessions elicited significant changes (p ≤ 0.05) in IL-6, IL-10 and osteoprotegerin concentration over time. IL-6 displayed an increase immediately after training WOD 1 [197 ± 109%] (p = 0.009) and 2 [99 ± 58%] (p = 0.045). IL-10 displayed an increase immediately after only WOD 1 [44 ± 52%] (p = 0.046), and decreased 24 and 48 h following WOD 2 (~40%; p = 0.018) as compared to pre-exercise values. Osteoprotegerin displayed a decrease 48 h following WOD 2 (~25%; p = 0.018) as compared with pre intervention. In conclusion, two consecutive extreme conditioning training sessions increase pro/anti-inflammatory cytokines with no interference on muscle performance in the recovery period.

Measuring nonlinear oscillations using a very accurate and low-cost linear optical position transducer

An accurate linear optical displacement transducer of about 0.2 mm resolution over a range of ∼40 mm is presented. This device consists of a stack of thin cellulose acetate strips, each strip longitudinally slid ∼0.5 mm over the precedent one so that one end of the stack becomes a stepped wedge of constant step. A narrowed light beam from a white LED orthogonally incident crosses the wedge at a known point, the transmitted intensity being detected with a phototransistor whose emitter is connected to a diode. We present the interesting analytical proof that the voltage across the diode is linearly dependent upon the ordinate of the point where the light beam falls on the wedge, as well as the experimental validation of such a theoretical proof. Applications to nonlinear oscillations are then presented—including the interesting case of a body moving under dry friction, and the more advanced case of an oscillator in a quartic energy potential—whose time-varying positions were accurately measured with our transducer. Our sensing device can resolve the dynamics of an object attached to it with great accuracy and precision at a cost considerably less than that of a linear neutral density wedge. The technique used to assemble the wedge of acetate strips is described.

The Reliability of a Rotational Power Assessment of the Core

Context: Most athletic upper-body power generation involves high levels of neuromuscular activation/coordination of a rotational nature. Therefore, it is important to assess athletic ability that replicates the rotational activity of athletes. However, a paucity of research currently measures rotational power of the core. Objective: Establish inter-day reliability of chop and lift mean power output via a linear position transducer on rotational reliant power athletes. Design: Controlled laboratory study. Setting: Professional cricket training facilities. Population: Eight male professional cricket players (age= 23±3.38 years, height= 186±10.06 cm, mass= 89.71±8.12 kg) with a resistance (>2 years) training background volunteered to participate in the study. Intervention: A linear position transducer was attached to the weight stack of a cable pulley system to determine the peak power outputs associated with a chop and lift movement. Assessment occurred on three occasions separated by at least seven days.Asymmetry, intraclass correlation coefficients (ICCs) and coefficient of variations (CV) were calculated and used to quantify the absolute and relative consistency of the testing procedures. Results: The mean peak power outputs for chop and lift ranged from 404 - 494W and 277-314W respectively, the power outputs differing minimally (2.7-6.3%) between the left and right sides. Coefficients of variation of 7.4% - 19% were reported, with intraclass correlation coefficients of 0.54 - 0.94 observed between testing occasions. Conclusion: Mean muscular power output associated with the lift assessment reported greatest reliability in well trained athletes.The asymmetry between sides was relatively small suggesting balanced multi-planar trunk development in the current throwing athletes. Equipment limitations (load related), training status and variable selection (mean or peak power) need to be considered prior to rotational assessment of the core. It is recommended that the lift movement is utilized in rotational power assessments, or that greater familiarization is undertaken when administering the chop assessment.

Velocity Drives Greater Power Observed During Back Squat Using Cluster Sets.

This investigation compared the kinetics and kinematics of cluster sets (CLU) and traditional sets (TRD) during back squat in trained (RT) and untrained (UT) men. Twenty-four participants (RT = 12, 25 ± 1 year, 179.1 ± 2.2 cm, 84.6 ± 2.1 kg; UT = 12, 25 ± 1 year, 180.1 ± 1.8 cm, 85.4 ± 3.8 kg) performed TRD (4 × 10, 120-second rest) and CLU (4 × (2 × 5) 30 seconds between clusters; 90 seconds between sets) with 70% one repetition maximum, randomly. Kinematics and kinetics were sampled through force plate and linear position transducers. Resistance-trained produced greater overall force, velocity, and power; however, similar patterns were observed in all variables when comparing conditions. Cluster sets produced significantly greater force in isolated repetitions in sets 1-3, while consistently producing greater force due to a required reduction in load during set 4 resulting in greater total volume load (CLU, 3302.4 ± 102.7 kg; TRD, 3274.8 ± 102.8 kg). Velocity loss was lessened in CLU resulting in significantly higher velocities in sets 2 through 4. Furthermore, higher velocities were produced by CLU during later repetitions of each set. Cluster sets produced greater power output for an increasing number of repetitions in each set (set 1, 5 repetitions; sets 2 and 3, 6 repetitions; set 4, 8 repetitions), and the difference between conditions increased over subsequent sets. Time under tension increased over each set and was greater in TRD. This study demonstrates greater power output is driven by greater velocity when back squatting during CLU; therefore, velocity may be a useful measure by which to assess power.

Comparison between single and combined data collection methods in loaded squat jump power output

BACKGROUND: The aim of this study was to compare linear position transducer force plate-based methods and more complex combinations of those for calculation of power output in loaded squat jump.MET ...

Reliability Analysis of Traditional and Ballistic Bench Press Exercises at Different Loads.

The purpose of this study was to determine test–retest reliability for peak barbell velocity (Vpeak) during the bench press (BP) and bench press throw (BPT) exercises for loads corresponding to 20–70% of one-repetition maximum (1RM). Thirty physically active collegiate men conducted four evaluations after a preliminary BP 1RM determination (1RM·bw-1 = 1.02 ± 0.16 kg·kg-1). In counterbalanced order, participants performed two sessions of the BP in one week and two sessions of the BPT in another week. Recovery time between sessions within the same week was 48 hours and recovery time between sessions of different weeks was 120 hours. On each day of evaluation the individual load-velocity relationship at each tenth percentile (20–70% of 1RM) in a Smith machine for the BP or BPT was determined. Participants performed three attempts per load, but only the best repetition (highest Vpeak), registered by a linear position transducer, was analysed. The BPT resulted in a significantly lower coefficient of variation (CV) for the whole load–velocity relationship, compared to the BP (2.48% vs. 3.22%; p = 0.040). Test–retest intraclass correlation coefficients (ICCs) ranged from r = 0.94–0.85 for the BPT and r = 0.91–0.71 for the BP (p < 0.001). The reduction in the biological within-subject variation in BPT exercise could be promoted by the braking phase that obligatorily occurs during a BP executed with light or moderate loads. Therefore, we recommend the BPT exercise for a most accurate assessment of upper-body velocity.

Comparison of Two Methods to Measure Snatch and Front Squat Bar Velocity.

While bar displacement has traditionally been measured using camera-based methods, several portable systems using cords connecting directly to the bar are now available. Because many weight training exercises involve the bar moving in multiple planes, which may change across load intensity, the validity of using a linear position transducer (LPT) is of significance. PURPOSE: To compare camera and LPT measurement of vertical bar velocity during front squats and snatches. METHODS: Healthy men (n=7) aged 18 to 35yrs completed one test session during which two repetitions of the front squat and snatch at 50%, 60% and 80% of their reported one repetition maximum (1RM) were completed. Order of exercises performed was randomized. Simultaneous measurement of bar displacement was made by a 12 camera system (Vicon, Oxford, UK) and a LPT (Tendo Power Analyzing Unit, Tendo Power Machines, Slovak Republic), from which peak velocities were computed. Correlational and 95% limits of agreement (LOA) analyses were conducted between the two methods. RESULTS: Strong relationships were revealed between the methods for both the front squat (50%: r=.96, 60%: r=.90, 80%: r=.97) and snatch (50%: r=.92, 60%: r=.99, 80%: r=.99). Camera estimated peak velocities were significantly greater for front squat at 50% (P=.018) and 60% (P=.031) and snatch at 60% (P=.004) and 80% (P=.003). Bias and 95% LOA during the front squat were: .09±.18m/s (50%), .09±.17m/s (60%), and .04±.14m/s (80%). Bias and 95% LOA during the snatch were .10±.52m/s (50%), .28±.32m/s (60%), and .26 ± .28m/s (80%). CONCLUSION: Stronger agreement was evident for the front squat compared to the snatch, which may be explained by the complexity of the snatch lift as it involves a degree of curvature during the second pull and catch. This explanation is plausible given research showing bar curvature during the second pull and catch increases as loads increase. However, given the relative agreement between these measurement techniques, this work does suggest a portable system may be efficacious for use in non-laboratory settings. As this study engaged intermediate lifters, future research should examine the agreement between measurement approaches in elite level lifters, particularly as such lifters may be less likely to increase the curvature of bar trajectory during a snatch life.

Effect of various practical warm-up protocols on acute lower-body power.

The purpose of this study was to compare the acute effect of box squats with barbell (BBSquat), box squats with elastic resistance bands (BandSquat), and static stretches (SStretch) on external power during a 20-kg weighted jump squat. Twelve male athletes performed each of the 3 warm-up protocols on separate occasions in a randomized order. Weighted jump squat power was assessed using a linear position transducer attached to the bar of a Smith machine. Jump power was measured pre-warm-up and 5 and 10 minutes post-warm-up protocol. The BBSquat protocol involved 3 sets of 3RM, BandSquat involved 3 sets of 3 repetitions using highest resistance elastic bands, and the SStretch protocol comprises two 30-second stretches for muscles of the lower limbs. Jump power significantly increased from pre-warm-up to 5 and 10 minutes post-warm-up for both the BandSquat and BBSquat protocols. There was no statistical difference in power values between BandSquat and BBSquat. Power output significantly decreased from pre-warm-up to 5 and 10 minutes post-warm-up for the SStretch protocol. The BandSquat was just as effective as BBSquat in augmenting acute jump power. The SStretch was detrimental to jump performance. A practical warm-up using relatively inexpensive and portable equipment such as elastic resistance bands was just as effective as a warm-up protocol that requires more substantial and less transportable equipment such as a squat rack and associated free weights. The BandSquat warm-up may be considered more accessible for athletes at various competition levels.