Background: The intensity or load of a strength training exercise is commonly considered to be the most important factor contributing to muscular strength and power. Traditionally in strength training, intensity is defined as the percentage of the maximum weight that can be lifted once i.e. 1 repetition maximum. For power development exercises, the velocity can be used to measure the intensity. A linear position transducer is able to measure kinetic and kinematic variables. Velocity-based training refers to the usage of a linear position transducer to track movement velocity of an exercise and thus, using velocity, rather than load, as a measurement of intensity. Purpose: The purpose of this systematic review was to provide an analysis of the existing velocity-based training research utilizing a linear position transducer. The study also aimed to investigate the validity and reliability of different commercial linear position transducers for kinetic and kinematic measurements.   Method: A systematic review was conducted from 19 studies on velocity-based training that met the selection criteria and underwent a quality assessment. Results: It was possible to predict the 1 repetition maximum using velocity and the minimal velocity threshold was stable across different relative intensities. Performing squats at either maximal velocity, or stopping at a velocity loss of <40% could significantly improve 1 repetition maximum, increase mean velocity during a set of squats as well as vertical jump performance. Two linear position transducer were found to have excellent validity and reliability for both kinetic and kinematic measurements. Conclusion: Velocity-based training was beneficial for enhancing neuromuscular adaptions and could be used to predict the 1 repetition maximum. When using of a linear position transducer for power development, it is suggested that it is valid and reliable for both kinetic and kinematic measurements.

The purpose of this study was to determine if concentric velocities of lighter loads of could be augmented if they are performed heavier working sets. Twelve trained males with experience in the barbell back squat performed a 5RM and completed two separate squat training session conditions that consisted of three sets of five repetitions with 85% of their 5RM. Both conditions differed in the placement of a reduced-load set that was either performed after the working sets or during the warm-up period. No significant differences were observed in the working set MCVs in both conditions. Additionally, no significant differences were observed amongst MCVs in the Down Set and equivalent warm-up set loads. The results of this study suggest that postactivation potentiation may not occur using a similar set-load scheme.

Abstract Background: The ability to produce a high power output can be the deciding factor in determining which athlete wins or loses in a sporting event. Power output can be measured in an exercise like the squat or bench press. The use of a force plate, or a force plate paired with a linear position transducer is considered the gold standard when measuring power output in an exercise like the squat or bench press. Linear position transducers or linear encoders have also been considered valid methods. Power output can also be measured by accelerometers. Purpose: The purpose of this study was to test the concurrent validity of the accelerometer Beast Sensor by measuring average power in explosive squatting and bench pressing at 40 % and 80 % of one repetition maximum (1RM). The linear encoder MuscleLab was used as criterion. Methods: 17 test subjects, five women and 12 men (average age 28 years) were recruited. Fifteen of the subjects completed two test sessions. The first session determined their 1RM. The second session took place 7-14 days later and measured average power output during two sets of three repetitions at 40 % and 80 % of the subjects 1RM in explosive squats and bench presses. The average power output of the repetitions was measured simultaneously by Beast Sensor and MuscleLab. For the Beast Sensor to be considered valid, a correlation coefficient of 0.9 or higher needed to be reached. Results: Beast Sensor demonstrated high or very high correlations with MuscleLab for average power output of explosive squats at 40 % of 1RM (rs = 0.91), and for explosive bench presses at 40 % (rs = 0.86) and 80 % of 1RM (rs = 0.74). However, for explosive squats at 80 % of 1RM, the correlation was low (rs = 0.42). All correlations were statistically significant with p-values of < 0.01. Beast Sensor was considered valid for squats at 40 % of 1RM, but neither at 80 % of 1RM in squats, nor at 40 % or 80 % of 1RM in bench presses. Conclusion: Beast Sensor showed high or very high correlations with the criterion MuscleLab in three of the four assessed data variables. Only the correlation for average power output of the explosive squats at 40 % of the subject’s 1RM reached the required correlation coefficient of 0.9 or higher for the Beast Sensor to be considered valid. Except for at 40 % of 1RM in squats, Beast Sensor missed a substantial amount of repetitions. Further studies examining the reliability of the Beast Sensor are therefore needed. / Abstrakt Bakgrund: Förmågan att producera hög effektutveckling (power) kan avgöra vilken idrottare som vinner eller förlorar en tävling. Effektutveckling kan mätas i övningar som knäböj och bänkpress. Detta kan göras med hjälp av en kraftplatta, eller en kraftplatta parad med en linear position transducer. Dessa metoder anses vara ”gold standard”, men linear position transducers eller linear encoders har också ansetts vara valida metoder. Effektutveckling kan även mätas med hjälp av en accelerometer. Syfte: Syftet med denna studie var att mäta samtidig validitet hos accelerometern Beast Sensor genom att mäta genomsnittlig effektutveckling i explosiva knäböj och bänkpressar vid 40 % och 80 % av en repetition max (1RM). MuscleLab, en linear encoder, användes som referensvärde.  Metod: 17 försökspersoner, fem kvinnor och tolv män (medelålder 28 år) rekryterades. Femton av försökspersonerna fullföljde deltagande. Vid det första testtillfället mättes 1RM. Det andra tillfället ägde rum 7-14 dagar senare och mätte genomsnittlig effektutveckling i explosiva knäböj och bänkpressar vid 40 % och 80 % av försökspersonernas uppmätta 1RM. Två set av tre repetitioner mättes vid 40 % och 80 % av 1RM i både knäböj och bänkpress. Repetitionerna mättes samtidigt av MuscleLab och Beast Sensor. För att Beast Sensor skulle anses vara valid behövde en korrelationskoefficient på 0.9 eller högre uppnås. Resultat: Beast Sensor uppvisade höga eller väldigt höga korrelationer med MuscleLab för genomsnittlig effektutveckling i explosiva knäböj vid 40 % av 1RM (rs = 0.91) och explosiva bänkpressar vid 40 % (rs = 0.86) och 80 % av 1RM (rs = 0.74). Dock uppmättes en låg korrelation för de explosiva knäböjen vid 80 % av 1RM (rs = 0.42). Alla korrelationer var statistiskt signifikanta med p-värden på < 0.01. Beast Sensor ansågs vara valid för att mäta effektutveckling vid 40 % av 1RM i knäböj, men varken vid 80 % av 1RM i knäböj, eller vid 40 % eller 80 % av 1RM i bänkpressar. Slutsats: Beast Sensor visade höga eller väldigt höga korrelationer med referensvärdet från MuscleLab för tre av de fyra uppmätta variablerna. Endast korrelationen för genomsnittlig effektutveckling i explosiva knäböj vid 40 % av 1RM uppnådde den korrelationskoefficient på 0.9 eller högre som krävdes för att Beast Sensor skulle anses vara valid. Förutom vid 40 % av 1RM i knäböj, missade Beast Sensor en väsentlig andel repetitioner. Därför finns det ett behov av fler studier som undersöker reliabiliteten hos Beast Sensor.