An Efficient Method of Key-Frame Extraction Based on a Cluster Algorithm

Abstract

The purpose of the present study was to investigate the effects of different configurations of repetitions within a set of deadlifts on the mechanical variables of concentric force, concentric time under tension, impulse, work, power, and fatigue. Eleven resistance trained men (age: 21.9 ± 1.0 years; deadlift 1 repetition maximum: 183.2 ± 38.3 kg) performed four repetitions of the deadlift exercise with a load equivalent to 90% of 1 repetition maximum under three different set configurations: Traditional (continuous repetitions); Doubles cluster (repetitions 1 and 2, and 3 and 4 performed continuously with a 30 s rest inserted between repetitions 2 and 3); Singles cluster (30 s rest provided between repetitions). The order of the sessions was counterbalanced across the subjects and the mechanical variables were calculated during each repetition from the synchronized signals recorded from force platforms and a motion analysis system. Relative to the Traditional set, the insertion of rest periods in the cluster set configurations resulted in greater time under tension (p < 0.001) and therefore, greater impulse (p < 0.001) during the repetitions. Reductions in power were observed during the cluster sets compared to the Traditional set (p = 0.001). The Doubles cluster set resulted in greater fatigue scores for power compared to the Traditional set (p = 0.04). The influence of cluster sets on mechanical variables appears to be mediated by the mechanical characteristics of the exercise (i.e. stretch-shortening cycle) and the competing physiological mechanisms of fatigue and potentiation.

Effects of Cluster Sets and Rest-Redistribution on Mechanical Responses to Back Squats in Trained Men

“…Since the relative external load was the same during each protocol, there was no difference in MF between protocols, in line with previous research ( Denton and Cronin, 2006 ; Moir et al, 2013 ; Tufano et al, 2016b ). There is a lack of PF data within the cluster set literature, but previously, Hardee et al (2012) showed that PF was better maintained when longer inter-repetition rest periods were used during three cluster sets of six power cleans performed with a load of 80% of 1RM.…”

“…Therefore, PF remained fairly steady during RR1, but was greater during successive repetitions compared to the first repetition of each 4-repetition segment in RR4 and CS4 ( Figure 2c ). Despite this being the first study to compare PF between individual repetitions of the back squat using cluster sets, the results from a previous study may shed light on this PF phenomenon ( Moir et al, 2013 ). In a study conducted by Moir et al (2013) , participants performed four repetitions of the deadlift in a row (i.e.…”

“…Despite this being the first study to compare PF between individual repetitions of the back squat using cluster sets, the results from a previous study may shed light on this PF phenomenon ( Moir et al, 2013 ). In a study conducted by Moir et al (2013) , participants performed four repetitions of the deadlift in a row (i.e. a traditional set), a cluster set of four individual repetitions with 30 s of inter-repetition rest, and a cluster set of four repetitions with 30 s of intra-set rest after every two repetitions.…”

“…a traditional set), a cluster set of four individual repetitions with 30 s of inter-repetition rest, and a cluster set of four repetitions with 30 s of intra-set rest after every two repetitions. The authors concluded that the additional rest periods during cluster sets had a negative effect on power output and culminated in greater concentric time under tension compared to the traditional set ( Moir et al, 2013 ). A lack of peak force data does not allow for a direct comparison with the present study, but an increase in time under tension (and a hypothesized decrease in movement velocity stated by the authors) in the repetitions that followed a 30 s rest period led the authors to believe that the stretch-shortening cycle was not as profound in the cluster set protocols compared to the traditional set when a repetition was preceded by another repetition ( Moir et al, 2013 ).…”

“…To create cluster sets, some researchers have added intra-set rest without changing the inter-set rest duration, increasing the total rest time ( Haff et al, 2003 ; Hardee et al, 2012 ; Tufano, et al, 2016b) ; whereas, others have equated the total rest time between protocols by redistributing the total inter-set rest time throughout the protocol ( Joy et al, 2013 ; Lawton et al, 2006 ; Oliver et al, 2015 ). These studies have generally implemented 30 s of inter-repetition rest ( Haff et al, 2003 ; Hardee et al, 2012 ; Moir et al, 2013 ), with a range from 6 s ( García-Ramos et al, 2015 ) to upwards of over 40 s ( Iglesias-Soler et al, 2014 ). Some studies include a different number of repetitions for each participant, resulting in individualized rest redistribution that cannot directly be compared to other participants within the same study or of other studies.…”