Abstract Background: Using a weight lifting belt when performing a variety of resistance exercises is becoming more and more common. The purpose of using a weight lifting belt is its supposed ability to reduce compressive forces on the lumbar spine and enhancement of athletic performance. Although the weight lifting belt has been proven to increase the intra abdominal pressure that helps reduces the shear forces during a squat, little is known about the weight lifting belts effect on the performance. Studies have suggested that wearing a weight lifting belt during a squat can increase the vertical velocity and range of motion. Few studies have focused on the power output, but improvements have been seen while wearing a weight lifting belt when performing a deadlift. Variables such as power, velocity and range of motion are of importance for an athlete when making individual training plans as well as measuring the progress. Therefore more research is needed to identify the actual influence of the weight lifting belt on the performance. Aim: The purpose of this study was to examine if weight lifting belts have an impact on an athletes ability to develop power, velocity or improve range of motion in a squat. Methods: Fifteen healthy men and women familiar with the squat exercise participated in the study. During the study they performed six repetitions of the squat divided into two sets, one set without a weight lifting belt and one with a weight lifting belt. Power and velocity were measured during every squat with a linear encoder and videotapes were made to later calculate the angles in the hip- and knee joints at the lowest position of the exercise. Results: No significant differences were found in power (p = 0.25) or concentric and eccentric velocity (p = 0.61, p = 0.16) with or without a weight lifting belt. Range of motion in the knee joint was greater when not wearing a weight lifting belt (p = 0.03), but no differences in the hip angles were found (p = 0.70). Conclusion: The result from the current study shows that when performing a squat the weight lifting belt has little to no effect on power, velocity or range of motion. Although a noticeable change in range of motion of the knee joint were observed, further studies on larger populations are needed to determine if it is of clinical value.

Background: A squat is a common exercise that is used in many areas of strength training and for different purposes and the literature is inconclusive when it comes to whether the weight lifting belt (WB) affects performance and/or is injury-preventing. The use of breathing techniques is common during heavy lifting and therefore the practice of the breathing teqnice; valsalva maneuver (VM) may be of interest to study and if this along with the WB can provide some advantages in power output and velocity. Aim: The specific aim of the study was to evaluate whether the velocity in the eccentric and the concentric phase of the squat, and the peak velocity in the concentric phases are affected in power output through the use of the VM when the subjects use or did not use a WB. Method: Fifteen subjects (10 men and 5 women) volunteered freely to participate and did a total of 12 squats divided in four different sets with three repetitions each on 75% of their self-reported one repetition maximum (1RM). The first two sets were either with or without WB and the third and fourth sets were either with or without the practice of the VM. The three conditions (with WB, with WB + VM and VA only) were compared to each other and to the control group (without any instructions and no WB) in terms of power output and velocity in the eccentric, concentric and peak velocity in the concentric phase of the squat. Result: There was no significant difference in power output when comparing the four different test conditions. The velocity in the eccentric, concentric and peak velocity in the concentric phase did not have a significant difference between the different test conditions. Conclusions: This study shows a different output compared to previous literature. The WB and the practice of VM did not affect the power output and velocity in a squat, alone or together. / Bakgrund: Det finns många olikheter i litteraturen när det gäller huruvida tyngdlyftarbältet påverkar prestationen och/eller om det minskar skaderisken. En knäböj är en vanlig övning som används inom många områden av styrketräning och för olika ändamål. Användning av andningstekniker är vanligt vid tunga lyft och därför kan utförandet av andningstekniken; valsalvamanövern vara av intresse att studera och om det tillsammans med lyftbältet kan ge effekt på effektutveckling och hastighet i lyft. Syfte: Syftet med studien var att utvärdera hastigheten i en knäböjs olika faser (excentriska, koncentriska och topphastigheten i den koncentriska fasen) och hur effektutvecklingen påverkas av lyftarbälte och valsalvamanövern. Metod: Femton personer (10 män och 5 kvinnor) deltog frivilligt och utförde totalt 12 knäböj i fyra olika sets med tre repetitioner på 75 % av testpersonernas självrapporterade 1RM. De första två seten var utförda antingen med eller utan tyngdlyftarbälte och de tredje och fjärde seten var utförda antingen med eller utan utövande av valsalvamanövern. Dessa tre förhållanden ( med lyftarbälte, med lyftarbälte + VA och VA endast) jämfördes med varandra och med kontrollgruppen ( ingen VM och inget lyftarbälte) med avseende på effektutveckling och hastigheten i den excentriska, koncentriska och topphastighet i knäböjens koncentriska fas. Resultat: Effektutvecklingen gav ingen signifikant skillnad i någon av de fyra olika förutsättningarna (med lyftarbälte, utan lyftarbälte, med bälte och valsalvamanövern och utan bälte och valsalvamanövern). Hastigheten i den excentriska, koncentriska och topphastigheten i den koncentriska fasen visade ingen signifikant skillnad mellan de fyra olika seten. Konklusion: Studien visade ingen skillnad vilket kan jämföras med tidigare litteratur där en skillnad fanns. Lyftarbältet och utförandet av valsalva manövern påverkade inte effektutvecklingen och/eller hastigheten när en knäböj utfördes.