Time Changes in Resisted Sprinting With a Weighted Vest: 5 % of Body Weight or Back Squat? The Use of the 1RM Back Squat and Body Weight as Load Strategy in Weighted Vest Sprinting

The purpose was to investigate whether runners who do not squat their body weight once will not be overloaded with a weight vest with a load of 5% of BW and will not maintain 95% intensity across ten repetitions of a 20-meter sprint. Eight adult female students (24,05±1,15 years old; body height 168±4,24 cm; body weight 60,39±5,53 kg) from the faculty of sports studies at Masaryk University in the Czech Republic participated in this study. Categories were: 1 = NBW (1RM in the squat is relative body weight ± 5 kg), 2 = LBW (1RM in the squat is lower than BW-5 kg) and 3 = HBW (1RM in the squat is higher than BW +5 kg). The measurements took place on three different days, each day running with another experimental condition: free sprinting, weighted vest sprinting with a 5% load of BW, and weighted vest sprinting with a 5% load of 1RM squat. With a weight vest with resistance at the level of 5% of body weight, during 49 sprints, the intensity decreased by a maximum of 4.82% (participant 4, NBW group, 1st run). Although, with weight vest resistance at the level of 5% of the 1RM back squats, during 68 sprints, the intensity decreased by a maximum of 6.59% (participant 1, NBW group, 8th run). It seems that the level of strength abilities of the lower limbs did not play a role in this, we can calculate 5% intensity from both BW and 1 RM squat. Since the HBW group could maintain the required intensity even at significantly higher weights than 5% BW, further research with a larger research sample is needed.