Effects of velocity loss during bench-press training with light relative loads

1 EFFECTS OF VELOCITY LOSS DURING BENCH-PRESS TRAINING WITH LIGHT RELATIVE LOADS Rodiles-Guerrero, L1,2., Sánchez-Valdepeñas, J 2,3., Cornejo-Daza, P.J 1,2,3., Páez-Maldonado, J 2,5., Cano-Castillo, C 1,2., Bachero-Mena, B1,2., Sánchez-Moreno, M2,4., Pareja-Blanco, F2,3 1. Department of Human Movement and Sport Performance, University of Seville, Spain 2. Science-Based Training Research Group, Department of Sports and Computer Sciences, Universidad Pablo de Olavide, Seville, Spain 3. Physical Performance and Sports Research Center, Department of Sports and Computer Sciences, Universidad Pablo de Olavide, Seville, Spain 4. Department of Physical Education and Sports, University of Seville, Seville, Spain 5. University of Osuna (Centre attached to the University of Seville), Osuna, Spain Running head title: Velocity loss in the bench-press with light loads Corresponding author: Luis Rodiles Guerrero Department of Human Movement and Sport Performance, University of Seville, Seville, SPAIN. Tel +34 95.542.10.06, email: [email protected] ORCID ID Rodiles Guerrero, L: 0000-0001-5928-4827 ORIGINAL ARTICLE Running head: Velocity loss in the bench-press with light loads Total word count: 3479 Abstract word count: 227 Number of figures and tables: 3 figures and 3 tables 2 ABSTRACT 1 Purpose: this study explored the effects of four bench-press (BP) training programs with 2 different velocity loss (VL) thresholds (0%, 15%, 25%, and 50%) on strength gains and 3 neuromuscular adaptations Methods: forty-six resistance-trained men (22.8 ± 4.4 years) 4 were randomly assigned into four groups that differed in the VL allowed within the set: 5 0% (VL0), 15% (VL15), 25% (VL25), and 50% (VL50). Training loads (40-55% 1RM), 6 frequency (2 sessions/week), number sets (3), and inter-set recovery (4 min) were 7 identical for all groups. Participants completed the following tests before and after an 8- 8 week (16 sessions) BP training program: 1) maximal isometric test, 2) progressive 9 loading test; and 3) fatigue test, in the BP exercise. During all tests, triceps brachii muscle 10 EMG was assessed. Results: after completing the RT program, no significant group × 11 time interactions were noticed for isometric and dynamic BP strength variables. The dose- 12 response relationship exhibited an inverted U-shaped relationship pattern with VL25 13 showing the greatest effect sizes for almost all strength variables analyzed. The total 14 number of repetitions performed during the training program increased as the VL 15 magnitude increased. Conclusions: the group that trained with high VL (50%), which 16 performed a total of 876 repetitions, did not provide additional strength gains than those 17 provided by 0%, 15%, and 25% of VL groups, which performed significant lower 18 repetitions (48, 357, and 547, respectively). These findings suggest that when light loads 19 (40-55% 1RM) are used, low and moderate VL thresholds (0-25%) provides a higher 20 training efficiency. 21 Keywords: resistance training, velocity-based training, level of effort, training 22 prescription, muscle strength, neuromuscular adaptations. 23 INTRODUCTION 24 Muscular strength is one of the main factors that may contribute to athletic performance 25 1. To induce neural and morphological strength-related adaptations, the manipulation of 26 training variables is critical 2,3. Balancing intensity and volume is crucial, since excessive 27 volume without adequate intensity may not challenge muscles enough to induce strength 28 gains, whereas too little volume may not provide enough stimulus for adaptations 4. 29 In recent years, the practicability of the velocity-based resistance training (RT) approach 30 for monitoring and real-time prescription of RT intensity and volume has been 31 demonstrated 5-7. In this context, velocity loss (VL) provides practitioners with a useful 32 3 and practical tool to monitor training volume and level of effort 8,9. Therefore, VL can be 33 used to determine when each set should be stopped. Regarding the bench-press (BP) 34 exercise, when a VL threshold of 50% is reached with intensities from 50% to 85% of 1- 35 repetition maximum (1RM), it means that it has been carried out three-quarters of the 36 total repetitions that could be completed before task failure, while a 25-30% VL indicates 37 that the athlete has performed nearly half-maximal repetitions before failure 8,9. 38 Longitudinal RT studies have already been conducted to examine the effect of RT with 39 different VL thresholds 10-- 18. Previous research focusing on the upper limb indicates that 40 due to the higher metabolic and mechanical stress, higher VL thresholds (25-50%) 41 maximized muscle hypertrophy 12. Conversely, as a consequence of increased motor unit 42 frequency, increased discharge doublets, and changes in fiber types, lower VL thresholds 43 (<25%) result in positive neuromuscular-related adaptations 12. These findings emerged 44 from training programs using intensities from 70% to 85% 1RM in the BP exercise 12. 45 Recent research 11 echoes these results, showing similar outcomes as Pareja-Blanco et al. 46 12 but with lighter intensities (55-70% 1RM). Notably, both studies highlighted an 47 inverted U-shaped relationship between VL threshold and strength performance 48 increases. Hence, when training BP with intensities from 55% to 85% 1RM it seems 49 necessary to exceed a certain magnitude of VL to maximize strength-related adaptations. 50 However, once a certain volume threshold is reached, adding more repetitions seems 51 ineffective in fostering additional strength gains. In fact, it might even diminish the earlier 52 strength-related adaptations stimulated by lower training volumes 11,12. 53 It is worth pointing out that both above-mentioned BP studies 11, 12 have been performed 54 with moderate to high loads (55-85% 1RM). Nonetheless, it would be interesting to know 55 if these findings could be extrapolated to lighter intensities (i.e., 40-55% 1RM) that could 56 be well-tolerated regardless of the population (i.e., novel athletes or people with low RT 57 background). Therefore, this study aimed to compare the effect of four VL thresholds – 58 0%, 15%, 25%, and 50%, on strength gains and neuromuscular adaptations during the BP 59 exercise using intensities ranging from 40% to 55% 1RM. Based on previous literature, 60 we hypothesized that despite a remarkably lower VL threshold, VLs of 15% and 25% 61 would result in similar or even greater strength adaptations compared to a high VL (50%); 62 and (2) it is necessary to exceed a certain magnitude of VL (VL0) to evoke both 63 neuromuscular and strength adaptations when training is performed with light loads 64 (40%–55% 1RM) in the BP exercise. 65 4 METHODS 66 Experimental Approach to the Problem 67 A randomized research design was used to analyze the effects of four BP training 68 programs, differing in the VL allowed in each set [0% (VL0), 15% (VL15), 25% (VL25), 69 and 50% (VL50)], with all groups using the same relative intensity (from 40 to 55% 70 1RM). All participants completed 2 training sessions each over an 8-week cycle in the 71 BP exercise. Seventy-two hours before (Pre-training) and after (Post-training) the training 72 intervention, participants performed the following BP tests, in the same order (as 73 described) and on the same: 1) maximal isometric test; 2) progressive loading test; and 3) 74 fatigue test. During all tests, the electromyography (EMG) signal of the triceps brachii 75 muscle was recorded. Two weeks before the Pre-training testing, all participants 76 underwent two preliminary sessions (one per week) during which they were familiarized 77 with the testing equipment and exercise protocol. All sessions took place at the same 78 venue, under the direct supervision of at least one investigator, at the same time of the 79 day (± 1 hour) for each subject and using the same equipment. 80 Subjects 81 Recruitment was performed through advertisements and community newsletters. To 82 participate in the study, the volunteers were required a minimum of 1.5 years of RT 83 background (1-3 sessions per week), with the BP exercise commonly used as a part of 84 their training program. The initial sample involved 50 resistance-trained men. Participants 85 were randomly assigned following an ABCDDCBA counterbalancing sequence, based 86 on their 1RM at Pre-training, into 4 groups differing in the VL threshold within the set: 87 VL0, VL15, VL25, and VL50. Due to illness (n = 3) and discontinued participation (n = 88 1), 46 subjects completed the training intervention (mean ± SD, age: 22.8 ± 4.4 years, 89 stature: 1.77 ± 0.06 m, and body mass: 75.9 ± 9.8 kg, relative BP-1RM: 0.96 ± 0.17 kg ∙ 90 kg-1). The final sample was distributed as follows: VL0, n = 10; VL15, n = 13; VL25, n 91 = 11; VL50, n = 12. All of the participants provided their informed consent, and the 92 experimental protocol was approved by the Local Research Ethics Committee. The study 93 was conducted in conformity with the policy statement regarding the use of human 94 subjects by the Declaration of Helsinki. 95 Procedures 96 5 Maximal isometric test 97 Subjects were laid down on a bench (Bench Fitness Line, Peroga, Murcia, Spain) that was 98 placed on a Smith machine (Fitness Line, Peroga, Murcia, Spain). Before testing, 99 participants underwent a general warm-up comprising 5 minutes of easy self-selected 100 pace running, followed by 5 minutes of upper-body joint mobilization exercises. Two 101 specific warm-up sets of the isometric BP were performed at 50% and 70% of 102 participants´ perceived maximal isometric force (MIF). The test consisted of performing 103 two 5-second maximal isometric BP repetitions with the bar placed 1 cm above the 104 participant’s chest (elbow joint angle ⁓40º, considering full extension as 180º). 105 Participants employed and replicated their own lifting grip (approximately 150% of the 106 biacromial distance) based on their previous experience with the BP exercise. Individual 107 width grips were recorded to be repeated during the rest of the test and training sessions. 108 A 1-minute rest was given between attempts. Subjects were instructed to push against the 109 bar as fast as hard as possible after the cue “Ready, set, go!” The testing procedure 110 followed the protocol described elsewhere 12. External forces were collected with a 111 dynamometric platform (F-500, Ergotech, Murcia, Spain) at a sampling rate of 1,000 Hz 112 and processed with specific software (T-Force System, Ergotech, Murcia, Spain). The 113 following parameters were assessed during each trial: i) MIF; ii) maximal rate of force 114 development (RFDmax), which was calculated as the maximal slope of the force-time 115 curve in 20 ms time intervals; and iii) the average tangential slope of the force-time curve 116 obtained over different time intervals (50, 100, 200, and 400 ms from the onset of force 117 production: RFD0-50, RFD0-100, RFD0-200, RFD0-400, respectively). The average value of 118 each variable in the two attempts was recorded for further analysis. 119 Progressive loading test 120 A detailed description of the BP testing protocol has been provided elsewhere 12. The 121 setting was similar to that described in the “Maximal isometric test” section. The 122 participants were instructed to perform the eccentric phase in a controlled way and to 123 maintain a static position for ~1 second at the end of this phase (i.e., bar resting on the 124 chest) for more reproducible and reliable measurements 19. Then, the bar was lifted at 125 maximal velocity upon hearing the order of the researchers. It was not allowed to throw 126 the bar at the end of the concentric phase. A linear velocity transducer (T-Force System 127 Ergotech, Murcia, Spain) was used for recording the mean propulsive velocity (MPV) of 128 6 every repetition 20.. An average of 6.1 ± 1.1 increasing loads were used for each subject. 129 Only the fastest repetition with each load was considered for subsequent analyses. The 130 initial load was set at 20 kg and progressively increased until the attained MPV was <0.30 131 m∙s-1 (~90% 1RM) 5. The 1RM was individually predicted from MPV attained against 132 the heaviest load of the test. The following variables were used for analysis: a) 1RM; b) 133 maximal unloaded velocity (V0), performed under free-weight conditions, against a rigid 134 plastic bar weighting <0.2 kg; c) average MPV attained against all absolute loads common 135 to Pre- and Post-training (AV); d) average MPV attained against absolute loads that were 136 lifted faster than 0.8 m∙s-1 at Pre-training (AV>0.8); and e) average MPV attained against 137 absolute loads that were lifted slower than 0.8 m∙s-1 at Pre-training (AV<0.8). These 138 outcome variables were chosen to analyze the extent to which the distinct training 139 interventions affected the different parts of the load-velocity relationship. 140 Fatigue test 141 Five minutes after the progressive loading test, the subjects were required to complete as 142 many repetitions as possible until reaching muscle failure with a load corresponding to 143 70% 1RM at Pre-training. The execution technique and devices used were those described 144 in the “Progressive loading test” section. This test was repeated at Post-training with the 145 same absolute load as in the baseline examination. The following variables were used for 146 further analyses: a) maximal number of repetitions to failure (MNR); and b) average MPV 147 attained against the same number of repetitions to Pre-training and Post-training (AV- 148 MNR). 149 EMG signal acquisition 150 After skin preparation, a surface EMG electrode was placed over the triceps brachii 151 muscle of the right arm according to SENIAM guidelines 21. A detailed description of this 152 test has been provided elsewhere 12. EMG signals were recorded during the isometric and 153 the progressive loading test using a parallel bar, bipolar surface electromyographic sensor 154 wireless TrignoTM EMG system, with a bandwidth filter between 20 and 450 Hz ± 10% 155 (Delsys Inc, MA, USA). The baseline noise was <5μV peak-to-peak and the sampling 156 rate was 1,926 Hz. The raw data from the EMG were stored in digital format using EMG 157 works Acquisition software (Delsys Inc, MA, USA) and smoothed by root mean square 158 (RMS) calculation using a moving window of 100 ms with an overlap of 99 ms. The RMS 159 was calculated for: a) the two attempts during the isometric test, b) the fastest repetitions 160 7 with each absolute load in the progressive loading test, and c) every repetition during the 161 fatigue test. RMS values were normalized to the RMS obtained from maximal isometric 162 contractions at the Pre-training. 163 Resistance training program 164 The descriptive characteristics of the RT program are presented in Table 1. The execution 165 technique and devices used were those described in the “Progressive loading test” section. 166 The four groups trained the BP exercise twice a week (training sessions being 48-72 h 167 apart) for 8 weeks using the same relative intensity (increased from 40% to 55% 1RM), 168 number of sets (3), and inter-set recovery (4 minutes), but differing in the VL threshold 169 allowed in each set. The VL0 group performed only one repetition per set (VL of 0%), 170 whereas the other groups (VL15, VL25, and VL50) stopped their set when the 171 corresponding VL threshold (15%, 25%, and 50% of VL, respectively) was achieved. 172 Therefore, the training groups differed in the number of repetitions performed per set and 173 the total number of repetitions completed during the training session (Table 1). Relative 174 loads were determined from the individual load-velocity relationship obtained from the 175 progressive loading test for each subject (R2 = 0.993 ± 0.007). Hence, the absolute load 176 (kg) was individually adjusted for each subject according to the individual velocity (± 177 0.03 m∙s-1) associated with the %1RM that was set for that session. Once the load (kg) 178 was adjusted, it was maintained for the 3 training sets. Subjects received immediate 179 velocity feedback while being encouraged to perform each repetition at maximal velocity. 180 The warm-up was standardized for all training groups, as follows: 5 minutes of jogging 181 at a self-selected easy pace, 2 minutes of joint mobilization exercises, a set of 6 BP 182 repetitions with 20 kg, followed by 2 sets of 6 and 4 repetitions with loads of 30% and 183 35% 1RM, respectively, for sessions 1-8 (in which the training load was 40% and 45% 184 1RM, respectively). An additional set of 3 repetitions with 45% 1RM was added for 185 sessions 9-16 (in which the training load was 50-55% 1RM). A 3-minute rest between the 186 warm-up sets was always used. The evolution of daily performance (estimated 1RM) was 187 measured from the fastest MPV attained with an absolute load in each training session 188 and from the individual load-velocity (R2 = 0.993 ± 0.007) relationship for each subject. 189 ***Insert Table 1 about here*** 190 Statistical analysis 191 8 Values are reported as mean ± standard deviation (SD). The sample size was calculated 192 using GPower (Version 3.1.9.2, Heinrich-Heine-Universität Düsseldorf, Düsseldorf, 193 Germany) introducing the following parameters: effect size (ES = 0.7 based on ES 194 observed in previous literature using a similar approach 12. Test-retest absolute reliability 195 was measured by the coefficient of variation (CV). Normality and homoscedasticity were 196 verified with Shapiro-Wilk and Levene’s tests, respectively. Data were analyzed using a 197 4 x 2 factorial ANOVA with Bonferroni´s post-hoc comparisons, using one between- 198 group factor (VL0 vs. VL15 vs. VL25 vs. VL50) and one within-group factor (Prevs. 199 Post-training). Relationships between changes in selected variables were analyzed using 200 Pearson's correlation coefficient (r). Statistical significance was established at the P ≤ 201 0.05 level. In addition, ES values were calculated using Hedge’s g on the pooled SD 22 202 using a purpose-built spreadsheet. The rest of the statistical analyses were performed 203 using SPSS software version 23.0 (SPSS Inc., Chicago, IL, USA). The dose-response 204 relationship between VL and RT-induced adaptations was assessed based on the ES 205 induced by each VL in the different training variables using a 2nd-degree polynomial 206 regression. Figures were designed using SigmaPlot 12.0 (Systat Software Inc, San Jose, 207 CA, USA) and GraphPad Prism version 8.0.0 for Windows (GraphPad Software, San 208 Diego, California USA). 209 RESULTS 210 The participation rate for all testing and training sessions was 100% in all groups. 211 Test-retest reliability values (CV values) were as follows: MIF (5.8%), RFDmax (16.0%), 212 RFD0-50 (21.9%), RFD0-100 (17.2%) RFD0-200 (10.5%), RFD0-400: (8.9%), MPV (5.9%), 213 and RMS (13.4%). No significant differences between groups were observed at Pre- 214 training for any of the variables analyzed (all P > 0.05). 215 Maximal isometric test 216 No significant group × time interactions were noticed (Table 2). Significant time effects 217 were observed for MIF (P<0.001), RFDmax, RFD0-50, RFD0-100, and RFD0-200 (P < 0.001 – 218 0.05). All groups showed significant improvements in MIF (P<0.05). The VL15 219 intervention induced significant gains in RFD0-50 and VL50 significantly increased RFD0- 220 200 (both P < 0.05). 221 ***Insert Table 2 about here*** 222 9 Progressive loading test and fatigue test 223 RT-induced adaptations in dynamic BP performance are reported in Table 3. No 224 significant group × time interactions were found. Significant time effects were observed 225 for all performance parameters analyzed (all P<0.001) except for V0, where any of the 226 groups induced significant gains. All groups showed significant enhancements in the rest 227 of the performance variables (i.e. 1RM, AV, AV<0.8, AV>0.8, MNR, and AV-MNR), 228 except the VL0 group in AV>0.8. Figure 1 depicts the relationships between VL and 229 gains (i.e., ES) in strength-related variables. 230 ***Insert Table 3 about here*** 231 ***Insert Figure 1 about here*** 232 233 EMG 234 No significant "group x time" interactions and time effects were observed for any of the 235 EMG variables analyzed (Figure 2). 236 ***Insert Figure 2 about here*** 237 Relationships between relative changes in strength performance variables 238 Table 4 shows the Pearson's correlation coefficients between individual relative changes 239 in strength performance variables. 240 ***Insert Table 4 about here*** 241 242 Training program 243 Descriptive characteristics of the training performed by the four groups are reported in 244 Table 1. The average of the fastest repetitions measured in each session, representing the 245 %1RM lifted in each training session, did not differ between groups. The mean velocity 246 (MPV all reps) attained during the training program decreased as the VL increased (P < 247 0.05). The training volume, and especially the repetitions performed at slow velocities 248 (i.e., 0.80 m·s-1), increased as the VL magnitude increased (Figure 3A). Figure 3B shows 249 the evolution of daily performance (expressed relative to the Pre-training values) in each 250 training session for all groups. 251 16 Figure 3. A) Number of repetitions performed in each velocity range, and total repetitions 471 completed during the training program by the four training groups. Between groups 472 significant differences (P < 0.05) with respect to: VL0: 0; VL15: 15, and VL25: 25. B) 473 Evolution of the estimated 1RM bench-press performance in each training session 474 expressed as a percentage of the initial Pre-training level for the four experimental 475 groups.. Data are mean ± standard deviation, N = 46. VL0: group that trained with a mean 476 velocity loss (VL) of 0% in each set (n =10); VL15: group that trained with a VL of 15% 477 (n =13); VL25: group that trained with a VL of 25% (n = 11); VL50: group that trained 478 with a VL of 50% (n = 12). 479 480