The physical preparation of any athlete requires an

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1 CHANGES IN MAXIMAL STRENGTH, VELOCITY, AND POWER AFTER 8WEEKS OF TRAINING WITH PNEUMATIC OR FREE WEIGHT RESISTANCE DAVID M. FROST, 1 STEFANIE BRONSON, 1 JOHN B. CRONIN, 2,3 AND ROBERT U. NEWTON 3 1 Faculty of Kinesiology and Physical Education, University of Toronto, Toronto, Ontario, Canada; 2 School of Sport and Recreation, Sport Performance Research Institute New Zealand, Auckland, New Zealand; and 3 School of Exercise and Health Sciences, Edith Cowan University, Joondalup, Australia ABSTRACT Frost, DM, Bronson, S, Cronin, JB, and Newton, RU. Changes in maximal strength, velocity, and power after 8 weeks of training with pneumatic or free weight resistance. J Strength Cond Res 30(4): , 2016 Because free weight (FW) and pneumatic (PN) resistance are characterized by different inertial properties, training with eir resistance could afford unique strength, velocity, and power adaptations. Eighteen resistance-trained men completed baseline tests to determine ir FW and PN bench press 1 repetition maximum (1RM). During FW session, 4 explosive repetitions were performed at loads of 15, 30, 45, 60, 75, and 90% 1RM to assess force, velocity, and power. Participants were n assigned to a FW or PN training group, which involved three 90-minute sessions per week for 8 weeks. Both intervention groups completed identical periodized programs with exception of resistance used to perform all bench press movements. Free weight participants significantly increased ir FW and PN 1RM (10.4 and 9.4%), and maximum (any load) force (9.8%), velocity (11.6%), and power (22.5%). Pneumatic-trained participants also exhibited increases in FW and PN 1RM (11.6 and 17.5%), and maximum force (8.4%), velocity (13.6%), and power (33.4%). Both interventions improved peak barbell velocity at loads of 15 and 30% 1RM; however, only PN-trained individuals displayed improvements in peak force and power at se same loads. Training with PN resistance may offer advantages if attempting to improve power at lighter relative loads by affording an opportunity to consistently achieve higher accelerations and velocities (F = ma), in comparison with FW. Exploiting inertial properties of resistance, wher mass, elastic or PN, could afford an opportunity to develop mixed-method training strategies and/or elicit Address correspondence to David M. Frost, d.frost@utoronto.ca. 30(4)/ Ó 2015 National Strength and Conditioning Association unique neuromuscular adaptations to suit specific needs of athletes from sports characterized by varying demands. KEY WORDS air resistance, athlete, bench press, force, periodization INTRODUCTION The physical preparation of any athlete requires an appreciation for loads, speeds, and movement patterns fundamental to ir sport. As such, re may be value in knowing how or why a particular mode of resistance (e.g., mass, elastic, and pneumatic [PN]) could afford an adaptation that would orwise be impossible, or at least difficult to achieve with anor modality (13). Simply because mass reflects type of resistance an athlete moves on a day-to-day basis (i.e., ir bodyweight), does not imply that it should be only method of loading used during training. For example, dissimilar inertial properties between free weight (FW) and PN resistance dictate that each resistance will offer a unique stimulus (11) and, refore, may be more suitable to achieve a particular response or adaptation to training. As an athlete progresses from phase to phase through a periodized program, coaches will modify repetitions, sets, loads, speeds, rest periods, and/or movement patterns in a linear or nonlinear fashion (4,24,26,27). However, rarely is re consideration given to changing mode of resistance, despite fact that transfer of training could be limited by inertial properties of loads being used. Free weight resistance, which comprises only mass, exhibits momentum once in motion; hence, reason we are able to leave ground when jumping. But this is also reason why athletes are pulled from bench when performing a FW bench press as quickly as possible. Once sufficient forces are applied to initiate motion, mass gains momentum, which reduces muscular effort required to complete repetition over range of movement (11). Furrmore, if load is not thrown, performer may need to actively decelerate barbell during latter half of pressing phase (i.e., produce a force in opposition to direction of travel (25)). 934

2 The popularity of band and PN resistance stems largely from fact that each modality offers a load comprisingminimal mass and refore less inertia and momentum in comparison with that of FW (13). Instead, external loads are created through band tension or air resistance, respectively, which may afford an opportunity to elicit unique training adaptations. For instance, higher accelerations can be achieved with external loads comprising less mass if same force is produced (i.e., F = ma), which suggests that eir modality could offer unique velocity-specific adaptations to training, or provide a means by which a particular coaching objective could be achieved in a safer simpler fashion. However, re may also be instances where FW resistance does afford an ideal stimulus and perhaps should be viewed as most appropriate method of external loading (e.g., increasing 1 repetition maximum [1RM] strength). Against this backdrop, our primary objective was to examine strength, velocity, and power adaptations exhibited by resistance-trained men in response to 2 eight-week periodized exercise programs, differing only in type of resistance (FW or PN) used to perform heavy and explosive bench press efforts. It was hyposized that training with PN resistance would elicit larger improvements in peak velocity and power at light loads, whereas training with FW resistance would be more conducive to increasing peak force and maximal strength. METHODS Experimental Approach to Problem Resistance-trained men (3 15 years of experience) completed 2 baseline tests to determine ir FW and PN bench press 1RM. During FW testing session, participants also performed sets of 4 explosive bench press repetitions at loads of 15, 30, 45, 60, 75, and 90% 1RM. A force plate and linear potentiometer were used to measure ground reaction force and barbell displacement, respectively. On completing baseline tests, participants were assigned to one of 2 training groups (FW or PN), each matched for 1RM strength. Individuals attended three 90-minute whole-body resistance training sessions each week over a 2-phase 8-week period. Each phase comprised of a strength (80 1RM) and power (30 45% 1RM) component. Both intervention groups completed identical training programs with exception of type of resistance used to perform all bench press movements. Once 8-week training program was completed, baseline tests were repeated. Participants FW and PN 1RM, and peak force, velocity, and power at each submaximal load were computed before and after training. Subjects Eighteen men with at least 3 years of resistance training experience and a maximum bench press greater than ir body weight volunteered to participate in this investigation. To detect a 10% difference with 80% power and a significance level of, it was estimated that 16 participants would be needed (8 in each group). At time of testing, all men reported ir resistance training frequency to be a minimum of 2 times per week. Their mean (6SD) age, height, body mass, and resistance training experience were 23.9 (64.1) years, 1.79 (60.07) m, 79.8 (611.8) kg, and 5.0 (63.8) years, respectively. The University s Office of Research Ethics approved investigation, and all participants gave ir informed consent before data collection began. The study conforms to Code of Ethics of World Medical Association (approved by ethics advisory board of Swansea University) and required players to provide informed consent before participation. Instrumentation Free weight testing was performed inside a standard power rack. A bench was secured to center of a portable force plate (Quattro Jump Model 9290AD, Kistler, Switzerland) using a customized steel bracket. Foot pegs extending horizontally from end of bracket were used to accommodate various foot positions; refore, participants were not obliged to place ir feet on bench or floor. Before each testing session, force plate was calibrated with known weights and n zeroed with weight of participant and bench. A linear position transducer (PT5A- 150, Celesco, Chatsworth, CA, USA) with a signal sensitivity of mv$v 21 per millimeter was secured to a wood plank and positioned approximately 1.5 m directly above center of barbell. The vertical position of barbell was zeroed before each repetition, and initial displacement was recorded as m. Displacement and force data were A/D converted using a 16-bit data acquisition board (PCI- 6220; National Instruments, Sydney, NSW, Australia) and sampled simultaneously at 2,000 Hz. Labview software (Version 8.1; National Instruments, Austin, TX, USA) was used to acquire, display, and store all data for furr analyses. A squat rack instrumented with PN technology (Keiser, Fresno, CA, USA) was used for all PN testing and training purposes. Resistance was generated through an air compressor (Keiser) and adjusted by pressing foot pedals located at base of rack. The rack permitted a traditional bench press to be performed with a PN load while maintaining all 6 permissible movement directions. Resistance was applied by way of cables that extended from a pulley system free to move in horizontal direction along tracks at base of rack. The cables were n attached to a lightweight 2.5 kg barbell (Keiser), designed specifically for use with PN squat rack. The grip diameter was identical to that of a standard Olympic barbell. A digital screen displayed PN load (in pounds) as calculated by software within system. Through pilot testing, it was determined that PN load could be accurately and reliably set at a predetermined resistance (e.g., 588N equals 60 kg) such that comparisons could be made with a FW load. This was confirmed for all testing trials through force plate data. VOLUME 30 NUMBER 4 APRIL

3 Training With Pneumatic or Free Weight Resistance Experimental Protocol Each participant attended 1 familiarization session and 2 testing sessions separated by a minimum of 72 hours. The familiarization protocol consisted of 6 sets of 4 repetitions with PN resistance using loads of 20, 30, 40, 50, 60, and 70% of an estimated FW 1RM, followed by 3 sets of 4 explosive FW efforts using absolute loads of 20, 40, and 60 kg; each separated by 3 minutes. Participants were allowed to selfselect ir grip and foot width; however, distances were measured so that y could be used throughout testing. During FW testing session, participants completed a 1RM test and 6 sets of 4 repetitions at loads equating to 15, 30, 45, 60, 75, and 90% of previously determined 1RM. Participants were able to complete all repetitions. Ten minutes of rest was given between 1RM test and commencement of submaximal load testing. Three to seven days after FW testing protocol, participants returned to determine ir PN 1RM. Each participant s 1RM was determined using a protocol similar to that described by Doan et al. (10). Participants were asked to perform 4 repetitions at 60% of ir estimated 1RM, 3 repetitions at 70% 1RM, 2 repetitions at 80% 1RM, and 1 repetition at 90% 1RM. These 4 sets were followed by a maximum of 5 attempts to identify ir actual 1RM. Three minutes rest was given between each set. All 1RM testing was conducted using a stretch shortening cycle (SSC) movement; however, in cases where barbell contacted chest or failed to come within 0.05 m of chest, it was disregarded and repeated after an additional 3 minutes. Subjects were encouraged to move barbell as quickly as possible but required to keep ir hips and back on bench and ir feet on floor (force plate). The PN 1RM was determined using same protocol; however, PN load was recorded to reflect total resistance as displayed on digital indicator and mass of lightweight barbell and collars (3 kg). Recorded loads were compared with force plate data to ensure accuracy. All PN loads were set at a rack height of 0.64 or 0.74 m (distance from pulley to bottom of cable attachment) by increasing resistance, as unpublished work from our laboratory has shown that this setup increases degree of linearity for progressively heavier loads. After 10 minutes of passive recovery, participants were asked to perform 2 single repetitions with lightweight barbell (Keiser) to establish a maximum barbell velocity. After FW 1RM test, 4 single repetitions, separated by 1 minute, were performed as explosively as possible at loads of 15, 30, 45, 60, 75, and 90% 1RM. Loads were assigned in an ascending order, each separated by 3 minutes rest, so that a systematic comparison could be made across participants. Any repetition that contacted chest or failed to come within 0.05 m of chest was disregarded and repeated after an additional 1 minute. Participants were required to keep ir hips and back on bench and feet on floor. On completion of baseline testing, each participant was assigned to a FW or PN training group, each matched for height, body mass, and FW 1RM. The intervention consisted of an 8-week periodized resistance training program designed to improve whole-body strength and power. An emphasis was placed on whole-body exercise for 2 reasons: (a) to accommodate needs/interests of participants so that y did not feel inclined to perform additional training outside of study setting and (b) to control all resistance training exposures over 8-week period. Participants attended three 90-minute sessions (including warm-up and cool down) each week and were coached by a National Strength and Conditioning Association accredited strength and conditioning specialist. With exception of resistance used to perform bench press, both training groups completed identical programs. The 8 weeks were separated into 2 phases, each including a strength (80 1RM) and power (30 45% 1RM) component (Table 1). For example, in phase 1, participants performed a heavy bench press on day 1 (4 3 4 repetitions at approximately 90% 1RM) and an explosive bench press on day 2 (6 3 3 repetitions at approximately 35% 1RM). Participants in FW group used ballistic repetitions (i.e., barbell was thrown at end of ascent phase) to perform ir power efforts. These repetitions were performed inside a standard power rack instrumented with a magnetic brake (Fitness Technology, Adelaide, Australia) that prevented any downward motion of barbell after point of release. However, all ballistic bench press repetitions did include an eccentric phase before being thrown (i.e., countermovement) so that all participants could make use of SSC. Individuals in PN group used specialized rack and were instructed to move load as fast as possible. During weeks 4 and 8, training volume was reduced to provide participants with a period of active recovery. Details of training program are outlined in Table 1. Participants were required to attend a minimum of 20/24 training sessions to complete FW and PN posttests, which began within 1 week of final training session. The new FW 1RM was used to assign loads for submaximal posttests so that pre-post comparisons could be used to assess wher exposure to PN resistance altered force-, velocity-, power-load relationship. However, it must also be noted that several factors such as nutrition, sleep, and time of day may have influenced determination of participants posttraining 1RM. For duration of testing and training, participants were asked to refrain from performing any formal resistance exercise on ir own or making changes to ir nutritional intake. Data Analyses The raw displacement data were filtered with a fourth-order, zero-phase low-pass Butterworth filter (10 Hz) and differentiated to calculate barbell velocity. Force data were filtered at 100 Hz to remove any high-frequency noise. Initiation of descent phase was defined as first instance of 936

4 VOLUME 30 NUMBER 4 APRIL TABLE 1. The 8-week training program completed by all participants.* Day 1 1A. Back squat (explosive) Phase 1 Phase 2 Week 1 Week 2 Week 3 Week 4 Week 5 Week 6 Week 7 Week 8 ;30% and 6, 120 s between 6 and 8 2A. Bench press 4 3 4@ (heavy) 2B. Romanian deadlift 4 3 4@ 2C. Rotational med ;30% ;35% @ ;35% @ ;40% + 2 ;40% + 2 ;45% @ ;45% @ 4 3 4@ 4 3 4@ 2 3 3@ 2 3 2@ ;92.5% 4 3 4@ 4 3 4@ 2 3 3@ 2 3 2@ ;92.5% ;92.5% ;92.5% ;92.5% ball Rest: 60 s between exercises, 90 s 3A. Horizontal pull-up B. Overhead lunge C. Abdominal pike exercises, 60 s Day 2 1A. Bench press (explosive) 1 and 6, 120 s between 6 and 8 2A. Wide pull-up (heavy) ;30% ;30% ;35% @ ;35% @ ;40% + 2 ;40% + 2 ;45% @ ;45% @ 4 3 4@ 4 3 4@ 4 3 4@ 2 3 3@ 2 3 2@ ;92.5% 2B. Hamstring curl C. Dynamic side bridge (continued on next page)

5 938 Rest: 60 s between exercises, 90 s 3A. Single leg squat B. 1 Arm standing press 3C. Med ball crunch exercises 60 s Day 3 1A. Neutral pull-up (explosive) 1 and 6, 120 s between 6 and 8 2A. Front squat (heavy) 2B. Push-up (weighted) 2C. AIS hip flexor stretch Rest: 60 s between exercises, 90 s 3A. 1 arm rotational press 3B. 1 arm 1 leg ;75% ;75% ;75% @ ;75% @ ;75% + 2 ;75% + 2 ;75% @ ;75% @ 4 3 4@ 4 3 4@ 4 3 4@ 2 3 3@ 2 3 2@ ;92.5% dumbbell row 3C. Hanging leg raise exercises, 60 s *The pneumatic group used a specialized rack to perform heavy and explosive bench press. The free weight group s explosive bench press was performed ballistically inside a rack equipped with a magnetic brake. Exercises described by same number (e.g., 1) and different letters (A, B, or C) were performed in sequence. For example, on day 1, bench press (2A), Romanian deadlift (2B), and med ball throw (2C) were performed in succession (e.g., 1 set of each before beginning set 2). Training With Pneumatic or Free Weight Resistance

6 TABLE 2. The pretraining and posttraining mean (SD) FW and PN 1 repetition maximum (kg), and maximum dynamic force, velocity, and power for individuals participating in FW and PN intervention.* 1 Rep maximum (kg) Maximum Group Test Free weight PN Force (N) Velocity (m$s 21 ) Power (W) FW Pre (20.0) (15.7) 1,259 (300) 4.23 (0.71) 1,291 (396) Post (18.0) (15.6) 1,382 (258) 4.72 (0.38) 1,582 (535) p Effect size PN Pre (18.4) 97.9 (16.7) 1,166 (209) 4.06 (0.88) 1,005 (257) Post (22.6) (20.8) 1,249 (259) 4.60 (0.48) 1,341 (359) p 0.001, Effect size FW/PN Inference Possibly trivial Likely PN Possibly FW Possibly trivial Possibly PN *FW = free weight; PN = pneumatic. p values and effect sizes are listed for each within-group pre-post comparison. The qualitative inference provided for each variable describes likelihood of a between-group intervention effect (possibly, 40 75%, likely,.75%). negative displacement, whereas end of ascent phase was defined as point at which force became zero or maximum barbell displacement. Using peak displacement alone to define end of ascent phase will underestimate mean force and power for submaximal loads if a period of negative work exists (12). Only ascent phase was analyzed. Peak velocity, force, and power (force 3 velocity) were computed using average of 4 repetitions. Pilot testing was performed to determine wher best repetition or average measurement should be included in analyses. Because data were highly variable (i.e., fastest rep was not same in every instance), average of 4 trials was thought to offer a much more stable and true representation of actual change posttraining. The peak barbell velocity and maximum dynamic force were defined as peak velocity from two 2.5 kg explosive repetitions and peak force from FW 1RM, respectively. Data from ascent phase were also expressed as a percentage of total barbell displacement so that pretraining and posttraining power-displacement profiles could be compared. Statistical Analyses Participants FW and PN 1RM, maximum (any load) dynamic force, barbell velocity and power, and peak velocity, force, and power at each submaximal FW load were computed. A 2-factor mixed-model analysis of variance was used to examine independent effects of group (FW and PN) and time (pre and post) on each dependent measure. Holm-Sidak post hoc comparisons were used to examine differences. Statistical significance was set at an alpha level of p # Effect sizes (ESs) were also computed to describe pre-post differences in each dependent measure for both training groups. The strength of ES was interpreted using general guidelines offered by Cohen (8), whereby magnitudes of 0.2, 0.5, and 0.8 corresponded to small, moderate, and large changes, respectively. The pre-post changes exhibited by each group were compared using magnitude-based inferences derived from p-values and effect statistics of an independent t-test (15). Qualitative descriptions of each inference were based on scale recommended by Hopkins (15): most unlikely,,0.5%; unlikely, 5 25%; possibly, 25 75%; likely, 75 ; very likely, %; most likely,.99.5%. RESULTS Four participants (3 FW, 1 PN) failed to meet attendance requirements and were removed from analyses. Given potential influence of dissimilar 1RMs at baseline, between-group comparisons are described using mechanistic inferences only. Free-Weight Trained After 8 weeks of training, participants increased (p # 0.05) ir FW and PN 1RM by 11.6 kg (10.4%, ES = 0.61) and 10 kg (9.4%, ES = 0.63), respectively (Table 2). Significant increases were also seen in maximum dynamic force (9.8%, ES = 0.44), peak barbell velocity (11.6%, ES = 0.87), and peak power (22.5%, ES = 0.62). Although participants improved ir FW and PN 1RM, FW training did not produce an increase in peak force at any submaximal load between 15 and 90% 1RM (Figure 1). Peak velocity significantly increased at 15% and 30% 1RM (ES.1.15); however, at 60% 1RM, it was found to be lower posttraining (ES = 1.65) (Figure 1). A significant increase in peak power was only noted at 45% 1RM (ES = 0.69) (Figure 1). Pneumatic Trained Participants who performed 8 weeks of bench press training with PN resistance exhibited significant increases of 11.8 kg VOLUME 30 NUMBER 4 APRIL

7 Training With Pneumatic or Free Weight Resistance Figure 1. The peak force (A), velocity (B), and power (C) exhibited by participants who trained with FW or PN resistance. Data are presented for relative loads of 15, 30, 45, 60, 75, and 90% 1RM before and after 8-week interventions. The superscript letters above each load denote a significant (p # 0.05) posttraining change (FW; PN). Asterisks (*) reflect size of effect (*an effect size between 0.5 and 0.8, whereas **an effect size above 0.8). The qualitative inference listed above each load comparison describes likelihood of a between-group intervention effect (possibly, 40 75%, likely,.75%). FW = free weight; PN = pneumatic; 1RM = 1 repetition maximum. 940

8 Figure 2. Pretraining and posttraining power-displacement profiles for strongest pneumatic (left side) and free weight (right side) trained participant at loads of 15, 30, and 45% 1RM. The data presented reflect average of 4 repetitions performed at that load. 1RM = 1 repetition maximum. (11.6%, ES = 0.57) and 17.1 kg (17.5%, ES = 0.91) in ir FW and PN 1RM, respectively (Table 2). Similar to ir FW counterparts, significant increases were also seen in ir maximum dynamic force (8.4%, ES = 0.35), peak barbell velocity (13.6%, ES = 0.77), and peak power (33.4%, ES = 1.08). In comparison with baseline tests, peak force achieved posttraining was significantly higher (ES = 0.92) when using 15% 1RM FW load (Figure 1). Similar to FW trained group, peak velocity was significantly higher at 15 and 30% 1RM (ES.0.58) and was also found to decrease (ES = 1.47) at 60% 1RM (Figure 1). Peak power was significantly higher posttraining at each load between 15 and 45% 1RM (ES.0.83) (Figure 1). Between-Group Comparisons No between-group differences were noted in pre-post improvement in FW 1RM or peak barbell velocity (possibly trivial,.37%). Training with PN resistance may have afforded a superior opportunity to improve PN 1RM (likely, 87%) and peak power (possibly, 40%), whereas FW program may have provided a better stimulus to increase maximum dynamic force (possibly, 68%). However, with light loads, PN intervention may have been a superior training stimulus to improve peak force (e.g., 85% likely to see superior benefit of PN resistance with a load of 15% 1RM; Figure 1). Eight weeks of PN training may have also provided a better opportunity to improve peak power, although advantage seems limited to lightest loads tests. Above 60% 1RM, FW intervention may have been better suited to improve peak power (Figure 1). A group effect was also seen with velocity PN training may have provided an advantage with light loads, but FW program seems to have been abler to improve peak velocity with loads above 60% 1RM. VOLUME 30 NUMBER 4 APRIL

9 Training With Pneumatic or Free Weight Resistance Figure 3. Pretraining and posttraining power-displacement profiles for strongest pneumatic (left side) and free weight (right side) trained participant at loads of 60, 75, and 90% 1RM. The data presented reflect average of 4 repetitions performed at that load. 1RM = 1 repetition maximum. Representative power-displacement profiles for PN and FW participants are presented in Figures 2 and 3. Because subtle differences in shape of participants profiles would mask effect of training (i.e., maximums and minimums did not align when normalized by barbell displacement), pretraining and posttraining data for strongest participant from FW (pre and post FW 1RM of 140 and 150 kg) and PN (pre and post FW 1RM of and 155 kg) groups are presented. The PN trained individual exhibited substantial changes during first half of ascent phase with loads of 15, 30, and 45% 1RM but failed to display similar improvements when load was furr increased. In contrast, most substantial adaptations exhibited by FW trained participant appeared during latter half of ascent phase, and to a much greater extent than his PN counterpart when performing with 3 highest loads. DISCUSSION The primary objective of this longitudinal training study was to examine strength, velocity, and power adaptations exhibited by resistance-trained men in response to 8 weeks of exercise using eir FW or PN resistance. Interestingly, despite performing all bench press movements with one type of resistance throughout training, participants in both groups significantly increased ir FW (10.4 and 11.6% for FW and PN groups) and PN 1RM (9.4 and 17.5%) posttraining. Limiting participants exposure to a particular type of resistance did not seem to impede potential strength-oriented 942

10 adaptations that could be achieved using eir training modality, as group mean improvements were of a similar magnitude to those reported previously (22 24,27). In fact, largest posttraining FW 1RM improvement was exhibited by a PN-trained participant ( kg), which supports notion that type of resistance used while training may not be needed to mimic that used during testing to maximize strength-oriented adaptations (21). As was suggested by Anderson et al. (1), it is also possible that using a combination of 2 resistances would have provided an even more favorable strength-oriented stimulus in comparison with using eir resistance alone if potential disadvantages of one resistance type could be accommodated by advantages of or. For example, during a FW bench press sufficient force must be produced to overcome inertia and accelerate barbell upwards; however, this also serves to increase barbell s momentum and reduce muscular effort required through midrange of motion (20). The use of pneumatics (or bands) will negate influence of momentum and thus provide an opportunity to engrain a coordination strategy that is better suited to maintaining a consistent muscular effort throughout range of motion (13). Given participants posttraining force, velocity, and power adaptations to each submaximal load, and unique physical demands of most sports, re may also be instances when a specific response would be better achieved by using a particular resistance. After 8 weeks of training, both groups improved ir 15 and 30% 1RM peak barbell velocity, but only PN-trained participants exhibited a corresponding increase in peak force. Since a similar increase in force was not exhibited at loads of 45 90% 1RM, this implies that individuals who trained with PN resistance were able to produce higher relative forces (% 1RM) posttraining when using lighter loads. Furrmore, because highest forces during a bench press are typically produced in-between or immediately after transition from descent to ascent phase when barbell acceleration is highest (7), observed increases in peak force could also reflect an improved rate of force development (RFD). Stevenson et al. (29) proposed that strength and conditioning professionals should consider using elastic resistance to improve RFD, which like PN resistance imposes a demand that is not influenced by inertia and momentum. Having an opportunity to train for 8 weeks with pneumatics, whereby higher velocities can be achieved consistently in a comparison with an equivalent load with FW (11), may have been more conducive to improving participants RFD. However, given evidence to suggest that performers intent to move quickly may be more important than ir actual movement speed (5,19), additional research is needed to substantiate this contention. Lending furr support for notion that type of resistance used while training could impact extent to which a specific adaptation is achieved at a submaximal load, only PN-trained participants exhibited significant increases in peak power at loads of 15 45% 1RM. Although small sample size of both groups may have biased se findings, viewed in combination with dissimilar powerdisplacement profiles of strongest FW- and PN-trained participants, each resistance may provide a unique training advantage for specific populations and/or objectives. For example, training load(s) needed to maximize power output for bench press and squat have been studied extensively in an attempt to identify a training stimulus that could elicit results outside of weight room environment (i.e., transfer to sport performance) (2,3,9,18). However, based on findings of this investigation, and those of ors e.g., (6,11,14,17,29), both magnitude of performers power output and manner in which it is produced (i.e., coordination) is likely influenced by type of resistance used during training. As such, it may be possible to change load(s) at which an individual produces ir highest power outputs (16,28), which could be of particular benefit for athletes who participate in sports characterized by high speeds and light to modest external loads (e.g., baseball, basketball). In se instances, it may also be advantageous to first identify loads and/or speeds that best characterize desired adaptations, so that an appropriate training stimulus (load, speed, and resistance) can be selected, rar than computing or choosing an optimal load for each individual based on ir current abilities. In this study, strongest PN-trained individual (pre and post) exhibited posttraining FW adaptations that resembled what would be expected from someone who had trained with a resistance characterized by little momentum and inertia; substantial changes in power output were seen during first half of ascent phase with light loads (i.e., 15 45% 1RM). In contrast, strongest FW-trained individual showed marked improvements during second half of ascent phase with loads of 60 90% 1RM, which highlights potential benefit of strategically choosing resistance type that best suits intended adaptation. The utility of block and undulating periodization models, whereby volume and intensity of training are progressed in a linear and nonlinear manner, respectively, are often compared when investigating most favorable training stimulus to improve strength and power in highly trained athletes (4,24,26,27). However, results of this investigation lend support to notion that perhaps type of resistance used while training should be considered as well. Pneumatic, band, and FW resistance are each characterized by unique mechanical properties that will influence training stimulus and thus performers adaptations. As such, for purpose of improving an individual s speed, strength, power, endurance, and/or whole-body coordination and control, re is likely merit in exploring potential benefit of acute and long-term training strategies that exploit advantages of specific resistance(s). PRACTICAL APPLICATIONS When designing a periodized program to improve athletes strength, speed, power, and or whole-body coordination and VOLUME 30 NUMBER 4 APRIL

11 Training With Pneumatic or Free Weight Resistance control, consideration should be given to type of resistance(s) that will be used while training. In addition to changing reps, sets, loads, speeds, rest periods, and/or movement patterns to elicit a particular adaptation, exploiting mechanical properties of resistance(s) (e.g., FW, elastic, and PN) could provide an opportunity to impose a stimulus and/or achieve an objective that would orwise be challenging to accomplish. The results of this study are that while both FW and PN resistance can be used to increase maximal strength, velocity, and power of experienced performers, training with PN resistance may have helped to facilitate unique force, velocity, and power adaptations when performing with lowest relative loads. Because PN resistance is characterized by minimal mass and momentum, performers can achieve higher velocities while performing with an equivalent load and will be forced to maintain a consistent muscular effort throughout range of motion. However, absence of mass and momentum could also make FW (or a combination of 2 resistances) a better option to elicit high force related adaptations, as was seen by among free weight trained participants above loads of 60% 1RM. In summary, having an appreciation for potential advantages and limitations of each resistance type will provide coaches and researchers with an opportunity to develop mixed-method training strategies to suit specific needs of athletes who participate in sports with different force-, velocity-, and movement-related demands. REFERENCES 1. Anderson, CE, Sforzo, GA, and Sigg, JA. The effects of combined elastic and free weight resistance on strength and power in athletes. 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