Comparison of the Acute Metabolic Responses to Traditional Resistance, Body-Weight, and Battling Rope Exercises

Abstract

Ratamess, NA, Rosenberg, JG, Klei, S, Dougherty, BM, Kang, J, Smith, CR, Ross, RE, and Faigenbaum, AD. Comparison of the acute metabolic responses to traditional resistance, body-weight, and battling rope exercises. J Strength Cond Res 29(1): 47–57, 2015—The purpose of this study was to quantify and compare the acute metabolic responses to resistance exercise protocols comprising free-weight, body-weight, and battling rope (BR) exercises. Ten resistance-trained men (age = 20.6 ± 1.3 years) performed 13 resistance exercise protocols on separate days in random order consisting of only one exercise per session. For free-weight exercise protocols, subjects performed 3 sets of up to 10 repetitions with 75% of their 1 repetition maximum. For the push-up (PU) and push-up on a BOSU ball protocols, subjects performed 3 sets of 20 repetitions. For the burpee and PU with lateral crawl protocols, subjects performed 3 sets of 10 repetitions. For the plank and BR circuit protocols, subjects performed 3 sets of 30-second bouts. A standard 2-minute rest interval (RI) was used in between all sets for each exercise. Data were averaged for the entire protocol including work and RIs. Mean oxygen consumption was significantly greatest during the BR (24.6 ± 2.6 ml·kg⁻¹·min⁻¹) and burpee (22.9 ± 2.1 ml·kg⁻¹·min⁻¹) protocols. For the free-weight exercises, highest mean values were seen in the squat (19.6 ± 1.8 ml·kg⁻¹·min⁻¹), deadlift (18.9 ± 3.0 ml·kg⁻¹·min⁻¹), and lunge (17.3 ± 2.6 ml·kg⁻¹·min⁻¹). No differences were observed between PUs performed on the floor vs. on a BOSU ball. However, adding a lateral crawl to the PU significantly increased mean oxygen consumption (19.5 ± 2.9 ml·kg⁻¹·min⁻¹). The lowest mean value was seen during the plank exercise (7.9 ± 0.7 ml·kg⁻¹·min⁻¹). These data indicate performance of exercises with BRs and a body-weight burpee exercise elicit relatively higher acute metabolic demands than traditional resistance exercises performed with moderately heavy loading.

Introduction

Resistance training is a modality shown to increase several fitness components (¹⁷). Although many participants train for increased muscle strength, hypertrophy, endurance, power, and motor performance (^17,25), another primary goal for many trainees is to augment energy expenditure (EE) to target body fat reductions. Body fat reductions are predicated, in part, on acute EE during each training session and the additional EE seen during the recovery period after the training sessions. In addition to the muscle action (²⁰), intensity (^10,32), volume (^9,22), repetition velocity (^1,11,19), exercise sequence (^7,26), and rest interval (RI) length in between sets and exercises (^6,24,26), the amount of muscle mass recruited during each exercise has been shown to be a primary contributor to the acute metabolic responses (^{1,6,13,14,20,26,27,29}). Several studies have examined machine-based resistance exercises and circuit resistance training protocols (^{1,14,18,22,33}). However, only few studies have examined free-weight exercise protocols, and these have used different exercise intensities, volumes, and RI lengths. Thus, comprehensive studies examining many free-weight exercises are needed to better quantify the metabolic demands of resistance exercise.

Metabolic resistance training programs have become popular in recent years. These programs consist of traditional low-to-moderate intensity resistance exercises as well as body-weight movements and exercises using implements with short RIs. In addition, some trainers integrate other modalities (i.e., plyometrics, speed and agility drills) into the programs. A goal of these programs is to maximize muscle mass involvement to increase EE. Body-weight exercises such as burpees, planks, and push-up (PU) variations are commonly included but little is known concerning the acute metabolic demands of these exercises.

Rope training has increased in popularity in numerous areas from general health and fitness trainees to professional athletes. Battling ropes (BRs) are used for multiple purposes, that is, climbing, pulling, and suspension training. However, BRs are most commonly used for undulations, or wave training, to increase strength, endurance, and provide potent metabolic and cardiovascular responses (^3,21). Waves are generated through multiple movement patterns as the ropes are anchored at a fixed point. The length and diameter of the ropes, as well as the velocity and amplitude of the waves, are thought to govern exercise intensity (²¹). However, only one study (⁸) has examined BR exercise to date.

The primary purpose of this study was to quantify acute oxygen consumption and EE of 7 traditional free-weight resistance exercises and compare these responses to body-weight and BR exercises. A popular fitness trend is the combination of resistance training programs using free weights, strength implements, and body-weight exercises. Thus, our intent was to provide a comparative metabolic profile of these different modalities. It was hypothesized that exercises stimulating the largest amount of muscle mass would elicit the greatest acute metabolic responses.

Methods

Experimental Approach to the Problem

To examine the primary hypothesis of this investigation, subjects were tested for

and maximal strength on 7 free-weight exercises and subsequently performed 13 resistance exercise protocols (using various levels of muscle mass) consisting of only one exercise per session. Subjects performed 3 sets of up to 10 repetitions with 75% of 1 repetition maximum (RM) for the free-weight protocols. In addition, a few popular body-weight and BR exercises were examined to compare their metabolic demands to that of traditional resistance exercise performance. For the burpee and PU with lateral crawl protocols, subjects performed 3 sets of 10 repetitions. For the PUs on the floor and BOSU ball protocols, subjects performed 3 sets of 20 repetitions. For the plank and BR circuit protocols, subjects performed 3 sets of 30-second bouts. Two-minute RIs were used in between sets of all exercises. Metabolic and performance data were collected during each protocol under close supervision. This study design enabled us to systematically examine the influence of muscle mass involvement on acute exercise performance and metabolic responses during resistance exercise and compare their metabolic responses to various body-weight and BR exercises. The main objective was to assess the exercises in a manner commonly performed in practical settings. Thus, a standard intensity, volume, and RI length was used for the free-weight exercises. However, it is difficult to equate intensity of body-weight and BR exercises to that of free-weight exercises. Thus, we felt it important to base our comparisons of free-weight and non–free-weight exercises on methods of how these exercises are commonly used while attempting to maintain similar set durations.

Subjects

Ten healthy resistance-trained men (age range = 19 to 22 years old) agreed to participate in this study (Table 1). Each subject initiated the study in a trained state (i.e., were resistance training 2–4 days per week), were current or former athletes, and none were taking any medications such as anabolic steroids known to affect resistance exercise performance. Subjects underwent 1 week of familiarization (2–3 sessions) with study procedures before testing. Familiarization focused on subjects' ability to perform all of the exercises comfortably while wearing a respiratory mask. During this time, height was measured using a wall-mounted stadiometer, and body mass was measured using an electronic scale. Percent body fat was estimated through a 3-site skinfold test. The sites measured were the pectoral, anterior thigh, and abdominal skinfolds using methodology previously described (¹²). Body density was calculated using the equation of Jackson and Pollock (¹²), and percent body fat was calculated using the equation of Siri (³⁰). The same research assistant performed all skinfold assessments. This study was approved by The College of New Jersey's Institutional Review Board, and each subject subsequently signed an informed consent document before participation. No subject had any physiological or orthopedic limitations that could have affected exercise performance as determined by completion of a health history questionnaire.

Table 1: Descriptive characteristics.*

Strength Testing

One-repetition maximum strength was assessed for 7 free-weight resistance exercises using a standard protocol (^16,23). For each exercise, a warm-up set of 5–10 repetitions was performed using 40–60% of the perceived 1RM. After a 1-minute RI, a set of 2–3 repetitions was performed at 60–80% of the perceived 1RM. Subsequently, 2–4 maximal trials were performed to determine the 1RM with 2–3 minutes RI between trials. Maximal strength was determined for a maximum of 2 exercises per session separated by 24–48 hours. A complete range of motion and proper technique was required for each successful 1RM trial. For the bench press (BP), the bar was lowered until it touched the lower-to-mid sternum (with no “bouncing”) and was lifted to full elbow extension (with no excessive arching of the back). For the back squat (SQ), subjects descended with the bar on the rear shoulders until their upper thighs were parallel to the ground. At that point, a “lift” signal was given by a research assistant (to ensure proper depth), and the subject ascended to the starting position. For the barbell curl, subjects began the exercise with elbows fully extended and subsequently flexed the elbows in control without extending the hips or “swinging” the weight upward. For the bent-over barbell row (BOR), subjects initiated the exercise from the floor position and raised the bar until it touched the upper rectus abdominis. For the high pull (HP), subjects began the exercise from the “hang” position above the knees and rapidly lifted the barbell as fast as possible until it reached the level of the inferior sternum. A research assistant visually confirmed proper range of motion for the exercise. For the lunge, subjects began with the barbell on their rear shoulders, stepped forward with their dominant leg, descended until the rear knee touched the ground, and then returned to the starting position in 1 step. For the conventional-style deadlift (DL) (i.e., arms were positioned lateral to the legs with a grip width wider than stance width), subjects lifted the bar from the ground until full hip extension was achieved. Assessment of 1RM strength enabled calculation of the protocol loads (i.e., 75% of 1RM).

Maximal Aerobic Capacity (VO₂max) Testing

All subjects reported to the laboratory for maximal aerobic capacity testing. Subjects refrained from exercise for at least 24 hours before each testing session.

was assessed using a progressive multistage ramp protocol on a treadmill (MedGraphics ULTIMA Metabolic System; MedGraphics Corporation, St. Paul, MN, USA). It consisted of 2-minute stages at a speed of 6.0 mph with increments in percent grade of 2.5% per stage. All subjects were verbally encouraged to continue exercise until volitional exhaustion. Breath-by-breath

data were obtained, and

was determined by recording the highest measure. Gas analyzers were calibrated before each trial using gases provided by MedGraphics Corporation: (a) calibration gas: 5% CO₂, 12% O₂, balance N₂ and (b) reference gas: 21% O₂, balance N₂.

Resistance Exercise Protocols

All subjects reported to the Human Performance Laboratory at least 2 hours after their last standardized meal on 13 occasions separated by at least 24 hours. Subjects refrained from caffeine consumption for at least 24 hours before each testing session. Upon arrival, each subject was encouraged to drink water ad libitum to prehydrate and was subsequently fitted with a respiratory mask that was placed over the subjects' face, fastened, and carefully checked for proper sealing. Subjects were also fitted with a Polar heart rate (HR) monitor (Polar Electro, Inc., Woodbury, NY, USA) that was used to measure HR at baseline (BL), after each set of resistance exercise, and after each minute of recovery. Subsequently, each subject was positioned on a reclining chair and sat quietly for 15 minutes before measurement of BL HR and oxygen consumption (which was recorded over a 3-minute period). Breath-by-breath oxygen uptake (

) was measured throughout each protocol through a metabolic system (MedGraphics ULTIMA Metabolic System; MedGraphics Corporation). Gas analyzers were calibrated with gases of known composition before collection of metabolic data. Heart rate data presented are the mean protocol values obtained after each set of resistance exercise and after each minute of recovery. During the familiarization period,

data were collected on 2 occasions to determine test-retest reliability. Reliability was shown to be high for the metabolic measurements (R = 0.90).

Following BL measures, each subject performed a warm-up consisting of 3 minutes of stationary cycling and 1–2 light-to-moderate sets (40–60% of 1RM) of each free-weight exercise and 1 set of each body-weight and BR exercise. The protocols consisted of performing 3 sets of each exercise on separate days. Only one exercise was assessed during each session to avoid the potential of 1 exercise influencing the metabolic responses of a subsequent exercise (^7,26). For free-weight exercises, 3 sets of up to 10 repetitions per set using 75% of 1RM with 2-minute RIs were performed. For each exercise, standard exercise technique was used (as described in the Strength Testing section), and only those repetitions that met the criteria were counted. For the lunge, repetitions were alternated between right and left sides during each set. Pilot data from our laboratory indicated a 9% larger metabolic response using the alternating version of the lunge vs. performing the lunge with the same leg forward for the entire set. For all exercises, resistance remained constant while total numbers of repetitions were recorded. Subjects used a self-selected cadence to maximize acute resistance exercise performance. Durations for each set of each exercise were recorded and subsequently analyzed.

For the BR protocol, subjects performed 3 sets of 30-second bouts of exercise using 2-minute RIs in between sets. Each set was divided into three 10-second bouts consisting of 3 BR exercises. Subjects performed 10 seconds of single-arm alternating waves, followed by 10 seconds of double-arm waves with a half-SQ, followed by 10 seconds of double-arm rope slams with a half-SQ. A research assistant kept time and provided a verbal “switch” signal to begin the next exercise. Each repetition was performed as rapidly as possible to maintain rope oscillations and maximize intensity. The BR used was 10.9 kg, 15.2 m (50 ft) in length, 3.8 cm thick and was anchored in a low position to a power rack using zip ties (with 1 loop) 10–12 in from the floor. Each BR protocol was recorded on video, and repetitions for each exercise were subsequently counted and analyzed.

For the PU and PU on a BOSU ball protocols, 3 sets of 20 repetitions were performed using 2-minute RIs in between sets. Twenty repetitions were performed due to the ease of performance and rapid cadence by which the body-weight PU is performed and to increase the duration of each set to be more similar to the other exercises assessed. The height of the BOSU ball was measured before each session to ensure standard inflation. The PU on the BOSU ball was performed with the flat base up and convex part on the ground. Hand position was standardized for each PU variation. For the PU with lateral crawl (PU-LC), subjects performed 3 sets of 10 repetitions with 2-minute RIs in between sets. For this exercise, subjects performed 1 PU, laterally crawled 3 steps to the right (while maintaining the PU position) as quickly as possible, performed a second PU, laterally crawled 3 steps back to the left as quickly as possible, and continued this pattern until 10 repetitions were completed. Tape markers were placed on the floor (at a length equal to each subject's grip width) to ensure subjects moved the required length with each crawl.

For the burpee, subjects performed 3 sets of 10 repetitions using 2-minute RIs in between sets. Each subject began the exercise in a standing position, descended into an SQ position with hands on the ground, extended the legs posteriorly to the PU position, performed an SQ thrust, ascended by to the starting position, and jumped to complete each repetition. For the plank, subjects maintained the prone isometric exercise position for 3 sets of 30-second bouts with 2-minute RIs in between sets (see Table 2 for comparisons).

Table 2: Comparison of the resistance exercise protocols.*

Metabolic and Cardiorespiratory Measurements

Heart rate, absolute

, relative

, respiratory exchange ratio (RER), and ventilation (V_E) data were recorded during the entire protocol. Individual breath-by-breath data points for all metabolic variables were averaged for the entire set and for the first 15 seconds of each minute for each RI in between sets (^24,26). The time corresponding to the initiation of each set, the time of the completion of each set, and the RI length between sets were precisely recorded and used subsequently for determination of each phase of the protocols. Gross EE per minute for each protocol was estimated by multiplying absolute

(L·min⁻¹) by 5.05 kcal·L⁻¹ because all RER values were ≥1.0 except for the plank. For the plank,

(L·min⁻¹) was multiplied by 4.86–4.92 kcal·L⁻¹ depending on RER. Baseline EE was estimated by multiplying absolute

(L·min⁻¹) by 4.80 kcal·L⁻¹ to match BL RER. Ventilation data are presented as the mean of each entire protocol.

Statistical Analyses

Descriptive statistics (mean ± SD) were calculated for all dependent variables. A 1 (group) × 13 (exercise) analysis of variance with repeated measures was used to analyze within-subject metabolic and performance data. Subsequent Tukey's post hoc tests were used to determine differences when significant main effects were obtained. For all statistical tests, a probability level of p ≤ 0.05 denoted statistical significance.

Results

Acute metabolic and HR responses to each exercise protocol are shown in Tables 3 and 4. Significant main effects were observed for relative

(p = 0.02) and EE (p = 0.04). The exercises yielding the highest

and EE responses were BR, burpee, SQ, PU-LC, DL, and lunge. The plank yielded the lowest

and EE responses. The BP, curl, BOR, PU, and BOSU PU yielded similar

and EE responses. Metabolic responses did not differ between performing PUs on a floor or BOSU ball; however, adding a lateral crawl to the PU significantly increased acute

and EE responses by 37–39%, respectively. Significant main effects were observed for V_E and HR. The largest acute V_E and HR responses were seen in BR followed by DL, burpee, and SQ. The lowest V_E and HR responses were seen in the plank. No significant main effects were observed in RER.

Table 3: Metabolic responses to the resistance exercise protocols.*

Table 4: V_E and HR responses to the resistance exercise protocols.*

Figures 1–3 depict the acute

responses to each exercise protocol. In Figure 1, the mean

seen during BR was significantly greater than the SQ, lunge, and DL protocols. In addition, SQ

was significantly higher than the lunge. No differences were observed between the DL and lunge. In Figure 2, the mean

observed during the HP was significantly greater than the BP and curl. No differences were observed between the BP, curl, and BOR. In Figure 3, the mean

observed during the burpee was significantly greater than the PU, BOSU PU, PU-LC, and plank. The mean

observed during the PU-LC was significantly greater than the PU, BOSU PU, and plank. No differences were observed between the PU and BOSU PU. The mean

observed for the plank was significantly lower than all other exercises. For all exercises in Figures 1–3 with the exception of the plank, the responses seen during R1 were significantly larger than the set or R2.

Figure 1:

responses of the SQ, DL, lunge, and battling rope exercises. BL = baseline; S = set number; RI = rest interval; SQ = squat; DL = deadlift. “*” p ≤ 0.05 between RI1 and each set and RI2; “#” p ≤ 0.05 between ropes and SQ, DL, and lunge; “$” p ≤ 0.05 between SQ and lunge.

Figure 2:

responses of the bench press, curl, bent-over row, and HP exercises. BL = baseline; S = set number; RI = rest interval; BP = bench press; BOR = bent-over row; HP = high pull. “*” p ≤ 0.05 between RI1 and each set and RI2; “#” p ≤ 0.05 between HP and BP and curl.

Figure 3:

responses of the burpee, plank, push-up, PU on BOSU ball, and PU with lateral crawl exercises. BL = baseline; S = set number; RI = rest interval; BUR = burpee; PU = push-up; BOSU PU = push-up on BOSU ball; PU-LC = push-up with lateral crawl. “*” p ≤ 0.05 between RI1 and each set and RI2 with the exception of the plank; “#” p ≤ 0.05 between burpee and plank, PU, BOSU PU, and PU-LC; “$” p ≤ 0.05 between PU-LC and plank, PU, and BOSU PU; “^” p ≤ 0.05 between plank and PU and BOSU PU.

Acute exercise performance data are presented in Table 5. For the free-weight and BR protocols, repetition performance was maintained across all 3 sets for most exercises with the exception of set 3 for the BP and curl that were both significantly reduced compared with the first set. Although total BR repetitions per set did not differ over 3 sets, there were significant differences (p < 0.001) for individual exercises within each set. Significantly more repetitions per set were completed for the single-arm alternating wave (23.1 ± 4.4) than the double-arm wave with half-SQ (18.3 ± 3.6) and double-arm slam with half-SQ (13.0 ± 1.7) exercises. For all exercises, set duration was similar across all 3 sets with the exception of HP where set 3 was significantly shorter than set 1. The duration of each set between exercises ranged from ∼14 seconds for the bent-over row and HP to ∼37 seconds for the SQ but these differences between exercises did not reach statistical significance (p = 0.12).

Table 5: Acute exercise performance.*

Discussion

This study provided a comprehensive comparison of a total of 13 exercises including 7 free-weight, 5 body-weight, and 1 BR circuit of exercises. For free-weight exercises, the largest acute metabolic responses were seen in the large muscle-mass exercises, that is, SQ, DL, and lunge. Lower metabolic responses were seen in the BP, curl, and bent-over row. Interestingly, the BR protocol produced the largest acute metabolic response of all exercises tested, and the plank provided the lowest acute metabolic response. The burpee, another popular total-body exercise, produced the second largest mean

response, and this response was significantly larger than all of the free-weight exercises. Finally, performing PUs on the floor vs. on a BOSU ball yielded similar metabolic responses. However, the metabolic response increased by 39% when a lateral crawl was added to the PU.

For free-weight exercises, the largest acute metabolic responses were seen in the SQ, DL, and lunge. These data support previous studies indicating that the acute

and EE responses are higher during large muscle-mass exercises than smaller muscle-mass exercises (^{1,13,19,20,26,27,29}). In particular, lower-body exercises have elicited the greatest acute

responses. The SQ has been shown to elicit greater acute metabolic responses than the BP (^{1,19,20,26,27}), curl (^1,20), overhead press (^1,13), lat pull-down (¹⁹), upright row (¹), and bent-over row (¹⁹). Bloomer (²) examined the SQ (13 sets of an average of ∼7 repetitions with 70% of 1RM with 90–120 seconds of rest in between sets) and reported a mean

response of 20.2 ml·kg⁻¹·min⁻¹, which was similar to data reported in this study. The DL has been shown to elicit greater metabolic responses than the row, BP, shoulder press, and lat pull-down (¹⁹). The leg extension has been shown to elicit higher acute

than the chest press and shoulder press (¹⁴). In addition, the leg press has been shown to elicit nearly double the acute

response than the chest fly (⁶). Thus, the results of this study extend these findings and also demonstrate that the alternating lunge is another lower-body exercise that yields a relatively large metabolic response.

Large muscle-mass–resistance exercise can elicit substantial elevations in

especially when coupled with short RIs or as part of circuit training (^18,26,33). Several studies have reported mean protocol

values in the range of 18–25 ml·kg⁻¹·min⁻¹ (^1,2,18,33). In this study, our large muscle-mass free-weight exercises elicited mean

responses of ∼17.3–19.6 ml·kg⁻¹·min⁻¹ despite only 3 sets performed and use of 2-minute RIs. Peak

values ranged from ∼28.7 to 32.5 ml·kg⁻¹·min⁻¹. Mean values elicited values ∼36–40% of

that are within reported ranges of 20–58% of

seen during various protocols (^{1,14,26,29,33}). Large muscle-mass exercises have elicited EE values of ∼8–11.5 kcal·min⁻¹ vs. ∼5.0–7.3 kcal·min⁻¹ in smaller mass exercises (^{1,14,24,26,29,33}). In this study, our small mass free-weight exercises yielded ∼5.1–6.0 kcal·min⁻¹ and the larger mass exercises yielded ∼7.2–8.2 kcal·min⁻¹, which were similar to previous reports (¹⁹) but lower than some studies (^1,29,33) presumably because of the low volume and 2-minute RIs used.

Another finding in this study was the similar metabolic responses between several of the smaller mass resistance exercises. We reported similar mean

responses between the BP, curl, and bent-over row exercises, that is, 12.2–12.5 ml·kg⁻¹·min⁻¹. Ballor et al. (¹) and McArdle and Foglia (²⁰) reported similar

responses in the BP and curl. However, the bent-over row response was surprising given its muscle mass involvement. Ballor et al. (¹) showed higher values during the bent-over row at various repetition speeds than either the BP or curl. One possible explanation for the discrepancy could be subjects performed the bent-over row with greater ease than the BP and curl in this study. For example, every subject completed all 10 repetitions per set for the bent-over row. However, subjects reached momentary muscular failure in both the BP and curl, and repetitions performed for both exercises during set 3 were significantly less than set 1. Farinatti et al. (⁷) reported that the acute metabolic response of the BP was significantly higher in women when it was performed third in sequence (in a semi-fatigued state after the triceps extension and shoulder press) compared with when it was performed first in sequence. Thus, the greater fatigue associated with the BP and curl could have increased metabolic demand as repetitions became slower (as evidenced by linear position transducer data not presented), and a nonsignificant increase in set duration was observed. Another possibility is the use of free weights for the bent-over row. Ballor et al. (¹) used hydraulic resistance exercise for the row that could increase the force requirements throughout the full range of motion, whereas a free weight may be accelerated early in motion thereby reducing tension at the end of the range of motion. One other possibility is that the exercise range of motion of the bent-over row may be slightly less than the BP or curl particularly because the torso is maintained slightly above a parallel position to the floor and the bar is lifted until it contacts the upper rectus abdominis. Thus, it is possible that technical and kinetic factors involved with the free-weight bent-over row may have lessened the metabolic response but this warrants further investigation.

The acute V_E and HR responses tended to parallel

data. The values reported in this study were comparable to a range of values observed in the literature. Several studies have reported V_E values of 16–69 L·min⁻¹ during resistance exercise with higher values seen during large muscle-mass exercises and when short RIs are used (^{1,2,14,20,24,26}). We reported a range of values from ∼32 to 53 L·min⁻¹ for all of the free-weight exercises. These values were similar to other studies examining the BP and SQ for 3–5 sets using 2-minute RIs (^24,26). In addition, average HR values per exercise protocol ranged from 114 to 136 b·min⁻¹ for the free-weight exercises in this study. Values were higher in the large muscle-mass exercises. The values for the large muscle-mass exercises were similar to those reported in some studies (^15,20) but were less than other studies (^1,2,26,32) presumably because of differences in volume, intensity, RI lengths, and the type of resistance used (i.e., free weight vs. hydraulic machines). These findings extend the current literature base and demonstrate exercise-specific V_E and HR responses to a variety of resistance exercises.

The exercise that produced the largest acute metabolic response was the BR circuit (∼51% of

). Battling rope protocols have increased in popularity in recent years and have been included in many types of metabolic training programs targeting muscle strength, endurance, and cardiovascular conditioning (^3,21). Battling ropes are used for multiple purposes, that is, climbing, pulling, and suspension training. However, BRs are most commonly used for wave training (^3,21). The size (length, weight, and diameter) of the ropes, as well as the velocity and amplitude of the waves and muscle mass involvement, are thought to govern the intensity of the exercises (²¹). However, few scientific data are available examining the efficacy of BRs. Fountaine and Schmidt (⁸) examined a 10-minute protocol where double-arm waves were performed for 15 seconds followed by a 45-second RI for 10 sets altogether and reported average HR of 163 b·min⁻¹, peak

of 40.2 ml·kg⁻¹·min⁻¹, and total EE of 622 kJ. In this study, we reported a peak

of 38.6 ± 4.7 ml·kg⁻¹·min⁻¹ and mean HR of 153.5 ± 13.9 b·min⁻¹ despite performing fewer sets, using a short circuit of 3 exercises instead of 1, and using a longer RI in between sets. Thus, based on limited research, it seems BR circuits pose a significant metabolic and cardiovascular stimulus although further research is warranted examining other exercises in addition to single-arm alternating and double-arm waves.

The second largest metabolic response was observed during the body-weight burpee exercise (∼47% of

). The burpee is a callisthenic-type exercise that stresses most major muscle groups. The variation used in this study involves SQs, SQ thrusts, a PU, and a jump-in-place combined into 1 exercise (other variations of the exercise have differences particularly for the PU and jump components). The burpee was created more than 80 years ago as a way of assessing coordination, strength, and agility fitness in soldiers and has been used as a conditioning exercise ever since. Our data show that the burpee provides a potent metabolic stimulus larger than that observed during several moderate-intensity free-weight exercises.

The results of this study showed that performing a PU on the floor and on a BOSU ball resulted in similar metabolic demands. Little is known about the performance of PUs on a BOSU ball. A recent study showed that training with PUs on a BOSU ball provided no advantage to performing PUs on the floor (⁴). Studies examining exercises performed on BOSU balls have generally shown reduced force output because of the instability (²⁸). In addition, EMG activity has been shown to be similar in most muscles tested between exercises on BOSU balls compared with the floor (²⁸). Using resistance-trained individuals, Wahl and Behm (³¹) reported that the moderate instability of BOSU balls did not result in greater muscle activation compared with performing exercises on the floor, whereas wobble boards and stability balls did increase stabilizer muscle activity. The authors suggested that trained individuals may already possess sufficient stability and a less-stable surface than a BOSU ball may be needed to challenge the neuromuscular system (³¹). Thus, it may be hypothesized that BOSU balls were not sufficient to augment muscle activation during the PU in our group of trained individuals, which could explain the lack of difference seen in the metabolic responses. However, adding a lateral crawl to the PU increased the acute metabolic demand significantly despite performing half of the full-range repetitions to account for the added time needed for the lateral motion. The additional activation of muscle mass of the trunk and lower body during the lateral crawl may have led to the increased metabolic response.

The lowest metabolic and HR responses were seen during the plank exercise. This was not surprising because the plank is predominantly an isometric exercise. Isometric exercises have been shown to elicit lower metabolic and HR responses compared with dynamic exercises (^5,20). McArdle and Foglia (²⁰) reported isometric sets of the BP, SQ, overhead press, and curl elicited approximately half of the

responses of their dynamic counterparts. Although the plank exercise is commonly used in training programs targeting increased trunk muscle strength and endurance, our data demonstrate that it is less metabolically challenging.

In summary, the BR protocol used in this study elicited the largest acute metabolic and HR responses compared with all exercises tested and the plank elicited the lowest acute metabolic response. The body-weight burpee exercise protocol elicited the second largest mean

response. For the free-weight exercises, the largest acute metabolic responses were seen in the large muscle-mass exercises, that is, SQ, DL, and lunge, and similar but lower metabolic responses were seen in the BP, curl, and bent-over row. Finally, performing PUs on the floor vs. on a BOSU ball yielded similar metabolic responses. However, the metabolic response increased when a lateral crawl was added to the PU. These data provide useful program design–related information to the practitioner regarding metabolic responses of several different resistance exercises.

Practical Applications

Weight loss and/or body fat reductions are goals associated with resistance training. Body fat reductions are predicated, in part, on acute EE during each training session and the additional EE seen during the recovery period (EPOC) after the training sessions. The selection of resistance exercises, in addition to the appropriate prescription of intensity, volume, and RI lengths, which augment EE, is critical to targeting body fat reductions and muscle endurance enhancement. The results of this study indicate that free-weight exercises that stress large muscle mass such as the SQ, DL, and lunge yield high acute mean EE (7.2–8.2 kcal·min⁻¹) when 3 sets of 10 repetitions with 75% of 1RM are used with 2-minute RIs. Interestingly, lower-intensity exercises such as the burpee (performed using body weight as a resistance) and a BR circuit elicited a greater acute metabolic response, eliciting 9.6–10.3 kcal·min⁻¹ of EE. These results support the inclusion of large muscle-mass exercises whether they use free weights, body weight, or implements such as ropes for resistance and can provide coaches and practitioners with useful metabolic data that can assist in training program design.