Influence of Resistance Exercise on Lumbar Strength in Older, Overweight Adults

Inclusion Criteria 

Participants must not have been involved in a regular resistance training program for at least 1 year, but may have engaged in low-intensity aerobic training equal to or less than 3 times a week. To be eligible for study participation, subjects underwent a medical examination performed by a physician specializing in geriatric medicine, a resting 12-lead electrocardiogram, and a graded exercise test to their respective symptom-limited maximum. Blood pressure, peak rate of oxygen consumption (Vo2peak), exercise test time, heart rate, and electrocardiographic activity were monitored during the symptom-limited graded exercise test. The subjects in this study were healthy men and women aged 60 to 83 with no pathologies (including LBP) that would confound or compromise their responses to exercise training. Eighty-four participants started the exercise training; 62 completed the protocol. Of the 22 who did not finish, 11 were dropped by the investigators for not adhering to the training protocol or dropped out voluntarily for reasons of inconvenience. The other 11 dropped out for one of the following reasons: moved out of the area, financial difficulties, or surgery or injury (detached retina, atrial fibrillation, liver cancer, renal stenosis, prostate cancer) not related to the study protocol.

Participants 

Participants were stratified into 2 groups based on body mass index (BMI). To account for other factors that could potentially influence strength in a nonobese versus obese comparison, we controlled for height among groups and ensured that all participants had similar recreational physical activity levels (via questionnaire) during the group assignment process prior to study enrollment.9 People with BMI values of 25kg/m2 or less were placed into the NOVW group, those with BMI values above 25kg/m2 were assigned to the OVW group.

After baseline testing, the subjects were rank ordered by composite strength (chest press 1 repetition maximum [1-RM] plus leg press 1-RM) and randomly assigned to either a nontraining group (CON) or an RX training group. There were a total of 4 participant groupings: NOVW-CON, NOVW-RX, OVW-CON, and OVW-RX. Participants placed into the control groups were asked to maintain their normal lifestyles and not to initiate an exercise program during the 6-month control period.

To be considered compliant and remain in the study, participants had to attend more than 85% of the possible exercise sessions. All participants received a comprehensive explanation of the proposed study, its benefits, inherent risks, and expected commitments with regard to time. After the explanation, all participants read and signed an informed consent document approved by the institutional review board at the University of Florida and in adherence with the guidelines of the American College of Sports Medicine (ACSM).10

Anthropometric and Body Composition Measures 

We used dual x-ray absorptiometry (DPX-L)a to obtain estimates of fat mass and fat-free mass (FFM). The calculation of these variables was accomplished using the DPX-L, version 1.3Z program,a for body composition supplied by the Lunar Radiation Corporation.

We also determined body composition by using the 7-site skinfold technique described by Pollock and Wilmore,11 utilizing the following sites: chest, axilla, triceps, subscapular, abdomen, suprailiac, and anterior thigh. All measurements were taken from the right side of the body with Lange calipers.b

Strength Testing 

The exercise testing equipment used in this investigation was MedX variable resistance machines.c We measured dynamic muscular strength by using 8 resistance exercises, which included: leg press, knee flexion, knee extension, chest press, seated row, overhead press, triceps extension, and elbow flexion. For each dynamic exercise, a 1-RM was determined. Participants were properly positioned in the machine and performed a dynamic warm-up using a light weight. The participant began the test by lifting a light weight and then incremental increases were made according to the difficulty with which the participant executed the previous lift. Lift difficulty was measured by having the participant rate his/her exertion level using the rating of perceived exertion (RPE) scale. Two- to 3-minute rests were provided between trials to prevent premature fatigue. The investigator continued to increase the weight lifted until reaching the maximum weight that could be lifted in 1 repetition with proper form. This was usually determined in 4 to 6 trials. Maximal strength was defined as the maximum weight that could be lifted through a full range of motion (ROM) with proper form.

Resistance Exercise Training 

The exercise training equipment used in this investigation was the MedX variable resistance machine. These machines were selected because their design allows each exercise to be performed in a seated position so that the participant can get in and out of the machine easily. Additionally, resistance loads can be increased in 0.9-kg increments, allowing the resistance used to be tailored to each participant. Participants were oriented to the proper positioning and movement on each machine using a light load (27Nm) in a session conducted prior to strength testing or training. The machines used for this study were abdominal crunch, leg press, knee extension, knee flexion, calf press, seated row, chest press, overhead press, elbow flexion, elbow extension, leg abduction, leg adduction, and lumbar extensions.

Participants in the RX groups were asked to report to the training facility 3 times a week for 24 weeks to perform dynamic variable resistance exercise under the supervision of trained personnel for all machines except the isolated lumbar extension exercise. Isolated lumbar extensions were performed once per week under the supervision of personnel certified for the use of MedX rehabilitation equipment. The rationale for training the lumbar extensor muscles only 1 day a week is derived from previous research indicating that training more than once a week often does not provide superior results to 1 day a week.12, 14 Graves et al12 showed equal gains in lumbar strength when people trained the lumbar extensors once a week when compared with 2 or 3 times a week for 12 weeks. Tucci et al14 showed that after 12 weeks of initial training at once per week, training once every 2 weeks, or once every 4 weeks maintained the initial strength gains. Each subject received appropriate instruction concerning warm-up and cool-down techniques, as well as how to monitor the intensity of the exercise using the RPE scale. Each subject performed 1 set on each of the resistance exercise machines. The regimen used in this study was designed to replicate what is recommended by the ACSM in its position stand regarding the exercise prescription for healthy adults, which has been shown to increase strength, physical function, and health in this population.16 Although more sets could be performed for more maximal gains, it was the goal of this work to train people in a way according to established guidelines using a regimen that they could carry forth when the study was complete. There was a 2-minute rest period allowed between machines. Each set consisted of 8 to 13 repetitions at 50% to 80% of their 1-RM. This regimen was chosen because 80% of 1-RM for 8 repetitions is commonly used in studies using older adults and corresponds to the lower repetition limit of the ACSM recommendations.16 For the RX groups, the load was increased by 5% when their RPE rating dropped below 18.15, 16, 17, 18 For abdominal crunch, calf press, leg abduction, and leg adduction the initial weights for training were chosen using a light weight and progressing to an appropriate resistance and repetition range using the RPE scale.16 The RX group performed 10 to 15 lumbar flexion-extension repetitions per exercise session.

Statistical Analyses 

Statistical analyses were performed using the SPSS software.d All data are expressed in mean ± standard deviation. Potential differences among the 4 groupings in descriptive variables and baseline lumbar and muscular strength values were analyzed using a 1-way analysis of variance (ANOVA) with a Tukey post hoc test. To examine the effect of the resistance training program, a repeated-measures ANOVA was performed from pre- to poststudy period testing sessions. The group membership (NOVW, OVW) and the training status (untrained, RX trained) were the between-group factors and time (pre- and post-RX training) was the within-group factor. When significant group by time interactions occurred, simple main effects were assessed using 1-way ANOVA with a Tukey post hoc test to determine where group differences occurred. Levels of significance were set at P less than .05.

Participant Characteristics 

Characteristics of the experimental groups are found in table 1. The OVW-CON and OVW-RX groups had greater body weights, BMI values, percentage of body fat levels and FFMs than their normal weight comparative controls (P<.05). All other variables did not differ significantly among groups (P>.05).

Table 1. Baseline Subject Characteristics

	Variable	NOVW-CON	NOVW-RX	OVW-CON	OVW-RX
	Age (y)	72.1±4.4	68.4±7.6	70.6±5.6	66.5±5.9
	Height (cm)	168±7	163±10	168±13	169±11
	Weight (kg)	64.9±8.8	59.9±10.7	81.8±14.4⁎	83.4±14.2⁎
	BMI (kg/m2)	22.8±1.6	22.3±2.1	28.8±2.4⁎	29.1±4.7⁎
	Body fat (%)	28.6±7.0	26.7±5.0	35.4±7.8⁎	33.0±7.0⁎
	Fat mass (kg)	30.7±6.6	30.1±6.5	38.8±7.2	36.7±8.1
	FFM (kg)	44.2±7.9	41.3±17.0	50.6±14.2⁎	53.2±13.0⁎
	Vo2peak (mL·kg−1·min−1)	24.1±1.2	18.9±6.1	20.8±4.7	21.5±4.6
	SL-GXT time (min)	11.5±2.2	11.4±3.2	11.4±3.1	11.9±2.8

NOTE. Values are mean ± standard deviation (SD). Abbreviation: SL-GXT, symptom-limited graded exercise testing.

⁎ Greater than comparative NOVW groups (NOVW-CON, NOVW-RX) at P<.05 (1-way ANOVA with Tukey post hoc test).

Overall Muscular Strength 

At baseline, 1-way ANOVA revealed that the OVW group had greater upper- and lower-body strength compared with the NOVW group (P<.05; table 2). However, many of these differences disappeared when the strength values were expressed relative to FFM (table 3).

Table 2. Baseline Absolute Strength Values for NOVW and OVW Participants

	Variable	NOVW (Nm)	OVW (Nm)
	Total upper body†	658±232	897±350⁎
	Total lower body‡	486±136	710±229⁎
	Total lumbar	714±328	1067±463⁎
	0° of lumbar flexion	62±42	89±58
	12° of lumbar flexion	85±44	125±71⁎
	24° of lumbar flexion	95±46	155±83⁎
	36° of lumbar flexion	107±51	175±85⁎
	48° of lumbar flexion	114±50	193±86⁎
	60° of lumbar flexion	121±53	198±85⁎

NOTE. Values are mean ± SD.

⁎ Different from NOVW P<.05 (1-way ANOVA). † Composite score of 1-RM values for chest press, elbow flexion, elbow extension, overhead press, and seated row. ‡ Composite score of 1-RM values for leg press, leg extension, and leg flexion.

Table 3. Baseline Relative Strength Values for NOVW and OVW Participants

	Variable	NOVW (Nm/kg FFM)	OVW (Nm/kg FFM)
	Total upper body†	9.8±17.3	15.2±3.9
	Total lower body‡	8.0±9.8	10.3±3.8
	Total lumbar	23.2±8.4	28.2±8.8
	0° of lumbar flexion	2.0±1.4	2.3±1.3
	12° of lumbar flexion	2.8±1.3	3.1±1.5
	24° of lumbar flexion	3.2±1.2	4.0±1.7
	36° of lumbar flexion	3.5±1.1	4.4±1.6⁎
	48° of lumbar flexion	3.7±1.2	4.8±1.5⁎
	60° of lumbar flexion	3.9±1.3	5.1±1.5⁎

NOTE. Values are mean ± SD.

⁎ Different from NOVW P<.05 (1-way ANOVA). † Composite score of 1-RM values for chest press, elbow flexion, elbow extension, overhead press, and seated row. ‡ Composite score of 1-RM values for leg press, leg extension, and leg flexion.

Repeated-measures ANOVA revealed a significant interaction between group assignment and force production from baseline to poststudy testing for absolute upper-body (F=10.322, P<.001) and lower-body (F=4.772, P=.005) strength, indicating group dependent change in force production (table 4). Similarly, repeated-measures ANOVA revealed a significant interaction between group assignment and force production from baseline to poststudy testing for relative upper-body (F=14.275, P<.001) and lower-body (F=3.341, P=.026) strength. Subsequent post hoc analysis with a 1-way ANOVA revealed that both the NOVW-RX and OVW-RX groups demonstrated increases in absolute (in newton meters; see table 4) and relative (in Nm/kg FFM; table 5) muscular strength (upper and lower body) as a consequence of the training regimen (P<.05). The strength scores are reported as total upper-body strength and total lower-body strength. Total upper-body strength was calculated by summing the 1-RM values for the chest press, elbow flexion, elbow extension, overhead press, and seated row exercises. Total lower-body strength was calculated by summing the 1-RM values for the leg press, leg extension, and leg flexion exercises. No changes in muscular strength were observed in the nontraining groups. When comparing the stratified group (NOVW-CON vs NOVW-RX, OVW-CON vs OVW-RX) no significant differences were noted in terms of absolute upper- or lower-body strength poststudy. However, 1-way ANOVA did reveal that the OVW-RX group had significantly greater total lower-body relative strength poststudy when compared with their OVW-CON counterparts (P=.013; see table 5).

Table 4. Changes in Absolute Upper- and Lower-Body Strength in NOVW and OVW Groups Before (Pre) and After (Post) the 24-Week Intervention Period

	Group	Upper Body (Nm)†		Lower Body (Nm)‡
		Pre	Post	Pre	Post
	NOVW-CON	664±230	663±244	532±144	516±141
	NOVW-RX	590±315	698±367⁎	394±168	444±149⁎
	OVW-CON	774±330	763±319	577±156	581±152
	OVW-RX	832±374	975±454⁎	529±276	632±349⁎

NOTE. Values are mean ± SD.

⁎ Different from pretraining baseline value within the same grouping at P<.05 (repeated-measures ANOVA). † Composite score of 1-RM values for chest press, elbow flexion, elbow extension, overhead press, and seated row. ‡ Composite score of 1-RM values for leg press, leg extension, and leg flexion.

Table 5. Relative Changes in Upper- and Lower-Body Strength in NOVW and OVW Groups Before (Pre) and After (Post) the 24-Week Intervention Period

	Group	Upper Body‡ (Nm/kg FFM)		Lower Body§ (Nm/kg FFM)
		Pre	Post	Pre	Post
	NOVW-CON	20.0±3.7	20.3±4.4	16.2±2.7	16.0±3.1
	NOVW-RX	21.0±4.7	25.2±5.3⁎	14.9±2.2	16.8±2.2⁎
	OVW-CON	20.1±3.0	20.7±2.9	15.5±1.2	15.8±0.8
	OVW-RX	22.1±5.3	27.6±5.9⁎	18.5±3.1	22.4±4.4⁎†

NOTE. Values are mean ± SD.

⁎ Different from pretraining baseline value within the same grouping at P<.05 (repeated-measures ANOVA). † Different from all other groups at the same time point P<.05 (1-way ANOVA with Tukey post hoc test). ‡ Composite score of 1-RM values for chest press, elbow flexion, elbow extension, overhead press, and seated row. § Composite score of 1-RM values for leg press, leg extension, and leg flexion.

Lumbar Muscle Strength 

At baseline, the OVW group had greater specific angle lumbar extension (lumbar flexion, 12°−60°) strength compared with the NOVW group (1-way ANOVA, P<.05; see table 2). When expressed in relative terms, only force output values from 38° to 60° of lumbar flexion were greater in the OVW group compared with NOVW (1-way ANOVA, P<.05; see table 3).

Repeated-measures ANOVA revealed a significant interaction between group assignment and force production from baseline to poststudy testing for absolute lumbar strength indicating a group-dependent change in force production (F=9.925, P<.001; table 6). Similarly, repeated-measures ANOVA revealed a significant interaction between group assignment and force production from baseline to poststudy testing for relative lumbar strength (F=4.636, P<.001; table 7). Subsequent post hoc analysis with a 1-way ANOVA revealed that both training groups improved absolute lumbar extension strength at each angle tested secondary to RX training (see table 6). However, to account for differences in strength due to body weight and individual adiposity values, relative isometric strength values were expressed per unit FFM (in Nm/kg FFM).19, 20 These values are shown in table 7. After the RX training, the OVW-RX and NOVW-RX groups demonstrated significantly elevated strength values at all lumbar flexion angles compared with pretraining values (P<.05). Additionally, at baseline the OVW participants had greater absolute lumbar extension strength compared with the NOVW-RX participants at 24° to 60° of lumbar flexion (P<.05).

Table 6. Absolute Maximal Isometric Lumbar Strength Values (in Nm) at 0° to 60° Range of Lumbar Flexion in NOVW and OVW Groups Before (baseline) and After the 24-Week Intervention Period (24wk)

	Group	Lumbar Flexion Angle (deg)
		0	12	24	36	48	60
	Pretraining (baseline)
	NOVW-CON	82±27	112±32	129±28	142±42	145±36	153±43
	NOVW-RX	46±43	65±43	72±43	80±40	86±42	92±42
	OVW-CON	141±85†	194±82†	231±116†	247±110†	246±102†	232±71†
	OVW-RX	84±52	115±66	143±75†	165±79†	188±84†	195±86†
	Posttraining (24wk)
	NOVW-CON	55±45	99±35	118±39	132±35	135±37	156±46
	NOVW-RX	86±47⁎	110±43⁎	122±41⁎	132±51⁎	132±51⁎	138±49⁎
	OVW-CON	122±93	163±131	193±92	228±115	241±111	273±102†
	OVW-RX	140±67⁎	181±72⁎	206±76⁎	220±76⁎†	228±77⁎†	226±79⁎†

NOTE. Values are mean ± SD.

⁎ Different from pretraining baseline value within the same grouping at P<.05 (repeated-measures ANOVA). † Different from NOVW-RX at the same time point at P<.05 (1-way ANOVA with Tukey post hoc test).

Table 7. Relative Maximal Isometric Lumbar Strength Values (in Nm/kg FFM) at 0° to 60° Range of Back Flexion in NOVW and OVW Groups Before (baseline) and After the 24-Week Intervention Period (24wk)

	Group	Lumbar Flexion Angle (deg)
		0	12	24	36	48	60
	Pretraining (baseline)
	NOVW-CON	2.4±1.0	3.4±0.9	3.8±0.6	4.2±0.7	4.3±0.7	4.5±0.8
	NOVW-RX	1.7±1.6	2.3±1.5	2.6±1.3	2.9±1.1	3.1±1.3	3.4±1.4
	OVW-CON	3.0±1.5	4.4±0.9	5.2±1.6†	5.7±1.4†	5.7±1.3†	5.4±0.8†
	OVW-RX	2.1±1.3	2.9±1.42	3.7±1.7	4.1±1.5	4.6±1.5†	5.0±1.5†
	Posttraining (24wk)
	NOVW-CON	1.5±1.0	2.9±0.6	3.5±0.8	4.0±0.8	4.1±0.8	4.7±1.0
	NOVW-RX	3.1±1.4⁎	4.0±1.2⁎	4.4±1.0⁎	4.8±1.0⁎	4.7±1.1⁎	5.0±1.1⁎
	OVW-CON	2.5±1.8	3.3±2.6	4.3±1.2	5.1±1.6	5.4±1.4	6.2±0.9
	OVW-RX	3.6±1.2⁎‡	4.8±1.3⁎‡	5.4±1.1⁎‡	5.7±1.1⁎‡	5.9±1.0⁎‡	6.0±1.0⁎‡

NOTE. Values are mean ± SD.

⁎ Different from pretraining baseline value within the same grouping at P<.05 (repeated-measures ANOVA). † Different from NOVW-RX at the same time point at P<.05 (1-way ANOVA with Tukey post hoc test). ‡ Different from NOVW-CON at the same time point at P<.05 (1-way ANOVA with Tukey post hoc test).

Total Lumbar Extensor Strength 

The strength scores of all the joint angles of lumbar extension were summed to determine the total lumbar extensor strength score. The difference in the lumbar extension strength from pre- to posttraining was then determined. The baseline absolute lumbar extension strength scores were greater in the OVW compared with the NOVW participants (1-way ANOVA, P<.05; see table 2). However, as with the other muscular strength measures, this difference was not apparent when expressed relative to FFM (1-way ANOVA, P>.05; see table 3). Repeated-measures ANOVA revealed a significant interaction between group assignment and force production from baseline to poststudy testing for absolute total lumbar strength, indicating a group dependent change in force production (F=12.599, P<.001). Similarly, repeated-measures ANOVA revealed a significant interaction between group assignment and force production from baseline to poststudy testing for relative total lumbar strength (F=8.867, P<.001; fig 1). Subsequent post hoc analysis with a 1-way ANOVA revealed that both the NOVW-RX and OVW-RX groups had greater absolute and relative strength changes compared with their nontrained counterparts (P<.05). Considering that total lumbar extension strength expression based on absolute terms (in newton meters) and per unit BMI yielded identical results, the pre- and posttraining total lower-extremity strength values are presented per kilogram of FFM in figure 1.

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Fig 1. Change in total lumbar extensor relative strength after 6 months of RX in older adults. *Different from pre-exercise value in the respective group at P<.05 (repeated-measures ANOVA).

Overview of Main Findings 

This investigation examined whether lumbar extension muscle strength deficits were present in overweight compared with normal weight older adults, and examined whether RX was effective in increasing lumbar extension strength in overweight older adults. There were 2 main findings from this study. First, lumbar extensor strength was greater in OVW compared with NOVW persons when expressed in absolute (in newton meters) but similar when expressed in relative (in Nm/kg FFM) terms. Second, RX significantly increased lumbar extension muscle strength and strength at specific angles throughout the ROM of lumbar extension as effectively in OVW as NOVW.

Lumbar Extensor Strength Deficits in Overweight Older Adults 

This investigation is the first to document that lumbar extension strength is similar in OVW compared with NOVW older adults. When expressed is absolute terms, the OVW participants apparently had greater lumbar extensor strength when compared with their NOVW counterparts. However, some of the differences disappeared when the data were expressed relative to FFM. There is a well-established link between body size and strength.19, 20 When expressed in absolute terms, the greater force produced by larger compared with smaller persons may be misleading. To properly compare people of different sizes, the data should be normalized to the amount of muscle mass (FFM).19, 20 If the data were expressed relative to body mass (not FFM) only, the strength values might be artificially lowered because both active (muscle) and nonactive (adipose) tissue would be accounted for in the denominator. A larger person would be placed at a comparative disadvantage. Muscle strength deficits have been reported in obese persons compared with nonobese persons in handgrip, knee extension, knee flexion, and trunk rotation exercise when adjusted for FFM using an allometric method.9 The strength difference between nonobese and obese persons was attributed to metabolic mechanisms of obesity at the muscle cell level.9 However, similar differences between OVW and NOVW persons were not found in the present investigation. When expressed per kilogram of FFM, both groups demonstrated similar lumbar extensor as well as upper- and lower-body strength. The differences between the present study and those of other investigations could be the relative health of our participants. As described, all participants in this study were subjected to a stringent screening process to ensure that they would be able to perform and complete the study protocol. Additionally, the participants in this investigation were classified by BMI as overweight, and not obese. Obesity is associated with unfavorable muscle fiber shifts that enhance fatigue and compromise force production.21 It is possible that muscle fiber alterations that could result in impaired force production may not be present in the OVW population or are too focal to result in gross strength deficits.

Obesity, weak lumbar extensors, and decreased paraspinal muscle endurance has been associated with chronic LBP.22 Additionally, muscle quality may be decreased due to obesity-related elevations in stored fat within skeletal muscle. Malenfant et al23 reported that the number of lipid droplets within all muscle fiber types was nearly doubled in obese compared with lean subjects. Therefore, paraspinal muscles of obese (particularly older obese) persons would have both decreased strength and endurance, which could influence the development of lumbar extension strength deficit. It is possible that overweight or obese persons may have similar lumbar extensor strength compared with their NOVW counterparts, but given their increased body mass, their level of strength may not be sufficient to prevent musculoskeletal alterations that contribute to the development of LBP. However, the patients in this study were free from LBP. Future investigations should compare the lumbar extensor strength and the influence of resistance exercise in overweight or obese persons with LBP compared with those who are free from LBP.

Improvement in Total Lower-Extremity Strength With RX 

The 6-month training protocol increased total lumbar extension strength in the OVW-RX and the NOVW-RX groups. This training protocol included exercises that isolated the lumbar muscles and a total body circuit. Previous investigations have shown that 20 weeks of isolated lumbar extension exercise can increase lumbar extensor strength from 17% at full flexion to 123% at full extension.24 In the present study, lumbar extension strength increased by 58% and 34% for the NOVW-RX and OVW-RX groups, respectively. In the present study, the participants trained for 4 weeks longer than previous trials, and the change in lumbar extension strength may be the result of increased force output from the lumbar extensors as well as increased strength of the truncal stabilizing musculature.

The increase in lumbar extension strength achieved with equipment that isolates the lumbar extension muscles and stabilizes the pelvis is greater than those observed with other types of equipment.4, 25, 26 Previous investigations have shown that lumbar extension exercise with Roman chair or without pelvic stabilization elicit either no change or inferior lower-extremity strength changes when compared with the isolating, stabilizing mode of training used in the present study.25, 26 Further, an isolating mode of exercise has been shown to effectively decrease the severity and development of LBP.4 However, what is not currently known is how lumbar extension exercise may influence the biomechanic derangements in pelvic tilt and lordosis associated with obesity. Future investigations are warranted to determine the RX effects on pelvic tilt and lordosis elicited by adiposity.

It is unclear if additional gains would be derived from regimens that utilize a greater volume of exercise (number of sets). There are data to indicate that periodized or multiple set regimens can confer additional gains when compared with single set regimens.16, 27 However, this has not been fully demonstrated in elderly or obese populations. Additionally, the influence of number of sets on lumbar extension strength following isolated lumbar extension exercise has not been investigated. It should be noted that the regimen utilized in this investigation has been demonstrated to be effective for improving muscular strength,15, 27, 28 cardiorespiratory fitness,29 and bone mineral density,30 as well as for decreasing homocysteine levels31 and indices of oxidative stress.32 Furthermore, the regimen utilized conforms to the guidelines established by the ACSM for improving muscular strength and endurance.16 Single set regimens have also been shown to be time efficient and associated with improved rates of adherence.33