Abstract
This study evaluates the effect of 3 months resistance and aerobic training on muscle strength and power in 17 male overweight and obese men. Subjects underwent either a resistance or aerobic training for a period of 3 months (three sessions per week). Peak isometric force, rate of force development, peak power and height of countermovement and squat jumps, reactive strength index, and mean power in the concentric phase of bench presses were all assessed prior to and after completing the training program. Results identified a significant increase of mean power during both countermovement bench presses at 30 kg (18.6%, p = .021), 40 kg (14.6%, p = .033), and 50 kg (13.1%, p = .042) and concentric-only bench presses at 30 kg (19.6%, p = .017) and 40 kg (13.9%, p = .037) after the resistance training. There was also a significant increase in the height of the jump (12.8%, p = .013), peak power (10.1%, p = .026), and peak velocity (9.7%, p = .037) during the countermovement jump and height of the jump (11.8%, p = .019), peak power (9.6%, p = .032), and peak velocity (9.5%, p = .040) during the squat jump. There were no significant changes in the reactive strength index, peak force, and the rate of force development after the resistance training. The aerobic group failed to show any significant improvements in these parameters. It may be concluded that 3 months of resistance training without caloric restriction enhances upper and lower body muscle power in overweight and obese men.
Introduction
Obesity is an emerging problem that poses significant challenges to strength and conditioning professionals. Decreases in endurance, range of movement of the spine and major joints, muscle strength, capacity to hold prolonged fixed postures, respiratory capacity, and visual control all have a negative effect on both work capacity and quality of life (Ettinger & Afable, 1994).
Changes in body mass and composition affect muscle strength. Higher absolute fat and lean mass values as compared with their leaner counterparts are reported in obese people (Katzmarzyk, Janssen, & Ardern, 2003; Xu, Mirka, & Hsiang, 2008). When normalized to body weight, strength is 6% to 10% lower in those who suffer from obesity. Despite greater muscle mass, they are significantly weaker than normal-weight subjects (Katzmarzyk et al., 2003). Reduced muscle strength could possibly stem from diminished muscle function, abnormal metabolism (lower oxidative capacity of muscle fibers, despite their hypertrophy), and lower physical activity levels, also exhibited by reduced motor unit activation during exercise (Lafortuna, Maffiuletti, Agosti, & Sartorio, 2005). Particularly, the knee flexor and extensor ratio is lower in the obese than for those with normal weight (Katzmarzyk et al., 2003). Lower flexor and extensor strength has a negative effect on the capacity to perform daily activities safely, as highlighted by a strong correlation between these factors (Stenholm et al., 2008). For example, rising from a chair takes longer (Davis, Ross, Preston, Nevitt, & Wasnich, 1998) and is more difficult with obesity (Vincent, Vincent, & Lamb, 2010). The total percentage of body fat has been identified as a predictor in a decrease in chair rise functionality (Foster et al., 2010).
These findings indicate that a training program for the overweight and obese should be aimed at enhancing muscle power rather than maximal strength. Weight lifting or progressive resistance training (PRT) is recommended for the obese by the American College of Sports Medicine (2001). PRT is defined as exercise whereby the resistance against which a muscle generates force is progressively increased over time (American College of Sports Medicine, 1998). It increases muscular size and strength, alters body composition by increasing lean body mass and decreasing visceral and total body fat (Treuth et al., 1995), and leads to changes in neuroendocrine and cardiovascular functions (Kraemer, Deschenes, & Fleck, 1988). Resistance training at intensities of between 60% and 100% of the one repetition maximum (1-RM) elicit structural, functional, and metabolic changes in skeletal muscle, with higher intensities leading to greater adaptations (Fiatarone Singh, 2000).
A systematic review and meta-analysis by Clark (2015) identified that that there is a necessity to include exercise in combination with diet to effectively elicit changes in body composition and biomarkers of metabolic issues. The combination resistance training (RT) was more effective than endurance training (ET) or a combination of RT and ET, particularly when progressive training volume of 2 to 3 sets for 6 to 10 repetitions at an intensity of ≥75% 1-RM, utilizing whole body and free-weight exercises, at altering body compositional measures and reducing total cholesterol, triglycerides, and low-density lipoproteins. Additionally, RT was more effective at reducing fasting insulin levels than ET or ET and RT. The inclusion of ET was more effective when performed at high intensity (e.g., ≥70% VO2max or HRmax for 30 minutes three to four times per week), or in an interval training style than when utilizing the relatively common prescribed method of low-to-moderate (e.g., 50% to 70% VO2max or HRmax for at least equal time) steady state method. Thus, indicating that focus of treatment should be on producing a large metabolic stress (as induced by RT or high levels of ET) rather than an energetic imbalance for adults who are overweight.
Recent guidelines on exercise for weight loss and weight maintenance include resistance training as part of the exercise prescription. It appears that aerobic training is the optimal mode of exercise for reducing both fat and body mass, while a program including resistance training is necessary for increasing lean mass in the middle-aged and the overweight/obese (Willis et al., 2012). According to Carnero et al. (2014), the overweight and obese are able to reduce their total and regional fat mass, regardless of the type of training (aerobic training, resistance training, or a combination of both). Marsh et al. (2013) identified that in older overweight and obese adults, a hypocaloric weight loss intervention led to significant declines in lean and appendicular lean body mass. Moreover, subjects who participated in the resistance training displayed significant improvements in their leg press power, but not in their knee extensor strength. However, muscle strength or power was not adversely affected in the other groups (no resistance training, pioglitazone or placebo).
It seems that resistance training elicits greater structural, functional, and metabolic changes in skeletal muscle than aerobic training, resulting in the enhancement of muscle strength and power. Weight lifting and resistance training are a potent stimulus to the neuromuscular system (Deschenes & Kraemer, 2002). Depending on the specific program design, resistance training can enhance strength, power, and/or local muscular endurance. These improvements in performance are directly related to the physiologic adaptations elicited through prolonged resistance training.
In practice, mainly tests of maximal strength and muscular endurance such as maximum repetition test and measurements of repetitive performance related to maximum strength or at a fixed resistance are utilized to evaluate the effect of such trainings on physiological and performance variables. However, experience indicates that testing of muscle power during resistance exercises represents a more appropriate alternative for the overweight and obese than the 1-RM approach. So far, there is little evidence regarding changes in power performance in this population evaluated by tests that resemble exercises performed during resistance training. Most tests currently in use can only be performed in a laboratory using mainly isometric or isokinetic dynamometry. Thus, few people benefit from testing on a sports field where exercise programs are usually carried out. Therefore, laboratory testing should be complemented with field testing to allow fitness professionals to assess the efficiency of the training and to design programs that will further increase performance. It can be assumed that muscle power would be a more sensitive parameter reflecting the effect of dynamic resistance training rather than tests of maximal muscle strength. This study evaluates the effect of 3 months of resistance and aerobic training programs on strength and power in overweight and obese men.
Method
Participants
A group of 17 male individuals (age 37.9 ± 5.1 years, height 182.6 ± 5.8 cm, weight 104.4 ± 14.8 kg, body mass index [BMI] 31.2 ± 3.7 kg/m2) volunteered to participate in the study. All participants were recreationally active, but were not involved in any form of aerobic, strength, and/or power training. Individuals with any chronic disease or regular use of pharmacotherapy were not eligible to enter the study. Participants were all fully informed regarding the procedures and the possible risks, and provided witnessed written informed consent prior to the study. All studies were approved by the Ethics Committee of the University Hospital Bratislava, Comenius University Bratislava, and by the Ethics Committee of the Bratislava Region Office and are conforming to the ethical guidelines of the Helsinki declaration.
Clinical phenotyping was performed before and after the intervention (Kurdiová et al., 2014). Body weight and height were used to calculate BMI (kg/m2). Waist circumference was measured at the midpoint between the lower border of the rib cage and the iliac crest. Bioelectric impedance was used to evaluate total and visceral adiposity and to estimate lean body mass (Omron BF511, Omron Healthcare Ltd., Matsusaka, Japan). Resting energy expenditure was measured after an overnight fast and following 30 minutes bed rest with the Ergostik (Geratherm Respiratory, Bad Kissingen, Germany) for a period of 30 minutes. Volume and dynamics/intensity of daily ambulatory activity were determined with accelerometers (Lifecorder plus, Kenz, USA) continuously within the 3 months of the intervention. Habitual free-living ambulatory activity was defined as daily life activities requiring more energy than 3 times the resting metabolic rate (>3METs). Participants were asked to keep their regular eating habits during the study.
Testing
Prior to the study, participants took part in a familiarization session, during which the correct exercise techniques were explained. Following this, testing was undertaken in random order on different days. After a standardized warm-up (i.e., dynamic flexibility and stretching routine) and a specific warm-up (e.g., two submaximal effort trials of bench press exercise with an initial weight), participants performed strength and power tests, as described below.
Maximum Voluntary Isometric Contraction
Participants performed three maximum voluntary isometric contractions using a FiTRO Linear Isokinetic Dynamometer (FiTRONiC, SVK). The participants were seated in a fixed chair with their lower legs placed on a leg press machine platform with a knee angle of 90°. Participants were carefully instructed to contract “as fast and forcefully as possible.” Online visual feedback of the instantaneous force was provided to the participants on a computer screen. Peak force, peak rate of force development (RFD), and RFD over time intervals of 0 to 100 and 0 to 200 ms were analyzed.
Countermovement Jump, Squat jump, and Drop Jump
Countermovement jumps (CMJ) were performed from full extension to a knee angle of 90°, followed immediately by an upward movement. Squat jumps (SJ) began from an initial semisquat position (90° knee flexion), determined from visual inspection, and once achieved, participants held the position for approximately 2 seconds before performing an upward movement on the command of the tester. The better of the two trials of the CMJ and SJ were taken for evaluation.
The drop jump (DJ) was performed from a height of 30 cm. Participants were instructed to drop off a platform and then quickly jump upward as high as possible. The most enhanced score of the two trials were utilized for analysis. Reactive strength index was calculated as a ratio of jump height and ground contact time.
A computer-based system FiTRO Force Plate was used to monitor basic biomechanical parameters involved in exercise (FiTRONiC, SVK). The system consists of a strain gauge force plate, electronics, 12-bit analog–digital convertor and software. Basic software from the same company (FiTRONiC, SVK) was used for calibration, data acquisition, storage, and analyses (integral and average calculation from specified intervals, time zoom). An analytical software module was utilized for the calculation of acceleration, velocity, displacement, and power from force–time curve. Vertical force (F) applied to the plate consists of weight (product of body mass m and gravitational constant g) and inertia component (product of body mass and vertical acceleration).
Bench Press
Bench presses were performed randomly with and without a countermovement (CM) and using maximal effort in the concentric phase of lifting. The initial weight of 20 kg was increased by 10 kg or 5 kg (at higher loads) up to maximal power. Rest intervals of 2 minutes were applied between repetitions with particular weights. The most enhanced results of the three trials (two at higher loads) were utilized for evaluation.
The CM chest press required the participants to lower the barbell to the chest without making contact when transitioning from the eccentric to concentric phase. Any repetitions that contacted the chest or failed to come within 0.05 m of the chest was disregarded and repeated after 1 minute of rest. Exercises without CM began from an initial position on the chest (the barbell about 0.05 m from the chest), and once achieved, participants held the position for approximately 2 seconds before performing an upward movement on the command of the tester. Each participant was observed during the exercise to ensure that no countermovement was performed. Participants were required to keep the same grip width for the entire testing protocol and to ensure that contact was maintained between their hips and back with the bench.
A computer-based system, FiTRO Dyne Premium, was utilized to monitor basic biomechanical parameters involved in the exercises (FiTRONiC, SVK). The system consists of a sensor unit based on precise encoder mechanically coupled with a reel. While pulling the tether (connected by means of small hook to the barbell axis) the reel rotates and measures velocity. Rewinding of the reel is guaranteed by a string producing force of approximately 2 N. Signals taken from a sensor unit are conveyed to the computer by means of USB cable. The system operates on the Newton’s law of universal gravitation (force equals mass multiplied by gravitational constant) and the Newton’s law of motion (force equals mass multiplied by acceleration). Instant force while moving a barbell in a vertical direction is calculated as the sum of gravitational force (mass multiplied by gravitational constant) and acceleration force (mass multiplied by acceleration). Acceleration of vertical movements (positive or negative) is obtained by derivation of vertical velocity, measured by a highly precise device, mechanically coupled with the barbell. Power is calculated as a product of force and velocity and the actual position by integration of velocity. Comprehensive software allowed the collection, calculation, and online display of the basic biomechanical parameters involved in the weight exercise. Previous studies have identified that measurements of peak and mean power during resistance exercises using the FiTRO Dyne Premium system provide reliable data (Jennings, Viljoen, Durandt, & Lambert, 2005; Zemková et al., 2015).
The device was placed on the floor and attached to the bar by a nylon tether. Participants performed the exercise while pulling on the nylon tether of the device. Peak and mean values of power and velocity were obtained throughout the entire concentric phase of lifting, as well as from the acceleration segment.
Training
The participants were randomly divided into two groups. While the first group underwent resistance training, the second group performed aerobic training for a period of 3 months (three sessions/week). All training sessions were supervised by exercise professionals. Adherence to the training program was monitored and regularly encouraged.
Aerobic performance and cardiovascular health status were assessed by a cardiologist in the recruitment process, and after completing the 3-month intervention. Maximal aerobic capacity (VO2max) was calculated from the continuous measurement of gas exchange (Ergostik, Geratherm Respiratory, Bad Kissingen, Germany) during an incremental exercise test (Lode-Corival cycle ergometer, Lode B.V., Groningen, The Netherlands) and expressed relative to lean body mass. Each session began with a standardized warm-up and ended with cool down stretching exercises. During the training, aerobic dancing, running, and spinning were alternated. During each session (of 1 hour duration) the exercise intensity was monitored by using a Polar RS300X (Polar, Finland). Intensity was maintained at 70% to 85% of maximal heart rate.
The resistance training program was designed according to the individual strength assessments at the beginning of the study. The strength training sessions were carried out at the FITGYM Fitness Centre of the Faculty of Physical Education and Sports, Comenius University in Bratislava. Participants performed the periodized strength-training program three times per week (Monday, Wednesday, and Friday) for 12 consecutive weeks via the use of equipment, free weight and machine resistance exercises. Participants were informed about training methods and the training equipment to ensure the safety of the workouts. Instructions outlining the proper and safe exercise technique for all exercises were provided before testing and training. All training sessions were carried out individually and trainees were under constant supervision. An experienced expert was present during every training session to ensure the exercises were performed correctly.
The aim of the resistance training program was to enhance maximal strength as well as explosive power when possible. Each session consisted of a brief warm-up, followed by exercises for strengthening the major muscle groups. Within two to three workouts, the optimal weight was selected. This period gave the participants the opportunity to practice technique and experiment with different resistances. The strength training program was designed according to the fundamental principles that ensure a progressive overload of the musculature. Progress was made through increasing the amount of weight, increasing the number of repetitions and sets, decreasing the amount of rest time between sets, and a combination of any of these according to the subject’s physical fitness. The exercises utilized standard free weights and equipment that is available in most gyms. This approach allowed participants to become familiar with the beginners weight training workout routine that can be easily followed after completion of the study.
Structure of the Sessions
Each session began with a general warm-up of 10 to 15 minutes and ended with static stretching of approximately 5 minutes. The total duration of training session was 60 to 70 minutes. Four to five specific resistance exercises were applied twice per week (Monday and Wednesday). The sequence of exercises was maintained throughout the study. While the Monday routine served as an upper body workout focusing on chest, shoulder, and arm muscles, the Wednesday routine exercised lower body—thigh, hips, and back muscles. The examples of strength training Sessions 1 and 2 are outlined in Table 1. The exercises of the third session (Friday) activated a larger muscle mass (multijoint) and core muscles (push-ups, squats, sit-ups, swing, seated lat pull-down, shoulder press, prone plank). The third session was carried out as the functional training via circuits (Table 2).
An Example of Training Sessions.
Circuit Training Sessions: Fridays (Functional Training).
Training Program
All strength-training exercises were performed using smooth and controlled concentric and eccentric muscle action. The weight loads were set differently and mainly reflected one’s level of strength, performance, and acute or chronic health problems. In each session, the participants completed a specific number of repetitions and sets depending on the intensity for that workout session (Table 3). The training progression incorporated three levels of difficulty by increasing the weight load (% 1-RM), repetitions/set, sets/exercise, and rest intervals. Exercise selection and load gradation–intensity was determined from the individual assessment prior to the beginning of the program. The initial 4 weeks (Phase 1) were used as an anatomical adaptation and familiarization phase, with intensity and volume being moderate. In the second phase (Weeks 5-8), the program used a gradual linear increase in intensity and duration as well. Subjects who completed the exercises correctly after 8 weeks of the training were progressed to a third difficulty level (Weeks 9-12).
Average Training Values for the Periodized Strength-Training Program.
Note. Days/week = the number of training days per week; RM = repetition maximum; intensity = the average intensity assessed in percent of 1 RM for each week; duration = the approximate total workout time each resistance training sessions.
A flowchart of the experimental protocol is provided in Figure 1.
Flowchart of the experimental protocol.
Statistical Analyses
Data analyses were performed using statistical program SPSS for Windows version 18.0 (SPSS, Inc., Chicago, IL). The effect of training programs on strength and power variables determined by maximum voluntary isometric contraction, squat, countermovement, and drop jumps, plus the bench press were evaluated using a two-way analysis of variance (ANOVA) with repeated measures. Factors considered included time (pretraining vs. posttraining) × group (resistance vs. aerobic). Where significant differences were detected (p ≤ .05), a Tukey post hoc test was utilized. Effect sizes (ES) are reported in the tables. Descriptive statistics include means and standard deviations. Statistically significant pre–post training changes are marked with a symbol (*p ≤ .05, **p ≤ .01).
Results
There were no significant pre–post intervention changes in anthropometric and body composition variables in any participants (weight from 104.4 ± 14.8 kg to 104.4 ± 15.4 kg, BMI from 31.2 ± 3.7 kg/m2 to 31.3 ± 4.0 kg/m2, and body fat from 30.6 ± 4.7% to 29.3 ± 5.1%). The obesity level in both groups was comparable before and after the training period. Results of pre–post training changes in strength and power variables after resistance and aerobic training in overweight and obese men are displayed in Tables 4 and 5.
Parameters of Strength and Power Prior to and After Resistance Training in Overweight and Obese Men.
Note. RFD = rate of force development; CMJ = countermovement jump; SJ = squat jump.
Parameters of Strength and Power Prior to and After Aerobic Training in Overweight and Obese Men.
Note. RFD = rate of force development; CMJ = countermovement jump; SJ = squat jump.
Maximal Muscle Strength and Rate of Force Development
Results from the ANOVA indicated no significant differences for the factors of group and time. There were no significant changes in any parameter after resistance training. After the aerobic training the values even slightly decreased.
Peak Power and Height of Countermovement and Squat Jumps
The ANOVA revealed a significant interaction effect of group × time for the jump parameters, which increased significantly more after resistance than aerobic training. There was a significant increase in the height of the jump (12.8%, p = .013), peak power (10.1%, p = .026), and peak velocity (9.7%, p = .037) during countermovement jumps after the resistance training. Parameters obtained during squat jumps also increased significantly after the resistance training, that is, the height of the jump (11.8%, p = .019), peak power (9.6%, p = .032), and peak velocity (9.5%, p = .040).
Reactive Strength Index
Regarding the reactive strength index determined from a drop jump, the ANOVA revealed no significant differences for the factors group × time. There were no significant changes identified after either the resistance or the aerobic training.
Mean Power in the Concentric Phase of Bench Press
As expected, the ANOVA revealed a significant main effect for group × time (p < .01), that is, there was a significant increase in power output following the resistance training but not after the aerobic training. More specifically, there was a significant increase of mean power in the concentric phase of the countermovement bench presses at 30 kg (18.6%, p = .021), 40 kg (14.6%, p = .033), and 50 kg (13.1%, p = .042). These values also increased significantly during concentric-only bench presses at 30 kg (19.6%, p = .017) and 40 kg (13.9%, p = .037; Figures 2a,b-above). The aerobic group failed to show any significant improvement in these parameters mainly due to the fact that their program did not include exercises for the upper limbs (Figures 2a,b-below).
Mean power during barbell bench presses performed (a) without and (b) with countermovement before and after (above) the resistance training and (below) the aerobic training (*p < .05).
Discussion
Three months of resistance training in previously untrained overweight and obese individuals enhanced power performance during the bench press as well as during squat and countermovement jumps. The training did not induce any significant changes in the parameters determined from the drop jump and maximum voluntary isometric contraction. More specifically, there was a significant increase in the height of the jump (12.8%), peak power (10.1%), and peak velocity (9.7%) during countermovement jumps following the resistance training. Parameters obtained during squat jumps also increased significantly after the training, that is, the height of the jump (11.8%), peak power (9.6%), and peak velocity (9.5%). There were no significant changes either in reactive strength index, maximal muscle strength, or the rate of force development following the resistance training.
It is important to point out that lower limb muscle power improved after the resistance training despite no changes in the weight (from 102.7 ± 13.0 to 102.8 ± 12.9 kg) and BMI (from 30.7 ± 3.3 to 30.8 ± 3.5 kg/m2). Obesity is associated with a lower strength-to-mass ratio (Koster et al., 2011; Vilaça et al., 2014; Zoico et al., 2004), and a higher muscle lipid content is associated with compromised muscle strength and power (Goodpaster et al., 2001; Hilton, Tuttle, Bohnert, Mueller, & Sinacore, 2008; Sipilä et al., 2004). It has been suggested that excess stored fat may limit the magnitude of improvement after the resistance training. For example, young adults with higher BMI and greater subcutaneous adipose tissue surrounding the bicep exhibited an attenuated gain in bicep strength with resistance training, despite a similar relative increase in muscle size as in those who were normal weight or had less subcutaneous adipose tissue (Pescatello et al., 2007; Peterson et al., 2011). Nevertheless, the study by Nicklas et al. (2015) identified that the addition of caloric restriction during resistance training improves mobility and does not compromise other functional adaptations to resistance training. Resistance training improved body composition and muscle strength and physical function in the obese. These findings, along with the observation in the present study support the incorporation of resistance training into obesity treatments regardless of whether caloric restriction is part of the intervention.
On the other hand, the aerobic group failed to show any significant improvements because the training stimuli were not sufficient to enhance lower body muscle power.
Contrary to these findings, a significant increase was previously identified in the absolute lower limb anaerobic power output evaluated by means of a jumping test after 3 weeks of aerobic (A: 13.7%) and aerobic plus strength training (AS: 18.1%), without any substantial difference between A and AS (Sartorio, Lafortuna, Massarini, & Galvani, 2003). The addition of strength training to A conditioning increased maximum strength. The maximum strength increase after the body weight reduction program determined by one maximal repetition test of lower and upper limb muscle groups was significantly greater in the AS group, ranging from 11.4% to 25.4% (A) and from 26.7% to 41.8% (AS).
Kraemer et al. (1999) discovered that maximum strength, as determined by 1-RM testing in the bench press and squat exercise, significantly increased for a diet group of overweight men that performed both aerobic and strength training three times per week for 12 weeks in both the bench press (+19.6%) and squat exercise (+32.6%). Sarsan, Ardiç, Ozgen, Topuz, and Sermez (2006) identified that a 12-week resistance training significantly improved 1-RM test of hip abductors, quadriceps, biceps, and pectorals compared with those in the control group. Only in the hip abductor muscle strength was there a significant increase in the resistance compared with the aerobic exercise group.
Interestingly, 1-RM significantly correlated with total fat (r = .56, p < 0.01), leg fat (r = .45, p < .05), and arm fat (r = .39, p < .05; Zavin et al., 2013). A short-term (3 week) mass reduction program (5 days/week) entailing exercise (aerobic and strength training) and energy-restricted diet in morbid obesity induced significant effects on body weight changes and composition as well as on maximum voluntary total isotonic strength and maximum leg power output (Sartorio, Maffiuletti, Agosti, & Lafortuna, 2005). After the intervention, maximum voluntary total isotonic strength improved significantly, while no change was detected in the maximum leg power output, although the maximum leg power output per unit body weight and fat-free mass increased significantly. In spite of the positive correlation of maximum voluntary total isotonic strength and maximum leg power output with fat-free mass, there was no detectable relation between the changes in body composition and those in motor performance. The improvement in maximum voluntary total isotonic strength and maximum leg power output was attributable to factors other than muscle mass change.
The extent of the functional and health benefits to be accrued from resistance training depends on factors such as initial performance and health status, along with the specification of program design variables such as frequency, duration, intensity, volume, and rest intervals (Deschenes & Kraemer, 2002). If possible, the power control should be taken from the parameters of a performance test (Kortmann & Schumacher, 2013). The present study, in addition to the assessment of power outputs of the lower limbs used in most of the studies, also evaluated the power performance of the upper limbs. There was a significant increase in mean power in the concentric phase of countermovement bench presses at 30 kg (18.6%), 40 kg (14.6%), and 50 kg (13.1%). These values increased significantly also during concentric-only bench presses at 30 kg (19.6%) and 40 kg (13.9%). Bench presses were performed with increasing weights up to maximal power. This approach represents a more specific and safe method for testing power performance in the overweight and obese than the measurement of 1-RM. Moreover, testing can be performed in fitness centers and training programs can be adjusted accordingly.
When trained properly (i.e., similar intensity and volume), functional and physiologic adaptations after resistance training were similarly notable among women and the elderly as they were among young men. However, in contrast to relative measurements, gender and age differences exist in the absolute magnitude of adaptation (Deschenes & Kraemer, 2002). Obesity-related variations in body composition differs considerably due to gender, and is responsible for differences in muscle performance. The higher muscle strength observed in obese subjects (both men and women) and in male subjects (both obese and normal weight) is accounted for by a greater amount of fat-free mass (Lafortuna, Maffiuletti, Agosti, & Sartorio, 2005). A limitation of the study was the relatively small sample size (n = 17) consisting of only male participants in spite of the fact that 35 participants completed the training program. However, most of the female participants underwent the aerobic training. Therefore, there is a lack of information on changes in strength and power performance after the resistance training in a group of women. For this reason, these findings cannot be generalized to the broader community based on this study alone.
Conclusions
A regular 3-month resistance training in previously untrained overweight and obese men led to an increase of muscle power in the upper body for 16% and lower body for 10% despite no changes in the body weight and BMI. Such improvements in power performance after a long-term sedentary lifestyle with lack of regular physical activity, may be beneficial for this population for increasing their quality of life, decreasing the risk of falling and a reduction in health-related consequences.
Footnotes
Declaration of Conflicting Interests
The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding
The authors disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This work was supported by the European Foundation for the Study of Diabetes (EFSD) and Lilly Research Fellowship Programme (No. 70995), and by the Scientific Grant Agency of the Ministry of Education, Science, Research and Sport of the Slovak Republic and the Slovak Academy of Sciences (No. 2/0191/15).