Adaptation response is very specific to the physiological demands experienced by the body and the frequency with which the stress is experienced. An individual who routinely goes to the gym ensures two things: 1) a frequency of physical activity has been established, and 2) more calories are being expended by the body than if the person was sedentary. For some reason, people believe that by simply being in an environment where physical activity occurs and engaging in some level of the activities, they should attain all the desired results associated with the activities. From a physiological standpoint, this is way off base, as specific research in the area indicates otherwise. An evaluation of a traditional approach to weight lifting and the common intensities used based on one’s own accord indicates these actions will likely yield a low caloric expenditure and no overload on the tissue. The obvious variable is the intensity. According to several research studies published in the Journal of Strength and Conditioning Research, most people self-selecting intensities train between 40-60% of 1RM but do not use corresponding repetition ranges that cause volitional failure and therefore do not stimulate any overload. The research also suggests that both men and women have a tendency to select intensities far below threshold for the repetitions they perform, which explains why so many people exercise with limited results.

In one study (Glass, 2004) analyzing self-selected loads, normal weight, untrained men and women with a mean age of 19.5 performed the seated chest press, leg extension, seated back row, military press, and biceps curl. The subjects self-selected the loads used for each exercise bout. Following the self-selection trials, the subjects were tested for their one repetition maximum (1RM) for each lift. Regardless of gender, and in all cases, the self-selected loads were below 60% 1RM. Also, lift intensities were found to be similar for men and women, ranging between 42 and 57% 1RM. Consistent with the aforementioned findings, the number of repetitions completed and ratings of perceived exertion responses did not differ between gender, and neither gender reached volitional failure when exercising. The research demonstrated that when left to their own devices, new exercisers do not select a lifting intensity sufficient to induce hypertrophic responses and subsequent strength increases.

The findings in the above study were reinforced by a later trial (Focht, 2007) that compared supervised exercise sessions using controlled intensities to subsequent self-selected exercise. A similar group of subjects – untrained women of college age – were asked to exercise at 75% of measured 1RM in a supervised weight training environment and then asked to train on their own using self-selected intensities for the same exercises. Both the rates of perceived exertion and intensities used were higher in the intensity-selected trial compared to the self-selected trial. Researchers concluded that untrained women are not likely to self-select a relative intensity sufficient to stimulate meaningful improvements in muscular hypertrophy or strength. These findings reinforce the fact that people seem to prefer to work out at a level that is below threshold, suggesting that using a personal trainer may be necessary for exercise participants to reach a level of training that will produce physiological improvements.

A recent study (Ratamuss, 2008) investigated this concept. The study examined the influence of a personal trainer on an individual’s resistance training program versus unsupervised resistance training on the self-selected intensities used during resistance exercise. Forty-six resistance-trained women with a mean age of 26 either trained individually or with a personal trainer. During their individual resistance training workouts, the women were asked to select a weight that enabled them to complete ten repetitions. The exercises they performed included the chest press, leg press, seated row, and leg extension. In a subsequent trial, each participant was tested for one repetition maximum (1RM) strength on each exercise. The self-selected intensity was then calculated based on a percent of each subject’s 1RM value. For self-selected relative intensity, the personal training group selected significantly greater intensities for each of the exercises. The interesting fact was that for each exercise used, the value selected by both groups was below the training threshold for improvements. In comparison, the intensities selected by the personal training group were at least 10% higher than the self-selected intensities, but in no exercise was the intensity greater than 60% used [Leg press (50% vs. 41%), Chest press (57.4% vs. 48%), Seated row (56% vs. 42%) and Leg Extension (43% vs. 38%)]. The average self-selected intensity for all exercises equaled approximately 51.4% in the personal training group and approximately 42.3% in the self-directed group. When the 1RM values were compared, the leg press, leg extension, and seated row were greater in the personal-trained group compared to the self-directed group. In all exercises except the leg press, the rates of perceived exertion values were significantly higher in the personal-trained group compared with the self-directed group as well. Researchers concluded that these results indicate that resistance training under the supervision of a personal trainer leads to greater initial 1RM strength values, self-selection of greater workout intensities, and greater ratings of perceived exertion values during resistance exercise. That being said, even with the use of a personal trainer, individuals do not perform the exercises at the same intensities when not directly under the supervision of the personal trainer.

Based on the findings from the different research trials, three relevant assumptions come to the forefront. The first is that although people exercise, self-selected exercise intensity is often too low to reap the adaptation benefits of improved strength and lean mass expected from routine resistance training. Secondly, personal trainers can have a positive effect on a person’s measured strength when compared to individuals that perform strength training without a personal trainer. Thirdly, those that train under the professional supervision of a personal trainer self-select higher intensities when left to their own accord than do individuals that have never used a trainer. These findings can be viewed as both positive and negative. Obviously, not only do personal trainers serve to improve a person’s strength when the client is under their guidance, the client may work harder on his or her own compared to participants working without the assistance of a personal trainer. On the other hand, regardless of supervision, people generally self-select training intensities that are too low for physical improvements because the exercise intensity used is sub-threshold.

This raises an important question: is education the key to changing a person’s training intensities from a sub-threshold level to an intensity value that exceeds threshold? In his 2004 trial, Glass et al. demonstrated that individuals who self-select loads for resistance training do so at a level that falls below the accepted threshold for overload and do not lift to volitional fatigue. In a recent study published in the Journal of Strength and Conditioning, Glass investigated the effects of education and experience on intensity selection. Using resistance training learning trials, Glass compared a control group composed of five women and three men, and a learning group of four women and four men, all of whom were novice weight lifters. The control group received an orientation on the proper use of the exercise machines employed for the trial, which included the seated chest press, leg extension, back row, biceps curl, triceps extension, and shoulder press. On a subsequent training day, the control group self-selected a training load by feel, as no weights were labeled. The learning group also received an initial orientation, but the subjects were tested for estimated 1 repetition maximum (1RM) on the seated chest press. On a subsequent day, the learning group completed two sets of the seated chest press at a weight that was 75% of the estimated 1RM. Additionally, each test subject was encouraged to lift until failure. On a third day, the learning group completed a self-selected trial identical to that of the control group. Following the completion of the trials, both groups were assessed for estimated 1RM on each of the machines used in the trials. Comparisons between the control group and the learning group on the blind self-selection of the chest press exercise demonstrated that the experience of learning the appropriate resistance to use for training before self-selecting a resistance had an impact on the load selected. In the educated group, the self-selected load on the chest press was 21% greater – about 65% of 1RM – compared to the control group, which averaged about 50% of 1RM. In the analysis of the other exercises, however, there were no significant differences in self-selected loads between groups. Glass et al found there were no significant differences in the number of repetitions performed or the rate of perceived exertion between groups. The authors concluded that although the learning trial of the chest press influenced the self-selected workload, the influence was not enough to change load self-selection. These findings further support the need for ongoing, supervised instruction. A cursory education in proper lifting technique and even load selection seems to carry very limited benefit for individuals exercising on their own.

This puts even greater emphasis on the need for more supervised exercise programs. Regardless of the environment or the type of training, aerobic trials yield similar results because people inherently gravitate towards exercise and physical activity that is perceived as comfortable. The problem lies in the fact that the very nature of working at comfortable levels suggests insufficient stress for adaptation improvements. To be sure, any exercise is better than none, and even low to moderate levels can benefit disease risk and management, but this strikes a significant blow to the idea the American people can and will exercise at a level that will positively affect the pandemic of diseases currently facing the nation. In fact all trends point in the opposite direction.

Glass et al. Journal of Strength and Conditioning Research. 2008 May;22(3):1025-9

Rassamus et al. Journal of Strength and Conditioning Research 2008 Jan;22(1):103-11

FochT, B.C. Journal of Strength and Conditioning Research 2007 Feb;21(1):183-7

Glass et al. Journal of Strength and Conditioning Research 2004 May;18(2):324-7