Lack of time is consistently cited as one of the most common external barriers to pursuit of a physical fitness routine (1,2). In a recent study, respondents were 46.7% likely to indicate “lack of time” as a serious barrier to regular exercise (1). As another barrier to a routine fitness regimen, “lack of facilities” was cited by 33.4% of respondents (1). Lack of time and lack of facilities are both legitimate difficulties that seem to be preventing a high number of people across the country from attaining the recommended 30 minutes of exercise 5 days a week (150 minutes total) (3). As the obesity epidemic continues to contribute substantially to the burden of domestic disease, initiatives aimed at encouraging physical fitness with consideration of the most common reported barriers to maintenance of a fitness regimen are imperative. Considering that lack of time and lack of facilities are among the predominant barriers to exercise, isometric exercise (IE) is an attractive option along with other body weight types of exercises.
Considering that lack of time and lack of facilities are among the predominant barriers to exercise, isometric exercise (IE) is an attractive option. IE is any form of exercise in which the myocytes tense but maintain a set length and do not shorten.
IE is any form of exercise in which the myocytes tense but maintain a set length and do not shorten (4). Such exercises have been used for decades for rehabilitation after orthopedic and other surgical procedures and for conditions in which arthrokinematic motion (motion between joint surfaces) is inhibited by pain such as rheumatoid arthritis, fibromyalgia, and osteoarthritis, especially in cases of acutely inflamed joints (5–8). IE as an emerging form of exercise for healthy individuals is a topic of much debate within the medical and fitness communities (9). Concerns over the safety of IE have been raised. Primary concern has focused on the increase in systolic blood pressure during the exercise phase, and individuals with hypertension have been advised to avoid IE routines in the past (9). Paradoxically, recent research has documented actual reductions in resting blood pressure in those who regularly participate in IE (10–15). Indeed, a recent meta-analysis published by Owen et al. (16) concluded that IE may be an effective addition to a lifestyle intervention plan aimed at lowering resting blood pressure. Moreover, a 2018 study by Wiles et al. (9) demonstrated that peak systolic blood pressure does not rise over dangerous levels during IE, even when undertaking intense isometric routines. Indeed, systolic blood pressure rose to a maximum of 173 ± 23 mmHg systolic, far below the American College of Sports Medicine’s recommendation of not exceeding 250 mmHg systolic during exercise. Still, individuals with certain medical conditions should seek guidance from a physician before initiating exercise of any kind, and IE is no exception. Preactivity screening tools such as the physical activity readiness questionnaire for everyone (PAR-Q+) can be used to effectively assess readiness to begin an exercise routine (17).
Although there is as yet no consensus on the safety of IE, evidence of its benefits continues to accumulate. In addition to the demonstrated reduction in resting systolic blood pressure (described earlier), IE has been associated with a host of positive outcomes. In a cohort of patients with low back pain, IE was shown to be effective in reducing the reported degree of pain while maintaining muscle activity (18). A recent meta-analysis evaluating isometric handgrip training chronicled not only reduction in blood pressure but also mitigation of oxidative stress and positive modulation of heart rate variability parameters (19). These data show that IE may exhibit some of the same cardiovascular benefits as other forms of exercise. In addition, IE can be performed at varying levels of intensity, which modulate the degree of anaerobic versus aerobic metabolism used to perform the exercise, and so practitioners can target both metabolic systems (20).
Although there is as yet no consensus on the safety of IE, evidence of its benefits continues to accumulate. In addition to the demonstrated reduction in resting systolic blood pressure (described earlier), IE has been associated with a host of positive outcomes.
In addition to positive alterations in vascular dynamics, IE is an effective strategy to build muscle strength (21–23). More research is needed to determine if IE is an effective strategy for improvement in bone density. Few studies have evaluated IE in terms of weight loss.
Available evidence indicates that IE has many of the same beneficial effects of other forms of exercise. What makes IE a valuable asset in the armamentarium of those who are interested in their health is the ease with which IEs can be performed. For those who are unable to dedicate a portion of their day to the direct pursuit of exercise (almost 50% as described previously), and for those for whom lack of equipment is a barrier to pursuit of exercise, IE may be the perfect solution. The goal of this article is to make a strong case for the use of regular IE. This author has provided an example fitness regimen of discrete IEs that can be incorporated into a normal day, performing each exercise at various intervals throughout the day as time allows.
AN EXAMPLE FITNESS REGIMEN
The following exercise regimen provides an example of how IE may be incorporated into a logical exercise framework. This author provides 4 days of exercise, to be performed throughout a 7-day period, allowing for other days to be dedicated to other forms of exercise or rest periods. These exercises should not be considered to take the place of the recommended 150 minutes of exercise a week (24). Instead, they should be used to add activity and muscular stimulation to a busy individual’s schedule. In addition, practitioners should be aware that three of the days are dedicated to the upper body, and 1 day is dedicated to the lower body. This uneven split is due to the difficulty for IE to be done in a discrete manner to target the lower body. Extra attention should be given to the lower body on days on which IE is not performed to account for this imbalance. The exercises can also be performed at home in the supine position as an isometric wall leg press on either a bed or the floor.
Each of these exercises can be completed in a discrete manner with no equipment whatsoever. The red force vector in the images indicates the direction of force applied by the working muscle. This author has suggested the addition of props to some of the exercises as an alternate way of completing the exercise. Given documented reduction in systolic blood pressure after performing IE of the lower body for four repetitions of 2 minutes each, this author suggests a protocol where exercises are held for 2 minutes each (9). Although available literature does not support beneficial effects in blood pressure reduction of IE holds of only 1 minute, practitioners also can experiment with holds of lesser duration. In addition, this author provides an alternative “high-intensity” method of training where holds are only held for 10 seconds, but at a higher level of intensity. This duration of hold has been linked with an increase in strength over a 5-week period (21). Longer holds may be associated with a greater reduction in systolic blood pressure, whereas shorter holds may lead to greater increase in strength. Participants should choose their routine based on their goals.
An appropriate rest period of 1 minute should follow each 2-minute isometric hold. A rest period of 30 seconds should follow the more intense 10-second holds. Rest periods can decrease as participants move from beginner to advanced routines (Table). The author encourages users to experiment with other forms of IE and to modulate the number of repetitions, interval length, and rest length based on perceived exertion. Exercisers should choose their protocol based on their perceived fitness level (beginner, intermediate, or advanced) (Table). Progression to higher-intensity levels should occur once exercisers feel their current regimen no longer correlates to the Borg CR-10 score indicated in Table 1B. The Borg CR-10 score (also known as the OMNI-Resistance Ratings of Perceived Exertion scale [OMNI-RES]) is a scale for monitoring perceived exertion ranging from 1 to 10, with 1 being “very weak” and 10 being “extremely strong” or “maximal” (25,26). In addition, practitioners are encouraged to experiment with modulation of the exercises to be done in a supine, prone, or seated manner.
In performing these exercises, practitioners must be aware of varying peak torques throughout the full range of motion of a muscle. Peak torque is a concept in exercise physiology, which is defined as the point at which maximal force can be generated by the targeted muscle (27). Although peak torque generally is considered to occur when the myocytes are at their rest position (i.e., neither fully extended nor flexed), heterogeneity exists given lack of consistency between angular point of maximal force generation and joint moment arm (a perpendicular distance from the line of force application to the axis of rotation (27). For this reason, this author suggests varying the angle at which the exercise is performed to achieve strength gains throughout the range of motion of the targeted muscle (Table 1B). This author suggests alternating between positions 1, 2, and 3 demonstrated in the figures found within this manuscript during each subsequent exercise to ensure proper attention to as much of the range of motion of the muscle as possible. Given the lack of documented superiority of single versus multijoint exercises, this author has included both forms of exercises in our protocol (28). While standing during performing these exercises, proper posture must be maintained with the spine in a neutral position, taking special care to maintain lumbar lordosis (29). Attention to maintenance of proper breathing is imperative, and exercisers should stop the exercises if they feel lightheaded or short of breath. By practicing proper breathing techniques, exercisers will reduce the risk of a Valsalva effect, which may cause significant elevations in blood pressure. During longer, lower-intensity holds, breathing should be consistent and nonlabored. During intense holds, the exerciser should exhale to ensure proper core stability.
Day 1: Chest, Triceps
Pectoralis fly: the nonworking arm should provide counterresistance as the exerciser attempts to adduct the working shoulder (right arm in image) toward the midline, tensing the pectoralis major and pectoralis minor muscles.
Triceps press-down: the nonworking arm (left arm in image) should provide counterresistance to forearm extension at the elbow, tensing the triceps brachii muscle.
Alternative exercise with a prop: the triceps brachii muscle also can be worked effectively through the use of resisted forearm extension at the elbow by pushing down on a table or other stationary object.
Day 2: Back, Biceps
One arm row: the nonworking arm should provide counterresistance to posterior shoulder extension of the working arm (right arm in image), tensing the latissimus dorsi, rhomboids, and trapezius muscles.
Alternative exercise with a prop: the latissimus dorsi, rhomboids, and trapezius muscles also can be worked effectively through the use of resisted shoulder adduction with extension by pulling on another surface such as a steering wheel or a table. In addition, a straight arm latissimus dorsi pull down can be performed using a table, bookshelf, or other prop which is above the head.
Trapezius shrug: the nonworking arm should provide counterresistance to upward shrugging of the working arm (right arm in image), tensing the trapezius muscle.
Alternative exercise with a prop: the trapezius muscles also can be worked effectively through the use of resisted upward shrugging by holding on to a chair, table, or appropriately heavy object.
Concentration curl: the nonworking arm (left arm in image) should provide counterresistance to superior motion of the forearm, tensing the biceps brachii muscle.
Day 3: Legs and Core
Squat flex: the muscles of the thigh (quadriceps femoris, gluteus maximus and minimus, and hamstrings) should be flexed while maintaining proper positioning of lordosis in the lumbar spine as demonstrated. Force should be applied against the floor in the direction of the red force vector.
Alternative exercise with a prop: the quadriceps femoris, gluteus maximus and minimus, and hamstrings muscles also can be worked effectively through the use of wall squats, and this exercise specifically has been shown to reduce systolic blood pressure (9).
Abdominal brace: the abdominal muscles should be flexed and the back should be maintained in a neutral position.
Day 4: Shoulder and Forearms
External rotation: the nonworking arm should provide counterresistance to external rotation of the working arm (right arm in image), tensing the infraspinatus and teres minor muscles as well as the posterior portion of the deltoid muscle. The exercise also should be performed in the opposing manner, with the nonworking arm providing counterresistance to internal rotation of the working arm, tensing the subscapularis, latissimus dorsi, teres major, and anterior deltoid.
Deltoid forward raise: the nonworking arm should provide counterresistance to superior motion of the working arm (right arm in image), tensing the anterior portion of the deltoid muscle. The exercise also can be done with the arm held parallel to the horizon.
Forearm flex: the nonworking arm should provide counterresistance to flexion or extension of the working arm (right arm in image), tensing the wrist flexor and extensor musculature.
Additional points of emphasis for the proposed routine:
- On single-side exercises, sides should be switched between repetitions to ensure equivalent effort bilaterally.
- Perceived effort of counterresistance from the nonworking side should reflect goals of the exerciser and should be based on the Borg CR-10 score. Significant counterresistance results in the use of anaerobic metabolism to support much of the ATP generation required for muscle function (20). More moderate resistance may be appropriate for those who are interested in a less intense workout with a higher percentage of energy generated in an aerobic fashion (20).
- Exercisers can experiment with small exercises of a few inches back and forth within the natural range of motion of the demonstrated exercise. Although this would make the exercises no longer isometric in nature, some individuals may prefer performing the exercises in this alternative manner.
- For those who wish to activate individual muscle groups in a specific way, the specific split routine documented in this manuscript may be superior. However, experimentation with different day split routines using the exercises demonstrated is encouraged. If a general full body workout is desired, participants can perform all of the exercises in one day, several times a week. Participants can also alternate upper body and lower body days.
- There are a substantial number of alternative IEs that can be performed to achieve a higher degree of muscle activation. Space restraints limit full exploration of such exercises, but several examples to use as starting points for participants who wish to continue to develop and improve upon their isometric regimen include the following: 1) wall press IEs to activate the hip abductor and adductor muscles; 2) shoulder internal and external rotation using a doorway or wall as a point of resistance; 3) latissimus dorsi activation through an isometric, double-arm pull down against the top of a table or desk, with the participant sitting or kneeling on the floor; and 4) IEs performed while lying in bed, such as pressing the fists into the mattress, holding a push-up position, single-arm rowing into the mattress, and leg presses with the feet against the wall.
The author conceived the idea presented in this article while waiting for the anesthesia team to anesthetize a patient before helping to assist in an orthopedic surgery procedure. Surgery, as a field with unpredictable work hours, can make finding time for dedicated exercise difficult. However, the physicality of the field requires much stamina and strength, and neglect of physical fitness can adversely affect job performance in surgery and in many other fields (30,31). The exercises presented in this article will allow individuals to achieve a surprisingly substantial workout in a very discrete manner, and in almost any situation during a lull period throughout the day.
The literature to date has not specifically evaluated the effect of IE on mental health parameters. Other forms of exercise have been shown to have substantial effects in mood elevation, alleviation of anxiety or depression, and improvement in sleep dynamics (32–35). IE is effective at stimulating the cardiovascular and skeletal muscular systems as has been discussed. Therefore, it is reasonable to assume that a similar endorphin and dopamine response may be seen with IE as is seen with other forms of exercise (36–39). Future research on the effect of IE on mental health is warranted.
Further investigation also should aim to quantify minimal effective doses of IE to further refine regimens such as the one described in this article. Studies could elucidate the degree of muscular fatigue that occurs with proper performance of the exercises and compare these metrics to exercise of other forms to assess the effectivity of IE in building strength and cardiovascular fitness. Currently, there is no consensus as to the degree of intensity of IE, which would provide therapeutic benefits for medical conditions such as hypertension, although a recent study indicates that effort levels as low as 30% of maximal intensity appear to be effective (40). Achieving further understanding of intensity levels of IE exercises and their modulation of health parameters would allow providers to better counsel their patients as to the specific goals of the workout regimen. Lastly, patient adherence to IE protocols should be assessed. Despite ease of performance of the exercises, discrete nature of the exercises, and lack of need for additional equipment, some patients may be resistant to the addition of such exercises to their daily life.
The evident convenience of IE coupled with its known health benefits should motivate health care practitioners and those committed to health education to recommend IEs to individuals who claim that they cannot exercise due to time constraints and lack of equipment. IE is safe, effective, and facile to use on a daily basis. IE can fit into virtually any schedule, no matter how demanding, and time and equipment constraints are eliminated. IE allows even the most overwhelmingly busy individuals to prioritize exercise, and to see lulls such as red lights in a new light — not as an annoying hindrance to a busy day but instead as a chance to move forward toward accomplishment of fitness goals.
IE can fit into virtually any schedule, no matter how demanding, and time and equipment constraints are eliminated. IE allows even the most overwhelmingly busy individuals to prioritize exercise, and to see lulls such as red lights in a new light — not as an annoying hindrance to a busy day, but instead as a chance to move forward toward accomplishment of fitness goals.
BRIDGING THE GAP
Isometric exercise is a safe and effective form of exercise which is underused, especially given “lack of time” as a chief reason for why individuals are unable to pursue a long-term exercise regimen in the United States. This author proposes a routine where participants engage in various isometric holds for 2-minute intervals. Health professionals themselves can use these exercises throughout the day and/or they can recommend them to their clients.
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