Previous investigations have indicated that prolonged standing and daily activity are likely to contribute to musculoskeletal and vascular symptoms. The symptoms include muscle fatigue, lactic acid accumulation, swelling, and soreness in human lower limbs [1
]. Many solutions have been proposed to effectively reduce these leg symptoms, such as using floor mats [2
] or graduated compression/elastic stockings [5
], appropriate work–rest cycles [7
] and static stretching [8
], and intermittent walking [9
]. However, these maneuvers are limited because most of them are related to the organizational strategies/regulations and are intervened directly in people’s works and activities.
The limitations of these methods make it feasible to exercise afterwards. One of the most popular methods is leg raising exercise because the exercise can be carried out by individuals. To eliminate leg fatigue and swelling, in Taiwan, many young women usually perform leg raising exercise while lying on a bed; the bedside wall supports the heels, and there is a widespread perception that leg raising before bedtime can prevent varicose veins on the legs [10
]. In addition, this exercise is also employed by many people (e.g., young women) for aesthetic purposes.
In clinical medicine, the aforementioned leg raising is called passive leg raising (PLR). As early as 1881, Forst described a leg raising test to provoke pain in patients with sciatica [11
]. The test is one of the methods currently used to predict the response of cardiac output to pretreatment fluid administration in patients with acute respiratory distress syndrome [12
]. It involves moving the patient from a semi-recumbent position to one in which the trunk is horizontal and the inferior limbs are passively elevated at approximately 45° [14
]. Passive leg raising also shifts blood from the lower extremities toward the intrathoracic compartment [17
]. Because leg raising is a simple and effective maneuver, it has recently attracted increasing interest for application in various tests for monitoring heart function [18
], assessing fluid responsiveness [19
], and unmasking pulmonary hypertension [20
]. However, before its popularity in fluid responsiveness tests, it was a rescue maneuver that had been used for years by first-aid rescuers. Zhang et al. [18
] suggested that PLR could improve cerebral and coronary perfusion and be a beneficial supplement to cardiopulmonary resuscitation (CPR), as it is not necessary to lift the legs too high above the ground. When the legs were lifted to 30°, 45°, 60°, and 90° from the ground, the volumes transferred from the legs to the upper body were 36%, 43%, 47%, and 50% of the initial volume in the legs, respectively.
Even though the PLR test has been well examined and its benefits have also been verified clinically, the effect of leg raising on fatigue and swelling of the lower limbs has received less attention, especially for healthy adults. Because of limited knowledge regarding leg raising from an ergonomic perspective, inappropriate raising or incorrect posture may cause physical discomfort or even pain. Unfortunately, no previous research addressed this issue. To fill the gap, we recruited nine young women as participants, who were instructed to perform leg raising under six test combinations of three postures and two time arrangements. The participants’ shank circumference (SC) reductions, as well as the discomfort ratings after performing each test combination were examined. We attempted to compare the effectiveness of these leg raising postures with different time arrangements on SC reduction.
Although leg raising test has been developed for clinical applications, the test is also currently used for eliminating shank stresses in healthy adults before bedtime. However, the effect of leg raising on fatigue and swelling elimination of the lower limbs is still unclear. This study therefore recruited nine young women to perform leg raising under six test combinations of three postures (namely lying supine, placing their feet and shanks on a yoga ball, and elevating the legs 60° against the wall) and two time arrangements (continuous vs. intermittent). The participants’ SC reductions and the discomfort ratings after performing each test combination were examined. Our results showed that leg raising on a yoga ball, including a 1-min rest in the middle of a 15-min period, produced the greatest reduction of SC among the six test combinations. However, simply lying supine produced a similar effect. Surprisingly, the leg raising exercise preferred by many young women (raising the legs against the wall at an angle) was not as effective as expected.
Results revealed that the SC values of three time sessions differed significantly from each other (Table 1
). The participants’ SCs increased significantly, with an average of 7.8 mm from morning to night. This may represent an accumulated leg strain (e.g., shank region) for normal daily activity. The increase in SC observed in this study was somewhat higher than the data (7.1 mm) obtained by Chen et al. [3
], where the participants were requested to remain standing still for 2 h. Table 1
also shows that the participants’ SCs decreased significantly after the leg raising test. However, their SCs still did not recover to the basic level seen in the morning; on average, only approximately 60% SC reduction was achieved. This result implies that leg raising exercise sustained over a 15-min period may be insufficient; how long is necessary for recovery to the original basis requires further investigation. However, it also depends on different leg raising maneuvers.
Leg raising posture how to influence the SC reduction was of interest in this study. As shown in Table 2
, the two-way ANOVA indicated that posture variable significantly affected SC reduction (p
< 0.05). The most efficient method for reducing SC was yoga ball usage (5.4 mm), followed by supine lying posture (4.6 mm), and wall-supported leg raising at 60° (3.1 mm). However, time arrangement had no significant effect on SC reduction. Because interaction effect of posture and time arrangement on SC reduction was significant, a cross analysis result showed that effect of time arrangement on SC reduction was dependent on what posture was employed; the effect was more notable when legs raised on a yoga ball (+2.6 mm) than against the wall (+1.0 mm), with a difference more than two times (Figure 2
). Our results further showed that raising the legs on a yoga ball with an intervening 1-min rest produced the greatest SC reduction (6.7 mm), whereas continuous wall-supported leg raising produced the least SC reduction (2.5 mm), indicating SC recovery rates of about 86% and 32%, respectively (Figure 2
). In addition, because the participants were requested to maintain the original posture for the 1-min rest in the intermittent condition, there was almost no time arrangement effect on SC reduction when performing the supine lying posture, as shown in Figure 2
Our present analyses imply that a short time break caused significantly different results. In comparison with this study, Chen et al. [3
] examined the effect of a prolonged 2-h standing period on SC increase and found that when participants stood for 20 min and relaxed for 1 min, the SC increase was reduced overall by approximately 40%. In other words, with only a short resting time, the participants could more effectively alleviate the load exerted on their legs. In this study, a similar phenomenon was observed with the legs raised on a yoga ball with a 1-min rest. This may be explained by a massage-like effect. Improved blood flow is a perceived benefit of massage and includes sustained reductions in muscle tightness [24
]. An intervening 1-min rest in leg raising with a yoga ball may accelerate blood flow in the legs due to the compress–relax–compress pattern, while the identical posture without rest statically compresses both the shanks and yoga ball, thus relatively slowing blood flow. Our present results showed no significant differences in SC reduction between the supine lying posture and yoga ball leg raising or between lying supine and wall-supported leg raising. Hence, a supine lying posture may also be effective for reducing SC; by contrast, wall-supported leg raising, which caused greater discomfort (score: 4.96) compared with the others (score: ~1.33), may be impractical. During wall-mounted leg raising, the participants’ heels were supported by the bedside wall, whereas their unsupported legs were hanging. In clinical practice, by contrast, the legs are raised and supported using the bed adjustment to avoid touching the patient and to minimize pain [26
]. These two postures are effectively quite different. Given the current study design and dependent variables measured, it is difficult to discern why wall-supported leg raising was ineffective, and further clarification is required.
Although the similar leg raising is performed, the purposes are quite different between clinical treatment and fatigue relief; the user populations are also different (patients vs. healthy adults). Leg raising exercise used by healthy population before bedtime is based mainly on a common intuition that raising the legs can help reduce leg fatigue and swelling, thus maintaining a slim shank shape. In addition to this aesthetic purpose, the exercise is also popular among employees who require prolonged periods of standing (e.g., nurses, salesclerks, and guards). Although few studies have considered that such exercise may improve symptoms in some patients with varicose veins [10
], the effectiveness of different raising postures for eliminating leg fatigue or swelling should be carefully identified.
This study has several limitations. One major limitation of this study is the relatively small and single-sex sample (9 young women with a mean age of 23.1 years) recruited in the test. Table 2
and Table 4
also shows that the 9 participants exhibited statistical powers ranging from 0.706 to 0.991, with a 0.05 alpha level for the test combinations used in this study. The power value of ≥0.8 is generally accepted in the analysis as suggested by Cohen [23
]. This indicates that the effect of posture on SC reduction may require further clarification through a larger sample size because the power value was somewhat less than 0.8 (i.e., 0.706), even though the effect of interaction of posture and time arrangement exhibited a high power value (i.e., 0.926). In this study, all the participants were young women, so the results may not be applicable to men. Another concern is that only a single objective index (i.e., SC reduction) was employed for assessing the effects of leg raising. Other clinical responses, such as volume transferred from the legs to the upper body, cardiac output, coronary perfusion pressure, and blood flow to the heart [18
], may alter interpretation of the results. Moreover, this study set the leg raising time for 15 min and the position at 60° based on our pilot survey; a longer testing time may yield different results. These limitations should be considered before applying the results.