The aim of the present study was to examine the effect of the pressure profile of compression stockings on muscle fatigue of the plantar flexors during repetitive calf-raise exercise. The main findings of the present study was that the magnitude of reduction of plantar flexion angle during the repetitive calf-raise exercise was greater in the CON than in the GRA, UNI and LOC conditions whereas no significant difference in RMS-EMG was observed among the conditions. These results suggest that peripheral muscle fatigue of the plantar flexors was lessened when wearing any of the compression stockings used in the present study. Thus, a graduated pressure profile is not an essential feature for compression stockings in order to reduce development of muscle fatigue during repetitive plantar flexion exercise.

The effectiveness of compression garments has gained much interest in recent years, although it remains unclear whether the use of compression garments such as stockings have a positive effect on muscle fatigue during exercise (e.g., see review by MacRae et al.). It is likely that one of the reasons for the non-consensus is the difference in pressure intensities provided by different compression garments. Information about a garment’s pressure intensity is essential to compare findings across studies. However, pressure intensities of compression garments have often gone unreported in previous studies. Among only a limited number of studies which reported the pressure intensities, it was noted that compression stockings with a pressure intensity of 30 mmHg at the ankle, 24 mmHg at the calf, and 14 mmHg at the knee produced a greater mean venous flow velocity at rest than did those with a lower pressure (18, 14, and 8 mmHg at the same positions, respectively) (Lawrence and Kakkar 1980). Moreover, Miyamoto et al. have investigated the influence of pressure intensities of graduated compression stockings on muscle fatigue of the triceps surae induced by repetitive calf-raise exercise. They demonstrated that the magnitude of reduced force-generating capacity of the muscle after the exercise was smaller only when using a graduated compression stocking with an adequate pressure (30 mmHg and 21 mmHg at the ankle and the muscle belly of the gastrocnemius, respectively) (Miyamoto et al. 2011), which is similar to the GRA of the present study. This is consistent with our finding that, after a 30 min submaximal running exercise, the extent of muscle fatigue evaluated by T2-weighted magnetic resonance imaging was smaller when wearing graduated compression stockings with high pressure intensities (27 mmHg and 21 mmHg at the ankle and the muscle belly of the gastrocnemius, respectively), but not when wearing those with low pressure intensities (18 mmHg and 14 mmHg) (unpublished data). These observations are consistent with the present finding that during the calf-raise exercise the extent of muscle fatigue was smaller in the GRA conditions as compared with those in the CON condition. Taken together, it is suggested that even when using a graduated compression stocking, an adequate pressure intensity is required to reduce development of muscle fatigue of the plantar flexors during exercise.

From a historical viewpoint, graduated compression stockings originate from medical applications. Previous studies have demonstrated increased venous blood flow velocity, reduced venous pooling, and improved venous return in non-active, resting post-operative patients (Lawrence and Kakkar 1980; Liu et al. 2008). Based on these findings, most sports compression stockings have employed a graduated pressure profile. As hypothesized, however, the present study revealed that such a graduated pressure profile is not an essential feature for compression stockings to reduce muscle fatigue development of the plantar flexors during repetitive calf-raise exercise. In the case of the lower leg (especially plantar flexors), the gastrocnemius composed of a relatively higher percentage of fatigable type II fibers is located at the proximal part as compared with the soleus. During the repetitive muscle contractions of plantar flexion, the magnitude of muscle fatigue was greater in the medial gastrocnemius than in the soleus (Miyamoto et al. 2011). This indicates that the proper pressure profiles obtained from clinical studies with resting patients are not directly applicable to dynamic exercise in healthy subjects.