Comparison of the effects of different foam rolling durations on knee extensors function.

Foam rolling (FR) intervention has recently attracted attention in sports and rehabilitation settings. However, the effects of FR using different rolling durations have not been fully clarified. Thus, this study focused on FR durations and examined the acute and prolonged (i.e., 20-min; 40-min, 60-min) effects of different FR intervention durations on maximal voluntary concentric contractions (MVC-CON), knee flexion range of motion (ROM), pain pressure threshold (PPT), and tissue hardness. The participants were 10 male university students (22.5 ± 1.0 years), and the target muscles were the dominant leg knee extensors. Three sets of 60-seconds FR interventions were performed in the randomized crossover trials in each condition. The three intervention conditions were fast (1 rolling/2 s, 30-repetition × 3 sets, 90 repetitions), medium (1 rolling/6 s, 10-repetition × 3 sets, 30 repetitions), and slow speed (1 rolling/12 s, 5-repetition × 3 sets, 15 repetitions). Before as well as immediately, 20-min, 40-min, and 60-min after the interventions, MVC-CON, ROM PPT, and tissue hardness were measured. The results showed no interaction effect in the acute effect but a main effect of time for all variables (p < 0.05). Also, no interaction was observed in prolonged effect, but main effects of time were observed in knee flexion ROM, PPT, and tissue hardness (p < 0.01) but not for MVC-CON. Post-hoc tests showed significant PPT (p < 0.05) and knee flexion ROM (p < 0.01) increases up to 20- and 60-minutes respectively after all interventions. Tissue hardness was significantly (p < 0.01) decreased up to 60-minutes after all interventions. This study showed that the FR intervention changed ROM, PPT, tissue hardness, and MVC-CON regardless of rolling duration and that the effects persisted up to 20-60 minutes.

The Acute Effect of Percussive Massage Intervention with and without Heat Application on Plantar Flexor Muscles' Passive and Active Properties.

Recently, percussive massage (PM) intervention using a handheld percussive massage device, namely a massage gun, has been used as an easy way to perform vibration functions. Additionally, a product has been developed that allows PM intervention and heat application to be performed simultaneously. Thus, this study aimed to compare the acute effects of PM intervention with and without heat application on dorsiflexion (DF) range of motion (ROM), passive stiffness, and muscle strength in the gastrocnemius muscle. Fifteen healthy young men (20.9 ± 0.2 years) participated in this study. We measured the DF ROM, passive torque at DF ROM (an indicator of stretch tolerance), passive stiffness, and maximum voluntary isometric contraction (MVIC) torque of the plantar flexor muscles before and immediately after 120 seconds PM intervention with and without heat application. The results showed that PM intervention with and without heat application significantly increased DF ROM and passive torque at DF ROM and decreased passive stiffness, not MVIC torque. These results suggest that PM intervention increased ROM and decreased passive stiffness regardless of the presence or absence of the heat application.

The effect of massage on the plantar flexor muscles during the fixation period in postoperative patients with an ankle fracture.

INTRODUCTION: Ankle fractures are one of the most common lower extremity fractures. After surgery, the ankle joint is often immobilized in a plantar flexion position, and there have been many reported cases of limited ankle joint range of motion. Therefore, the purpose of the present study was to investigate the effect of regular massage interventions on ankle joint range of motion after removal of fixation. METHODS: The massage group comprised 30 patients who had sustained an ankle fracture and had undergone surgical fixation, physical therapy, and massage between November 2020 and March 2022. These subjects received a 3-min massage twice daily, five times a week. The control group consisted of 38 patients who had sustained an ankle fracture between January 2015 and September 2020 and had undergone surgical fixation as well as regular physical therapy. RESULTS: The respective ankle dorsiflexion and plantarflexion ranges of motion after cast removal were 2.50 ± 7.2° and 42.3 ± 7.2° in the massage group and -8.62 ± 2.9° and 34.8 ± 8.3° in the control group. An unpaired t-test showed that the ankle dorsiflexion and plantarflexion ranges of motion in the massage group were significantly greater than those in the control group (p = 0.036 and p < 0.01). CONCLUSIONS: Our results indicate that regular 3-min massage interventions of the plantar flexors could prevent the progression of a range of motion limitations in postoperative patients with an ankle fracture more effectively than regular physical therapy alone.

Trends and associations between kinesiophobia and knee function from preoperatively to three and six months postoperatively in patients post-ACL reconstruction surgery.

OBJECTIVE: This study aimed to clarify the relationship between the transition of kinesiophobia and knee joint function from the preoperative period to three months postoperative, the time to resume running, six months post-ACLR, and the goal time to resume sports. METHODS: 54 patients who underwent initial ACLR were included in this study. The Tampa Scale for Kinesiophobia-11 (TSK-11) was used to assess kinesiophobia. One-way ANOVA was performed for the preoperative, three-month postoperative, and six-month postoperative endpoints. To examine changes in knee function associated with changes in TSK-11, we calculated correlations between the differences at each time point. RESULTS: TSK-11 decreased significantly at both three and six months postoperatively compared with the preoperative level, but there was no significant change between three months and six months postoperatively. Similar to the decrease in TSK-11 from preoperatively to three and six months postoperatively, there was an improvement in flexion ROM, Pain, Subjective knee function, but none of these changed significantly from three to six months postoperatively. CONCLUSION: There may be significant improvements in knee function associated with TSK-11 reduction up to three months postoperatively.

The contralateral effects of foam rolling on range of motion and muscle performance.

A single bout of foam rolling (FR) can acutely increase joint range of motion (ROM) without detrimental effects on subsequent muscle performance. Similarly, long-term FR training can increase ROM, while muscle performance seems to be unaffected. Although the acute and long-term effects of FR on the treated muscle are understood, the impact of FR on the contralateral side is not well known. Therefore, this scoping review aims to summarize the current evidence on the acute and long-term effect of FR on the ipsilateral limb on ROM and muscle performance (i.e., maximum force, rate of force development, jump height) for the contralateral (non-treated) limb. Potential explanatory mechanisms are also discussed. There is evidence that a single bout of FR on the ipsilateral limb increases ROM of the contralateral limb; however, evidence is limited for long-term effects. The most likely mechanism for contralateral ROM increases is a reduced perception of pain. With regard to isolated muscle contractions, no changes in muscle performance (i.e., maximum voluntary isometric contraction, maximum voluntary dynamic contraction) were found in the contralateral limb after a single bout of FR on the ipsilateral limb. Notably, only one study reported large impairments in rate of force development of the contralateral limb following FR on the ipsilateral leg, possibly due to decreased motor unit recruitment. Furthermore, to date there are only two studies examining the long-term FR training of the ipsilateral limb on performance (i.e., maximal strength and jump performance) which reported moderate improvements. Although, trivial to very large changes on a variety of parameters were found in this study, the functional and practical relevance of our findings should be interpreted with caution.

The Effect of Single Bout Treatment of Heat or Cold Intervention on Delayed Onset Muscle Soreness Induced by Eccentric Contraction.

We studied the preventive effects of heat or cold therapy after repeated eccentric contraction against torque reduction, muscle soreness, and range of motion (ROM) due to delayed-onset muscle soreness (DOMS). A total of 42 healthy male subjects were randomly allocated into three groups: the HEAT group received heat therapy using an ultra-short-wave device; the ICE group received ice therapy using an ice pack; the Control group received no intervention. The measurements included maximal voluntary isometric, concentric, and eccentric elbow flexion torque, elbow extension ROM, pressure pain threshold, and muscle soreness with stretching muscle thickness and echo intensity. The measurements were taken before (pre), after (post), after (t-post), one-four days after, and seven days after the muscle damage protocol. The results showed the main effect of time on all measurements, but no significant interactions were observed. The results of this study suggest that heat or cold therapy in the first 30 min after intense eccentric exercise is insufficient to exert a preventive effect against DOMS.

Effects of capacitive and resistive electric transfer and hot pack interventions on the autonomic nervous system in young women.

The effects of thermotherapy on autonomic nervous system activity and subjective sensations of fatigue and arousal are unclear. This study compared the effects of capacitive and resistive electric transfer (Cret) interventions (deep thermotherapy) and hot packs (superficial thermotherapy) on autonomic nervous system activity in healthy young women (n = 16). Heart rate and RR interval were measured using electrocardiography, and the coefficient of variation (CV) of the RR interval was used to evaluate autonomic nervous system activity. The subjective relaxation effect was evaluated using the Roken Arousal Scale (RAS) - a fatigue arousal index. The intervention was performed on the lumbar region for 20 minutes for both Cret and hot pack. After each intervention, the CV values increased only in the Cret condition, whereas the heart rate decreased in both conditions. This suggests that parasympathetic activity was enhanced in the Cret condition. In contrast, the subjective relaxation evaluation observed a psychological relaxation effect under both conditions. Our results suggest that Cret application in the lumbar region has greater relaxation effects than hot pack application in the same region.

Effects of stretching intensity on range of motion and muscle stiffness: A narrative review.

BACKGROUND: No review has yet investigated acute and chronic effects of different stretching intensities, including constant-angle (CA) and constant-torque (CT) stretching. OBJECTIVE: This review aimed to investigate the acute and chronic effects of different stretching intensities on the range of motion (ROM) and passive properties. METHODS: PubMed, Scopus, and Google Scholar were used for literature search. Advanced search functions were used to identify original studies using the terms stretching intensity, constant-torque stretching, constant-angle stretching, ROM, passive stiffness, shear elastic modulus in the title or abstract. The keywords were combined using the Boolean operators "AND" and "OR". The search for articles published from inception until 2021 was done in electronic databases. RESULTS AND CONCLUSION: Five studies compared CA and CT stretching. Three studies reported a greater decrease in passive stiffness, and two studies reported a greater ROM increase after CT than CA stretching. Twelve studies investigated the acute effects of different stretching intensities, and six reported a greater ROM increase at higher stretching intensities. Five studies reported a greater decrease in passive stiffness at higher stretching intensities, but three reported no significant differences in passive stiffness among stretching intensities. Five studies investigated the chronic effect, and four reported no significant difference in ROM change among different intensities. Three studies reported no significant changes in passive stiffness after the stretching program. We suggest that the acute effect of higher stretching intensity, including CT stretching, was more effective for changes in ROM and passive stiffness, but the chronic effect was weak.

An Intense Warm-Up Does Not Potentiate Performance Before or After a Single Bout of Foam Rolling.

Foam rolling (FR) is a common intervention used as a warm-up to increase the range of motion (ROM) of a joint, without changes in subsequent performance. It has been shown that, in similar techniques (e.g., stretching), an additional intense warm-up can lead to performance potentiation. However, to date, it is not clear if this also holds true for FR, and if this effect is similar in both sexes. Thus, the purpose of this study was to compare the effects of an intense warm-up either before or after FR with the effects of FR without any additional intense warm-up, in both females and males. In total, 27 volunteers (14 male, 13 female) visited the laboratory on three separate days. Each participant was randomly assigned to one of the three interventions. ROM was assessed with a Sit n' Reach box, and countermovement jump (CMJ) height with a force plate, both before and after the interventions. In addition, maximum voluntary isometric contraction (MVIC) peak torque and maximum voluntary dynamic contraction (MVDC) peak torque were assessed with a dynamometer. ROM increased to the same extent following the interventions in all groups, with a large magnitude of change (P < 0.001; d = 1.12 to 1.83). In addition, male participants showed significantly higher increases in ROM when the intense warm-up was performed after FR (P < 0.001; d = 1.44), but not without the intense warm-up (P = 0.45; d = 0.57) or when the intense warm-up was performed before FR (P = 0.24; d = 0.69). No significant changes in CMJ height, MVIC peak torque, or MVDC peak torque were observed (P > 0.05). We therefore conclude that the time-efficient athlete might skip further intense warm-up, besides FR, when the goal is to increase ROM and to sustain performance parameters.

A comparison of a single bout of stretching or foam rolling on range of motion in healthy adults.

PURPOSE: Stretching and foam rolling are common warm-up exercises and can acutely increase the range of motion (ROM) of a joint. However, possible differences in the magnitude of change on ROM between these two interventions on the immediate and prolonged effects (e.g., 10 min after the intervention) are not yet well understood. Thus, the purpose of this review was to compare the immediate and prolonged effects of a single bout of foam rolling with a single bout of stretching on ROM in healthy participants. METHODS: In total, 20 studies with overall 38 effect sizes were found to be eligible for a meta-analysis. For the main analysis, subgroup analysis, we applied a random-effect meta-analysis, mixed-effect model, respectively. The subgroup analyses included age groups, sex, and activity levels of the participants, as well as the tested muscles, the duration of the application, and the study design. RESULTS: Meta-analyses revealed no significant differences between a single stretching and foam rolling exercise immediately after the interventions (ES = 0.079; P = 0.39) nor a difference 10 min (ES = - 0.051; P = 0.65), 15 min (ES = - 0.011; P = 0.93), and 20 min (ES = - 0.161; P = 0.275) post-intervention. Moreover, subgroup analyses revealed no other significant differences between the acute effects of stretching and foam rolling (P > 0.05). CONCLUSION: If the goal is to increase the ROM acutely, both interventions can be considered as equally effective. Likely, similar mechanisms are responsible for the acute and prolonged ROM increases such as increased stretch tolerance or increased soft-tissue compliance.

Relationship between changes in passive properties and muscle strength after static stretching.

BACKGROUND: The association between decreased muscle strength of rate of force development (RFD) immediately after static stretching (SS) and change in muscle stiffness or muscle slack has remained unclear. OBJECTIVE: This study aimed to investigate the association between changes in muscle strength and RFD and muscle stiffness or muscle slack immediately after SS. METHODS: Sixteen healthy male non-athlete volunteers participated in this study. The maximal voluntary contraction torque and shear elastic modulus of medial gastrocnemius muscle were measured before and after 300 s of SS intervention. RESULTS: The results showed that maximal voluntary contraction torque and RFD at 100, 150, and 200 ms decreased significantly after the 300-s SS (p < 0.01). Additionally, shear elastic modulus at 0° (decrease in muscle stiffness) and slack angle decreased (increase in slack length) significantly after the 300-second SS (p < 0.01). However, no significant association was observed between changes in muscle strength and changes in mechanical properties of the MG. CONCLUSION: These results suggested that the decrease in muscle strength and RFD could not be associated with changes in the passive mechanical properties of the medial gastrocnemius muscle.

A Comparison of the Effects of Foam Rolling and Stretching on Physical Performance. A Systematic Review and Meta-Analysis.

Foam rolling and stretching with its various techniques are frequently used as a warm-up routine to increase the range of motion of a joint. While the magnitude of the changes in range of motion between foam rolling and stretching (static and dynamic techniques) is similar, it is not clear if this also holds true for performance parameters (e.g., strength, jump height). The purpose of this meta-analysis was to compare the effects of an acute bout of foam rolling (with and without vibration) with an acute bout of stretching (with all techniques included) on performance parameters in healthy participants. We assessed the results from 13 studies and 35 effect sizes by applying a random-effect meta-analysis. Moreover, by applying a mixed-effect model, we performed subgroup analyses with the stretching technique, type of foam rolling, tested muscle, treatment duration, and type of task. We found no significant overall effect, and the analysis revealed only a trend of the performance parameters in favor of foam rolling when compared to stretching (when considering all techniques). Significantly favorable effects of foam rolling on performance were detected with subgroup analyses when compared to static stretching, when applied to some muscles (e.g., quadriceps) or some tasks (e.g., strength), when applied for longer than 60 s, or when the foam rolling included vibration. When foam rolling was compared to dynamic stretching or applied in the non-vibration mode, the same magnitude of effect was observed. While the present meta-analysis revealed no significantly different effect between foam rolling and stretching (including all techniques) prior to exercise, differences could be observed under specific conditions.

The Accumulated Effects of Foam Rolling Combined with Stretching on Range of Motion and Physical Performance: A Systematic Review and Meta-Analysis.

Although it is well known that both stretching and foam rolling can acutely increase the range of motion (ROM) and affect performance, the effects of a combined treatment (foam rolling and stretching) are not yet clear. Hence, the purpose of this meta-analysis was to compare the combined effect to that of stretching or foam rolling alone on both ROM and performance. We assessed the effect of a combined treatment on ROM and compared it to the effect of stretching, foam rolling, and a control condition by applying a random-effect meta-analysis. We also applied the same model to compare the effect of the combined treatment on performance. Moreover, by applying a mixed-effect model, we performed subgroup analyses with the stretching technique, type of foam rolling, tested muscles, type of task, and the order of the combined treatment. We found a significant overall effect on ROM change when comparing the combined treatment with the control condition (effect size (ES) = -0.332); however, no significant effect was found when comparing it to stretching (ES = 0.032) or foam rolling alone (ES = -0.225). The meta-analysis revealed no significant overall effect on performance when the combined treatment was compared to stretching alone (ES = -0.029). However, the subgroup analysis for performance revealed a superior effect for the combined treatment compared to stretching alone, but only if foam rolling was followed by stretching (ES = -0.17), and not vice versa. Athletes do not have to combine stretching with foam rolling since no additional effect was observed. However, to increase performance, the combination of foam rolling followed by stretching can lead to greater improvements.

The Acute and Prolonged Effects of Different Durations of Foam Rolling on Range of Motion, Muscle Stiffness, and Muscle Strength.

"Foam Rolling" has been used in sports settings to increase range of motion and decrease muscle stiffness without decreasing muscle strength and athletic performance. However, there has been no study investigating the acute and prolonged effect of different durations of foam rolling intervention on muscle stiffness, and the minimum foam rolling intervention duration required to decrease muscle stiffness is unclear. Therefore, the purpose of this study was to investigate the acute and prolonged effect of different durations of foam rolling intervention on ROM, muscle stiffness, and muscle strength. The 45 participants were randomly allocated to 1 of 3 groups (30 s × 1 times group vs 30 s × 3 times group vs 30 s× 10 times group). The outcome measures were dorsiflexion range of motion, shear elastic modulus of medial gastrocnemius, and muscle strength before, 2 min and 30 min after foam rolling intervention. There were no significant differences before and 2 min after foam rolling intervention in 30 s×1 time group, whereas dorsiflexion range of motion was increased in both 30 s×3 times group (p = 0.042, d = 0.26) and 30 s× 10 times group (p < 0.01, d = 0.33). However, the increase in dorsiflexion range of motion was returned to baseline value after 30 minutes in both 30 s × 3 times group and 30 s × 10 times group. In addition, there were no significant changes in shear elastic modulus and muscle strength in all groups. This study suggested that foam rolling for more than 90 s or more of foam rolling was effective in order to increase the range of motion immediately without changing muscle stiffness and muscle strength.

Comparison of the Acute Effects of Hold-Relax and Static Stretching among Older Adults.

Various stretching techniques are generally recommended to counteract age-related declines in range of motion (ROM) and/or increased muscle stiffness. However, to date, an effective stretching technique has not yet been established for older adults. Consequently, we compared the acute effects of hold relax stretching (HRS) and static stretching (SS) on dorsiflexion (DF) ROM and muscle stiffness among older adults. Overall, 15 elderly men and nine elderly women (70.2 ± 3.9 years, 160.8 ± 7.8 cm, 59.6 ± 9.7 kg) were enrolled, and both legs were randomized to either HRS or SS stretching. We measured DF ROM and muscle stiffness using a dynamometer and ultrasonography before and after 120 s of HRS or SS interventions. Our multivariate analysis indicated no significant interaction effects, but a main effect for DF ROM. Post-hoc tests revealed that DF ROM was increased after both HRS and SS interventions. Moreover, multivariate analysis showed a significant interaction effect for muscle stiffness. Post-hoc tests revealed that muscle stiffness was decreased significantly after only SS intervention. Taken together, our results indicated that both HRS and SS interventions are recommended to increase ROM, and SS is recommended to decrease muscle stiffness in older adults.

Sex Differences in the Mechanical and Neurophysiological Response to Roller Massage of the Plantar Flexors.

Self-massage using foam rollers, sticks, or balls has become a popular technique to enhance joint range of motion (ROM). Although increases are reported to be larger in females than males, the mechanisms of this observation are unclear. The present study aimed to investigate the effect of roller massage (RM) on ROM, passive tissue stiffness, and neurophysiological markers as a function of sex. Males (n = 15, 22.8 ± 2.9 yrs.) and females (n = 14, 21.1 ± 0.7 yrs.) performed three 60-second bouts of calf RM. Outcomes assessed pre-, and post-intervention included passive dorsiflexion (DF) ROM, passive tissue stiffness, passive torque, DF angle at the first stretch sensation, shear elastic modulus, and spinal excitability. DF ROM (+35.9 %), passive torque at DF ROM (+46.4 %), DF angle at first stretch sensation (+32.9 %), and pain pressure threshold (+25.2 %) increased in both groups (p<.05) with no differences between males and females (p > 0.05). No changes were observed for passive stiffness, shear elastic modulus, and spinal excitability (p > 0.05). Roller massage may increase ROM independently of sex, which, in the present study, could not be ascribed to alterations in passive stiffness or neurophysiological markers. Future studies may further elucidate the role of sensory alterations as possible factors driving RM-induced changes in flexibility.

Effects of a Thermal Agent and Physical Activity on Muscle Tendon Stiffness, as Well as the Effects Combined With Static Stretching.

CONTEXT: A recent review or article reported that thermal agents (TA) or physical activity (PA) can increase range of motion (ROM) and that the combination of TA with stretching is superior to performing stretching only. However, since ROM is affected by the psychological factors, it is questionable whether these studies measured the effect of these interventions on muscle flexibility. By measuring muscle stiffness, the authors attempted to evaluate the effect these interventions on muscle flexibility. OBJECTIVE: To compare the individual effects of TA and PA on muscle flexibility, as well as their effectiveness when combined with static stretching (SS). DESIGN: Crossover trial. SETTING: University research laboratory. PARTICIPANTS: 15 healthy men without a history of orthopedic disease in their lower limbs. INTERVENTIONS: 15 minutes of 3 different conditions: hot pack as TA, pedaling exercise as PA, and the control group with no TA or PA intervention, followed by 3 min of SS for the hamstrings. MAIN OUTCOME MEASURES: Joint angle and passive torque of the knee during passive elongation were obtained prior to interventions, after 3 kinds of intervention, and after SS. From these data, muscle-tendon-unit (MTU) stiffness of the hamstrings was calculated. RESULTS: Although knee-joint ROM increased with both TA and PA (P < .05), there were no significant differences in MTU stiffness between pre- and postintervention measurements for either of the interventions (TA, P = .477; PA, P = .377; control, P = .388). However, there were similar significant decreases in MTU stiffness between postintervention and post-SS for all conditions (P < .01). CONCLUSIONS: TA and PA did not decrease MTU stiffness, and combining these interventions with SS did not provide additional decreases in MTU stiffness compared with performing SS alone.

Acute Effects of Stretching on Passive Properties of Human Gastrocnemius Muscle-Tendon Unit: Analysis of Differences Between Hold-Relax and Static Stretching.

CONTEXT: Hold-relax stretching (HRS) and static stretching (SS) are commonly used to increase joint range of motion (ROM) and decrease muscle stiffness. However, whether there are differences between acute effects of HRS and SS on end ROM, passive torque, and muscle stiffness is unclear. In addition, any differences between the mechanisms by which HRS and SS lead to an increase in end ROM are unclear. OBJECTIVE: To compare the acute effects of HRS and SS on the passive properties of the gastrocnemius muscle-tendon unit (MTU), end ROM, passive torque, and muscle stiffness in vivo and to investigate the factors involved in increasing end ROM. DESIGN: Crossover experimental design. PARTICIPANTS: 30 healthy men (21.7 ± 1.2 y) with no history of neuromuscular disease or musculoskeletal injury involving the lower limbs. INTERVENTION: Both HRS and SS of 30 s were repeated 4 times, lasting a total of 2 min. MAIN OUTCOME MEASURES: End ROM, passive torque, and muscle stiffness were measured during passive ankle dorsiflexion using a dynamometer and ultrasonography before and immediately after HRS and SS. RESULTS: The results showed that end ROM and passive torque at end ROM significantly increased immediately after both HRS and SS, whereas muscle stiffness significantly decreased. In addition, the percentage change in passive torque at end ROM on use of the HRS technique was significantly higher than that after use of the SS technique. However, the percentage change in muscle stiffness after SS was significantly higher than that with HRS. CONCLUSION: These results suggest that both HRS and SS can effectively decrease muscle stiffness of the gastrocnemius MTU and that HRS induces a change in the passive torque at end ROM--i.e., sensory perception--rather than changing muscle stiffness.

Mulberry latex rich in antidiabetic sugar-mimic alkaloids forces dieting on caterpillars.

Since ancient times, mulberry leaves (Morus spp.) have been used to rear the silkworm Bombyx mori. Because the silkworm grows well on mulberry leaves, the toxicities and defensive activities of these leaves against herbivorous insects have been overlooked. Here we show that mulberry leaves are highly toxic to caterpillars other than the silkworm B. mori, because of the ingredients of the latex, a milky sap exuded from mulberry leaf veins. The toxicity of mulberry leaves was lost when the latex was eliminated from the leaves, and artificial diets containing latex showed toxicity. Mulberry latex contained very high concentrations of alkaloidal sugar-mimic glycosidase inhibitors reported to have antidiabetic activities, such as 1,4-dideoxy-1,4-imino-D-arabinitol, 1-deoxynojirimycin, and 1,4-dideoxy-1,4-imino-D-ribitol. The overall concentrations of these inhibitors in latex reached 1.5-2.5% (8-18% dry weight) in several mulberry varieties, which were approximately 100 times the concentrations previously reported from whole mulberry leaves. These sugar-mimic alkaloids were toxic to caterpillars but not to the silkworm B. mori, indicating that the silkworm can circumvent the mulberry tree's defense. Our results suggest that latex ingredients play key roles in defense of this tree and of other plants against insect herbivory, and they imply that plant latexes are treasuries of bioactive substances useful as medicines and pesticides.

Papain protects papaya trees from herbivorous insects: role of cysteine proteases in latex.

Many plants contain latex that exudes when leaves are damaged, and a number of proteins and enzymes have been found in it. The roles of those latex proteins and enzymes are as yet poorly understood. We found that papain, a cysteine protease in latex of the Papaya tree (Carica papaya, Caricaceae), is a crucial factor in the defense of the papaya tree against lepidopteran larvae such as oligophagous Samia ricini (Saturniidae) and two notorious polyphagous pests, Mamestra brassicae (Noctuidae) and Spodoptera litura (Noctuidae). Leaves of a number of laticiferous plants, including papaya and a wild fig, Ficus virgata (Moraceae), showed strong toxicity and growth inhibition against lepidopteran larvae, though no apparent toxic factors from these species have been reported. When the latex was washed off, the leaves of these lactiferous plants lost toxicity. Latexes of both papaya and the wild fig were rich in cysteine-protease activity. E-64, a cysteine protease-specific inhibitor, completely deprived the leaves of toxicity when painted on the surface of papaya and fig leaves. Cysteine proteases, such as papain, ficin, and bromelain, all showed toxicity. The results suggest that plant latex and the proteins in it, cysteine proteases in particular, provide plants with a general defense mechanism against herbivorous insects.