Effects of Omega-3 fatty acids supplementation and resistance training on skeletal muscle

BACKGROUND & AIMS

The aim of this study was to investigate the omega-3 fatty acids supplementation, and resistance training on muscle strength and mass.

METHODS

A review was conducted by searching relevant randomized controlled trials investigating the effects of omega-3 fatty acids supplementation and resistance training on skeletal muscle strength and mass. Three experts independently performed a thorough examination of the literature database and conducted the systematic review and meta-analysis.

RESULTS

Four studies were ultimately included in the systematic review after screening. The results of the meta-analysis revealed that the supplementation of omega-3 fatty acids and resistance training significantly improved muscle strength compared to the placebo-controlled group. However, no significant effects were observed in the effect for muscle mass.

CONCLUSIONS

The interventions of omega-3 fatty acids supplementation and resistance training show promise as a countermeasure against muscular dysfunction. While further research is warranted to investigate its effects on skeletal muscle mass, the findings of this study hold implications for maintaining and/or improving the quality of life to elderly people.

Effects of single and repeated bouts of flywheel exercise on jump performance and muscle damage in athletes and non athletes

BACKGROUND

Although recent studies have investigated the effects of flywheel (FW) training on muscle function, the effects of transient FW exercise on jump performance in athletes are unknown. This study examined the effects of single and repeated bouts of FW squat exercises on jump performance and muscle damage in male collegiate basketball players.

METHODS

The participants were 10 healthy college-age men (nonathletes) and 11 male basketball players (athletes). The intervention involved 100 squat exercises (10 repetitions × 10 sets) using an FW device. To examine the repeated-bout effects, the protocol was conducted again after a 2-week interval. Squat jumps, countermovement jumps, drop jumps, and rebound jumps were evaluated as jump performance, while isometric maximal voluntary contraction (MVC) torque in knee extension, muscle soreness, range of motion, thigh circumference, muscle thickness, and echo intensity were evaluated as markers of muscle damage. Measurements were taken at baseline, immediately after exercise, 24 h later, and 72 h later.

RESULTS

The jump performance of nonathletes decreased after exercise (p < 0.05), while that of the athletes did not. The results were similar for muscle soreness. MVC torque decreased significantly after the first exercise in both groups (p < 0.05) and was significantly lower in the nonathletes versus athletes. Significant repeated-bout effects were found for muscle soreness in nonathletes but not athletes.

CONCLUSIONS

These results suggest that a single bout of FW exercise reduces jump performance in male nonathletes but not basketball players.

Home-based high-intensity interval training improves cardiorespiratory fitness: a systematic review and meta-analysis

BACKGROUND

High-intensity interval training (HIIT) is an effective methods to improve maximal oxygen uptake. However, there is no definitive conclusion about the specific effectiveness of home-based HIIT. This review investigated the effects of home-based HIIT on cardiorespiratory fitness in a systematic review and meta-analysis.

METHODS

Four electronic databases were searched (PubMed, Cochran database, Web of Science, Igaku Chuo Zasshi) for studies through March 25, 2023. Eligibility criteria include randomized controlled trials of home-based HIIT in adult people regardless disease or handicaped. Comparisons were made between non-exercise controls, laboratory-based HIIT, and moderate-intensity continuous training (MICT). The primary outcome was defined as cardiorespiratory fitness and the secondary outcome was defined as patient-reported outcomes. The standardized mean difference (SMD) with 95% confidence intervals (CIs) was calculated for quantitative indices. The random-effect model was used as the pooling method.

RESULTS

Two hundred seven studies were identified, and 15 satisfied the inclusion criteria. The meta-analysis for cardiorespiratory fitness showed superiority of home-based HIIT to non-exercise controls (SMD 0.61, 95% CI: 0.21, 1.02). However, no significant difference in cardiorespiratory fitness was observed between home-based HIIT and lab-based HIIT (SMD: -0.35, 95%CI: -0.73, 0.03). Also, no significant difference was observed between the home-based HIIT and MICT (SMD 0.34, 95% CI: -0.05, 0.73).

CONCLUSION

These results indicated that home-based HIIT was an effective intervention for improving cardiorespiratory fitness in healthy adults and patients. Importantly, this review found no significant differences in cardiorespiratory fitness between home-based HIIT and the group of laboratory HIIT and MICT, highlighting its comparable effectiveness and potential as a practical and valuable exercise intervention.

Klotho regulates the myogenic response of muscle to mechanical loading and exercise

NEW FINDINGS

What is the central question of this study? Does the hormone Klotho affect the myogenic response of muscle cells to mechanical loading or exercise? What is the main finding and its importance? Klotho prevents direct, mechanical activation of genes that regulate muscle differentiation, including genes that encode the myogenic regulatory factor myogenin and proteins in the canonical Wnt signalling pathway. Similarly, elevated levels of klotho expression in vivo prevent the exercise-induced increase in myogenin-expressing cells and reduce exercise-induced activation of the Wnt pathway. These findings demonstrate a new mechanism through which the responses of muscle to the mechanical environment are regulated.

ABSTRACT

Muscle growth is influenced by changes in the mechanical environment that affect the expression of genes that regulate myogenesis. We tested whether the hormone Klotho could influence the response of muscle to mechanical loading. Applying mechanical loads to myoblasts in vitro increased RNA encoding transcription factors that are expressed in activated myoblasts (Myod) and in myogenic cells that have initiated terminal differentiation (Myog). However, application of Klotho to myoblasts prevented the loading-induced activation of Myog without affecting loading-induced activation of Myod. This indicates that elevated Klotho inhibits mechanically-induced differentiation of myogenic cells. Elevated Klotho also reduced the transcription of genes encoding proteins involved in the canonical Wnt pathway or their target genes (Wnt9a, Wnt10a, Ccnd1). Because the canonical Wnt pathway promotes differentiation of myogenic cells, these findings indicate that Klotho inhibits the differentiation of myogenic cells experiencing mechanical loading. We then tested whether these effects of Klotho occurred in muscles of mice experiencing high-intensity interval training (HIIT) by comparing wild-type mice and klotho transgenic mice. The expression of a klotho transgene combined with HIIT synergized to tremendously elevate numbers of Pax7+ satellite cells and activated MyoD+ cells. However, transgene expression prevented the increase in myogenin+ cells caused by HIIT in wild-type mice. Furthermore, transgene expression diminished the HIIT-induced activation of the canonical Wnt pathway in Pax7+ satellite cells. Collectively, these findings show that Klotho inhibits loading- or exercise-induced activation of muscle differentiation and indicate a new mechanism through which the responses of muscle to the mechanical environment are regulated.

Association of MMP3 gene polymorphism and sex on recovery of muscle strength after eccentric exercise

Individual differences in recovery of muscle strength after eccentric exercise may be influenced by sex and genotype. A candidate genetic polymorphism associated with response during muscle recovery is the MMP3 gene rs522616 polymorphism, encoding matrix metalloproteinase (MMP-3). Here, we investigated the effect of the MMP3 gene rs522616 polymorphism and sex on recovery of muscle strength after eccentric exercise. A total of 95 healthy subjects (50 men and 45 women) performed five sets of six maximal eccentric elbow flexion exercises. Maximal voluntary contraction (MVC) torque, range of motion (ROM), and muscle soreness, as well as blood parameters [creatine kinase (CK) and interleukin-6 (IL-6)], were assessed immediately before and after and 1, 2, 3, and 5 days after eccentric exercise. No significant time × group interaction in MVC torque after exercise was observed between groups in both sexes. Furthermore, sex differences were identified in the area under the curves (AUC) of CK and IL-6, both of which were higher in men than those in women. A significant genotype-sex interaction was identified in the recovery of MVC, calculated by subtracting the MVC immediately after exercise from the MVC on day 5 after eccentric exercise. The G allele showed a significantly lower recovery of MVC than the AA genotype in men. However, no significant differences were observed in women. This study demonstrated the interaction between the MMP3 rs522616 polymorphism and sex in recovery of muscle strength after eccentric exercise.NEW & NOTEWORTHY Sex differences were identified in the AUC of creatin kinase (CK) and interleukin 6 (IL-6) after eccentric exercise, both of which were greater in men. A genotype-sex interaction was identified in recovery of maximal voluntary contraction (MVC). The G allele showed a significantly lower recovery of MVC than AA genotype in men. To our knowledge, this is the first study to report the interaction between MMP3 gene rs522616 polymorphism and sex difference on recovery of muscle strength after eccentric exercise.

Eicosapentaenoic Acid and Medium-Chain Triacylglycerol Structured Lipids Improve Endurance Performance

PURPOSE

The effects of intake of STGs containing esterified eicosapentaenoic acid (EPA) and medium-chain triglycerides (MCTs) on cardiorespiratory endurance have not yet been reported. This study aimed to examine the efficacy of interesterified structured lipids EPA and MCTs on cardiorespiratory endurance.

METHODS

This 8-week randomized double-blind placebo-controlled parallel-group study involved 19 healthy men. The participants were randomly assigned to a group that received interesterified structured lipids EPA and MCTs (STG group, 9 participants) or a group receiving a PM of EPA and MCTs (PM group, 10 participants). The outcome measures were time to exhaustion (TTE) and time to reach the anaerobic threshold in the peak oxygen uptake (VO2peak) test, VO2peak, and anaerobic threshold.

RESULTS

The increase in TTE in the VO2peak test after the intervention period compared with before the intervention period was significantly greater in the STG group (53 ± 53 s) than in the PM group (-10 ± 63 s; p < 0.05). Similarly, the increase in time to reach the anaerobic threshold was significantly greater in the STG group (82 ± 55 s) than in the PM group (-26 ± 52 s; p < 0.001).

CONCLUSION

This study demonstrated that the consumption of interesterified structured lipids EPA and MCTs improved endurance in humans.

Pedal cadence does not affect muscle damage to eccentric cycling performed at similar mechanical work

Purpose: This study aimed to investigate muscle damage when performing equal mechanical work of fast and slow pedaling speed by eccentric muscle actions (ECCs) cycling.

Methods: Nineteen young men [mean ± standard deviation (SD) age: 21.0 ± 2.2 years; height: 172.7 ± 5.9 cm; and body mass: 70.2 ± 10.5 kg] performed maximal effort of ECCs cycling exercise with fast speed (Fast) and slow speed trials (Slow). First, subjects performed the Fast for 5 min by one leg. Second, Slow performed until the total mechanical work was equal to that generated during Fast other one leg. Changes in maximal voluntary isometric contraction (MVC) torque of knee extension, isokinetic pedaling peak torque (IPT), range of motion (ROM), muscle soreness, thigh circumference, muscle echo intensity, and muscle stiffness were assessed before exercise, and immediately after exercise, and 1 and 4 days after exercise.

Results: Exercise time was observed in the Slow (1422.0 ± 330.0 s) longer than Fast (300.0 ± 0.0 s). However, a significant difference was not observed in total work (Fast:214.8 ± 42.4 J/kg, Slow: 214.3 ± 42.2 J/kg). A significant interaction effect was not observed in peak values of MVC torque (Fast:1.7 ± 0.4 Nm/kg, Slow: 1.8 ± 0.5 Nm/kg), IPT, muscle soreness (Fast:4.3 ± 1.6 cm, Slow: 4.7 ± 2.9 cm). In addition, ROM, circumference, muscle thickness, muscle echo intensity, and muscle stiffness also showed no significant interaction.

Conclusion: The magnitude of muscle damage is similar for ECCs cycling with equal work regardless of velocity.

Omega-3 fatty acids enhance the beneficial effect of BCAA supplementation on muscle function following eccentric contractions

Background

Methods

Results

Conclusions

A juvenile climbing exercise establishes a muscle memory boosting the effects of exercise in adult rats

AIM

Investigate whether juvenile exercise could induce a long-term muscle memory, boosting the effects of exercise in adults.

METHODS

We devised a 5-week climbing exercise scheme with food reward administered to male juvenile rats (post-natal week 4-9). Subsequently, the animals were subjected to 10 weeks of detraining (week 9-19) without climbing and finally retraining during week 19-21.

RESULTS

The juvenile exercise increased fiber cross-sectional area (fCSA) by 21% (p = 0.0035), boosted nuclear accretion by 13% (p = 0.057), and reduced intraperitoneal fat content by 28% (p = 0.007) and body weight by 9% (p = 0.001). During detraining, the fCSA became similar in the animals that had been climbing compared to naive controls, but the elevated number of myonuclei induced by the climbing were maintained (15%, p = 0.033). When the naive rats were subjected to 2 weeks of adult exercise there was little effect on fCSA, while the previously trained rats displayed an increase of 19% (p = 0.0007). Similarly, when the rats were subjected to unilateral surgical overload in lieu of the adult climbing exercise, the increase in fCSA was 20% (p = 0.0039) in the climbing group, while there was no significant increase in naive rats when comparing to the contralateral leg.

CONCLUSION

This demonstrates that juvenile exercise can establish a muscle memory boosting the effects of adult exercise. The juvenile climbing exercise with food reward also led to leaner animals with lower body weight. These differences were to some extent maintained throughout the adult detraining period in spite of all animals being fed ad libitum, indicating a form of body weight memory.

Prior beetroot juice ingestion offsets endothelial dysfunction following prolonged sitting

Nutritional strategies to prevent endothelial dysfunction following prolonged sitting remain largely unknown. Given that beetroot juice (BRJ) ingestion enhances nitric oxide (NO) bioavailability, we aimed to evaluate whether prior BRJ ingestion would prevent sitting-induced endothelial dysfunction in the leg. Eleven healthy young males (n = 7) and females (n = 4) underwent two experimental trials of prolonged sitting with prior: 1) placebo ingestion (PL trial) and 2) BRJ ingestion (BRJ trial). All subjects ingested 140 ml of PL or BRJ (~0.0055 or ~12.8 mmol of nitrate, respectively) immediately before 3 h of sitting. Pre and post-sitting measurement of popliteal artery flow-mediated dilation (FMD) and blood pressure, and blood collection were undertaken. During the sitting period, an hourly assessment of popliteal artery diameter and blood velocity, blood pressure, and blood collection was performed. Popliteal artery blood flow and shear rate were significantly and similarly reduced during the sitting period in both trials (p < 0.001). Plasma nitrate and NOx (total nitrite and nitrate) concentrations were significantly increased relative to baseline in the only BRJ trial, and the overall concentrations were significantly higher in the BRJ trial (p < 0.001). Popliteal artery FMD was significantly reduced after the sitting period in the PL trial (p < 0.05), whereas no reduction was observed in the BRJ trial. Therefore, prior BRJ ingestion would prevent sitting-induced leg endothelial dysfunction via enhancing NO bioavailability.

Slow-Speed Low-Intensity but Not Normal-Speed High-Intensity Resistance Exercise Maintains Endothelial Function

Purpose: High-intensity resistance exercise two or three times a week has been considered optimal for muscle hypertrophy, although it can remarkably elevate blood pressure (BP). In contrast, slow-speed resistance exercise with low intensity and tonic force generation (slow-low) can induce muscle hypertrophy without elevating BP. However, it is unclear how endothelial function changes after slow-low. Therefore, this study examined whether slow-low would maintain brachial artery endothelial function in comparison with normal-speed with high intensity resistance exercise (normal-high) and normal-speed with low-intensity resistance exercise (normal-low). Methods: Eleven healthy young men performed leg-extensions with slow-low (3 sets of 8 repetitions at 50% of 1RM), normal-high (3 sets of 8 repetitions at 80% of 1RM), and normal-low (3 sets of 8 repetitions at 50% of 1RM). Flow-mediated dilation (FMD) in the brachial artery was evaluated at pre-exercise and at 10, 30, and 60 min after exercise. Result: The results showed that normal-high caused significant impairment of FMD at 30 (3.7 ± 2.7%) and 60 (3.7 ± 2.8%) min after exercise (P < .05). In contrast, slow-low and normal-low showed no significant difference from baseline. FMD was significantly lower in normal-high compared with slow-low and normal-low at 30 and 60 min after exercise (P < .05). Additionally, systolic BP was significantly higher during normal-high compared with slow-low and normal-low (P < .05). Conclusion: We concluded that slow-low did not impair brachial artery FMD concomitant with lower systolic BP, and may therefore be a useful mode of exercise training to improve muscle hypertrophy without provoking transient endothelial dysfunction.

Abstract P4-11-11: Effect of home-based smartphone-supported high-intensity interval training on cardiorespiratory fitness in breast cancer survivors: A randomized controlled trial of the habit-B program

Background: A strategy for maintaining and/or improving cardiorespiratory fitness (CRF) in the growing population of cancer survivors is of major clinical importance in the COVID-19 era. With the aim of increasing CRF, recent studies have focused on the use of high-intensity interval training (HIIT) in supervised experimental settings, which appeared to be more beneficial than usual care in cancer survivors at all stages of treatment and aftercare. However, the effect of unsupervised HIIT on increasing CRF in breast cancer survivors is not known. Purpose: To determine whether the newly developed habit-B program, which involves home-based smartphone-supported HIIT using body-weight exercises, improves CRF in early-stage breast cancer survivors. We hypothesized that the habit-B program would improve VO2peak compared with a control group. Methods: This single-center, 12-week, parallel-group, single-blind, randomized controlled trial involved 50 women with stage I-IIa breast cancer, aged 20 to 59 years, who had completed initial treatment except for hormone therapy. Participants wore a smartwatch and were randomized to either the exercise or control group from May 27, 2019 through November 30, 2020. The planned sample size was 60 patients to detect the increase of 2.0 ml/kg/min change in VO2peak with a standard deviation of 2.6 ml/kg/min, one-sided significance level of 2.5% and 80% power. The exercise group underwent home-based HIIT using a smartphone and a Fitbit Versa thrice weekly for 12 weeks (three times per week). The primary outcome was the 12-week change in peak oxygen uptake (VO2peak; mL/kg/min) between the groups. Other outcomes included muscle strength, 6-min walk test, resting heart rate, physical activity, fatigue, safety, and quality of life. Results: Of the 50 participants, 44 (exercise group, n=23; control group, n=21) completed the CRF assessment and 6 did not because of issues related to the COVID-19 pandemic. The change in VO2peak increased significantly in the exercise group (0.9 [95%CI, 0.1 to 1.7]) compared with the control group (-0.8 [95%CI, -1.5 to -0.1]) (mean difference, 1.7 [95% CI, 0.7 to 2.7], p &lt; .01). Leg strength also increased significantly in the exercise group compared with the control group (mean difference, 13.5 [95% CI, 2.9 to 24.1], p &lt; .01). Changes in other outcomes were not significantly different between the groups. Conclusion: A home-based HIIT intervention can lead to improved cardiorespiratory fitness and muscle strength in early-stage breast cancer survivors; however, a multicenter pragmatic clinical trial is required to confirm the benefits of the habit-B program.

Table 1.Demographic and medical characteristicsCharacteristicshabit-B (n = 25)Control (n = 25)Age, mean (SD), y48 (6)49 (5)Body mass index, mean (SD), kg/m221.0 (2.2)20.9 (2.0)Diastolic blood pressure, mean (SD), mmHg78 (8)81 (10)Systolic blood pressure, mean (SD), mmHg119 (13)129 (11)Alcohol consumption, n (%)≤weekly8 (32)5 (20)1–6 drinks per week15 (60)19 (76)Daily2 (8)1 (4)Highest Education, n (%)Junior high school0 (0)1 (4)High school3 (12)0 (0)College or more22 (88)24 (96)Employment status, n (%)Full- or part-time worker21 (84)21 (84)On leave1 (4)0 (0)Housewife3 (12)4 (16)Time the patient can use for herself, n (%)&lt;14 hours/week10 (40)5 (20)14–25 hours/week8 (32)11 (44)&gt;25 hours/week7 (28)9 (36)Past history of medical illness, n (%)6 (24)6 (24)Breast cancer stageI18 (72)18 (72)IIA7 (28)7 (28)TumorEstrogen receptor positive24 (96)25 (100)Progesterone receptor positive24 (96)24 (96)HER2 positive1 (4)0 (0)Receiving hormone therapy, n (%)24 (96)23 (92)Tamoxifen, n (%)18 (72)18 (72)Anastrozole, n (%)1 (4)4 (16)Other, n (%)5 (20)1 (4)Receiving radiotherapy, n (%)11 (44)12 (48)Time since surgery, mean (SD) months5 (4)6 (4)

Table 2.Changes in cardiorespiratory fitness and muscle strength from baseline to week 12habit-B (n = 21)Control (n = 23)Between-group differenceMean (SD)Mean (SD)Mean (95% CI)ESpPrimary endpointVO2peak (ml/kg/min)Baseline25.0 (3.0)24.9 (4.6)Week 1225.9 (2.8)24.1 (4.0)Within-group difference0.9 (1.7)-0.8 (1.6)1.7 (0.7 to 2.7)1.06&lt;0.01Secondary endpointCardiorespiratory fitness6-min walk test (m)Baseline586 (43)603 (59)Week 12615 (42)631 (68)Within-group difference30 (30)29 (40)1 (-21 to 23)0.260.93VO2peak (L/min)Baseline1.33 (0.18)1.32 (0.29)Week 121.39 (0.23)1.29 (0.26)Within-group difference0.06 (0.11)-0.03 (0.09)0.10 (0.03 to 0.16)0.95&lt;0.01Muscle strengthGrip strength (kgw)Baseline22.4 (3.8)23.3 (4.2)Week 1223.2 (4.2)23.7 (3.4)Within-group difference0.8 (2.0)0.4 (2.1)0.4 (-0.9 to 1.6)0.260.53Leg press one-repetition maximum (kg)Baseline93.6 (24.3)98.7 (40.6)Week 12106.6 (26.7)98.2 (30.9)Within-group difference13.0 (15.9)-0.5 (18.1)13.5 (2.9 to 24.1)0.790.01Chair stand test (s)Baseline14.4 (3.2)13.7 (2.5)Week 1213.5 (2.9)13.3 (2.5)Within-group difference-0.9 (2.7)-0.4 (1.8)-0.5 (-1.9 to 0.9)-0.210.50

Citation Format: Eisuke Ochi, Katsunori Tsuji, Tomomi Narisawa, Yoichi Shimizu, Aya Kuchiba, Akihiko Suto, Kenjiro Jimbo, Shin Takayama, Taro Ueno, Naomi Sakurai, Yutaka J Matsuoka. Effect of home-based smartphone-supported high-intensity interval training on cardiorespiratory fitness in breast cancer survivors: A randomized controlled trial of the habit-B program [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P4-11-11.

Abstract P4-10-21: High-intensity interval training in breast cancer survivors: A systematic review

Background: To review the settings and outcomes of high-intensity interval training (HIIT) interventions for breast cancer survivors, and to explore the feasibility of prescribing exercise for breast cancer survivors. Methods: A systematic search of electronic databases was conducted for studies published up to May 31, 2020. Eligibility criteria included randomized controlled trials of HIIT intervention in breast cancer survivors. Studies were grouped by whether the intervention was conducted during or after breast cancer treatment, and intervention methods and outcomes were reviewed within each group. Results: Twenty-six studies were identified, and 13 satisfied the inclusion criteria. Intervention was conducted during treatment in 8 studies, and after treatment in 5. Intervention duration ranged from 3 to 16 weeks, with 2 or 3 sessions per week, for a total of 9 to 36 sessions. All interventions were supervised; 12 were lab-based, and 1 was community-based. One of most promising outcomes was improvement of cardiorespiratory fitness by HIIT. Conclusion: This review found that all studies on HIIT for breast cancer survivors investigated lab-based, supervised interventions, but not home-based or unsupervised. HIIT is a time-efficient method for increasing cardiovascular function in breast cancer survivors, but further research is necessary to determine its effects on other outcomes.

Table 1.Characteristics of the included studies with intervention during treatmentStudySample sizeDuration and frequency (total times)ModeIntensityInterval and recovery durationsSupervised. OR. UnsupervisedLab-based. OR. Home and community-basedLee et al.308 weeks, 3×/week (24)Cycle ergometer90% Peak Power Output7×1 min cycling, 2 min active recovery, total 19 minSupervised by exercise trainerLab-basedMijwel et al.18216 weeks, 2×/week (32)Cycle ergometer16-18 RPE3×3 min cycling, 1 min passive recovery, total 11 minSupervised by exercise physiologist or oncology nurseLab-basedMijwel et al.2316 weeks, 2×/week (32)Cycle ergometer16-18 RPE3×3 min cycling, 1 min passive recovery, total 11 minSupervised by exercise physiologist or oncology nurseLab-basedMijwel et al.20616 weeks, 2×/week (32)Cycle ergometer16-18 RPE3×3 min cycling, 1 min passive recovery, total 11 minSupervised by exercise physiologist or oncology nurseLab-basedSchulz et al.166 weeks, 2×/week (12)Cycle ergometer85-100%VO2peak10×1 min cycling, 1 min load-less recovery, total 19 minSupervised by professionalLab-based

Table 2.Characteristics of the included studies with intervention after treatmentStudySample sizeDuration and frequency (total times)ModeIntensityInterval and recovery durationsSupervised . or . UnsupervisedLab-based. or. Home and community-basedAlizadeh AM et al.5212 weeks, 3×/week (36)Treadmill90-95% HRmax4×4 min running, 3 min passive recovery, total 25 minSupervised by exercise physiologistLab-basedAlizadeh S et al.8012 weeks, 3×/week (36)Treadmill90-95% HRmax4×4 min running, 3 min passive recovery, total 25 minSupervised by exercise physiologistLab-basedNorthey et al.1712 weeks, 3×/week (36)Cycle ergometerMaximal effort4×30 s, 2 min rest, total 10 minSupervised, supervisor not describedLab-basedDolan et al.336 weeks, 3×/week (18)TreadmillInitial: 65% VO2peak, Interval 50% VO2peak. Last: 95% VO2peak, Interval: &lt; 60% VO2peakFirst week: 4-6×4 min, 3 min interval, total 25-39 min. last week: 4-6×2 min, 2 min interval, total 25-39 minSupervised, supervisor not describedLab-based

Citation Format: Katsunori Tsuji, Yutaka J Matsuoka, Eisuke Ochi. High-intensity interval training in breast cancer survivors: A systematic review [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P4-10-21.

Accuracy of exercise-based tests for estimating cardiorespiratory fitness and muscle strength in early-stage breast cancer survivors in Japan

PURPOSE

We aimed to examine whether cardiorespiratory fitness and leg strength can be estimated based on their relationship with physical performance tests in Japanese breast cancer survivors.

METHODS

Participants were 50 sedentary women aged 20 to 59 years who have received breast surgery in the past 2 to 13 months after diagnosis of invasive breast cancer (stage I-IIa). Cardiorespiratory fitness and leg strength were measured by peak oxygen consumption (VO₂peak), and one-repetition maximum for leg press (leg press 1RM). Physical performance tests were performed 6-min walk test, chair stand test, and grip strength. Using multiple regression analysis, we developed prediction equations for VO₂peak and leg strength based on their associations with the physical performance tests. The validity of the estimation equations was assessed using Bland-Altman plots.

RESULTS

Mean age, VO₂peak, and leg press 1RM were 48 ± 6 years, 25.0 ± 3.6 mL/kg/min, and 95 ± 32 kg, respectively. Multiple regression analysis yielded 6-min walk test distance, age, height, and body weight as predictors of VO₂peak. Measured VO₂peak and predicted VO₂peak showed a moderate positive correlation (r = 0.463, p < 0.001). Chair stand test, grip strength, age, height, and body weight were selected as predictors of leg press 1RM. There was a strong positive correlation between predicted and measured leg press 1RM (r = 0.754, p < 0.001).

CONCLUSION

The results suggest that leg strength can be predicted using physical performance tests. However, further examination may be needed to determine whether cardiorespiratory fitness can be predicted based on 6-min walk test.

Oncology care providers' awareness and practice related to physical activity promotion for breast cancer survivors and barriers and facilitators to such promotion: a nationwide cross-sectional web-based survey

Purpose

A known barrier to getting breast cancer survivors (BCSs) to engage in habitual exercise is a lack of information on recommended physical activity levels provided to them by oncology care providers (OCPs). However, the actual situation in Japan remains unclear. This study sought to clarify OCPs’ awareness and practice related to Japan’s physical activity recommendation for BCSs and to ascertain barriers to routine information provision.

Methods

We conducted a web-based survey involving members of the Japanese Breast Cancer Society (JBCS) and the Japanese Association of Cancer Rehabilitation between Dec. 2018 and Feb. 2019.

Results

Of 10,830 members, 1,029 (9.5%) responded. Only 19.1% were aware of the details of the JBCS physical activity recommendation, and only 21.2% routinely provided physical activity information to BCSs. Factors related to being aware of the recommendation details were 1) availability of the guidelines, 2) experience reading relevant parts of the guidelines, and 3) involvement in multidisciplinary team case meetings. Barriers to routine information provision were 1) absence of perceived work responsibility, 2) underestimation of survivors’ needs, 3) lack of resources, 4) lack of self-efficacy about the recommendation, and 5) poor knowledge of the recommendation.

Conclusions

Only one fifth of the OCPs routinely provided physical activity information. Barriers to provision were poor awareness, self-efficacy, and attitudes and unavailable resources. The physical activity recommendation needs to be disseminated to all OCPs and an information delivery system needs to be established for BCSs to receive appropriate information and support to promote their engagement in habitual physical activity.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00520-021-06706-8.

Polyunsaturated Fatty Acids, Exercise, and Cancer-Related Fatigue in Breast Cancer Survivors

Cancer-related fatigue (CRF) is one of the most frequently reported and disabling symptoms in cancer survivors. With its negative impact on the activities of daily living, work, social activities, and mood, CRF causes severe impairment of quality of life. A previous study showed that omega-6 polyunsaturated fatty acid (PUFA) supplementation unexpectedly reduced CRF compared with omega-3 PUFA supplementation and that omega-6 PUFA supplementation reduced pro-inflammatory serum markers in fatigued American breast cancer survivors. Meanwhile, a recent meta-analysis of individual patient data revealed significant benefits of exercise interventions on CRF. Recently, we completed our randomized controlled trial among early-stage Japanese breast cancer survivors, in which we examined the effect of baseline blood PUFA characteristics on change in CRF during the 12-week trial by exercise group and confirmed that increased Cancer Fatigue Scale (CFS) was associated with both docosahexaenoic acid (DHA) (p = 0.06) and omega-3 index (p = 0.08) at baseline in all participants (n = 46, omega-6/omega-3 ratio = 6.79, SD = 1.90). On the contrary, DHA at baseline was positively correlated with change in CRF (r = 0.40, p = 0.06) in the control group (n = 24, omega-6/omega-3 ratio = 7.0). Moreover, eicosapentaenoic acid (EPA) at baseline was positively correlated with leg strength (r = 0.39, p = 0.10) in the exercise group. In conclusion, blood PUFA balance might be associated with the effect of exercise on CRF. In addition, higher EPA in individuals who conducted exercise likely has a beneficial effect on muscle strength. Further investigation is needed to clarify the interaction between PUFAs and exercise for alleviating CRF.

Impact of a single bout of resistance exercise on serum Klotho in healthy young men

BACKGROUND

It has been shown that Klotho protects vascular endothelial function. Given that a single bout of resistance-exercise-induced hypertensive stimulus causes endothelial dysfunction, we postulated that acute resistance exercise would reduce serum Klotho levels. In this respect, the reduction in serum Klotho levels would be associated with the response of flow-mediated dilation (FMD). Therefore, the purpose of this study was to investigate the impact of acute resistance exercise on the Klotho response in serum. In addition, we examined the relationship between the serum Klotho and FMD responses following acute resistance exercise.

METHODS

Twelve untrained men participated in this study (20.4 ± 0.3 years). Following baseline measurements (blood pressure, blood collection, FMD), subjects performed leg extensions, which consisted of 10 repetitions for five sets at 70% of one-repetition maximum. After the exercise, measurement of blood pressure, blood collection, and FMD assessment were repeated for 60 min. We analyzed Klotho and endothelin-1 (ET-1) concentrations in blood serum.

RESULTS

As expected, the exercise significantly elevated blood pressure and led to decreased FMD (p < 0.05). However, Klotho concentrations were significantly increased following exercise (p < 0.05). No correlation was observed in Klotho and FMD responses following acute resistance exercise. However, there was a significant positive correlation between Klotho and ET-1 in response to resistance exercise (p < 0.05).

CONCLUSION

In conclusion, the present study reveals that serum Klotho significantly increased following a single bout of resistance exercise. However, the increase in Klotho may not associate with the acute reduction in endothelial function.

Comorbid insomnia among breast cancer survivors and its prediction using machine learning: a nationwide study in Japan

OBJECTIVE

Insomnia is an increasingly recognized major symptom of breast cancer which can seriously disrupt the quality of life during and many years after treatment. Sleep problems have also been linked with survival in women with breast cancer. The aims of this study were to estimate the prevalence of insomnia in breast cancers survivors, clarify the clinical characteristics of their sleep difficulties and use machine learning techniques to explore clinical insights.

METHODS

Our analysis of data, obtained in a nationwide questionnaire survey of breast cancer survivors in Japan, revealed a prevalence of suspected insomnia of 37.5%. With the clinical data obtained, we then used machine learning algorithms to develop a classifier that predicts comorbid insomnia. The performance of the prediction model was evaluated using 8-fold cross-validation.

RESULTS

When using optimal hyperparameters, the L2 penalized logistic regression model and the XGBoost model provided predictive accuracy of 71.5 and 70.6% for the presence of suspected insomnia, with areas under the curve of 0.76 and 0.75, respectively. Population segments with high risk of insomnia were also extracted using the RuleFit algorithm. We found that cancer-related fatigue is a predictor of insomnia in breast cancer survivors.

CONCLUSIONS

The high prevalence of sleep problems and its link with mortality warrants routine screening. Our novel predictive model using a machine learning approach offers clinically important insights for the early detection of comorbid insomnia and intervention in breast cancer survivors.

Cardiorespiratory fitness in breast cancer survivors: a randomised controlled trial of home-based smartphone supported high intensity interval training

BACKGROUND

A strategy for maintaining and/or improving cardiorespiratory fitness (CRF) in the growing population of cancer survivors is of major clinical importance, especially in the COVID-19 era. The effect of unsupervised high-intensity interval training (HIIT) on increasing CRF in breast cancer survivors is unknown.

PURPOSE

The purpose of this study was to determine whether the newly developed habit-B programme, which involves home-based smartphone-supported HIIT using body weight exercises, improves CRF in early-stage breast cancer survivors.

METHODS

This single-centre, 12-week, parallel-group, single-blind, randomised controlled trial involved 50 women with stage I-IIa breast cancer, aged 20-59 years, who had completed initial treatment except for hormone therapy. Participants were randomised to either the exercise or control group. The primary outcome was the 12-week change in peak oxygen uptake [Formula: see text]. Other outcomes included muscle strength, 6 min walk test, resting heart rate, physical activity, fatigue, safety and quality of life.

RESULTS

The change in [Formula: see text] and leg strength increased significantly in the exercise group compared with the control group (p<0.01). Changes in other outcomes were not significantly different between the groups.

CONCLUSION

A home-based HIIT intervention can lead to improve CRF and muscle strength in early-stage breast cancer survivors.

Eccentric exercise causes delayed sensory nerve conduction velocity but no repeated bout effect in the flexor pollicis brevis muscles

PURPOSE

This study was aimed at investigating the effect of eccentric contractions (ECCs) of flexor pollicis brevis muscles (FPBMs) on motor and sensory nerve functions as well as the ipsilateral repeated bout effect (IL-RBE) and contralateral (CL)-RBE of motor and sensory nerve conduction velocities following ECCs.

METHODS

Thirty-two young healthy men (age: 19.6 ± 0.2 years, height: 173.2 ± 1.2 cm, body mass: 69.7 ± 1.9 kg) performed two bouts of ECCs. During the first ECCs bout (ECCs-1), all participants performed 100 ECCs with 1 hand; for the second bout, 3 groups (2 weeks [W]: n = 11, 4W: n = 10, 8W: n = 11) performed ECCs with both hands 2, 4, or 8 weeks after ECCs-1. The maximal voluntary isometric contraction (MVC), range of motion (ROM), visual analog scale for pain (VAS), motor and sensory nerve conduction velocities were measured before, immediately after, and 1, 2, 3, and 5 days after ECCs.

RESULTS

ECCs-1 decreased the MVC, limited the ROM, developed VAS, and decreased the motor and sensory nerve conduction velocities compared to non-exercise hand (p < 0.05). The repeated bout effect was observed in the ROM for IL-RBE in 2W and 4W, VAS for IL-RBE in 2 W, and ROM and VAS for CL-RBE in 2W (p < 0.05). However, RBEs of MVC and motor and sensory nerve conduction velocities were not observed, and no differences were confirmed depending on the interval.

CONCLUSION

In the present study, ECCs of the FPBM caused a sensory nerve dysfunction, while IL- or CL-RBE was not observed.

4-week eicosapentaenoic acid-rich fish oil supplementation partially protects muscular damage following eccentric contractions

BACKGROUND

We previously showed 8-week of fish oil supplementation attenuated muscle damage. However, the effect of a shorter period of fish oil supplementation is unclear. The present study investigated the effect of fish oil, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), for 4 weeks on muscular damage caused by eccentric contractions (ECCs) of the elbow flexors.

METHODS

Twenty-two untrained men were recruited in this double-blind, placebo-controlled, parallel design study and the subjects were randomly assigned to the EPA and DHA group (EPA and DHA, n = 11) and placebo group (PL, n = 11). They consumed either EPA 600 mg and DHA 260 mg per day or placebo supplement for 4 weeks prior to exercise. Subjects performed 60 ECCs at 100 % maximal voluntary contraction (MVC) using a dumbbell. Changes in MVC torque, range of motion (ROM), upper arm circumference, muscle soreness, echo intensity, muscle thickness, serum creatine kinase (CK), and interleukin-6 (IL-6) were assessed before exercise; immediately after exercise; and 1, 2, 3, and 5 days after exercise.

RESULTS

ROM was significantly higher in the EPA and DHA group than in the PL group immediately after performing ECCs (p < 0.05). No differences between groups were observed in terms of MVC torque, upper arm circumference, muscle soreness, echo intensity, and thickness. A significant difference was observed in serum CK 3 days after ECCs (p < 0.05).

CONCLUSIONS

We concluded that shorter period EPA and DHA supplementation benefits joint flexibility and protection of muscle fiber following ECCs.

High-intensity interval training in breast cancer survivors: a systematic review

Background

To review the settings and outcomes of high-intensity interval training (HIIT) interventions for breast cancer survivors, and to explore the feasibility of prescribing exercise for breast cancer survivors.

Methods

A systematic search of electronic databases was conducted for studies published up to May 31, 2020. Eligibility criteria included randomized controlled trials of HIIT intervention in breast cancer survivors. Studies were grouped by whether the intervention was conducted during or after breast cancer treatment, and intervention methods and outcomes were reviewed within each group.

Results

Twenty-six studies were identified, and 13 satisfied the inclusion criteria. Intervention was conducted during treatment in 8 studies, and after treatment in 5. Intervention duration ranged from 3 to 16 weeks, with 2 or 3 sessions per week, for a total of 9 to 36 sessions. All interventions were supervised; 12 were lab-based, and 1 was community-based. One of most promising outcomes was improvement of cardiorespiratory fitness by HIIT.

Conclusion

This review found that all studies on HIIT for breast cancer survivors investigated lab-based, supervised interventions, but not home-based or unsupervised. HIIT is a time-efficient method for increasing cardiovascular function in breast cancer survivors, but further research is necessary to determine its effects on other outcomes.

Plasma Eicosapentaenoic Acid Is Associated with Muscle Strength and Muscle Damage after Strenuous Exercise

Background: Although the ingestion of total omega–3 fatty acids (omega–3) is positively related with muscular strength in older persons, little is known about the effect of omega–3 plasma levels on muscular function before and after exercise in young men. Moreover, omega–3 supplementation has a positive role in exercise-induced acute muscle damage. This study investigated the relationship between plasma omega–3 in the blood and promotion and preservation of muscle strength after eccentric contractions (ECCs) in young men. Methods: Thirty-two healthy young men participated in this study. We assessed plasma omega–3 level and the maximal voluntary contraction (MVC). Twenty-six out of them exercised 60 ECCs at 100% MVC. We measured the MVC torque, flexibility before and immediately after exercise, 1–5 days post exercise. Results: The levels of eicosapentaenoic acid (EPA) and EPA/arachidonic acid were positively associated with muscle strength (p < 0.05). Higher levels of omega–3 EPA and docosahexaenoic acid prevented the reduction in the MVC and limited joint flexibility after ECCs. Conclusions: The present study reveals that higher levels of EPA are important to promote muscle strength and preserve the strength loss after exercise.

Aging of the immune system and impaired muscle regeneration: A failure of immunomodulation of adult myogenesis

Skeletal muscle regeneration that follows acute injury is strongly influenced by interactions with immune cells that invade and proliferate in the damaged tissue. Discoveries over the past 20 years have identified many of the key mechanisms through which myeloid cells, especially macrophages, regulate muscle regeneration. In addition, lymphoid cells that include CD8+ T-cells and regulatory T-cells also significantly affect the course of muscle regeneration. During aging, the regenerative capacity of skeletal muscle declines, which can contribute to progressive loss of muscle mass and function. Those age-related reductions in muscle regeneration are accompanied by systemic, age-related changes in the immune system, that affect many of the myeloid and lymphoid cell populations that can influence muscle regeneration. In this review, we present recent discoveries that indicate that aging of the immune system contributes to the diminished regenerative capacity of aging muscle. Intrinsic, age-related changes in immune cells modify their expression of factors that affect the function of a population of muscle stem cells, called satellite cells, that are necessary for normal muscle regeneration. For example, age-related reductions in the expression of growth differentiation factor-3 (GDF3) or CXCL10 by macrophages negatively affect adult myogenesis, by disrupting regulatory interactions between macrophages and satellite cells. Those changes contribute to a reduction in the numbers and myogenic capacity of satellite cells in old muscle, which reduces their ability to restore damaged muscle. In addition, aging produces changes in the expression of molecules that regulate the inflammatory response to injured muscle, which also contributes to age-related defects in muscle regeneration. For example, age-related increases in the production of osteopontin by macrophages disrupts the normal inflammatory response to muscle injury, resulting in regenerative defects. These nascent findings represent the beginning of a newly-developing field of investigation into mechanisms through which aging of the immune system affects muscle regeneration.

Fast-Velocity Eccentric Cycling Exercise Causes Greater Muscle Damage Than Slow Eccentric Cycling

This study aims to investigate muscle damage occurring in the early and recovery phases after fast-velocity and slow-velocity eccentric cycling. Eleven untrained men (age, 20.0 ± 1.7 years; height, 171.3 ± 6.8 cm; weight, 61.8 ± 7.7 kg; and %body fat, 13.2 ± 2.9%) performed slow-velocity maximal isokinetic eccentric cycling (slow-velocity; 30°/s) with one leg and fast-velocity (fast-velocity; 210°/s) isokinetic eccentric cycling with the other leg. Changes in maximal voluntary isokinetic concentric contraction (MVCC) torque at velocities of 30 and 210°/s, range of motion (ROM), and muscle soreness were assessed by pressure using a digital muscle stiffness instrument; thigh circumference, muscle echo intensity, and muscle stiffness were assessed before exercise, and immediately after exercise, 1 day, and 4 days after exercise. Comparing with the results obtained for slow-velocity cycling (post: 215.9 ± 32.3 Nm, day 1: 192.9 ± 47.4 Nm, day 4: 184.3 ± 47.2 Nm) and before exercise, MVCC after fast-velocity cycling significantly decreased at immediately (160.4 ± 43.5 Nm), 1 day (143.6 ± 54.1 Nm), and 4 days (150.1 ± 44.5 Nm) after exercise (p < 0.05). Significant increase in muscle soreness for vastus lateralis was observed after fast-velocity cycling (41.2 ± 16.9 mm) compared with slow-velocity cycling (23.7 ± 12.2 mm) 4 days after exercise (p < 0.05). However, no significant difference in muscle soreness was observed for rectus femoris and vastus medialis at any time points after exercise. In addition, no significant differences were observed in the ROM, thigh circumference, muscle echo intensity, and muscle stiffness. In conclusion, fast-velocity eccentric cycling causes a decrease in muscle strength and an increase in soreness as compared to slow-velocity eccentric cycling.

Maintenance of endothelial function following acute resistance exercise in females is associated with a tempered blood pressure response

Acute resistance exercise-induced hypertensive stimulus impairs endothelial function in males. Because prior work indicates that female subjects have a tempered blood pressure response to acute resistance exercise, we hypothesized that, compared with males, females would better maintain endothelial function following resistance exercise and that this preservation would be associated with a lower hypertensive stimulus. Twenty-nine young healthy males (n = 16) and females (n = 13) participated in this study. All subjects performed a session of resistance exercise (leg extension) at the same relative workload [65% of one repetition maximum (1RM)]. The blood pressure response to exercise was characterized, and brachial artery flow-mediated dilation (FMD) was measured before and after. Males performed a second experimental trial in which the blood pressure response to resistance exercise was matched to that of females. This was accomplished by reducing the workload (~25% of 1RM). When resistance exercise was performed at the same relative workload, the systolic blood pressure was greater in males compared with females. Congruently, resistance exercise caused a significant impairment in FMD in males but not in females (P < 0.001). When the exercise workload was reduced in males, they no longer displayed an impairment in FMD following resistance exercise and, as such, the sex difference was abolished (P > 0.05). The present study reveals that acute resistance exercise transiently impairs endothelial function in young, healthy males but not in age-matched females. Notably, the maintenance of endothelial function in females is associated with a lower blood pressure response during resistance exercise.NEW & NOTEWORTHY The present data demonstrate for the first time that acute resistance exercise impairs endothelial function in young, healthy male but not female subjects. In addition, we show that the preservation of endothelial function in females is associated with a mitigated blood pressure response during resistance exercise. Accordingly, this work portrays a sexual dimorphism in the barostress response, and ensuing vascular effects, to resistance exercise.

Muscular endurance and muscle metabolic responses to 8 weeks of omega-3 polyunsaturated fatty acids supplementation

BACKGROUND

It has been well known that exercise training improves muscular endurance; however, whether nutritional strategies can be used to enhance muscular endurance remains unclear. Herein, we tested the hypothesis that 8 weeks of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) supplementation, known to promote oxygen availability and lipid metabolism, would attenuate muscular fatigue caused by numerous muscle contractions.

METHODS

Nineteen healthy men were randomly assigned to a placebo group (n = 9) and fish oil group (n = 10) in a double-blind fashion. The fish oil group consumed EPA-rich fish oil that contains 600-mg EPA and 260-mg DHA per day for 8 weeks. The placebo group received matching capsules for the same duration of time. After the 8-week intervention, subjects performed muscular endurance test that was repeated knee extensions with weights equal to 40% of the subject's body weight.

RESULTS

Maximal repetitions to exhaustion were recorded. In addition, maximum isometric voluntary muscle contraction (MVC), muscle metabolism using near-infrared spectroscopy, and blood lactate were measured during the test. Subjects in both groups reached exhaustion after the muscular endurance test, while the maximal repetitions did not differ between the groups. Similarly, there is no significant difference in oxygen saturation in muscle tissue (StO2), an index of muscle oxygen availability, between the groups. Also, MVC and blood lactate did not change between groups.

CONCLUSION

In conclusion, the present study provided evidence that muscle fatigue caused by knee extensions cannot be attenuated by EPA and DHA supplementation in healthy subjects.

Data Validation and Verification Using Blockchain in a Clinical Trial for Breast Cancer: Regulatory Sandbox

Background

The integrity of data in a clinical trial is essential, but the current data management process is too complex and highly labor-intensive. As a result, clinical trials are prone to consuming a lot of budget and time, and there is a risk for human-induced error and data falsification. Blockchain technology has the potential to address some of these challenges.

Objective

The aim of the study was to validate a system that enables the security of medical data in a clinical trial using blockchain technology.

Methods

We have developed a blockchain-based data management system for clinical trials and tested the system through a clinical trial for breast cancer. The project was conducted to demonstrate clinical data management using blockchain technology under the regulatory sandbox enabled by the Japanese Cabinet Office.

Results

We verified and validated the data in the clinical trial using the validation protocol and tested its resilience to data tampering. The robustness of the system was also proven by survival with zero downtime for clinical data registration during a Amazon Web Services disruption event in the Tokyo region on August 23, 2019.

Conclusions

We show that our system can improve clinical trial data management, enhance trust in the clinical research process, and ease regulator burden. The system will contribute to the sustainability of health care services through the optimization of cost for clinical trials.

Low-Dose of β-Hydroxy-β-Methylbutyrate (HMB) Alleviates Muscle Strength Loss and Limited Joint Flexibility Following Eccentric Contractions

Objectives

The excessive exercise including eccentric contractions (ECCs) cause the reduction of maximal strength, limitation of range of motion (ROM), developed muscle soreness, and muscle swelling for several days from immediately after exercise. Therefore, it is important to promote the recovery of muscle damage and minimize decreases in muscle function and muscle soreness after exercise. We recently examined the effects of 2- and 4-week β-hydroxy-β-methylbutyrate (HMB) supplementation (3 g/day) on ECCs-induced muscle damage. As the result, both the 2- and 4-week treatments decreased muscle strength reduction, ROM, and muscle swelling. However, the optimal dose of HMB required for decreasing muscle damage remains unknown. Therefore, this study investigated the supplemental effect of low-dose HMB on muscle damage after ECCs of human elbow flexor muscles.

Methods

Twenty untrained men (age, 21.0 ± 1.3 years) were completed the double-blind, placebo-controlled, parallel design study. The subjects were randomly assigned to the ingestion of HMB supplement (HMB, n = 10) or placebo group (PL, n = 10). After the subjects of 1.5 g HMB or placebo pills per day for 2 weeks, they performed six sets of 10 ECCs at 100% maximal voluntary contraction (MVC) using dumbbell. Changes in MVC torque, ROM, upper arm circumference, and muscle soreness were assessed before, immediately after, 1, 2, 3, and 5 days after exercise.

Results

The MVC torque was significantly higher in the HMB than in the PL group immediately after (HMB, −56.8%; PL, −67.1%) as well as 3 (HMB: −25.5%, PL: −48.7%) and 5 (HMB: −22.5%, PL: −44.0%) days after performing ECCs (p &lt; 0.05). Additionally, the ROM was significantly higher in the HMB than in the PL group immediately after (HMB, −29.8%; PL, −50.5%) and 5 (HMB: −26.1%, PL: −43.3%) days after performing ECCs (p &lt; 0.05). However, no between-group differences were observed in upper arm circumference, and muscle soreness.

Conclusions

The results demonstrated that 1.5 g/day HMB significantly inhibits the reduction in muscle strength and ROM after ECCs. In addition, 1.5 g/day HMB has no effect on muscle soreness, swelling, or stiffness. We conclude that 1.5 g/day of HMB supplementation plays a role in preventing muscle damage after performing ECCs, even if the effects are limited.

Funding Sources

The present study was supported by a research funding by Kobayashi Perfumery Co., Ltd.

Low Dose of β-Hydroxy-β-Methylbutyrate (HMB) Alleviates Muscle Strength Loss and Limited Joint Flexibility following Eccentric Contractions

Objective: The optimal dose of β-hydroxy-β-methylbutyrate (HMB) required for decreasing muscle damage remains unknown. Therefore, this study investigated the supplemental effect of low-dose HMB on muscle damage following eccentric contractions (ECCs) of human elbow flexors.Methods: Twenty untrained men (aged 20-26; height, 169.4 ± 5.7 cm; weight, 68.2 ± 11.3 kg; body mass index, 23.7 ± 3.3) completed the double-blind, placebo-controlled, parallel design study. The subjects were randomly assigned to the ingestion of HMB supplement (HMB, n = 10) or placebo group (PL, n = 10). After the subjects of 1.5 g HMB or placebo pills per day for 2 weeks, they performed six sets of 10 ECCs at 100% maximal voluntary contraction (MVC) using dumbbell. Changes in MVC torque, range of motion (ROM), upper arm circumference, muscle soreness, and muscle stiffness were assessed before, immediately after, 1, 2, 3, 5 days after exercise.Results: MVC torque was significantly higher in the HMB group than in the PL group immediately after (HMB, -56.8%; PL, -67.1%) as well as 3 (HMB: -25.5%, PL: -48.7%) and 5 (HMB: -22.5%, PL: -44.0%) days after performing ECCs (p < 0.05). Additionally, ROM was significantly higher in the HMB group than in the PL group immediately after (HMB, -29.8%; PL, -50.5%) and 5 (HMB: -26.1%, PL: -43.3%) days after performing ECCs (p < 0.05). No between-group differences were observed in other muscle damage markers.Conclusion: The low-dose HMB supplementation demonstrated a moderate overall impact and played a beneficial role in muscle dysfunction and joint flexibility following ECCs.

Abstract P6-11-21: Oncology care providers’ attitudes, practices, barriers and facilitators of physical activity promotion in breast cancer survivors: A nation-wide cross sectional web-based survey

[Backgrounds] Many breast cancer survivors (BCSs) still remain physically inactive. Lack of receiving physical activity (PA) information from oncology care providers (OCPs) is known as one of patient-reported barriers to get exercise habits. [Methods] To clarify OCPs’ attitudes, practices, barriers and facilitators of PA promotion in BCSs, we conducted web-based surveys for all members of Japanese Breast Cancer Society (JBCS) and Japanese Association of Cancer Rehabilitation from Dec. 2018 to Feb. 2019. [Results] Of 10,830 OCPs who asked to answer the web-based survey, 1,029 (9.5%) responded. Of those, 17% recognized contents about PA recommendation in JBCS guidelines in detail. And, 23% informed BCSs about benefits of PA routinely. Logistic regression analysis showed that the associated factors about OCPs’ routinely informing about benefits of PA were as follows: 1) recognition that explaining to BCSs about PA includes in OCPs’ own job roles (OR: 5.9, 95% confident interval (95%CI)=2.48-14.02, p&lt;0.001), 2) recognition that explanation about PA is necessary for over 60% BCSs (OR: 2.4, 95%CI=1.46-4.11, p&lt;0.001), 3) presence of exercise programs in their own institutions (OR: 1.9, 95%CI=1.07-3.46, p=0.028), 4) recognition that explaining to BCSs about PA was one of OCPs’ own roles in their institute(OR: 1.8, 95%CI=1.09-2.92, p=0.022), 5) awareness of detailed contents about PA recommendation in JBCS guidelines (OR: 1.7, 95%CI=1.13-2.70, p=0.012), 6) presence of OCPs’ confidence about informing about PA (OR: 1.6, 95%CI=1.10-2.47, p=0.016), 7) presence of outpatient consultation by nurses (OR: 1.6, 95%CI=1.09-2.29, p=0.017), 8) belief in certainty of association between PA and breast cancer death risk (OR: 1.6, 95%CI=1.05-2.34, p=0.027), 9) high levels of PA in OCPs (OR: 1.04, 95%CI=1.02-1.06, p&lt;0.001). Logistic regression analysis showed that the associated factors about OCPs’ awareness of detailed contents about PA recommendation in JBCS guidelines were as follows: 1) to have already seen the part of epidemiology and diagnosis in JBCS guidelines 2018 (OR: 4.3, 95%CI=3.46-16.95, p&lt;0.001), 2) presence of OCPs’ confidence about informing about PA (OR: 3.0, 95%CI=1.92-4.63, p&lt;0.001), 3) recognition that explaining to BCSs about PA includes in OCPs’ own job roles (OR: 2.9, 95%CI=1.34-6.36, p=0.007), 4) to have checked clinical practices by reading JBCS guidelines 2018 (OR: 2.4, 95%CI=1.10-5.27, p=0.028), 5) belief in certainty of association between PA and breast cancer death risk (OR: 2.0, 95%CI=1.24-3.09, p=0.004), 6) presence of case meeting about BCSs’ healthy lifestyle or survivorship care with multidisciplinary team as needed (OR: 1.7, 95%CI=1.16-2.61, p=0.008). [Discussions and Conclusion] This study clarify OCPs’ attitudes and practices about PA promotion in BCSs. To facilitate PA promotion, educational/training program for OCPs, development of institutional resources and research to prove benefits of PA in Japanese population are required. And, conducting case meeting with multidisciplinary team and checking clinical practices by looking at the evidences will enhance dissemination and implementation of the guideline.

Citation Format: Yoichi Shimizu, Katsunori Tsuji, Eisuke Ochi, Ryo Okubo, Taichi Shimazu, Noriatsu Tatematsu, Naomi Sakurai, Hiroji Iwata, Yutaka Johnnie Matsuoka. Oncology care providers’ attitudes, practices, barriers and facilitators of physical activity promotion in breast cancer survivors: A nation-wide cross sectional web-based survey [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P6-11-21.

Study protocol for a nationwide questionnaire survey of physical activity among breast cancer survivors in Japan

INTRODUCTION

A major concern is that few cancer survivors meet the guidelines for recommended levels of physical activity. No studies have investigated physical activity among breast cancer survivors nationwide in Japan. Therefore, the aims of this study are to identify the levels of physical activity among breast cancer survivors, to examine factors-related physical activity among breast cancer survivors and to identify breast cancer survivors' preferences for and interest in exercise programmes in order to inform the future programme development.

METHODS AND ANALYSIS

We will administer a cross-sectional survey using a self-report questionnaire to breast cancer survivors. At each of 50 facilities selected to include a variety of institutional backgrounds according to the population distribution of different regions throughout Japan, we will consecutively distribute the questionnaire to 30 outpatients who have completed initial treatments, except for hormone therapy. The target sample size is 1500 survivors. We will calculate descriptive statistics for each measurement item and perform univariate and multivariate analyses using outcome measures (eg, physical activity and quality of life) related to physical, psychological, social and environmental factors.

DISCUSSION

This is the first nationwide survey of physical activity levels among breast cancer survivors in Japan. Identifying the factors associated with physical activity will help us to develop, disseminate and implement programmes that encourage more survivors to adhere to physical activity guidelines.

ETHICS AND DISSEMINATION

The protocol was approved by the Institutional Review Board (IRB) of the National Cancer Center on 11 January 2019 (ID: 2018-295). In addition, many of the participating facilities required ethical approval from their local IRBs, while others did not. Accordingly, approval from the local IRBs of individual facilities was obtained when required. The findings will be disseminated through peer-reviewed publications and conference presentations.

Eccentric contraction-induced muscle damage in human flexor pollicis brevis is accompanied by impairment of motor nerve

BACKGROUND

Eccentric contractions (ECCs) cause muscle damage. In addition, we showed that ECCs induce nerve dysfunction and damage with rats and human.

PURPOSE

We aimed to evaluate motor nerve conduction velocity (MCV) for flexor pollicis brevis muscle (FPBM) after ECCs.

METHODS

Twelve men (years, 19.8 ± 1.7 years; height, 172.4 ± 7.0 cm; weight, 64.0 ± 8.6 kg) performed maximal 100 ECCs on their FPBM of non-dominant hands with torque dynamometer. The dominant hands were control (CON). Maximal voluntary contraction (MVC), range of motion (ROM), DOMS, and MCV were assessed before, immediately post, and 1, 2, and 5 days after ECCs. MCV was calculated as the distance by stimulation divided by the latencies of the waveforms generated. Values were statistically analyzed by two-way ANOVA, and the significance level was set at P < .05.

RESULTS

Decreases in MVC immediately (-32.9%) to 5 days after ECCs were significantly greater (P < .05) than for the CON group. ROM showed a significant decrease immediately (-21.6%) after ECCs compared with before ECCs and CON group (P < .05). DOMS after ECCs increased at 1 and 2 days (5.0 cm) after ECCs compared with before ECCs and CON (P < .05). Also, MCV after ECCs delayed significantly from immediately (-36.4%), 1, 2, and 5 days after ECCs compared with CON (P < .05), while no significant change in M-wave amplitude was observed over time for both ECCs and CON.

CONCLUSION

The present study showed that ECCs of the FPBM cause a significant delay in MCV of median nerve.

Eight weeks of fish oil supplementation does not prevent sitting-induced leg endothelial dysfunction

Prolonged sitting impairs leg endothelial function and this impairment is thought to be mediated by a sustained reduction in blood flow-induced shear stress. However, whether nutritional strategies can be used to prevent sitting-induced leg endothelial dysfunction remains unknown. Herein, we tested the hypothesis that 8 weeks of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) supplementation would prevent endothelial dysfunction associated with sitting. Nineteen healthy men were randomly assigned to a placebo group or EPA+DHA group in a double-blind fashion. The EPA+DHA group was administered EPA-rich fish oil, containing 600 mg EPA and 260 mg DHA per day for 8 weeks. The placebo group received matching capsules for the same duration of time. Popliteal artery flow-mediated dilation (FMD) was measured at baseline and before and after a 3-h sitting period. During sitting, blood pressure, popliteal artery diameter, and blood velocity were measured every hour. Throughout the sitting period, popliteal artery blood flow and shear rate were markedly and similarly reduced in both groups (P < 0.05). However, counter to the hypothesis, 3 h of sitting impaired popliteal artery FMD to the same extent in both groups (P < 0.05). In conclusion, daily EPA and DHA supplementation is not effective at preventing the detrimental effects of prolonged sitting on leg endothelial function. Novelty We provide evidence that sitting-induced leg endothelial dysfunction in young healthy subjects cannot be remediated by a nutritional strategy known to produce cardiovascular benefits. This could be partially due to the low total dose of EPA and DHA administered.

Effect of home-based high-intensity interval training and behavioural modification using information and communication technology on cardiorespiratory fitness and exercise habits among sedentary breast cancer survivors: habit-B study protocol for a randomised controlled trial

INTRODUCTION

Maintaining high levels of physical activity helps to maintain and improve physical health and quality of life, and plays a role in reducing adverse effects due to cancer treatments. Moreover, a greater degree of cardiorespiratory fitness is associated with reduced risk of all-cause mortality. However, there are no home-based programme for improving cardiorespiratory fitness using body weight exercises for breast cancer survivors. This study will assess the efficacy of the newly developed habit-B programme on maximum oxygen uptake compared with treatment as usual with wearable device. The effects of this programme on exercise habits, level of physical activity, physical fitness and subjective indices will also be investigated.

METHODS AND ANALYSIS

This is a 12-week, parallel-group, single-blind, randomised controlled trial. Allocation will be managed by a central server using a computer-generated random allocation sequence provided by an independent data centre. Participants will be assigned to the habit-B programme (high-intensity interval training, exercise counselling + guidance, home-based exercise support using information and communication technology, and a wearable device) or treatment as usual with a wearable device. Subjects will be sedentary women aged 20-59 years who have received breast surgery in the past 2-13 months after the diagnosis of invasive breast cancer (stages I-IIa) and have never received chemotherapy except for hormone therapy. The primary endpoint is the change in peak oxygen uptake (VO_2peak; mL/kg/min) between the groups after 12 weeks of intervention.

ETHICS AND DISSEMINATION

The study protocol was approved by the Institutional Review Board of the National Cancer Center Japan on 28 February 2019 (ID: 2018-347). The findings will be disseminated through peer-reviewed publications and conference presentations.

TRIAL REGISTRATION NUMBER

UMIN000036400.

Prior cycling exercise does not prevent endothelial dysfunction after resistance exercise

PURPOSE

Resistance exercise impairs endothelial function acutely. Therefore, it becomes important to devise an effective strategy for preventing acute endothelial dysfunction after resistance exercise. Herein, we tested the hypothesis that resistance exercise-induced temporal endothelial dysfunction is prevented by prior cycling.

METHODS

Twelve young healthy subjects completed two randomized experimental trials: (1) resistance exercise only trial (RE trial), (2) resistance exercise with prior cycling trial (C + RE trial). Following baseline brachial artery flow-mediated dilation (FMD), the subjects maintained the supine position for 45 min in the RE trial; the subjects performed a 45 min of cycling (67.0 ± 1.7% HRmax) in the C + RE trial. After 45 min of resting or cycling, the subjects performed resistance exercise (69.7 ± 4.0 kg) at the same time points. Following the resistance exercise, they were asked to rest in the supine position for 60 min. Then FMD were repeated at 10, 30 and 60 min after the resistance exercise in both trials.

RESULTS

The increased blood flow and shear rate after resistance exercise did not differ between trials, and these changes disappeared following resting in the supine position for 60 min. There was no significant interaction in %FMD responses. Both trials caused impairment in %FMD after the resistance exercise, and statistical significance was observed at 30 and 60 min after resistance exercise in the RE trial.

CONCLUSION

The present study revealed that cycling for 45 min prior to resistance exercise was not sufficient to prevent the acute endothelial dysfunction after resistance exercise.

Short-term cycling restores endothelial dysfunction after resistance exercise

Resistance exercise impairs endothelial function. Therefore, it is of paramount importance to devise an effective strategy for restoring endothelial function after resistance exercise. Herein, we tested the hypothesis that resistance exercise-induced endothelial dysfunction would be restored by low-to-moderate intensity cycling. Seventeen young healthy subjects completed two randomized experimental trials: (a) resistance exercise only trial; and (b) cycling after the resistance exercise trial. Following baseline brachial artery flow-mediated dilation (FMD), subjects performed the resistance exercise. Following the resistance exercise, they were asked to rest in the supine position for the assessments of FMD. Subjects in the resistance exercise only trial maintained this supine position for 60 minutes, whereas those in the other trial cycled for 10 minutes after the resistance exercise trial. Subjects were again asked to rest in the supine position after cycling. Then FMD were repeated at 30 and 60 minutes after the resistance exercise in both trials. In the resistance exercise only trial, the increased blood flow and shear rate were disappeared after 1 hour of resting in the supine position, but were maintained in those in the cycling after the resistance trial due to subsequent cycling. Both trials caused a significant impairment in FMD at 10 minutes after the resistance exercise (P < 0.05). This decline was sustained for 60 minutes in the resistance exercise only trial. However, the impaired FMD was restored in the cycling after the resistance exercise trial. In conclusion, impaired endothelial function after the resistance exercise can be restored with 10 minutes of low-to-moderate intensity cycling.

Supplementation of eicosapentaenoic acid-rich fish oil attenuates muscle stiffness after eccentric contractions of human elbow flexors

Background

This study aimed to investigate the effect of supplementation of fish oil rich in eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) on the damage of the biceps brachii after eccentric contractions (ECCs) of the elbow flexors, particularly focusing on muscle stiffness.

Methods

Sixteen men were included in this double-blind, placebo-controlled, parallel design study and the participants were randomly assigned to the EPA and DHA supplement group (EPA, n = 8) and placebo group (PL, n = 8). They consumed either EPA 600 mg and DHA 260 mg per day or placebo supplement for 8 weeks prior to exercise. Moreover, they performed six sets of 10 ECCs at 100% maximal voluntary contraction (MVC) using a dumbbell. Changes in MVC torque, range of motion (ROM), upper arm circumference, muscle soreness, muscle echo intensity, and muscle stiffness were assessed before exercise; immediately after exercise; and 1, 2, and 5 days after exercise.

Results

MVC torque and ROM were significantly higher in the EPA group than in the PL group after ECCs (p < 0.05). Muscle soreness, upper arm circumference, and muscle echo intensity were significantly higher in the PL group than in the EPA group after ECCs (p < 0.05). In addition, muscle stiffness at 150° was significantly higher in the PL group than in the EPA group immediately after ECCs (p < 0.05).

Conclusion

The present study showed that EPA and DHA supplementation has a positive role in inhibiting muscle stiffness after ECCs.

Trial registration

This trial (UMIN000028165) was registered on 10th/July/2017.

Two and Four Weeks of β-Hydroxy-β-Methylbutyrate (HMB) Supplementations Reduce Muscle Damage Following Eccentric Contractions

OBJECTIVE

This study investigated the effect of β-hydroxy-β-methylbutyrate (HMB) supplementation for either 2 or 4 weeks on the muscle damage after elbow flexors after eccentric contractions (ECCs).

METHODS

Twenty-eight untrained men were completed the double-blind, placebo-controlled, parallel design study. The subjects were randomly assigned to the ingestion of HMB supplement for 2 weeks (HMB 2-week, n = 10), for 4 weeks (HMB 4-week, n = 10), or a placebo group (PL, n = 8). Subjects of HMB 2-week and HMB 4-week consumed 3 g HMB per day, and they performed 6 sets of 10 ECCs at 100% maximal voluntary contraction (MVC) using a dumbbell. Changes in MVC torque, range of motion (ROM), upper arm circumference, muscle soreness, and muscle stiffness were assessed before, immediately after, and 1, 2, and 5 days after exercise.

RESULTS

MVC torque and ROM were significantly higher in the HMB 2-week and HMB 4-week groups than in the PL group after ECCs (p < 0.05). The upper arm circumference was significantly smaller in the HMB 2- and 4-week groups than in the PL group after ECCs (p < 0.05). In addition, muscle stiffness at 150° was significantly lower in the HMB 2- and 4-week groups than in the PL group at immediately after ECCs (p < 0.05). However, there was no difference in all outcomes between HMB 2-week and HMB 4-week.

CONCLUSION

We concluded that more than 2 weeks of HMB supplementation has a positive role for untrained subjects to prevent the muscle damage after ECCs.

Muscular recruitment is associated with muscular function and swelling following eccentric contractions of human elbow flexors

BACKGROUND

This study investigated the relationship between muscle fiber recruitment and the magnitude of muscle damage by isotonic eccentric contractions (ECCs).

METHODS

Ten healthy men (age: 27.2±6.0 y, height: 174. 0±5.3 cm, body mass 70.1±2.1 kg) were recruited in this study. Subjects performed 30 ECCs of the elbow flexors using a dumbbell adjusted to 40% and 80% one repetition maximum of each individual. The dependent variables maximal voluntary isometric contraction (MVC) torque, Range of Motion (ROM), delayed onset muscle soreness (DOMS), cross-sectional area (CSA) and transverse relaxation time (T2) of magnetic resonance imaging (MRI) were measured immediately before, immediately after and 1, 3, and 5 days after each exercise.

RESULTS

The decreased MVC and limited ROM were significantly greater for 80% than that 40% (P<0.05) at immediately after ECCs. However, no significant difference between 40% and 80% was found for DOMS. CSA at 5 days after ECCs was significantly higher 80% (P<0.05) than 40% (P<0.05). No significant changes in post T2 (acute T2) was found for 40%, but an increased acute T2 was observed in 80% (P<0.05). We found a significant correlation between the change in T2 at immediately after and MVC at immediately after (r=0.77, P<0.05). In addition, a significant correlation between the change in T2 at immediately after and change in CSA at 3 days after (r=-0.83, P<0.05) was found.

CONCLUSIONS

We conclude that the muscle strength loss and swelling following ECCs are related to the muscle fiber recruitment.

Contralateral repeated bout effect after eccentric exercise on muscular activation

PURPOSE

The purpose of this study was to investigate the contralateral and ipsilateral repeated bout effects of eccentric contractions (ECCs) on muscle fiber activation using transverse relaxation time (T2) of magnetic resonance imaging (MRI).

METHODS

Eleven men (22.3 ± 2.9 years) performed two bouts of 30 maximal ECCs of the elbow flexors spaced 2 weeks apart. Initially, all subjects performed 30 ECCs for one arm (ECC1). After 2 weeks, they performed 30 ECCs for both ipsilateral arm (IL-RBE) and contralateral arm (CL-RBE). Measurements were maximal voluntary isometric contraction (MVC) torque, range of motion (ROM), muscle soreness, cross-sectional area (CSA), and T2 at before, immediately after, 1, 2, 3, and 5 days after ECCs.

RESULTS

The loss of MVC torque, limited ROM, and developed muscle soreness and CSA were inhibited for IL-RBE and CL-RBE compared with ECC1 (p < 0.05). The acute T2, which is an indicator of the activation of muscle fibers, was longer for IL-RBE and CL-RBE than ECC1 (p < 0.05). Otherwise, no significant difference between IL-RBE and CL-RBE was observed in other measurements.

CONCLUSION

Our results suggest that one of the mechanisms for CL-RBE of ECCs is the increase in muscle fiber activation. In addition, the magnitude of protective effect for CL-RBE was similar to the IL-RBE in untrained young men.

Higher Training Frequency Is Important for Gaining Muscular Strength Under Volume-Matched Training

Background: This study investigated the effect of volume-matched strength training programs with different frequency and subsequent detraining on muscle size and strength.

Methods: During a training period of 11 weeks, untrained subjects (age: 22.3 ± 0.9 years, height: 173.1 ± 4.8 cm and body mass: 66.8 ± 8.4 kg) performed knee-extension exercise at 67% of their estimated one-repetition maximum either one session per week (T1 group: 6 sets of 12 repetitions per session; n = 10) or three sessions per week (T3 group: 2 sets of 12 repetitions per session; n = 10). Rating of perceived exertion (RPE) and muscle stiffness were measured as an index of muscle fatigue and muscle damage, respectively. The magnitude of muscle hypertrophy was assessed with thigh circumference and the quadriceps muscle thickness. The changes in muscle strength were measured with isometric maximum voluntary contraction torque (MVC).

Results: During the training period, RPE was significantly higher in the T1 than in the T3 (p < 0.001). After 11 weeks of training, both groups exhibited significant improvements in thigh circumference, muscle thickness, and MVC compared with baseline values. However, there was a significant group difference in MVC improvement at week 11 (T1: 43.5 ± 15.5%, T3: 65.2 ± 23.2%, p < 0.05). After 6 weeks of detraining, both groups showed the significant decreases in thigh circumference and muscle thickness from those at the end of training period, while no significant effect of detraining was observed in MVC.

Conclusion: These results suggest that three training sessions per week with two sets are recommended for untrained subjects to improve muscle strength while minimizing fatigue compared to one session per week with six sets.

High-intensity resistance exercise with low repetitions maintains endothelial function

Resistance exercise impairs endothelial function, and this impairment is thought to be mediated by sustained elevation in blood pressure. Herein, we tested the hypothesis that resistance exercise-induced endothelial dysfunction would be prevented by high-intensity resistance exercise with low repetitions. This type of resistance exercise is known to induce temporal elevation in blood pressure due to low repetitions and a long resting period between sets. Thirteen young healthy subjects completed three randomized experimental trials as follows: 1) moderate-intensity exercise with moderate repetitions (moderate-moderate trial), 2) low-intensity exercise with high repetitions (low-high trial), and 3) high-intensity exercise with low repetitions (high-low trial). After baseline brachial artery flow-mediated dilation (FMD) and blood pressure measurements, subjects performed resistance exercise according to the different types of trials. Thereafter, brachial artery FMD and blood pressure measurements were repeated 10, 30, and 60 min after the exercise. Exercise-induced increases in blood flow and shear rate were significantly lower in the high-low trial than in the other two trials ( P < 0.05). Although systolic blood pressures were significantly elevated after exercise in all trials ( P < 0.05), the magnitudes of rise in blood pressure increase were significantly lower in the high-low trial than in the moderate-moderate and low-high trials ( P < 0.05). Moderate-moderate and low-high trials caused a significant impairment in brachial artery FMD ( P < 0.05), which could be prevented through high-intensity resistance exercise with low repetitions (  > 0.05). In conclusion, endothelial function was maintained by conducting high-intensity resistance exercise with low repetitions. NEW & NOTEWORTHY Data from the present study reveal that high-intensity resistance exercise with low repetitions can maintain endothelial function. Thus, this study provides the first evidence that the detrimental vascular effects of resistance exercise are preventable when resistance exercise is performed in high intensity with low repetitions. Listen to this article's corresponding podcast at https://ajpheart.podbean.com/e/type-of-resistance-exercise-and-endothelial-function/ (Japanese version: https://ajpheart.podbean.com/e/japanese-language-podcast-type-of-resistance-exercise-and-endothelial-function/ ).