Effects of lunges inserted in walking (eccentric walking) on lower limb muscle strength, physical and cognitive function of regular walkers.

INTRODUCTION: Walking is a popular exercise but does not increase lower limb muscle strength and balance. We hypothesized that muscle strength, physical and cognitive function would be improved by inserting lunges in conventional walking. METHODS: Eleven regular walkers (54-88 years) who had more than 5000 steps in exercise walking a day at least 5 days a week participated in this study. They walked as usual for the first 4 weeks and included lunges and descending stairs or slope walking (i.e., eccentric walking) for the next 8 weeks. The steps of eccentric walking were gradually increased from 100 to 1000 steps per week over 8 weeks. RESULTS: The average steps per day were 10,535 ± 3516 in the first 4 weeks, and 10,118 ± 3199 in the eccentric walking period without a significant difference. No significant changes in maximal voluntary isometric contraction torque of the knee extensors (MVC), 30-s chair stand (CS), 2-min step, balance assessed by center of pressure movement area with eyes close, sit and reach, a digit symbol substitution test (DSST) for cognitive function were observed in the first 4 weeks. However, significant (P < 0.05) improvements were evident in MVC (18.6 ± 15.7%), CS (24.2 ± 17.3%), balance ( - 45.3 ± 34.5%), and DSST (20.8 ± 16.7%) from weeks 4 to 12. Serum complement component 1q concentration decreased (P < 0.05) from weeks 4 to 12, although no changes in serum glucose, triglyceride, and cholesterol concentrations were observed. CONCLUSION: These results supported the hypothesis, and suggest that eccentric walking provides effects that are not achieved by conventional walking.

The Effect of Prior Creatine Intake for 28 Days on Accelerated Recovery from Exercise-Induced Muscle Damage: A Double-Blind, Randomized, Placebo-Controlled Trial.

Despite the known beneficial effects of creatine in treating exercise-induced muscle damage (EIMD), its effectiveness remains unclear. This study investigates the recovery effect of creatine monohydrate (CrM) on EIMD. Twenty healthy men (21-36 years) were subjected to stratified, randomized, double-blind assignments. The creatine (CRE) and placebo (PLA) groups ingested creatine and crystalline cellulose, respectively, for 28 days. They subsequently performed dumbbell exercises while emphasizing eccentric contraction of the elbow flexors. The EIMD was evaluated before and after exercise. The range of motion was significantly higher in the CRE group than in the PLA group 24 h (h) post exercise. A similar difference was detected in maximum voluntary contraction at 0, 48, 96, and 168 h post exercise (p = 0.017-0.047). The upper arm circumference was significantly lower in the CRE group than in the PLA group at 48, 72, 96, and 168 h post exercise (p = 0.002-0.030). Similar variation was observed in the shear modulus of the biceps brachii muscle at 96 and 168 h post exercise (p = 0.003-0.021) and in muscle fatigue at 0 and 168 h post exercise (p = 0.012-0.032). These findings demonstrate CrM-mediated accelerated recovery from EIMD, suggesting that CrM is an effective supplement for EIMD recovery.

Assessing the validity of two-dimensional video analysis for measuring lower limb joint angles during fencing lunge.

Introduction: The fencing lunge (lunge), characterized by minimal body rotation, offers a movement well-suited for 2D video analysis. However, to the best of our knowledge, the validity of 2D video analysis for fencing has not been verified. This study aimed to validate 2D video analysis by comparing lower limb joints (hip, knee, and ankle joints) angles during lunge using both 2D video analysis and 3D motion analysis methods. Methods: Twenty-two male fencers performed lunge trials that were simultaneously recorded using eight motion capture cameras (Qualisys Miqus M1) and two digital video cameras (Sony AX-450 and AX450a). Results: The 2D video analysis results exhibited an extremely large correlation in knee joint angles of the front and rear legs in the sagittal with those from 3D motion analysis (r = 0.93-0.99). However, while a robust correlation was found between the ankle joint angles of the front and rear legs (r = 0.82-0.84), a large bias was also observed (-5.23° to -21.31°). Conversely, for the hip joints of the rear leg, a moderate correlation (r = 0.31) and a large bias (-10.89°) were identified. Conclusions: The results of this study will contribute to the development of coaching using 2D video analysis in competition settings because such analysis can be a useful alternative to 3D motion analysis when measuring the knee joint angle of the front leg and rear leg in the sagittal plane. However, for the ankle joint angle, further research on the optimal shooting position and height of the digital video camera is needed, whereas for the hip joint angle, 3D motion analysis is recommended at this time.

Relationships between Changes in Muscle Shear Modulus, Urinary Titin N- Terminal Fragment, and Maximum Voluntary Contraction Torque after Eccentric Exercise of the Elbow Flexors.

The study aimed to investigate the relationships between the shear modulus of the biceps brachii (BB) and brachialis muscle (BA) and the total of the two (BB+BA), and urinary titin N-terminal fragment (UTF), maximum voluntary isometric contraction (MVC), and other indirect markers. Fifteen healthy men performed five sets of 10 eccentric contractions using a dumbbell corresponding to 50% of MVC at 90° measured at baseline. The elbow joint of the left arm was extended from 90° to 180° (180° = full extension) in 5 s in the exercise, and was returned with support from the examiner to prevent concentric contraction. Shear modulus of BB and BA were measured by ultrasound shear wave elastography, and UTF, MVC, and range of motion of the elbow joint (ROM) were recorded before; immediately after; and 1, 24, 48, 72, 96, and 168 h after the exercise. After calculating the shear modulus of BB and BA, two values were added (BB+BA). The shear modulus peaked at 48 h, UTF peaked at 96 h, MVC and ROM changed largest at immediately, and muscle soreness peaked at 48 h post-exercise. Significant (p < 0.05) relationships were found between changes in BB shear modulus and BA shear modulus (r = 0.874), BB+BA shear modulus (r = 0.977), UTF (r = 0.681), and MVC (r = -0.538). Significant (p < 0.05) relationships were also observed between changes in BA shear modulus and BB+BA shear modulus (r = 0.957), UTF (r = 0.682), MVC (r = -0.522), and ROM (r = -0.600). Moreover, significant (p < 0.05) relationships were observed between changes in BB+BA shear modulus and UTF (r = 0.703), MVC (r = -0.549), and ROM (r = -0.547). These results indicate that shear modulus of each muscle (i.e., BB and BA) provide more precise information about muscle damage than UTF, MVC and ROM.

The Effect of Contrast Water Therapy on Dehydration during Endurance Training Camps in Moderate-Altitude Environments.

The effects of contrast water therapy (CWT) on dehydration at moderate altitudes during training camps remain unknown. We hypothesized that CWT reduces dehydration resulting from training at moderate altitudes and improves performance, akin to conditions at sea level. A 13-day endurance training camp was held at a moderate altitude of 1100 m and included 22 university athletes, who were divided into two groups (CWT group, n = 12; control (CON) group, n = 10). The sample size was calculated based on an α level of 0.05, power (1 ß) of 0.8, and effect size of 0.25 based on two-way ANOVA. Longitudinal changes over 13 days were compared using a two-group comparison model. Additionally, 16 athletes participated in an additional performance verification analysis. Subjective fatigue, body mass, and water content (total body water (TBW), extracellular water (ECW), and intracellular water) were measured using bioimpedance analysis every morning, and the titin N-terminal fragment in urine (UTF) was measured as an index of muscle damage. For performance verification, 10 consecutive jump performances (with the reactive strength index (RSI) as an indicator) were evaluated as neuromuscular function indices. The results indicated that the UTF did not significantly differ between the two groups. Moreover, the ECW/TBW values, indicative of dehydration, on days 4 and 5 in the CWT group were significantly lower than those in the CON group. However, there was no significant difference in RSI between the two groups. Therefore, although CWT reduces dehydration in the early stages of the training camp, it may not affect performance.

The Validity and Reliability of a Smartphone Application for Break-Point Angle Measurement during Nordic Hamstring Exercise.

Background: A recently developed smartphone application (Nordic Angle) allows the automatic calculation of the break-point angle (BPA) during Nordic hamstring exercise (NHE) without transferring the collected data to a computer. The BPA is the point at which the hamstrings are unable to withstand force. However, the validity of the BPA values obtained by this method has not been examined. Hypothesis/Purpose: This study aimed to evaluate the validity and reliability of the Nordic Angle by comparing the BPA values of the Nordic Angle with those of two-dimensional motion analysis software that can calculate the angles and angular velocities of various joints. Study Design: Cohort assessing Validity and Reliability. Methods: The validity of the Nordic Angle BPA data was verified by Spearman's correlation test for consistency with the movement analysis data, and the magnitude of the correlation was indicated by rs. The agreement between these measurements was examined using the Bland-Altman analysis. The reliability of the Nordic Angle and motion analysis was examined using the intraclass correlation coefficient (ICC) (1,k) based on data from repeated trials within a day. Results: Although the spearman correlation between the Nordic angle and the angle determined using motion analysis did not reach statistical significance (p = 0.052), a very large correlation was present (rs = 0.75). The difference between the mean values of the Nordic Angle and motion analysis was 0.4 ± 2.1°, and the limits of agreement ranged from -3.9° to 4.6°. In two BPA measurements, the Nordic Angle showed perfect reliability (ICC = 1.00, p < 0.001), while motion analysis showed nearly perfect reliability (ICC = 0.97, p < 0.001). Conclusion: The Nordic Angle, which has both validity and reliability, may be appropriate for field measurement because it allows immediate feedback of BPA and the measurement of many athletes. Level of evidence: 3b©The Author(s).

Damage and recovery of the intrinsic and extrinsic foot muscles from running a full marathon.

PURPOSE: To investigate the effects of full marathon running on intrinsic and extrinsic foot muscle damage and to determine the relationship with the height change of the longitudinal foot arch following full marathon completion. METHODS: Magnetic resonance imaging-measured transverse relaxation time (T2 ) of the abductor hallucis (ABH), flexor digitorum brevis (FDB) and quadratus plantae (QP), flexor digitorum longus (FDL), tibialis posterior (TP), and flexor hallucis longus (FHL) from 22 collegiate runners were assessed before and 1, 3, and 8 days after full marathon running. The three-dimensional foot posture of 10 of the 22 runners was further obtained using a foot scanner system before and 1, 3, and 8 days after the marathon. RESULTS: Marathon-induced increases in T2 were observed in the QP, FDL, TP, and FHL 1 day after the marathon (+7.5%, +4.7%, +6.7%, and +5.9%, respectively), with the increased T2 of TP persisting until 3 days after the marathon (+4.6%). T2 changes of FDL and FHL from pre-marathon to DAY 1 showed direct correlations with the corresponding change in the arch height ratio (r = 0.823, p = 0.003, and r = 0.658, p = 0.038). CONCLUSION: The damage and recovery response from a full marathon differed among muscles; QP, FDL, TP, and FHL increased T2 after the marathon, whereas ABH and FDB did not. In addition, T2 changes in FDL and FHL and the arch height ratio change were correlated. Our results suggest that the extrinsic foot muscles could be more susceptible to damage than the intrinsic during marathon running.

Chrono-exercise: Time-of-day-dependent physiological responses to exercise.

Exercise is an effective strategy to prevent and improve obesity and related metabolic diseases. Exercise increases the metabolic demand in the body. Although many of the metabolic health benefits of exercise depend on skeletal muscle adaptations, exercise exerts many of its metabolic effects through the liver, adipose tissue, and pancreas. Therefore, exercise is the physiological state in which inter-organ signaling is most important. By contrast, circadian rhythms in mammals are associated with the regulation of several physiological and biological functions, including body temperature, sleep-wake cycle, physical activity, hormone secretion, and metabolism, which are controlled by clock genes. Glucose and lipid tolerance reportedly exhibit diurnal variations, being lower in the evening than in the morning. Therefore, the effects of exercise on substrate metabolism at different times of the day may differ. In this review, the importance of exercise timing considerations will be outlined, incorporating a chrono-exercise perspective.

Changes in Muscle Shear Modulus and Urinary Titin N-Terminal Fragment after Eccentric Exercise.

This study aimed to investigate the relationship between the muscle shear modulus of the biceps brachii, urinary titin N-terminal fragment (UTF), and other damage markers after eccentric exercise. Seventeen healthy males performed five sets of ten eccentric exercises with dumbbells weighing 50% of the maximum voluntary contraction (MVC) at the elbow joint. Muscle shear modulus with range of interest set to only biceps brachii muscle measured by ultrasound shear wave elastography, UTF, MVC, range of motion (ROM), and soreness (SOR) were recorded before, immediately after, and 1, 24, 48, 72, 96, and 168 h after eccentric exercise. Each marker changed in a time course pattern, as found in previous studies. The peak shear modulus showed a moderate negative correlation with peak MVC (r = -0.531, P < 0.05) and a strong positive correlation with peak UTF (r = 0.707, P < 0.01). Our study results revealed a significant relationship between muscle strength, shear modulus measured by ultrasound SWE, and titin measured by UTF, as a non-invasive damage marker after eccentric exercise to track changes in EIMD.

Ice slurry ingestion improves physical performance during high-intensity intermittent exercise in a hot environment.

Ice slurry ingestion enhances exercise performance by lowering the core body temperature. However, an operational issue related to this ingestion is the requirement for a high intake of 7.5 g·kg-1 to produce the desired effects. We investigated the effects of the intake of low amounts of ice slurry at -2°C on the tympanic temperature and exercise performance during repeated high-intensity intermittent exercises in a hot environment. This study was a randomized, crossover study, with a 6-day washout period. Twelve university rugby union players performed two 30-min sessions of high-intensity intermittent exercises separated by a 15-min half-time break on a cycle ergometer in a hot environment (28.8°C ± 0.1°C, 49.5% ± 0.6% relative humidity). The participants ingested 450 g of -2°C-ice slurry (ICE), or a 30°C-beverage (CON) having the same composition as ICE, or 30°C-water (WAT) during the half-time break. The tympanic temperature and skin temperature were measured as the physiological data, and the peak power and mean power as the exercise performance data. The tympanic temperature at the half-time break and beginning of the 2nd session was significantly lower in the ICE group as compared with the CON and WAT groups. The skin temperature at the half-time break was significantly lower in the ICE group as compared with the WAT group. While the peak power and mean power during the 2nd session were significantly greater in the ICE group as compared with the CON and WAT groups. Our findings suggest that even the intake of lower amounts, as compared with those used in previous studies, of low-temperature ice slurry can reduce the body temperature and improve the peak power. These results suggest that intake of low-temperature ice slurry as a strategy for internal body cooling is useful for improving endurance exercise performance in hot environments.

Late-afternoon endurance exercise is more effective than morning endurance exercise at improving 24-h glucose and blood lipid levels.

Background: Glucose and lipid tolerance reportedly exhibit diurnal variations, being lower in the evening than in the morning. Therefore, the effects of exercise on glucose and blood lipid levels at different times of the day may differ. This study aimed to investigate the effects of short-term endurance exercise intervention in the morning versus late afternoon on 24-h blood glucose variability and blood lipid levels. Methods: Twelve healthy young men participated in a randomized crossover trial. The participants were assigned to morning (09:00-11:00) or late afternoon (16:00-18:00) endurance exercise for a week, consisting of supervised exercise sessions on Mondays, Wednesdays, and Fridays. In the morning and evening trials, the participants walked for 60 min on a treadmill at approximately 60% of maximal oxygen uptake (VO2max). Following a 2-week wash-out period, the participants performed the exercise training regimen at another time point. Continuous glucose monitoring was used to evaluate blood glucose fluctuations during each 24-h trial period. Blood samples were collected before and after each intervention to examine blood lipid and hormonal responses. Results: Examination of the area under the curve (AUC) of the glucose level changes for 24 h after the late afternoon versus morning exercise intervention revealed significantly lower values for the former versus the latter (P < 0.01). The AUC of glucose level changes after each meal was also lower after the late afternoon versus morning intervention, and significantly lower values were observed in the late afternoon versus morning trial for breakfast and dinner (P < 0.05, P < 0.01). In addition, a significant decrease in triglycerides (TG) and TG/high-density lipoprotein cholesterol (HDL-C) was noted after versus before the late afternoon intervention (P < 0.05). Conclusions: These results suggest that late afternoon endurance exercise is more effective than morning endurance exercise at improving 24-h glucose and triglyceride levels.

Changes in biceps brachii muscle hardness assessed by a push-in meter and strain elastography after eccentric versus concentric contractions.

Changes in biceps brachii muscle hardness assessed by a push-in meter (PM) and strain elastography (SE) were compared between eccentric (ECC) and concentric contractions (CON) of the elbow flexors to test the hypothesis that muscle hardness would increase greater after ECC. Ten men performed 5 sets of 10 ECC with their non-dominant arms and 5 sets of 10 CON with their dominant arms using a dumbbell corresponding to 50% of maximum voluntary isometric contraction (MVIC) force at 90º elbow flexion. Before and 1-4 days after the exercise, MVIC force, elbow joint angles, upper-arm circumference, and muscle soreness as muscle damage makers, and biceps brachii muscle hardness at maximally extended elbow joint by PM and SE were measured. Changes in these measures over time were compared between ECC and CON. All muscle damage markers showed greater changes after ECC than CON (p < 0.001). Muscle hardness assessed by PM and SE increased (p < 0.05) and peaked at 4 days post-ECC with 154.4 ± 90.0% (PM) and 156.2 ± 64.2% (SE) increases from the baseline, but did not change significantly after CON. The changes in muscle hardness post-ECC were correlated between PM and SE (r = 0.752, p < 0.001). A correlation (p < 0.001) between the normalized changes in resting elbow joint angle and changes in muscle hardness assessed by PM (r = - 0.772) or SE (r = - 0.745) was also found. These results supported the hypothesis and suggest that the increases in muscle hardness after ECC were associated with muscle damage (increased muscle stiffness), and PM and SE detected muscle hardness changes similarly.

The acute mechanism of the self-massage-induced effects of using a foam roller.

INTRODUCTION: Maintaining flexibility, often defined as range of motion (ROM), is important. Recently, self-massage using a foam roller (FR) has been used in clinical and/or sports settings to effectively and immediately improve ROM. Many studies have found significant increases in ROM following the FR intervention; however, the mechanism of the effect is unclear. We aimed to clarify this mechanism regarding the ROM effects following the FR intervention by evaluating local tissue and autonomic nervous system responses. METHOD: The study employed a crossover design that included a comparison between non-intervention (CON trial: left leg) and intervention (FR trial: right leg) groups. Fourteen volunteers participated. Nine outcomes (passive maximum ankle ROM [ROM with a specified and non-specified passive strength], tissue hardness, skin temperature, water contents, circumference, blood flow velocity, pressure pain threshold, autonomic nervous system, and heart rate) were investigated before (PRE) and 0 min (POST0), 20 min (POST20), 40 min (POST40), and 60 min (POST60) post intervention. RESULTS: Skin temperature, impedance, and circumference changed significantly following the intervention, and increased ROM with non-specified strength was observed. DISCUSSION: Although we found that the FR intervention influenced skin temperature, impedance, circumference, and ROM, adaptability to the intervention may differ depending on an individual's characteristics. Females and/or individuals with a high body water content could obtain greater positive ROM effects than males and/or individuals with a low body water content. CONCLUSION: These findings suggest that the FR intervention may be an effective method to improve ROM, with alterations of skin temperature, impedance, and circumference.

Increase in foot arch asymmetry after full marathon completion.

Long-distance running results in lowering of the foot medial longitudinal arch, but it is unknown whether the left and right arches decrease equally. This study aimed to determine whether foot arch asymmetry increases upon completion of a full marathon and to identify factors capable of explaining the degree of asymmetry of navicular height and navicular height displacement. The three-dimensional foot posture data of 74 collegiate runners were obtained using an optical foot scanner system before (PRE) and immediately after (POST) a full marathon. The navicular height and arch height ratio (normalised navicular height by foot length) of both feet significantly decreased from PRE to POST full marathon completion (44.3 ± 6.3 mm versus 40.8 ± 6.5 mm, 17.8 ± 2.5 versus 16.6 ± 2.7, respectively; p < 0.001, both). The asymmetry of the arch height ratio was significantly greater POST than PRE marathon. Multiple linear regression analysis indicated that the POST-race Asymmetry Index (AI) of navicular height was significantly predicted by the PRE-race AI of navicular height; navicular height displacement was predicted by PRE-race navicular height and the marathon time. Full marathon running induced increasing asymmetry and lowering of the medial longitudinal arch in runners.

Greater knee varus angle and pelvic internal rotation after landing are predictive factors of a non-contact lateral ankle sprain.

OBJECTIVES: This study aimed to clarify the kinematic, kinetic characteristics associated with lateral ankle sprain. DESIGN: A 16-month prospective cohort study. SETTING: Laboratory. PARTICIPANTS: A total of 179 college athletes. MAIN OUTCOME MEASURES: Joint kinematics, moment during single-leg landing tasks, and ankle laxity were measured. The attendance of each participating team, injury mechanism, existence of body contact, presence of orthosis, with or without medical diagnosis, and periods of absence were recorded. RESULTS: Twenty-nine participants incurred lateral ankle sprain during non-contact motion. The Cox regression analysis revealed that greater knee varus peak angle (hazard ratio: 1.16 [95% confidence interval: 1.10-1.22], p < 0.001) and greater pelvic internal rotation peak angle toward the support leg were associated with lateral ankle sprain (hazard ratio: 1.08 [95% confidence interval: 1.02-1.15], p = 0.009). The cut-off values for each predictive factor were -0.17° (area under the curve = 0.89, p < 0.001) and 6.63° (area under the curve = 0.74, p < 0.001), respectively. CONCLUSIONS: A greater knee varus peak angle and pelvic internal rotation peak angle after single-leg landing are predictive factors for lateral ankle sprain.

Effects of Self-myofascial Release Using a Foam Roller on Range of Motion and Morphological Changes in Muscle: A Crossover Study.

ABSTRACT: Yoshimura, A, Inami, T, Schleip, R, Mineta, S, Shudo, K, and Hirose, N. Effects of self-myofascial release using a foam roller on range of motion and morphological changes in muscle: a crossover study. J Strength Cond Res 35(9): 2444-2450, 2021-Self-myofascial release using a foam roller (FR) is effective in improving range of motion (ROM) in at least some conditions. However, its mechanism is still unclear. Therefore, this study investigated potential acute muscle morphological changes after the FR intervention and aimed to clarify the mechanism of increases in ROM by the FR intervention. We hypothesized that the FR intervention may increase ROM because of changes in fascicle length (FL) and aponeurosis displacement. This crossover study, involving 22 male university students (21.5 ± 1.3 years, 170.6 ± 4.0 cm, and 64.1 ± 8.9 kg; mean ± SD), compared the FR intervention targeting the gastrocnemius muscle with the control trial. The outcome measures were maximum passive ankle ROM, morphology of the gastrocnemius muscle (FL and aponeurosis displacement) during passive ankle plantar flexor movement, degree of pain during the FR intervention, and sensation of the triceps surae muscle. Although ROM of both dorsiflexion and plantar flexion increased significantly after the FR intervention (p < 0.01), no significant differences were found in FL and aponeurosis displacement before and after the FR intervention. The mean perception of pain during the FR intervention was rated as "slightly uncomfortable," corresponding to a 2.3 ± 2.4-cm on a 9.5-cm visual analog scale. We found that the FR intervention did not influence the morphology of muscle. It is necessary to investigate other factors related to ROM as the next step of this study.

Biceps brachii muscle hardness assessed by a push-in meter in comparison to ultrasound strain elastography.

This study investigated the relationship between push-in meter (PM) and ultrasound strain elastography (USE) for biceps brachii (BB) muscle hardness. BB hardness of 21 young men was assessed by PM and USE during rest and isometric contractions of six different intensities (15, 30, 45, 60, 75, 90% of maximal voluntary contraction: MVC) at 30°, 60° and 90° elbow flexion. Muscle hardness (E) was calculated from the force-displacement relationship in PM, and strain ratio (SR) between an acoustic coupler (elastic modulus: 22.6 kPa) and different regions of interest (ROIs) in BB was calculated and converted to Young's modulus (YM) in USE. In resting muscle, E was 26.1 ± 6.4 kPa, and SR and YM for the whole BB was 0.88 ± 0.4 and 30.8 ± 12.8 kPa, respectively. A significant (p < 0.01) correlation was evident between E and logarithmical transformed SR (LTSR) for the ROI of whole BB (r = - 0.626), and E and converted YM (r = 0.615). E increased approximately ninefold from resting to 90% MVC, and E and LTSR (r = - 0.732 to - 0.880), and E and converted YM for the SR above 0.1 were correlated (r = 0.599-0.768, p < 0.01). These results suggest that muscle hardness values obtained by PM and USE are comparable.

Regional differences in hamstring muscle damage after a marathon.

Previous studies suggest that marathon running induces lower extremity muscle damage. This study aimed to examine inter- and intramuscular differences in hamstring muscle damage after a marathon using transverse relaxation time (T2)-weighted magnetic resonance images (MRI). 20 healthy collegiate marathon runners (15 males) were recruited for this study. T2-MRI was performed before (PRE) and at 1 (D1), 3 (D3), and 8 days (D8) after marathon, and the T2 values of each hamstring muscle at the distal, middle, and proximal sites were calculated. Results indicated that no significant intermuscular differences in T2 changes were observed and that, regardless of muscle, the T2 values of the distal and middle sites increased significantly at D1 and D3 and recovered at D8, although those values of the proximal site remained constant. T2 significantly increased at distal and middle sites of the biceps femoris long head on D1 (p = 0.030 and p = 0.004, respectively) and D3 (p = 0.007 and p = 0.041, respectively), distal biceps femoris short head on D1 (p = 0.036), distal semitendinosus on D1 (p = 0.047) and D3 (p = 0.010), middle semitendinosus on D1 (p = 0.005), and distal and middle sites of the semimembranosus on D1 (p = 0.008 and p = 0.040, respectively) and D3 (p = 0.002 and p = 0.018, respectively). These results suggest that the distal and middle sites of the hamstring muscles are more susceptible to damage induced by running a full marathon. Conditioning that focuses on the distal and middle sites of the hamstring muscles may be more useful in improving recovery strategies after prolonged running.