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.

Entry phase in men's backward dive pike: association between the shoulder joint and trunk angles.

BACKGROUND: A high prevalence of lower back pain has been observed in competitive divers. Hyperextension of the lumbar vertebrae during water entry is considered the main mechanism behind the incidence of lower back pain in divers. Therefore, this study aimed to investigate the influence of the shoulder angle on the entry alignment. METHODS: Posture angles of 13 male drivers (age: 16.8±2.9 years) who were invited to the national training camp in 2012 by Japan Swimming were recorded at the time of water entry via 201B using a high-speed camera. RESULTS: A negative correlation was observed between shoulder joint flexion and trunk extension angles on water entry. In addition, the trunk angle was significantly different between groups. For the lower back pain group, 210.4±5.7°, and in the non-lower back pain group, 199.9±9.0°, angles were observed with a larger extension of the trunk on water entry in the lower back pain group. CONCLUSIONS: The alignment on water entry was associated with the occurrence of lower back pain. Which suggested that enough shoulder flexibility can prevent the incidence of lower back pain.

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.

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.

Changes in the Linear Relationship between Muscle Contraction Intensity and Muscle Hardness after Rectus Femoris Muscle Strain.

OBJECTIVE: Joint torque differences between healthy and rehabilitated legs are often measured as a clinical index of recovery from muscle strain injury. Unfortunately, it should be noted that this is a questionable evaluation measure of the muscle after injury because it is a composite value including related cooperating muscles. Meanwhile, the use of ultrasound elastography for the measurement of individual muscle mechanical properties (i.e., muscle hardness) has recently expanded. The purpose of this study was to examine, using ultrasound elastography, the differences in the linear relationship between muscle contraction intensity and muscle hardness during knee extension in athletes who had recovered from grade II rectus femoris muscle strain injury through comparison of the healthy and rehabilitated legs. METHODS: Six athletes participated. Rectus femoris muscle hardness, determined during isometric contraction at 10%, 20%, 30%, and 40% of maximum voluntary contraction, was evaluated using ultrasound strain elastography. RESULTS AND CONCLUSION: The results indicated that for the healthy legs, the strain ratios, as indicated by muscle hardness, decreased linearly (became harder) with contraction intensity, but the strain ratios for the rehabilitated legs decreased nonlinearly. These results show the danger of judging the recovery period using only the difference between healthy and rehabilitated muscle strengths and the importance of evaluating individual muscles.

Tracking of Time-Dependent Changes in Muscle Hardness After a Full Marathon.

Inami, T, Nakagawa, K, Yonezu, T, Fukano, M, Higashihara, A, Iizuka, S, Abe, T, and Narita, T. Tracking of time-dependent changes in muscle hardness after a full marathon. J Strength Cond Res 33(12): 3431-3437, 2019-We sought to identify changes in individual muscle hardness after a full marathon and to track time-dependent changes using ultrasound strain elastography (SE). Twenty-one collegiate marathon runners were recruited. Muscle hardness (i.e., strain ratio, SR) was measured using SE for the rectus femoris (RF), vastus lateralis (VL), biceps femoris (BF) long head, tibialis anterior (TA), gastrocnemius medial (GM) head, and soleus (SOL) muscles at the following time points: pre (PRE), immediately post (POST), day-1 (D1), day-3 (D3), and day-8 (D8), after a full marathon. We found that the SR decreased after the full marathon (i.e., the muscle became harder), and that the lowest SR across all measured muscles was observed on D1. Although there was no difference in the magnitude of change in SR between the muscles of the thigh, that of the MG and SOL were significantly larger than that of the TA. Muscle hardness in the vastus lateralis, biceps femoris, and SOL recovered at D8 (i.e., nonsignificant difference from PRE), whereas recovery of rectus femoris and gastrocnemius medial hardness at D8 was not observed. Thus, the degree of change in muscle hardness does not occur uniformly within the lower extremity muscles. In particular, changes in muscle hardness of the TA after a full marathon are small compared with other muscles and time-dependent changes in each muscle vary during recovery. The features of muscle hardness identified in this study will be useful for coaches when mentoring runners on proper forms and for training advisers and therapists who seek to address deficiencies in running.

Foot posture alteration and recovery following a full marathon run.

Prolonged running results in lowering of the foot arch and a low arch is associated with subsequent chronic injuries. Foot posture alteration and recovery following a marathon run remain unknown. Therefore, the present study aimed to evaluate foot posture alteration following a full marathon run. The three-dimensional foot posture data of 11 collegiate runners were obtained using an optical foot scanner system before, and immediately, 1 day, 3 days, and 8 days after a full marathon. The navicular height and arch height ratio significantly decreased from before to immediately, 1 day, 3 days, and 8 days after the marathon (navicular height: before, 44.2 ± 5.0 mm; immediately after, 39.4 ± 5.5 mm; 1 day, 37.7 ± 6.2 mm; 3 days, 38.7 ± 5.5 mm; 8 days, 37.6 ± 5.7 mm; arch height ratio: before, 18.4 ± 1.9; immediately after, 16.5 ± 2.5; 1 day, 15.7 ± 2.5; 3 days, 16.2 ± 2.6; 8 days, 15.6 ± 2.2, P < 0.001, respectively). By contrast, the dorsal height significantly increased from before and immediately after to 1 day after the marathon, and then significantly decreased until 8 days after the marathon (P < 0.001). These results indicate that the recovery patterns of the dorsal and navicular heights following a marathon did not coincide; the dorsal height rose temporally at 1 day after and subsequently decreased, but the navicular height decreased throughout the 8-day period after the marathon. More than one week may be necessary for sufficient foot alignment recovery from marathon-induced changes.

Critical factors for the prevention of low back pain in elite junior divers.

BACKGROUND/AIM: During competitive diving, divers jump up from 1 to 3 m springboards or 5 to 10 m platforms and dive into the water. The impact forces are very large in the water entry phase, and, as such, microtraumatic injuries are common due to the tremendous physical stress placed on the diver. Low-back pain (LBP) is the most frequently reported symptom in divers. This study aimed to extract possible risk factors related to LBP from physical and technical characteristics in Japanese elite junior divers. METHODS: Eighty-three elite junior divers (42 men and 41 women) in Japan were included in this study. LBP was assessed by a questionnaire, interview and physical examination during a national training camp. Morphological data, physical fitness and diving skills were also evaluated. The factors related to LBP were extracted by using logistic-regression analysis and the forward-selection method (likelihood ratio). RESULTS: A total of 37.3% (31 reports) of back pain occurred in the lumbar region. Shoulder flexibility (OR 0.919; 95% CI 0.851 to 0.992) and age (OR 0.441; 95% CI 0.239 to 0.814) were recognised as factors related to LBP in male-elite junior divers, whereas only age (OR 0.536; 95% CI 0.335 to 0.856) was a factor in female-elite junior divers. CONCLUSIONS: Our results suggest that shoulder flexibility is important for preventing LBP in elite-male junior divers, since they require full shoulder flexion during the water entry phase. Limited shoulder flexibility could cause lumbar hyperextension when adjusting for the angle of water entry.