Hamstrings on focus: Are 72 hours sufficient for recovery after a football (soccer) match? A multidisciplinary approach based on hamstring injury risk factors and histology.

This study aimed to assess acute and residual changes in sprint-related hamstring injury (HSI) risk factors after a football (soccer) match, focusing on recovery within the commonly observed 72-h timeframe between elite football matches. We used a multifactorial approach within a football context, incorporating optical and ultrastructural microscopic analysis of BFlh (biceps femoris long head) muscle fibres, along with an examination of BFlh fibre composition. Changes in sprint performance-related factors and HSI modifiable risk factors were examined until 3 days after the match (MD +3) in 20 football players. BFlh biopsy specimens were obtained before and at MD +3 in 10 players. The findings indicated that at MD +3, sprint-related performance and HSI risk factors had not fully recovered, with notable increases in localized BFlh fibre disruptions. Interestingly, match load (both external and internal) did not correlate with changes in sprint performance or HSI risk factors nor with BFlh fibre disruption. Furthermore, our study revealed a balanced distribution of ATPase-based fibre types in BFlh, with type-II fibres associated with sprint performance. Overall, the results suggest that a 72-h recovery period may not be adequate for hamstring muscles in terms of both HSI risk factors and BFlh fibre structure following a football match.

Hamstring Muscle Volume as an Indicator of Sprint Performance.

ABSTRACT: Nuell, S, Illera-Domínguez, V, Carmona, G, Macadam, P, Lloret, M, Padullés, JM, Alomar, X, and Cadefau, JA. Hamstring muscle volume as an indicator of sprint performance. J Strength Cond Res 35(4): 902-909, 2021-This study aimed to compare mechanical properties and performance during sprinting, as well as thigh muscle volumes (MVs), between national-level sprinters and physically active males. In addition, the relationships between thigh MVs and sprint mechanical properties and performance were investigated. Seven male sprinters and 9 actives performed maximal-effort 40-m sprints. Instantaneous velocity was measured by radar to obtain theoretical maximum force (F0), the theoretical maximum velocity (V0), and the maximum power (Pmax). For MV assessment, series of cross-sectional images of each subject's thigh were obtained by magnetic resonance imaging for each of the quadriceps and hamstring muscles and the adductor muscle group. Sprinters were faster over 10 m (7%, effect size [ES] = 2.12, p < 0.01) and 40 m (11%, ES = 3.68, p < 0.01), with significantly higher V0 (20%, ES = 4.53, p < 0.01) and Pmax (28%, ES = 3.04, p < 0.01). Sprinters had larger quadriceps (14%, ES = 1.12, p < 0.05), adductors (23%, ES = 1.33, p < 0.05), and hamstrings (32%, ES = 2.11, p < 0.01) MVs than actives. Hamstrings MV correlated strongly with 40-m sprint time (r = -0.670, p < 0.01) and V0 (r = 0.757, p < 0.01), and moderately with Pmax (r = 0.559, p < 0.05). Sprinters were significantly faster and had greater V0 and Pmax than active males. Larger MVs were found in sprinters' thighs, especially in the hamstring musculature, and strong correlations were found between hamstring MV and sprint mechanical properties and sprint performance.

Acute Changes in Hamstring Injury Risk Factors After a Session of High-Volume Maximal Sprinting Speed Efforts in Soccer Players.

BACKGROUND: Maximal sprinting speed (MSS) overexposure is associated with increased risk of injury. This study aimed to describe changes in sprint performance-related factors and hamstring strain injury (HSI) risk factors after a high-volume sprinting session in soccer players. HYPOTHESIS: A high-volume sprinting session can induce acute changes in several sprint performance-related factors (sprint time and mechanical properties) and HSI risk factors (posterior chain muscle strength, hamstring range of motion, and dynamic lumbo-pelvic control [LPC], measured as changes in anterior pelvic tilt [APT] during maximal speed sprinting). STUDY DESIGN: Prospective observational case series. LEVEL OF EVIDENCE: Level 4. METHODS: Fifteen active male amateur soccer players participated. Changes in sprint performance-related factors and HSI risk factors were examined for 72 hours after high-volume MSS efforts (H-VMSSE) using a soccer-contextualized multifactorial approach. Muscle damage proxy markers (hamstring perceived soreness and creatine kinase) were also examined. RESULTS: H-VMSSE induced decrements in sprint performance-related factors. Significant reductions in theoretical maximal horizontal velocity (P < 0.01; effect size [ES], -0.71) and performance (P = 0.02; ES, -0.59) were observed for 48 and 72 hours after H-VMSSE. Small but significant reductions in posterior chain muscle force-generating capacity were detected for 48 and 72 hours after H-VMSSE for the nondominant (P < 0.03; ES, -0.60) and dominant (P < 0.04; ES, -0.40) leg. Finally, players exhibited persistent small, albeit nonsignificant (P = 0.06; ES, 0.53), decreases in dynamic LPC (APT increases) for 72 hours after H-VMSSE. CONCLUSION: H-VMSSE induced declines in both sprint performance-related factors and HSI risk factors. Sprinting can alter a player's anatomic structure by increasing APT during the maximum speed phase of the sprint. CLINICAL RELEVANCE: A soccer-contextualized multifactorial approach might allow for the regulation of MSS dosage depending on individual HSI risk factor status, thereby serving as a tailored "vaccine" for sprinting needs.

Physiological demands of cyclists during an ultra-endurance relay race: a field study report.

This study was to describe and compare the physiological demands of ultra-endurance cyclists during a 24 h cycling relay race. Eleven male athletes (means +/- SD: 34.8 +/- 5.6 years; 71.6 +/- 4.9 kg; 174.6 +/- 7.3 cm; BMI 23.5 +/- 0.5 kg/m2; VO2 max: 66.0 +/- 6.4 ml/kg/min) participated in the study; eight in teams with a format of four riders (4C) and three in teams with six riders (6C). To investigate exercise intensity, heart rate (HR) was recorded while cycling using portable telemetric monitors. Three different exercise intensities were defined according to the reference HR values obtained during a pre race laboratory incremental VO2 max test: Zone I (< anaerobic threshold [AT]), Zone II (between AT and the respiratory compensation point [RCP]), Zone III (> RCP). Total volume and intensity were integrated as a single variable (training impulse: TRIMP). The score for TRIMP in each zone was computed by multiplying the accumulated duration in this zone by a multiplier for this particular zone of exercise intensity. The average intensity did not differ between cyclists in 4C (means +/- SD; 4C: 87 +/- 3 HRmax) and 6C (87 +/- 1% of HRmax), despite the higher volume performed by 4C (means +/- SD; 4C: 361 +/- 65; 6C: 242 +/- 25 per min; P = 0.012). These differences in total exercise volume significantly affected the values TRIMP accumulated (means +/- SD; 4C: 801 +/- 98, confidence interval [CI] 95%: 719 - 884; 6C: 513 +/- 25, CI 95%: 451 - 575; P = 0.012). The ultra-endurance threshold of 4C and 6C athletes lies at about 87% of HRmax for both. Although the intensity profile was similar, the TRIMP values differed significantly as a consequence of the higher volume performed by the 4C cyclists.

Hypertrophic muscle changes and sprint performance enhancement during a sprint-based training macrocycle in national-level sprinters.

Abstract This study aimed to analyse changes in sprint performance, muscle volumes (MVs) and sprint mechanical parameters (SMPs) in national-level sprinters performing a 5-month indoor sprint-based training macrocycle (SBTM). Twelve well-trained sprinters were tested on three different occasions throughout the SBTM. Testing procedures included: sprint performance over 10m, 40m, 80m, 150m, and 300m; MRI of thighs, to compute MVs of quadriceps, hamstrings and adductors; and a 40m sprint using a radar gun to assess SMPs such as theoretical maximal horizontal force, theoretical maximal horizontal velocity (V0), maximal power and index of force application (DRF). Improvements in sprint performance of between 4% and 7% (ES = 0.46-1.11, P < 0.01) were accompanied by increments in: quadriceps of 6% (ES = 0.41, P < 0.01), hamstrings of 10% (ES = 0.62, P < 0.01), adductors of 12% (ES = 0.87, P < 0.01), V0 of 5% (ES = 0.40, P < 0.01) and DRF of 7% (ES = 0.91, P < 0.01). In conclusion, during the SBTM after the off-season, moderate hypertrophic changes occur in sprinters. Moreover, the greater increase in hamstrings and adductors, compared with quadriceps, might be related to the prominent role of these muscle groups in sprinting. Furthermore, the SBTM was likely effective at developing sprint performance in sprinters, thereby endorsing the idea that sprint-specific training is crucial for highly trained individuals. Finally, our results support the notion that V0 or the "velocity-oriented" force-velocity profile is determinant of performance in sprinters.

Sex differences in thigh muscle volumes, sprint performance and mechanical properties in national-level sprinters.

The purpose of this study was to determine and compare thigh muscle volumes (MVs), and sprint mechanical properties and performance between male and female national-level sprinters. We also studied possible relationships between thigh MVs and sprint performance. Nine male and eight female national-level sprinters participated in the study. T1-weighted magnetic resonance images of the thighs were obtained to determine MVs of quadriceps, hamstrings and adductors. Sprint performance was measured as the time to cover 40 and 80 m. Instantaneous sprint velocity was measured by radar to obtain theoretical maximum force (F0), theoretical maximum velocity (V0) and maximum power (Pmax). When MVs were normalized by height-mass, males showed larger hamstrings (13.5%, ES = 1.26, P < 0.05) compared with females, while quadriceps and adductors showed no statistically significant differences. Males were extremely faster than females in 40 m (14%, ES = 6.68, P < 0.001) and in 80 m (15%, ES = 5.01, P < 0.001. Males also showed increased sprint mechanical properties, with larger F0 (19%, ES = 1.98, P < 0.01), much larger Pmax (46%, ES = 3.76, P < 0.001), and extremely larger V0 (23%, ES = 6.97, P < 0.001). With the pooled data, hamstring and adductor MVs correlated strongly (r = -0.685, P < 0.01) and moderately (r = -0.530, P < 0.05), respectively, with sprint performance; while quadriceps showed no association. The sex-stratified analysis showed weaker associations compared with pooled data, most likely due to small sample size. In conclusion, males were faster than females and showed larger MVs, especially in hamstrings. Moreover, regarding the thigh muscles, hamstrings MV seems the most related with sprint performance as previously proposed.

Recovery of assisted overground stepping in a patient with chronic motor complete spinal cord injury: a case report.

BACKGROUND: Clinical studies have shown that after incomplete spinal cord lesions at the thoracic level, patients can develop functional gait patterns through gait training. To date, however, training has been ineffective in producing gait in patients with clinically motor complete spinal cord lesions. OBJECTIVE: Here we report a patient with chronic motor complete spinal cord injury who regained locomotor function with assistance after intensive gait rehabilitation treatment. METHODS: A fifteen year old female patient had sustained motor complete spinal cord injury (T6, AIS B) 2 years earlier, with severe bilateral extensor spasticity, and ineffective previous gait training with robotic systems. The therapy consisted of two months of gait training with a robotic system combined with bilateral functional electrical stimulation (FES) of the peroneal nerve, and one month of gait training with a special walker and FES of the left leg and occasionally on the right leg, due to flexor reflex could sometimes be initiated by the patient in the right leg without electrical stimulation. Neurophysiological studies and ten metres test were done. RESULTS: At the end of training, the patient was able to cover a distance of 200 metres without FES with a walker and assistance from a physiotherapist, who pulled the walker with each step to help her to accomplish effective overground stepping. Motor and somatosensory evoked potentials were absent in the lower limbs. CONCLUSION: Even after a motor complete lesion with some preservation of sensory pathways, the spinal cord may be able to retain some of its locomotor function through intensive gait rehabilitation.