Region‐dependent hamstrings activity in Nordic hamstring exercise and stiff‐leg deadlift defined with high‐density electromyography

Recent studies suggest region‐specific metabolic activity in hamstring muscles during injury prevention exercises, but the neural representation of this phenomenon is unknown. The aim of this study was to examine whether regional differences are evident in the activity of biceps femoris long head (BFlh) and semitendinosus (ST) muscles during two common injury prevention exercises. Twelve male participants without a history of hamstring injury performed the Nordic hamstring exercise (NHE) and stiff‐leg deadlift (SDL) while BFlh and ST activities were recorded with high‐density electromyography (HD‐EMG). Normalized activity was calculated from the distal, middle, and proximal regions in the eccentric phase of each exercise. In NHE, ST overall activity was substantially higher than in BFlh (d  =  1.06 ± 0.45), compared to trivial differences between muscles in SDL (d  =  0.19 ± 0.34). Regional differences were found in NHE for both muscles, with different proximal‐distal patterns: The distal region showed the lowest activity level in ST (regional differences, d range = 0.55‐1.41) but the highest activity level in BFlh (regional differences, d range = 0.38‐1.25). In SDL, regional differences were smaller in both muscles (d range = 0.29‐0.67 and 0.16‐0.63 in ST and BFlh, respectively) than in NHE. The use of HD‐EMG in hamstrings revealed heterogeneous hamstrings activity during typical injury prevention exercises. High‐density EMG might be useful in future studies to provide a comprehensive overview of hamstring muscle activity in other exercises and high‐injury risk tasks.     

Electromyographic activity of posterior kinetic chain muscles during hamstring strengthening exercises

ObjectivesTo compare the muscle activation of the biceps femoris (BF), semitendinosus (ST), gluteus maximus (GM), and contralateral erector spinae (ES) in four specific eccentric hamstring-oriented exercises using overground maximal sprints as an EMG normalization method.Designcross-sectional study.Participantstwenty-four healthy athletes participated in this study.Main outcome measuresThe maximum EMG activation of all targeted muscles was measured during maximal sprints and four hamstring exercises: Nordic hamstring (NH), Russian belt (RB), glider (GL) and lying kick (LK). Maximum EMG activation during sprints were used to normalize EMG muscle activation.ResultsRB and GL showed lower hamstrings activation (from 15.71% to 39.23% and from 26.34% to 31.23%, respectively), so these exercises may be used as the first step of the retraining. The higher hamstring activation was reached in the NH (from 20.15% to 66.81%) and the LK (from 50.5% to 61.2%). Regarding muscles comparison, BF and ST were the most dependent on the exercise ranging from 26.67% to 62.22%, and from 26.34% to 66.81%, respectively.ConclusionsMuscle activation is dependent on the exercise procedure. RB and GL should be used as a first step because of their low activation. Instead, NH and LK should be used at the last phases of retraining process. Considering the synergistic activation of the PKC muscles during LK, and because of its unilateral and explosive characteristics, LK seems a suitable exercise for retraining PKC muscles in general.     

Acute hamstring strain injury in track‐and‐field athletes: A 3‐year observational study at the Penn Relay Carnival

This study aimed to observe the incidence rates of hamstring strain injuries (HSIs) across different competition levels and ages during the Penn Relays Carnival. Over a 3‐year period, all injuries treated by the medical staff were recorded. The type of injury, anatomic location, event in which the injury occurred, competition level, and demographic data were documented. Absolute and relative HSI (per 1000 participants) were determined, and odds ratios (ORs) were calculated between sexes, competition levels, and events. Throughout the study period 48 473 athletes registered to participate in the Penn Relays Carnival, with 118 HSIs treated by the medical team. High school girls displayed lesser risk of HSI than high school boys (OR = 0.55, P = 0.021), and masters athletes were more likely than high school‐ (OR = 4.26, P < 0.001) and college‐level (OR = 3.55, P = 0.001) athletes to suffer HSI. The 4 × 400‐m relay displayed a greater likelihood of HSI compared with the 4 × 100‐m relay (OR = 1.77, P = 0.008). High school boys and masters‐level athletes are most likely to suffer HSI, and there is higher risk in 400‐m events compared with 100‐m events.     

The impact of sport and active recreation injuries on physical activity levels at 12 months post‐injury

The aim of this study was to evaluate the impact of serious sport and active recreation injury on 12‐month physical activity levels. Adults admitted to hospital with sport and active recreation‐related injuries, and captured by the Victorian Orthopaedic Trauma Outcomes Registry were recruited to the study. Changes between preinjury and 12 month post‐injury physical activity was assessed using the short International Physical Activity Questionnaire (IPAQ). Independent demographic, injury, and hospital variables were assessed for associations with changes in physical activity levels, using multivariate linear regression. A total of 324 patients were recruited, of which 98% were followed up at 12 months. Mean short IPAQ scores decreased from 7650 METS (95% CI: 7180, 8120) preinjury to 3880 METS; (95% CI: 3530, 4250) post‐injury, independent of functional recovery. Education level and occupation group were the only variables independently associated with changes in physical activity levels post‐injury. These results highlighted that sport and active recreation injuries lead to significant reductions in physical activity levels. Hence, the prevention of sport and active recreation injuries is important when considering promotion of activity at a population level.     

Early versus late start of open kinetic chain quadriceps exercises after ACL reconstruction with patellar tendon or hamstring grafts: a prospective randomized outcome study

The purpose of the present investigation was to evaluate physical outcome after anterior cruciate ligament (ACL) reconstruction with early versus late initiation of open kinetic chain (OKC) exercises for the quadriceps in patients operated on either patellar tendon or hamstring grafts. Sixty-eight patients, 36 males and 32 females, with either patellar tendon graft (34 patients) or hamstring graft (34 patients) were enrolled in this study. All patients were randomly allocated to either early (the 4th postoperative week) or late (the 12th postoperative week) start of OKC exercises for the quadriceps, resulting in four subgroups: patellar tendon reconstruction, early start (P4) or late start (P12) of OKC quadriceps exercises, hamstring tendon reconstruction, early start (H4) or late start (H12) of quadriceps OKC exercises. Prior to surgery and 3, 5 and 7 months later, assessments of range of motion (goniometer), anterior knee laxity (KT-1000), postural sway (KAT 2000), thigh muscle torques (Kin–Com dynamometer) and anterior knee pain (anterior knee pain score) were evaluated. No significant group differences were found in terms of range of motion 3, 5 and 7 months postoperatively. The H4 group showed a significantly higher mean difference of laxity over time of 1.0 mm (CI: 0.18–1.86) than the P4 group (P = 0.04). Within the same type of surgery, the H4 against the H12, the mean difference over time was 1.2 mm (0.37–2.1) higher in the H4 group than in the H12 group (P = 0.01). There were no significant group differences in terms of postural sway or anterior knee pain at the different test occasions. Significant differences in trends (changes over time) were found when comparing the four groups, for both quadriceps muscle torques (P < 0.001) and hamstring muscle torques (P < 0.001). All groups, except the P4 group, reached preoperative values of quadriceps muscle torques at the 7 months follow-up. In the H4 and the H12 groups, significantly lower hamstring muscle torques at the 7 months follow-up compared with preoperative values were found. In conclusion, early start of OKC quadriceps exercises after hamstring ACL reconstruction resulted in significantly increased anterior knee laxity in comparison with both late start and with early and late start after bone–patellar tendon–bone ACL reconstruction. Furthermore, the early introduction of OKC exercises for quadriceps did not influence quadriceps muscle torques neither in patients operated on patellar tendon nor hamstring tendon grafts. On the contrary, it appears as if the choice of graft affected the strength of the specific muscle more than the type of exercises performed. Our results could not determine the appropriate time for starting OKC quadriceps exercises for patients who have undergone ACL reconstruction with hamstring tendon graft. Future studies of long-term results of anterior knee laxity and functional outcome are needed.     

Examining accelerometer validity for estimating physical activity in pre‐schoolers during free‐living activity

The present study examined the efficacy of accelerometers for the assessment of free play physical activity (PA) in pre–school‐aged children with consideration of epoch length and wear location. Following ethics approval, parental informed consent, and child assent, 66 pre‐schoolers aged 3‐4 years (30 females and 36 males) wore an accelerometer (ActiGraph GT3X; sampling at 100 Hz) on their non‐dominant wrist and their right hip during 1 hour of free play. Concurrently, direct observation, using the OSRAC‐P, was used to determine sedentary behavior (SB), light (LPA), or moderate‐to‐vigorous (MVPA) intensity PA. For the ActiGraph, vertical axis counts and summed vector magnitude (VM) for hip, and VM for wrist, were downloaded using 5‐, 10‐, 15‐, and 30‐second epoch lengths. Accelerometer counts were averaged over each 30 seconds to match the observation periods. Receiver operating curve analysis was used to evaluate the ability of the ActiGraph to predict SB, LPA, and MVPA. SB and MVPA obtained from wrist‐ and hip‐worn accelerometers demonstrated fair agreement with direct observation (AUC => 0.7). LPA determined by accelerometer had poor agreement with observed LPA, for both the hip and wrist placement (AUC = 0.53‐0.56), with weak levels of specificity (0.34‐0.43), although sensitivity was fair (0.74‐0.84). This study is the first to examine accelerometer validity, considering wear location and epoch in pre‐schoolers during free play, and suggests that the ActiGraph is a fair measure for SB and MVPA in pre‐school children. Neither placement performed predominantly better irrespective of epochs or used count data (vertical axis, VM).     

The influence of meniscal lesions on reflex activity in the hamstring muscles

Meniscal lesions are among the most common knee injuries and substantially affect the mechanical function of the knee joint. In addition, the presence of mechanoreceptors in the meniscus suggests that the menisci are also involved in the sensorimotor control of the knee. The objective of this study was to investigate the influence of an isolated meniscal lesion on the reflex behaviour of the hamstring muscles, which are involved in the sensorimotor control of the knee joint. For this purpose, we mechanically induced tibial translation in 19 patients in a standing position and analysed the biphasic response of the hamstrings consisting of a short-latency response (SLR) and a medium-latency response (MLR). Moreover, we determined anterior tibial translation. A comparison of electromyographic data for the healthy legs versus the injured legs showed no significant differences in either SLRs or MLRs. Although there was a tendency to an increase in tibial translation, no significant difference between the legs in anterior tibial translation was found. In conclusion, our experimental work did not reveal any substantial effects of a meniscal lesion on the reflex behaviour of the hamstrings. Our data suggest that the menisci appear to play only a minor role for the sensorimotor induced anterior posterior knee stability.     

Shoulder and arm muscle activity during elastic band exercises performed in a hospital bed

Objective: Muscle atrophy is a common side-effect of bed rest during hospitalization. However, resistance training may minimize or even prevent these complications. Therefore, we evaluated the efficiency of four upper-body elastic resistance exercises that could be performed while lying or sitting in a hospital bed.

Methods: Twenty-two healthy subjects performed three repetitions of each exercise in a supine and seated position with a perceived intensity of 3 (low) and 8 (high) on the Borg CR10 Scale. Surface electromyography was collected from 12 shoulder and arm muscles (e.g. trapezius, deltoideus, and biceps brachii), and normalized to a maximal voluntary isometric contraction (nEMG).

Results: During all exercises performed at high intensity, moderate (>40%) to high (>60%) levels of nEMG were found for the majority of the analysed muscles, e.g. deltoideus (from 37% to 69%, median 57.5%), trapezius (from 43% to 66%, median 51%), and infraspinatus (from 54% to 66%, median 59%), with the exception of pectoralis major (from 29% to 47%, median 39.5%) and latissimus dorsi (from 15% to 22%, median 18.5%). No significant differences were found between the supine and seated positions for any of the exercises.

Conclusion: This study showed that high levels of shoulder and arm muscle activity can be achieved while lying or sitting in a hospital bed using appropriate exercises with elastic bands. The data presented here can be used by physiotherapists as a guideline for selecting suitable and effective strengthening exercises during in-hospital rehabilitation to counteract bed-rest related muscle atrophy in the upper body.     

Acute hamstring injuries in Danish elite football: A 12‐month prospective registration study among 374 players

The purpose of the present study was to examine the incidence rates of acute hamstring injuries in Danish elite football sustained during training or match play. Furthermore, it was our intention to document details about the recurrence, severity and the injury seasonal distribution. Hamstring injuries among 374 elite football players were registered prospectively during a 12‐month period. A total of 46 first‐time and eight recurrent hamstring injuries were registered. The incidence rates for incurring a first‐time hamstring injury showed a significantly (P<0.01) greater incidence rate per 1000 h during match play compared with training. Of 32 players who reported a hamstring injury in the 12‐month period before the study, eight (25%) incurred an injury that fulfilled the criteria for a recurrent injury. In 69% of the injuries, the severity of injury was categorized as moderate (8–28 days from injury to injury free) and 18% as severe (>28 days from injury to injury free). Each team sustained a mean of 3.4 hamstring injuries per season, with a mean of 21.5 days missed per injury (range 3–136; median 16 days per injury). The seasonal distribution showed an accumulation of injuries in the first 2 months after a 3.5‐month mid‐season winter break.     

Self‐reported health‐enhancing physical activity recommendation adherence among 64,380 finnish adults

The Finnish recommendations for health‐enhancing physical activity (PA) for adults (≥18 years) recommend: (i) ≥150 minutes of moderate‐to‐vigorous‐intensity physical activity (MVPA) and (ii) activities that develop muscle strength and balance ≥2 days/week. However, adherence to these recommendations among the Finnish adults is currently unknown. This study reports on the self‐reported adherence to the PA recommendations and associations with sociodemographic factors among Finnish adults. Data were used from the Finnish “Regional Health and Well‐being Study.” In 2013‐2014, postal questionnaires were sent to 132,560 persons, with 69,032 responding (response rate =52.1%). The weighted proportions adhering to the: (i) MVPA recommendation, (ii) sufficient muscle‐strengthening activity (≥2 days/week), (iii) sufficient balance training (≥2 days/week), and (iv) Finnish health‐enhancing PA recommendations (Finnish recommendations) were calculated. Associations with sociodemographic variables (eg, age, education level, self‐rated health) were assessed using multiple logistic regression analyses. Of 69,032 respondents, 92.6% (n=64,380, response rate =48.6%, 18‐98 years) reported on their physical activity levels. A total of 31.2% (95% CI: 30.8%‐31.6%) met the aerobic MVPA recommendation, 17.2% (95% CI: 16.9%‐17.6%) reported sufficient muscle‐strengthening activity, 6.7% (95% CI: 6.4%‐6.9%) reported sufficient balance training, and 10.8% (95% CI: 10.5%‐11.1%) met the Finnish recommendations. In the adjusted analysis, those with poorer self‐rated health, older age, lower education levels, and those classified overweight or obese were independently associated with lower odds of meeting the Finnish recommendations. The vast majority of Finnish adults do not meet the full PA recommendations. Public health action is needed to increase PA in Finland.     

Comparison of gluteus maximus and hamstring electromyographic activity and lumbopelvic motion during three different prone hip extension exercises in healthy volunteers

ObjectiveTo compare the surface electromyography (EMG) amplitude of the hip joint, including the gluteus maximus (GM), biceps femoris (BF), and semitendinosus (ST) muscles generated by three different exercises: prone hip extension (PHE), prone table hip extension (PTHE), and prone table hip extension with 90° knee flexion (PTHEK), with compensatory pelvic motions.DesignRepeated-measure within-subject intervention.ParticipantsSixteen-healthy males (mean age = 23.4 ± 2.2 years).Main outcome measuresEMG was used to collect EMG signals from the GM, erector spinae (ES), BF, and ST muscles. Furthermore an electromagnetic tracking motion analysis was also performed to measure the compensations.ResultsEMG amplitude differed significantly among the three conditions (PHE vs. PTHE vs. PTHEK) (p < 0.05). The mean GM muscle activity increased significantly during the PTHEK (70.93% and 13.75% increases in %MVIC compared with the PHE and PTHE, respectively) (p < 0.01). However, there was no significant difference in the kinematic data for rotation or anterior tilting angle of the pelvis among the three conditions (p > 0.05).ConclusionsThese results suggest that the PTHEK can be recommended as an effective method to strengthen the GM muscle without increased BF or ES muscle activities and without compensatory pelvic motions.     

No association between rate of torque development and onset of muscle activity with increased risk of hamstring injury in elite football

Hamstring injuries remain a significant burden in sports that involve high‐speed running. In elite male football, hamstring injury has repeatedly been identified as the most common non‐contact injury, representing 12% of all injuries. As the incidence remains high, investigations are aimed at better understanding how to improve prevention efforts. Intrinsic risk factors such as strength have been investigated extensively in a cohort of professional football players; however, other intrinsic measures of neuromuscular function have not been studied in this cohort. This study aims to investigate the association between timing of hamstring muscle activity onset and the rate of torque development during the early phase of isokinetic strength testing with risk of hamstring injury in professional football players in a prospective cohort study. All teams (n = 18) eligible to compete in the premier football league in Qatar underwent a comprehensive strength assessment during their annual periodic health evaluation at Aspetar Orthopaedic and Sports Medicine Hospital in Doha, Qatar. Variables included rate of torque development and timing of muscle activity onset. A total of 367 unique players (60.6% of all QSL players) competed for 514 player seasons (103 players competed both seasons) and sustained 65 hamstring injuries. There was no difference in the onset of muscle activity between the biceps femoris and medial hamstrings comparing the injured to uninjured players. For both onset of muscle activity and rate of torque development, there were no significant differences between any of the variables (P  > .05), with small effect sizes detected across all the different variables (d < 0.3). Rate of torque development and onset of muscle activity were not associated with a risk of future hamstring injury. The use of these measures as part of a periodic health evaluation to identify risk of hamstring injury is unsupported.     

The deficits of isometric knee flexor strength in lengthened hamstring position after hamstring strain injury

ObjectiveTo investigate the effects of knee flexion angle on peak torque, rate of torque development (RTD) during isometric contraction and hamstring flexibility after hamstring strain injury (HSI).DesignCross-sectional.SettingControlled laboratory research.ParticipantsFourteen male athletes with a history of HSI and 14 athletes without HSI (controls).Main outcome measuresHamstring flexibility was evaluated using active knee extension test. Isometric knee flexion peak torque and RTD were determined at 30°, 60°, and 90° of knee flexion measured by an isokinetic dynamometer.ResultsIndividuals with a history of HSI had statistically significant, moderate deficits in isometric peak torque at 30° of knee flexion (P = 0.037; effect size = 0.55) in the HSI limb than in the uninjured limb, but not at 60° and 90° of knee flexion. In the control group, no significant differences in isometric peak torque at any angle were found between limbs. No differences in peak RTD and flexibility were found between limbs in both groups.ConclusionsIsometric peak torque at 30° of knee flexion was lower in the injured limb than in the uninjured limb. Isometric strength deficits after HSI tended to be affected by lengthened hamstring angles.     

Muscle activation patterns in the Nordic hamstring exercise: Impact of prior strain injury

This study aimed to determine: (a) the spatial patterns of hamstring activation during the Nordic hamstring exercise (NHE); (b) whether previously injured hamstrings display activation deficits during the NHE; and (c) whether previously injured hamstrings exhibit altered cross‐sectional area (CSA). Ten healthy, recreationally active men with a history of unilateral hamstring strain injury underwent functional magnetic resonance imaging of their thighs before and after six sets of 10 repetitions of the NHE. Transverse (T2) relaxation times of all hamstring muscles [biceps femoris long head (BFlh); biceps femoris short head (BFsh); semitendinosus (ST); semimembranosus (SM)] were measured at rest and immediately after the NHE and CSA was measured at rest. For the uninjured limb, the ST's percentage increase in T2 with exercise was 16.8%, 15.8%, and 20.2% greater than the increases exhibited by the BFlh, BFsh, and SM, respectively (P < 0.002 for all). Previously injured hamstring muscles (n = 10) displayed significantly smaller increases in T2 post‐exercise than the homonymous muscles in the uninjured contralateral limb (mean difference ?7.2%, P = 0.001). No muscles displayed significant between‐limb differences in CSA. During the NHE, the ST is preferentially activated and previously injured hamstring muscles display chronic activation deficits compared with uninjured contralateral muscles.     

脑损伤患者家庭康复治疗对日常生活能力的影响

目的探讨家庭康复提高脑损伤患者生活质量的作用和意义。方法 64例脑损伤患者分为A、B组,两组患者早期康复治疗和恢复期治疗相同。维持期A组在社区(干休所)或家庭延续康复治疗;B组患者自行在家练习。回家后3个月,随访时评定神经功能缺损程度、运动功能及日常生活活动能力。结果 B组患者三项评分有所改善,但没有A组明显(P<0.01)。结论规范的三级康复治疗体系中的家庭康复对于脑损伤患者的日常生活活动能力的提高具有明显促进作用。