Accelerated chilling and modified atmosphere packaging affect colour and colour stability of injection-enhanced beef round muscles

Two experiments were conducted to examine the effects of hot boning, modified atmosphere packaging, and injection enhancement on the oxidative and sensory properties of beef round muscles. The beef knuckle (quadriceps muscles) was partially hot boned within 1.5 h postmortem from one randomly selected side of each beef carcass (n = 14), whereas the quadriceps on the opposite side remained intact throughout a 48-h chilling period. At 5 d postmortem, biceps femoris, semimembranosus, vastus lateralis, and rectus femoris muscles from both hot- and cold-boned sides were injected with an enhancement solution consisting of water, salt, phosphate, and natural flavorings (rosemary) at either 6 (Exp. 1) or 10% (Exp. 2) of fresh muscle weight. Enhanced muscles were then processed into 2.54-cm-thick steaks, which were allotted randomly to high-oxygen (HiOx; 80% O2:20% CO2) or ultra-low oxygen (LoOx; 80% N2:20% CO2) modified atmosphere packaging. Regardless of hot boning or enhancement, steaks packaged in LoOx had lower thiobarbituric acid-reactive substances values (P < 0.05), more beef flavor intensity (P < 0.05), fewer off flavors (P < 0.05), and were more tender (P < 0.05) than steaks packaged in HiOx. Hot boning the knuckle had no effect on oxidative (P > or = 0.99) and sensory properties (P > or = 0.85). Increasing the level of injection enhancement from 6 to 10% introduced more rosemary and phosphate into the muscles, thereby decreasing the extent of oxidation, but also imparting a nontypical beef flavor. Packaging in LoOx atmosphere offered the optimal result of decreased oxidation and improved tenderness, without detriment to flavor. Injection enhancement (both 6 and 10%) created off-flavors attributable to the enhancement solution; however, the 10% injection seemed to offer more resistance to lipid oxidation.

(1) Background: Squatting is one of the common closed-kinetic chain (CKC) exercises for knee rehabilitation. Some patients cannot perform squatting exercises on land occasionally due to knee pain. Several studies had suggested that lower limb muscle activities are lower in water than on land while performing CKC exercises. The purpose of this study is to investigate the surface electromyography (sEMG) activities of Rectus femoris (RF) and Biceps femoris (BF) muscles when doing a squatting exercise in water and on land. (2) Methods: This was a cross-sectional experimental study. A total of 20 healthy participants (10 males, 10 females) were recruited by convenience sampling. The sEMG of RF and BF muscles in water and on land were collected and the knee motions were videotaped. Participants were instructed to perform closed kinetic-chain back squatting exercises at a specific speed (30 beats per minute) in water and on land at angular speed of 45°/s. Eight repetitions of the squatting exercise (0–90° knee flexion) were performed. The mean percentage maximal voluntary contraction (%MVC) between two muscles was compared in two conditions. The %MVC of RF and BF muscles at different specific knee flexion angles (30°, 60° and 90° knee flexion) was also identified. (3) Result: Muscle activities of RF (p = 0.01) and BF (p < 0.01) muscles were significantly lower in water than on land. The %MVC of RF and BF muscles was found to be 15.01% and 10.68% lower in water than on land respectively. For different knee angle phases, the differences in %MVC between land and water had significant difference for both RF muscles and BF muscles. (4) Conclusion: This study found a difference of mean percentage MVC of RF and BF muscles between land and water in different phases of squatting. The water medium reduced the two muscles’ activities to a similar extent. The result showed that the aquatic environment allows an individual to perform squatting with less muscle activation which may serve as an alternative knee exercise option for patients who encounter difficulty in land squatting due to lower limb muscle weakness or a high level of knee pain.

Objective Use T 2 mapping to evaluate the fatty infiltration of thigh muscles in Duchenne muscular dystrophy (DMD) patients, so as to analyze the value of T 2 mapping and T 2 relaxation time in the diagnosis of DMD. Methods Sixteen DMD patients who were admitted from January 2004 to January 2013 in our hospital and were diagnosed by clinical confirmation and gene detection have participated into this study. These 16 male patients formed the DMD group. Six age- and sex-matched healthy boys were selected as control group. Clinical functional scale, thigh axial T 1 WI-turbo spin echo (TSE), T 2 WI-TSE, spectral attenuated inversion recovery (SPAIR)-T 2 WI and T 2 mapping were performed in both 2 groups. T 1 WI fatty infiltration scale and T 2 relaxation time were assessed in adductor magnus, gracilis, adductor longus, sartorius, rectus femoris, vastus intermedius, vastus medialis, vastus lateralis, biceps femoris, semitendinosus and semimembranosus. Spearman rank correlation was conducted to assess the correlation between T 2 relaxation time and T 1 WI fatty infiltration scale or clinical functional scale. Results Compared with control group, the T 2 relaxation time of 8 muscles (adductor magnus, adductor longus, rectus femoris, vastus intermedius, vastus medialis, vastus lateralis, biceps femoris and semimembranosus) in DMD group were prolonged ( P < 0.05, for all). The longest average T 2 relaxation time was found in adductor magnus. The T 2 relaxation time of adductor magnus, vastus intermedius, vastus lateralis, biceps femoris, rectus femoris, adductor longus and vastus medialis was positively correlated with T 1 WI fatty infiltration scale ( P < 0.05, for all), and the T 2 relaxation time of adductor magnus and semimembranosus was positively correlated with clinical funetional scale ( P < 0.05, for all). A positive correlation was found in adductor magnus between T 2 relaxation time and both T1WI fatty infiltration scale ( r s = 0.867, P = 0.000) and clinical functional scale ( r s = 0.651, P = 0.005). Conclusions T 2 relaxation time could be used in the quantitative and objective analysis of DMD clinical severity, and adductor magnus was considered to be the most valuable muscle to reflect the clinical severity of DMD. DOI: 10.3969/j.issn.1672-6731.2015.06.004

Objective To assess the contraction and coordination changes in the anterior and posterior thigh muscles of patients recovering from cerebral infarction,and to provide objective references for targeted rehabilitation programs. Methods Eighteen cerebral infarction patients with mild hemiparesis (the patient group) and eighteen age- and sex-matched healthy volunteers (the healthy group) were investigated. The surface-electromyographic (sEMG) signals of their vastus medialis,rectus femoris,vastus lateralis,biceps femoris,semitendinosus and semimembranosus were recorded during knee joint flexion and extension in the prone position.The sEMG signals from both legs were recorded for the patient group,but only from the left leg in the healthy group.The standardized root mean square (stRMS) signals and the co-contraction ratios (CRs) were compared and analysed, Results The stRMSs of the rectus femoris,vastus lateralis and vastus medialis on the patients' affected side during knee extension were significantly higher than those in the healthy group at baseline and follow-up.The stRMSs of the biceps femoris and semitendinosus-semimembranous on the patients' unaffected side were significantly higher than those of the affected side and the healthy group during knee flexion at baseline.The CRs during knee flexion on the patientsˊ affected side at baseline and follow-up were significantly higher than those of the unaffected side at baseline. Conclusions After cerebral infarction,the functioning of both the anterior and posterior thigh muscles on the affected side are impaired.The rectus femoris are the most severely impaired knee extensors,and the biceps femoris,semitendinosus and semimembranous are impaired equally in knee flexion.The thigh flexors and extensors lose their normal antagonist-agonist contraction modes.The functions of both the anterior and posterior thigh muscles should be emphasized during rehabilitation to improve abnormal contraction. Key words: Infarction ; Thigh muscles ; Surface-electromyography ; Rehabilitation

Objective To test the differences in diffusion properties-namely fractional anisotropy (FA) and apparent diffusion coefficient(ADC)-between amateur marathon runners and healthy volunteers′ thigh muscles using diffusion tensor imaging (DTI) at rest. Methods Thirty amateur marathon runners(Group A) and 20 healthy volunteers (Group B) were recruited. All were males and their age was between 28 to 53 years. All subjects underwent both thigh DTI examination. DTI parameters FA and ADC were evaluated in thigh muscles(rectus femoris, vastus lateralis, vastus intermedius, vastus medialis, adductor longus, adductor magnus, biceps femoris long head, semitendinosus and semimembranosus)in all subjects. We tested the differences in diffusion properties between GroupA and B using independent sample t test. Results The average FA value of the thigh muscles measured in Group A was (0.24±0.03), which was significantly lower than that in Group B=(0.27±0.03)(t=5.164,P<0.01). The average ADC value of the thigh muscles measured in Group A was (1.74±0.10)×10-3mm2/s, which was significantly higher than that in Group B=(1.70±0.09)×10-3mm2/s (t=2.060,P<0.05). The FA value of Group A was lower than that of Group B in the rectus femoris, vastus lateralis, vastus medialis, biceps femoris long head, semitendinosus and semimembranosus (P<0.05). The ADC value of Group A was higher than that of Group B in the vastus intermedius, vastus medialis and biceps femoris long head (P<0.05). Conclusions In the absence of positive findings from conventional MRI, DTI technique can non-invasively assess the subtle changes in the bilateral thigh muscles of amateur marathon runners at rest in the early stage of microscopic molecular level, providing important imaging evidence for early changes in skeletal muscle caused by marathon. Key words: Athletic injuries; Muscle, skeletal; Magnetic resonance imaging; Diffusion tensor imaging; Marathon

A Single Intravenous Injection of Adeno-associated Virus Serotype-9 Leads to Whole Body Skeletal Muscle Transduction in Dogs

Analysis of EMG Signals During Walking of Healthy Children

Objective To analyze the characteristics of fat infiltration into the muscles of patients with Becker and Duchenne muscular dystrophy (DMD) so as to provide a guide for rehabilitation therapy. Methods Twenty-three children with Becker muscular dystrophy (BMD) and 47 with DMD who had never been treated with glucocorticoids were enrolled. MRI was performed on both of their thigh muscles. T1 weighted images were used to assess the fat infiltration of their thigh muscles using a 0-5 modified version of Mercuri′s scale. The progression of fatty infiltration of the thigh muscles in BMD was analyzed using descriptive statistics. The differences in fat infiltration between BMD and DMD were analyzed using rank sum tests. Results In patients with BMD the adductor magnus most often showed severe fat infiltration, followed by the biceps femoris, quadriceps, semimembranosus and semitendinosus, while the sartorius, gracilis and adductor longus had the lowest percentages of severe fat infiltration. Among the BMD patients the adductor magnus, biceps femoris and quadriceps showed moderate to severe involvement at the age of 8 to 9. The semimembranosus and semitendinosus showed moderate to severe involvement at the age of 10 to 11, and the sartorius, gracilis and adductor longus showed mild to moderate involvement after 15 years of age. Among the age groups of 8, 9, 10 and 11 years old, the median total fat infiltration scores were 10, 22, 28 and 25 respectively among the BMD patients, and 29, 34, 34 and 30 respectively among the DMD patients. At age 8 significant differences between the BMD and DMD patients were observed in the infiltration scores of the adductor magnus, biceps femoris, vastus lateralis, rectus femoris, vastus medialis, vastus intermedius and in the total scores. At age 9 significant differences persisted in the scores of the adductor magnus, rectus femoris, vastus medialis, vastus intermedius and the total scores. Conclusions The muscle MRIs showed significant differences in the degree of fatty infiltration between BMD and DMD patients. These findings may be useful when designing therapeutic regimens and rehabilitation programs for patients with BMD and DMD. Key words: Muscular dystrophy; Muscles, Skeletal; Fatty infiltration

Introduction: Cycle time-trial performance is a function of the highest sustainable power output. The first (VT-1) and second (VT-2) ventilatory thresholds are practical tools for coaches and athletes to set training zones and exercise intensity. Specifically, VT-2 is closely linked to critical power, a primary determinant of endurance performance. The cascade of physiological events in the organs responsible for power production accompanying these respiratory thresholds remains contentious and yet to be fully characterized. Electromyographic (EMG) thresholds have been identified in leg muscles during incremental exercise while near infrared spectroscopy (NIRS) has revealed thresholds in both muscle deoxygenation and cerebral oxygenation towards the end of an incremental exercise test. However, the relative timing of the different muscle and brain oxygenation and muscle electrical activity responses to each other is unclear. Purpose: The aim of the present study was to examine the thresholds of cerebral and muscle oxygenation, along with muscle electrical activity during a ramp exercise test in relation to VT-1 and VT-2. Methods: Twenty-five recreational cyclists (mean±SD: age 37±8yrs, body mass 78±13kg, height 178±8cm, VO 2 max 53±8mL/kg/min) completed a ramp exercise test to exhaustion on an electromagnetically braked cycle-ergometer with a work rate increment of 25 W/min. Throughout the test, continuous measures of expired gas (breath-by-breath), prefrontal cortex and vastus lateralis (VL) oxygenation via NIRS, and EMG Root Mean Square activity for the VL, rectus femoris (RF), and biceps femoris (BF) muscles were recorded. Thresholds were defined by a double-linear model. Results: The results are summarized in Figure 1. VT-1 and VT-2 occurred at 57 ± 6% and 81 ± 6% of the exercise, respectively. There was a threshold in both cerebral deoxyhaemoglobin and oxyhaemoglobin (56±13% and 56±8% of exercise, respectively) which were not significantly different from VT-1 ( P >0.86, cohens d 0.8). Only one threshold could be identified for muscle parameters with a threshold in muscle oxyhaemoglobin (78±9% of exercise), attenuation in muscle deoxyhaemoglobin (80±8% of exercise), and increase in EMG activity of VL, RF and BF (89±5%, 82±14% and 85±9% of exercise, respectively). The thresholds in BF and VL EMG activity occurred after VT-2 ( P 0.6). Conclusion: The threshold in cerebral oxygenation parameters occurred at both VT-1 and VT-2. Conversely, the present investigation failed to support a role for VL muscle oxygenation and electrical activity at VT-1, but did display a threshold at or after VT-2. The changes in cerebral oxygenation and in BF and VL electrical activity occurred after VT-2, suggesting that the metabolic and ventilatory events characterizing this latter cardiorespiratory threshold may affect both cerebral and muscle oxygenation levels and subsequent muscle recruitment responses. These physiological mechanisms are important factors in describing key training concepts and performance capability; for instance critical power. Any marked rise in muscle recruitment above VT-2 or critical power will result in early onset of fatigue and limit exercise performance.

Guidelines encouraging social distancing, limited outings, and remote work due to COVID-19 have increased sedentary periods and reduced levels of physical activity. These habits increase the risk of metabolic diseases, obesity, cardiovascular disease, and diabetes mellitus. The World Health Organization recommends muscle-strengthening exercises as well as regular physical activity to promote overall health. This study investigates the effect of a wearable hip exoskeleton on muscle activity and heart rate during anaerobic exercise in 40 healthy adults (mean age of 40.00 ± 11.51 years; n = 20 females). Bot Fit, a wearable hip-type robotic exoskeleton, was developed by Samsung Electronics Co., Ltd. (Suwon, Republic of Korea) to enhance the effects of both aerobic and anaerobic exercise. All study participants performed a fitness exercise protocol, including knee-ups, good mornings, squats, mountain climbs, kick-backs, reverse lunges, and split jacks, with and without a Bot Fit. To evaluate the effect of anaerobic exercise with the Bot Fit, muscle activity and heart rate were measured during fitness exercises with and without a Bot Fit. Measured muscles were the rectus abdominis (RA), erector spinae (ES), rectus femoris (RF), vastus lateralis (VL), vastus medialis (VM), biceps femoris (BF), tibialis anterior (TA), gastrocnemius medialis (GCM), and gluteus maximus (GM). During anaerobic exercises with the Bot Fit, there was a significant increase in muscle activity compared to exercising without the Bot Fit. Muscle activity increased significantly in the RA, RF, VL, BF and TA muscles during knee-ups; in the ES, BF, and GM during good mornings; in the RF, VL, VM, BF, and GM during squats; in RA, RF, VL, VM, and GM during mountain climbs; in the RA and BF during kick-backs; in the RF, BF, and GCM during reverse lunges; and in the RF and VL during split jacks (p < 0.05). Heart rates showed a statistically significant increase during good mornings, mountain climbs, and reverse lunge exercises while wearing the Bot Fit (p < 0.05). This study demonstrated that anaerobic exercises by healthy adults using a Bot Fit led to enhanced activation of abdominal and lower-limb muscles as well as an improved heart rate, maximizing the effect of anaerobic exercise compared with the same exercise protocol without a Bot Fit. This suggests that use of a Bot Fit can increase the effectiveness of anaerobic exercise in healthy adults.

Timing of Muscle Activation is Altered During Single-Leg Landing Tasks Following ACL Recontruction at the Time of Return to Sport

The objective of this study was to determine the retail shelf stability of beef chuck and round muscles enhanced with ammonium hydroxide, salt, and carbon monoxide. A split plot design was used for each of 3 muscles [triceps brachii (TB), biceps femoris (BF), and rectus femoris (RF)] with 2 treatments (0 and 20% pump), 3 dark storage periods (1, 2, and 3 wk), and 3 replications in the whole plot and retail display period as the split plot. There were a total of 12 subprimals per treatment per dark storage period (n = 72 each). Individual steaks were cut to a thickness of 2.54 cm and packaged in a modified-atmosphere package (MAP). The TB was packaged in a high-oxygen MAP (80% oxygen, 20% carbon dioxide). The BF and RF were packaged in a low-oxygen MAP (100% carbon dioxide). At the completion of each dark storage period, steaks were subjected to 7 d of simulated retail display. Steaks were used for objective and subjective color measurements, total plate counts, and determination of retail purge and oxidation. For all muscles, total plate counts were always numerically greater in injected steaks. Triceps brachii steaks held in dark storage for 3 wk and displayed at retail for 4 or more days all exceeded 10(7) log of cfu/cm(2) for aerobic plate count. Biceps femoris and RF steaks packaged in a low-oxygen MAP had much lower bacterial counts, with levels below 4.2 log of cfu/cm(2), even after 7 d of retail display. Oxidation values for the TB were extremely high (ranging from 12.3 to 26.6), whereas the BF and RF had values that were much lower (< or =1.0 mg of malonaldehyde/kg of muscle), likely due to the oxidation occurring in a high-oxygen MAP for the TB. Enhanced TB steaks proved to have greater color stability (less discoloration) than nonenhanced TB steaks. In addition, the BF and RF (low-oxygen MAP) steaks had better color stability (more stable redness values) than TB (high-oxygen MAP) steaks, although TB steaks initially exhibited a brighter red color. Retail display life was enhanced by packaging in 100% carbon dioxide, and enhanced steaks exhibited greater color stability in retail display than control steaks.

The aim of this study was to compare gluteus maximus-to-hamstring (GM:H) co-activation, hamstrings-to-quadriceps (H:Q) co-activation, and mean muscle activity in the vastus lateralis (VL), vastus medialis (VM), rectus femoris (RM), gluteus maximus (GM), semitendinosus (ST), and bicep femoris (BF) muscles across a range of training loads (40%, 50%, 50%, 70%, 80% 90% 1RM) of the barbell back squat in resistance trained females. Surface electromyography (EMG) was observed in 18 healthy resistance trained females for the VL, VM, RM, GM, ST, and BF during the ascending and descending phase of the back squat. During the ascending phase, the VL, VM, RM, GM, ST, and BF displayed significantly more EMG activation at 90% 1RM compared to 40%-70% (p < .03). During the descending phase, there were no significant differences displayed in mean muscle activity at 40%-80% of 1RM compared to 90% of 1RM. There were no significant differences in H-Q co-activation and GM-H co-activation during the ascending or descending phase across external loads. These findings are similar to the results found in similar studies using male participants and support that higher training intensities (80%-90% 1RM) of the barbell back squat significantly activate muscles surrounding the hip compared to lower loads (40%-70%). The results of this study also suggest that training intensities of 80% 1RM and 90% 1RM elicits the similar musculature activation in the muscle surrounding the hip in resistance trained females.

Fast-myosin in frozen histological sections of eight, 10, 11 and nine muscles of the upper forelimb, lower forelimb, upper hindlimb and lower hindlimb, respectively, of goats was quantified by an immunohistochemical micromethod based on the enzyme-linked immunosorbent assay. The structure of the muscles is well preserved during the immunohistochemical measurement. High fast-myosin levels (more than 201 mg/g total protein) were observed in the triceps brachii (lateral head), rectus femoris, vastus lateralis, semitendinosus, semimembranosus, gastrocnemius (lateral head) and long digital extensor muscles. In contrast, low fast-myosin levels (less than 50 mg/g) were found in the triceps brachii (medial head), superficial digital flexor, vastus intermedialis, and soleus muscles. Fast-myosin-positive fibres (type II or fast-twitch type) were distributed more in the superficial regions than in the deeper regions in the triceps brachii (lateral and long heads), biceps brachii, brachialis, biceps femoris, vastus lateralis, vastus medialis, semimembranosus and gastrocnemius (lateral and medial heads) muscles. In contrast, type IIfibres were distributed more in the deeper regions than in the superficial regions in the extensor carpi radialis, deep digital flexor, cranial tibial, deep digital flexor and superficial digital flexor muscles. When the results obtained by the immunohistochemical micromethod were compared with those obtained by biochemical techniques and by histomorphometrical analyses, high correlations were noted. This technique could be used in research projects to study the muscle characteristics that determine meat quality.

Muscle activity patterns of six alpine skiers were compared during nine runs each of wedge (W), short radius parallel (P), and giant slalom (GS) turns. Bipolar surface electrodes were placed over 12 muscles on the right side of the body: anterior tibialis, medial gastrocnemius, vastus medialis, vastus lateralis, rectus femoris, medial hamstrings, biceps femoris, gluteus maximus, adductors, rectus abdominis, external obliques, and erector spinae. Repeated measures ANOVA was used to test for differences in average and peak EMG amplitudes between W, P, and GS (P < 0.1). Average amplitude was significantly different between all turning styles (W < P < GS) for four muscles (vastus lateralis, medial hamstrings, biceps femoris, and external obliques) and significantly less for W versus P or GS for four muscles (anterior tibialis, vastus medialis, rectus femoris, and rectus abdominis). The gluteus maximus was the only muscle that had significantly greater activity in W than P. Average amplitude was greater than 50% MVC for the vastus medialis, vastus lateralis, biceps femoris, gluteus maximus, and adductors in all conditions; and for the anterior tibialis, medial hamstrings, and rectus femoris in GS and P; and for the medial gastrocnemius and erector spinae in GS. Peak amplitude was greater than 150% maximal voluntary contraction (MVC) for the vastus medialis, vastus lateralis, biceps femoris, gluteus maximus, and adductors in all conditions, and for the medial gastrocnemius, rectus femoris, and erector spinae in GS. This research indicates that with the exception of the gluteus maximus, greater muscle activity is required in GS followed by P and W turns.