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PubMed1997

The effect of seasonal heat stress on rigor development and the incidence of pale, exudative turkey meat.

Heat stress is one of the prominent ante-mortem stressors that elicits pale, soft, and exudative meat characteristics in stress-susceptible pigs. Industry reports of exudative turkey meat increase in the early summer with the onset of prolonged high temperatures. To study the effect of seasonal heat exposure on turkeys, 122 17-wk-old Nicholas tom turkeys were subjected in January either to growth temperatures of 16/24 C (night/day) (control) or to elevated temperatures of 32/38 C (night/day) (heat-stressed, HS). Turkeys were processed at 21 wk of age in a manner simulating commercial conditions. Pectoralis muscle samples were taken at 15 min (prechill), 2 h (postchill), and 24 h and analyzed for R-value, pH, and color. At 2 h, the remaining intact Pectoralis muscle was harvested, aged on ice for 23 h, and analyzed for drip loss and cook loss. Percentage mortality and carcass weights were not significantly different between treatments. By 15 min post-mortem, the HS birds exhibited a faster pH decline and had higher R-values that persisted through 24 h. The HS birds were also paler in color and exhibited increased drip loss and cook loss when compared to controls; however, expressible moisture was not different between treatments. In addition, the HS birds had a higher frequency of abnormal birds than controls when birds were grouped as normal (L* < 53) or abnormal (L* > 53).

Animals↗

PubMed2000

Treatment of recurrent postoperative mediastinitis with granulated sugar.

BACKGROUND: The authors report their experience with granulated sugar as dressing technique in the treatment of postoperative mediastinitis refractory to a closed irrigation system. METHODS: Between January 1990 and January 1998, mediastinitis developed in 61 (0,93%) of 6521 patients who had undergone open heart surgery. Diagnosis of sternal infections was based on wound tenderness, drainage, cellulitis, fever associated with sternal instability. All of them were initially treated with surgical debridement and closed chest irrigation. Nine patients with postcardiotomy mediastinitis refractory to closed chest irrigation underwent open dressing with granulated sugar. All of them were febrile with leukocytosis and positive wound cultures. RESULTS: Bacteria isolated were staphylococcus aureus in 6 cases, staphylococcus epidermidis in 2 and pseudomonas in 1. Redebridement was performed in all cases and the wound was filled with granulated sugar four times a day. Fever ceased within 4.3+/-1.3 days from the beginning of treatment and WBC became normal after 6.6+/-1.6 days. Three patients had hyperbaric therapy as associated treatment. Complete wound healing was achieved in 58.8+/-32.9 days (three patients underwent successful pectoralis muscle flaps). CONCLUSIONS: Sugar treatment is a reasonable and effective option in patients with mediastinitis refractory to closed irrigation treatment. It may be used either as primary treatment or as a bridge to pectoralis muscle flaps.

Aged↗

PubMed2004

Primary or delayed closure for the treatment of poststernotomy wound infections?

OBJECTIVE: The methods of primary versus delayed wound closure for the treatment of sternal wound infections after cardiac surgery were retrospectively compared. METHODS: From January 2001 to March 2003, 132 patients (median age 66 years, male to female ratio 88:44) with sternal wound infection after cardiac surgery were treated at our department. After thorough debridement, 35 patients received preconditioning of the wound before implementation of definitive therapy; the remainder (97 patients) were treated with immediate closure. RESULTS: From the 35 patients with preconditioning, 19 patients proceeded to delayed primary closure, whereas the remaining 14 patients were referred to plastic reconstruction with a pectoralis muscle flap. Primary success rate in this group was 100%. In the immediate primary closure group, 33 patients experienced 1 or more therapy failures, resulting in a recurrence rate of 39%. Fifteen patients received a pectoralis muscle flap as definite treatment modality. CONCLUSIONS: Immediate primary closure is associated with a high rate of local infection recurrence. Surgical debridement and conditioning of the wound until resolution of infections with delayed primary closure or plastic reconstruction is suggested as the more appropriate treatment modality, with promising results.

Adult↗

PubMed2001

Isometric axial rotation of the trunk in the neutral posture.

The purpose of this study was to measure the torque, the magnitude of the electromyogram (EMG) signal and the phase relationship of 14 muscles during trunk axial rotation. Fifty normal healthy volunteers (27 males and 23 females) with no lower-back injury participated in the study. The subjects were seated in an upright position in the axial rotation tester (AROT) after applying surface electrodes bilaterally to the following muscles: pectoralis major, rectus abdominis, external oblique, internal oblique, latissimus dorsi, and erector spinae at T10 and L3. They were stabilized from the hip down, and the shoulder harness of the AROT was applied to their shoulders. These subjects performed maximal isometric axial rotations to the left and right in a random order. The torque and 14 channels of EMG were monitored, and their magnitude, slope of the increase in magnitude, and timing of the anticipation and onset activity were determined. The results revealed that the females produced 65% of the torque of their male counterparts. The pattern and magnitude of EMG in performing these tasks were significantly different between males and females (P<0.01). Males generated the greatest activity in their ipsilateral latissimus dorsi followed by their contralateral external oblique muscles. In the females, maximal EMG activity was observed in their contralateral pectoralis muscle. Thus, under the current experimental conditions, the females employed a different muscle recruitment strategy compared to the males. Each muscle involved in axial rotation was significantly different from the other (P < 0.01). The timing pattern for these activities was inconsistent, implying that there is no fixed-order phasic recruitment of the torso muscles during maximal isometric axial rotation.

Adolescent↗

PubMed2003

Heavier chicks at hatch improves marketing body weight by enhancing skeletal muscle growth.

This study examined some of the factors connected with the greater marketing weight observed in chicks hatching with higher BW. Examination of chicks hatching from maternal flocks of different ages indicated that BW at hatch increased quadratically and yolk sac weight linearly with age, whereas components of the gastrointestinal tract showed no significant trend. Growth of pectoralis muscles and gastrointestinal tract were compared in chicks hatching at the same weight from maternal flocks of 28 and 64 wk of age and in chicks from the same maternal flock (44 wk old) hatching at different weights. The results indicated that no differences were found among chicks hatching with the same weight from maternal flocks of different ages. In contrast, in chicks from the same maternal flock hatching at different weights the gastrointestinal tract tended to compose a smaller proportion of BW in large chicks, and its growth was not correlated with performance. Liver proportions were greater in heavier chicks. Pectoralis growth and satellite cell numbers and activity were greater in heavier chicks through 5 d posthatch, and pectoralis muscles were heavier at marketing. Examination of some of the growth factors involved suggested that in heavier chicks satellite cells underwent higher proliferation and earlier differentiation during their critical period of activity in the immediate posthatch days. To determine when these differences in activity were established, examination of 15-d embryonic myoblast activity indicated that at this stage activity was already greater in the heavier eggs. This finding suggests that programming of muscle growth may be completed in late embryonic stages. This study suggests that enhanced satellite cell activity is involved in increased growth of chicks hatching with higher BW.

Aging↗

PubMed1989

Growth and development of broiler breeders. 2. Independent effects of dietary formulation versus body weight on skeletal and muscle growth.

The relationship between body weight gain, nutrient intake, and skeletal and muscle growth in broiler breeder pullets was studied in two experiments. A total of 720 and 540 pullets were started in Experiments 1 and 2, respectively. In the first study, growing pullets were fed either a 15% protein, 2,885 kcal ME/kg pullet grower diet or a 23% protein, 3,133 kcal ME/kg broiler starter diet from 2 to 16 wk of age. Within each dietary treatment, there were three body weight groupings (light, control, heavy) achieved by manipulating weekly feed allowances. At 8, 12, and 16 wk of age, 12 pullets from each diet and body weight grouping were killed for muscle [pectoralis major] and skeletal (shank, keel, tibia, clavicle) measurements. As body weight increased, so did skeletal growth, but there were no significant differences in skeletal measurements related to diet. At 12 and 16 wk of age, pullets fed the broiler starter diet had significantly larger p. major muscles. In Experiment 2, growing pullets were fed restricted diets: 1) the 15% protein grower diet (control), 2) the broiler starter diet adjusted weekly to the same calculated calorie intake as that obtained with the grower diet (broiler starter calorie), or 3) the broiler starter diet adjusted to the same calculated protein intake as the grower ration (broiler starter protein). At 16 wk, there were no significant differences between body weight or skeletal measurements of the control and broiler starter calorie treatments. Pullets in the broiler starter calorie treatment did have significantly larger pectoralis muscles and less abdominal fat than those fed the 15% grower diet. Pullets in the broiler starter protein treatment were significantly lighter and had shorter bones, less abdominal fat, and smaller p. major muscles than those in the control treatment.

Analysis of Variance↗

PubMed1998

Rigor mortis development at elevated temperatures induces pale exudative turkey meat characteristics.

Development of rigor mortis at elevated post-mortem temperatures may contribute to turkey meat characteristics that are similar to those found in pale, soft, exudative pork. To evaluate this effect, 36 Nicholas tom turkeys were processed at 19 wk of age and placed in water at 40, 20, and 0 C immediately after evisceration. Pectoralis muscle samples were taken at 15 min, 30 min, 1 h, 2 h, and 4 h post-mortem and analyzed for R-value (an indirect measure of adenosine triphosphate), glycogen, pH, color, and sarcomere length. At 4 h, the remaining intact Pectoralis muscle was harvested, and aged on ice 23 h, and analyzed for drip loss, cook loss, shear values, and sarcomere length. By 15 min post-mortem, the 40 C treatment had higher R-values, which persisted through 4 h. By 1 h, the 40 C treatment pH and glycogen levels were lower than the 0 C treatment; however, they did not differ from those of the 20 C treatment. Increased L* values indicated that color became more pale by 2 h post-mortem in the 40 C treatment when compared to the 20 and 0 C treatments. Drip loss, cook loss, and shear value were increased whereas sarcomere lengths were decreased as a result of the 40 C treatment. These findings suggested that elevated post-mortem temperatures during processing resulted in acceleration of rigor mortis and biochemical changes in the muscle that produced pale, exudative meat characteristics in turkey.

Animals↗

PubMed2006

[Myositis as a 'radiation-recall phenomenon' following palliative chemotherapy with carboplatin-gemcitabin for non-small-cell pulmonary carcinoma].

A 58-year-old woman suffered pain due to a stage-IV adenocarcinoma of the right upper-lung lobe with signs of growth into the right axilla. Palliative local radiotherapy directed at the primary tumour followed by combination chemotherapy with carboplatin-gemcitabin led to partial remission. During the fourth and last cycle of her three-months course of chemotherapy, the patient again complained of pain in the right half of the thorax; later, a local swelling of the pectoralis muscles was found. She was diagnosed with myositis as a delayed reaction to irradiation (radiation-recall phenomenon) based on the clinical symptoms (redness of the skin, pain and distinct swelling) but especially on the basis of a CT-scan. This revealed a clear swelling of the pectoralis muscles, even though the tumour was in remission. The possibility of myositis as a radiation-recall phenomenon should be borne in mind whenever a patient presents with skin changes or pain within a previous irradiation field during chemotherapy with, for example, gemcitabin.

Antineoplastic Agents↗

PubMed1986

Is there morphological separation between the spinal cord motor nuclei which innervate the heads of a multiheaded muscle?

Horseradish peroxidase was injected into the individual heads of the pectoralis muscles of the dog or applied to the nerve which supplies each of these heads. The location and numbers of labeled motoneurons in the spinal cord were studied using light microscopy. There was longitudinal overlap of the pectoral nuclei, but no separation in their mediolateral or dorsoventral positions. The cutaneous trunci muscle motor nucleus is distinctly separate from the motor nuclei of the pectoral muscles, even though they share a common nerve supply. The methods of horseradish peroxidase application to the cut nerve or injection into the muscle are compared.

Animals↗

PubMed2004

Helical tomotherapy as a means of delivering accelerated partial breast irradiation.

A novel treatment approach utilizing helical tomotherapy for partial breast irradiation for patients with early-stage breast cancer is described. This technique may serve as an alternative to high dose-rate (HDR) interstitial brachytherapy and standard linac-based approaches. Through helical tomotherapy, highly conformal irradiation of target volumes and avoidance of normal sensitive structures can be achieved. Unlike HDR brachytherapy, it is noninvasive. Unlike other linac-based techniques, it provides image-guided adaptive radiotherapy along with intensity modulation. A treatment planning CT scan was obtained as usual on a post-lumpectomy patient undergoing HDR interstitial breast brachytherapy. The patient underwent catheter placement for HDR treatment and was positioned prone on a specially designed position-supporting mattress during CT. The planning target volume (PTV) was defined as the lumpectomy bed plus a 20 mm margin. The prescription dose was 34 Gy (10 fx of 3.4 Gy) in both the CT based HDR and on the tomotherapy plan. Cumulative dose-volume histograms (DVHs) were generated and analyzed for the target, lung, heart, skin, pectoralis muscle, and chest wall for both HDR brachytherapy and helical tomotherapy. Dosimetric coverage of the target with helical tomotherapy was conformal and homogeneous. "Hot spots" (> or =150% isodose line) were present around implanted dwell positions in brachytherapy plan whereas no isodose lines higher than 109% were present in the helical tomotherapy plan. Similar dose coverage was achieved for lung, pectoralis muscle, heart, chest wall and breast skin with the two methods. We also compared our results to that obtained using conventional linac-based three dimensional (3D) conformal accelerated partial breast irradiation. Dose homogeneity is excellent with 3D conformal irradiation, and lung, heart and chest wall dose is less than for either HDR brachytherapy or helical tomotherapy but skin and pectoral muscle doses were higher than with the other techniques. Our results suggest that helical tomotherapy can serve as an effective means of delivering accelerated partial breast irradiation and may offer superior dose homogeneity compared to HDR brachytherapy.

Brachytherapy↗

PubMed1993

Expression of phospholamban mRNA during early avian muscle morphogenesis is distinct from that of alpha-actin.

We have studied the expression of phospholamban during the early development of chick embryos by in situ hybridization and have compared it to that of alpha-cardiac and alpha-skeletal actin. In adult cross-striated muscles there is only one phospholamban gene and it is expressed exclusively in the heart and slow muscles. In the heart phospholamban transcripts were first detected at stage 14 in the region of presumptive ventricle and at stage 20 in the atrium. In the myotomal portion of the somites phospholamban mRNA was first detected at stage 20, which lagged behind the appearance of the alpha-actins. In the limb rudiments all three mRNAs were barely detectable through stage 24, but increased by stage 28+. However, quantitative analysis of signal intensity at stage 28+ indicated that less phospholamban mRNA is present in the limb bud than in the myotome since for phospholamban the ratio of the signal density in the myotome to that in the limb rudiments was about twice the value of the ratio determined for the alpha-actins. Northern blot analysis of embryonic day 11 chick fast pectoralis muscle showed that phospholamban mRNA was not detected in vivo while alpha-cardiac actin mRNA was. Moreover, no phospholamban mRNA was detected in primary cultures derived from pectoralis muscle of the same age. In concert with previous observations that phospholamban is not detectable at stage 30-32 in wing or thigh muscle, these results suggest that phospholamban mRNA is expressed independently of the alpha-actins in the limb buds during early myogenesis.

Actins↗

PubMed1999

[Malignant lymphoma: magnetic resonance tomography findings in residual supradiaphragmatic space-occupying lesions].

PURPOSE: Evaluation of MR imaging in patients with Hodgkin's lymphoma and high grade non-Hodgkin's-lymphoma and mediastinal residual mass after first line chemotherapy. MATERIALS AND METHODS: MR imaging (1.5 T) was performed in 36 patients (Hodgkin's lymphoma n = 26, NHL n = 10) after first line chemotherapy). Twenty patients had inactive residual mass, 16 patients had residual lymphoproliferative lesions. T1- and T2-weighted spin echo images were visually analysed by a score index (range 1-5) as well as quantification of enhancement by signal-intensity-ratios SImax/SIplain). RESULTS: For the differentiation between residual lymphoproliferative activity and inactive residual mass, the highest accuracy was obtained for the signal intensity of residual mass on T2-w-SE compared to pectoralis muscle (94% sensitivity, 80% specificity, likelihood ratios: 4.0 [LR+]; 0.3 [LR-]). The cut-off value of the SI ratio was calculated retrospectively at 1.96 (p > 0.05). CONCLUSIONS: Differentiation between inactive (fibrotic) and lymphoproliferative (active) residual mediastinal mass is possible by MR imaging using as parameter the size reduction after therapy and the signal intensity on T2-w-SE in comparison to pectoralis muscle. Thus study suggests an additional value using the SI ratio for the differentiation.

Adult↗

PubMed1998

The qualification of different free muscle transplants to reconstruct mimic function: an experimental study in rabbits.

With the scutuloauricularis muscle, we developed a new model for experimental free transplantation of mimic muscles in the rabbit and studied the qualification of different muscles for free functional grafting into the position of the facial muscle, which is to be replaced. Forty adult female white New Zealand rabbits were distributed to four groups of 10 rabbits each. In group 1, the operative techniques of the new transplantation models were developed in the scutuloauricularis muscle, the pectoralis descendens muscle, and a comparable part of the rectus femoris muscle. In group 2, the scutuloauricularis muscle was transplanted orthotopically with microneurovascular anastomoses on the left side; in group 3, the pectoralis descendens muscle was transplanted into the position of the scutuloauricularis after its removal; and with the animals in group 4, a piece of the rectus femoris muscle was transplanted into the position of the mimic muscle after its removal. In all muscle transplants, the neurovascular supply was reestablished microsurgically by end-to-end anastomoses to the superficial temporal vessels and direct nerve coaptation to the facial nerve branches supplying originally the scutuloauricularis muscle. Nine months after transplantation, force measurements were performed in all transplanted muscles and the scutuloauricularis muscles of the control side. Cross-sections stained for ATPase after alkaline preincubation at pH 10.4 were used for computer-assisted planimetry of the muscle fibers. The orthotopically transplanted scutuloauricularis muscles reached with 2.84 (+/-1.04) N for maximal tetanic tension on the average 87.7 (+/-32.1) percent of that of the control scutuloauricularis muscles, the pectoralis descendens muscles with 4.25 (+/-2.15) N on the average 188.7 (+/-100.7) percent of that of the controls, and the pieces of rectus femoris muscles 6.62 (+/-2.16) N or 185.3 (+/-45.4) percent of that of the controls. All three muscles were identified as fast contracting muscles before and after transplantation. By transplantation, the content of type II muscle fibers changed from 58.2 to 68.0 percent in the scutuloauricularis muscle, from 62.4 to 74.4 percent in the musculus pectoralis descendens, and from 92.5 to 82.8 percent in the rectus femoris muscle. For the first time, an experimental model for free transplantation of mimic muscles was developed and functionally assessed. The most important result of this study was the fact that the double-sized muscle grafts developed twice the force of the control scutuloauricularis muscles, although reinnervated by the original muscle nerve branch. This result underlines the usefulness of overdimensioning during clinical muscle transplantation. It was also shown that parts of big muscles can be grafted with results similar to those experienced with complete smaller muscles.

Adenosine Triphosphatases↗

PubMed2003

The latero-central glandular pedicle technique for breast reduction.

The relatively high number of complications and disadvantages of the conventional techniques in breast reduction combined with our expertise in restoring sensation in breast reconstructive procedures, led to the development of a new technique that was crystallised from the traditional techniques and is able to overcome most of their disadvantages. The key issue of the technique is that the nipple is vascularised and innervated on a column of glandular tissue that remains in contact in its posterior part with the pectoralis muscle and its perforators and in its lateral aspect to the lateral pillar of breast tissue. Due to the ptosis that develops during the process of hypertrophy, this column will gain sufficient length to be turned upwards into the new position of the nipple. Resection of glandular tissue is performed cranially, medial and inferior to this column. Undermining of the skin is reduced to an absolute minimum and glandular resections are always performed in the shape of a wedge. In this way, undermining of the breast gland over the pectoralis muscle is avoided. The glandular pedicles are sutured together after loosely fitting the glandular cone with the nipple into its new position. The long term results of the first 68 cases were reviewed and compared to our experience with the superior dermal pedicle technique combined with the vertical scar as described by Lassus and later by Lejour. Due to increased vascularisation of the nipple-areolar complex (NAC), wound complications were markedly reduced with the new technique. Sensation in the NAC was preserved in almost all cases. There was a high satisfaction about the obtained aesthetical results in regard to shape and volume. Increased viability of the NAC, a reduced rate of wound complications and preservation of sensation in NAC are the main advantages of this technique. Additionally, flattening of the NAC is avoided by the support by glandular tissue behind the NAC that improves projection and hereby the aesthetic conic appearance of both breast and nipple.

Adult↗

PubMedDate not supplied

[A new (?) multiple abnormality complex similar to the Poland syndrome].

The report describes a case Poland's Syndrome - like in which the hypoplasia of the left major pectoralis muscle was associated with: subtotal aplasia of sternal body, severe hypoplasia of the ipsilateral scapula, humerus and forearm bones, tetradactyly in the ipsilateral hand, partial defect of the diaphragm with thoracic migration of the left hepatic lobe and secondary dextrocardia (false dextrocardia). Syndactyly was absent. The contribution is aimed to join out the radiological characteristics of the syndrome as well as the specific contribution provided in the case by Ultrasounds and aortography. Furthermore, the analysis of the case seems to indicate a strict relationship between the abnormalities of diaphragm, pectoralis muscle and homolateral upper limb.

Abnormalities, Multiple↗

PubMedDate not supplied

Plasticity in body composition in breeding birds: what drives the metabolic costs of egg production?

Body composition in vertebrates is known to show phenotypic plasticity, and changes in organ masses are usually rapid and reversible. One of the most rapid and reversible changes is the transformation of the female avian reproductive organs before breeding. This provides an excellent system to investigate the effects of plasticity in organ size on basal metabolic rate (BMR) through relationships between organ masses and BMR. We compared body composition of female European starlings (Sturnus vulgaris) during various reproductive stages over 3 yr and investigated the pattern of changes in reproductive and nonreproductive organ mass during follicular development and ovulation. Furthermore, we analyzed the relationship between organ mass and resting metabolic rate (RMR) in nonbreeding, laying, and chick-rearing females. Our analysis revealed marked variation in organ masses between breeding stages but no consistent pattern among years except for kidney and pectoralis muscle. Furthermore, changes in nonreproductive organs did not parallel the cycle of growth and regression of the reproductive organs. The oviduct gained 62% of its 22-fold increase in mass in only 3 d, and oviduct regression was just as rapid and began even before the final egg of the clutch was laid, with 42% of the oviduct mass lost before laying of the final egg. In laying females, 18% of variation in mass-corrected RMR was explained by the mass of the oviduct (r2=0.18, n=80, P<0.0005), while pectoralis muscle mass in nonbreeding individuals and liver and gizzard mass in chick-rearing females were the only organs significantly related to RMR (r2=0.31-0.44). We suggest that the nonreproductive organs are affected more by changes in local ecological conditions than the reproductive state itself and that the activity and maintenance cost of the oviduct is high enough that selection has led to a very tight size-function relationship for this organ.

Animals↗

PubMed2003

How cockatiels (Nymphicus hollandicus) modulate pectoralis power output across flight speeds.

The avian pectoralis muscle must produce a varying mechanical power output to achieve flight across a range of speeds (1-13 m s(-1)). We used the natural variation in the power requirements with flight speed to investigate the mechanisms employed by cockatiels (Nymphicus hollandicus) to modulate muscle power output. We found that pectoralis contractile function in cockatiels was generally conserved across speed and over a wide range of aerodynamic power requirements. Despite the 2-fold range of variation in muscle power output, many aspects of muscle performance varied little: duration of muscle shortening was invariant, and overall wingbeat frequency and muscle strain varied to a lesser degree (1.2-fold and 1.4-fold, respectively) than muscle power or work. Power output was primarily modulated by muscle force (accounting for 65% of the variation) rather than by muscle strain, cycle frequency or changes in the timing of force production relative to muscle strain. Strain rate and electromyogram (EMG) results suggest that the additional force was provided via increasing pectoralis recruitment. Due to their effect on the transformation of muscle work into useful aerodynamic work, changes in wing position and orientation during the downstroke probably also affect the magnitude of muscle force developed for a given level of motor recruitment. Analysis of the variation in muscle force and airflow over the wing suggests that the coefficients of lift and drag of the wing vary 4-fold over the speed range examined in this study.

Analysis of Variance↗

PubMed1999

Kinematics of flap-bounding flight in the zebra finch over a wide range of speeds

It has been proposed elsewhere that flap-bounding, an intermittent flight style consisting of flapping phases interspersed with flexed-wing bounds, should offer no savings in average mechanical power relative to continuous flapping unless a bird flies 1.2 times faster than its maximum range speed (Vmr). Why do some species use intermittent bounds at speeds slower than 1.2Vmr? The 'fixed-gear hypothesis' suggests that flap-bounding is used to vary mean power output in small birds that are otherwise constrained by muscle physiology and wing anatomy to use a fixed muscle shortening velocity and pattern of wing motion at all flight speeds; the 'body-lift hypothesis' suggests that some weight support during bounds could make flap-bounding flight aerodynamically advantageous in comparison with continuous flapping over most forward flight speeds. To test these predictions, we studied high-speed film recordings (300 Hz) of wing and body motion in zebra finches (Taenopygia guttata, mean mass 13.2 g, N=4) taken as the birds flew in a variable-speed wind tunnel (0-14 m s-1). The zebra finches used flap-bounding flight at all speeds, so their flight style was unique compared with that of birds that facultatively shift from continuous flapping or flap-gliding at slow speeds to flap-bounding at fast speeds. There was a significant effect of flight speed on all measured aspects of wing motion except percentage of the wingbeat spent in downstroke. Changes in angular velocity of the wing indicated that contractile velocity in the pectoralis muscle changed with flight speed, which is not consistent with the fixed-gear hypothesis. Although variation in stroke-plane angle relative to the body, pronation angle of the wing and wing span at mid-upstroke showed that the zebra finch changed within-wingbeat geometries according to speed, a vortex-ring gait with a feathered upstroke appeared to be the only gait used during flapping. In contrast, two small species that use continuous flapping during slow flight (0-4 m s-1) either change wingbeat gait according to flight speed or exhibit more variation in stroke-plane and pronation angles relative to the body. Differences in kinematics among species appear to be related to wing design (aspect ratio, skeletal proportions) rather than to pectoralis muscle fiber composition, indicating that the fixed-gear hypothesis should perhaps be modified to exclude muscle physiology and to emphasize constraints due to wing anatomy. Body lift was produced during bounds at speeds from 4 to 14 m s-1. Maximum body lift was 0.0206 N (15.9 % of body weight) at 10 m s-1; body lift:drag ratio declined with increasing air speed. The aerodynamic function of bounds differed with increasing speed from an emphasis on lift production (4-10 m s-1) to an emphasis on drag reduction with a slight loss in lift (12 and 14 m s-1). From a mathematical model of aerodynamic costs, it appeared that flap-bounding offered the zebra finch an aerodynamic advantage relative to continuous flapping at moderate and fast flight speeds (6-14 m s-1), with body lift augmenting any savings offered solely by flap-bounding at speeds faster than 7.1 m s-1. The percentage of time spent flapping during an intermittent flight cycle decreased with increasing speed, so the mechanical cost of transport was likely to be lowest at faster flight speeds (10-14 m s-1).

Journal Article↗