Effect of leg extension training on concentric and eccentric strength of quadriceps femoris muscles

Ten healthy male subjects carried out bilateral concentric leg extension training twice a week for 8 weeks. Before and after the training, maximal voluntary isometric and isokinetic strength and cross-sectional areas of the quadriceps femoris were measured. Maximal bilateral leg extension power increased significantly after the training. Isometric and concentric unilateral strength did not change significantly before and after the training, while eccentric strength at 0.52 and 1.05 rad·s⁻¹ increased after the training with no changes in cross-sectional area. The correlations between strength and cross-sectional area increased significantly after the training. It was speculated that the increase in eccentric strength of knee extensors was due to modification of the neural inhibition during eccentric muscle actions.     

Tendinopathy and Doppler activity: the vascular response of the Achilles tendon to exercise

BACKGROUND: Intratendinous Doppler activity has been interpreted as an equivalent of neovessels in the Achilles tendon and as a sign of tendinosis (AT). AIM: To evaluate the vascular response as indicated by color Doppler activity after repeated loading of both symptomatic and non-symptomatic Achilles tendons. MATERIAL AND METHODS: Ten non-trained, healthy subjects ran 5 km. Ultrasound (US) Doppler activity was determined before and after the exercise. Eleven patients with chronic AT performed 3 x 15 heavy-load eccentric exercise. The Achilles tendons were scanned before and immediately after the exercise. RESULTS: Non-symptomatic: six Achilles tendons in five subjects had intratendinous Doppler activity before the exercise. All but two subjects (80%) had intratendinous Doppler activity after running. Symptomatic: all patients had Doppler activity in the tendons, with a median color fraction before eccentric exercise of 0.05 (range 0.01-0.33). The Doppler activity did not disappear after exercise. Tendons with a color fraction below the median at baseline increased significantly after the exercise (P=0.02). CONCLUSION: The mere presence of Doppler in the Achilles tendon does not per se indicate disease. Eccentric exercise does not extinguish the flow during or after one training session in patients with chronic AT.     

Isometric training and long‐term adaptations: Effects of muscle length,intensity, and intent: A systematic review

Isometric training is used in the rehabilitation and physical preparation of athletes, special populations, and the general public. However, little consensus exists regarding training guidelines for a variety of desired outcomes. Understanding the adaptive response to specific loading parameters would be of benefit to practitioners. The objective of this systematic review, therefore, was to detail the medium‐ to long‐term adaptations of different types of isometric training on morphological, neurological, and performance variables. Exploration of the relevant subject matter was performed through MEDLINE, PubMed, SPORTDiscus, and CINAHL databases. English, full‐text, peer‐reviewed journal articles and unpublished doctoral dissertations investigating medium‐ to long‐term (≥3 weeks) adaptations to isometric training in humans were identified. These studies were evaluated further for methodological quality. Twenty‐six research outputs were reviewed. Isometric training at longer muscle lengths (0.86%‐1.69%/week, ES = 0.03‐0.09/week) produced greater muscular hypertrophy when compared to equal volumes of shorter muscle length training (0.08%‐0.83%/week, ES = ?0.003 to 0.07/week). Ballistic intent resulted in greater neuromuscular activation (1.04%‐10.5%/week, ES = 0.02‐0.31/week vs 1.64%‐5.53%/week, ES = 0.03‐0.20/week) and rapid force production (1.2%‐13.4%/week, ES = 0.05‐0.61/week vs 1.01%‐8.13%/week, ES = 0.06‐0.22/week). Substantial improvements in muscular hypertrophy and maximal force production were reported regardless of training intensity. High‐intensity (≥70%) contractions are required for improving tendon structure and function. Additionally, long muscle length training results in greater transference to dynamic performance. Despite relatively few studies meeting the inclusion criteria, this review provides practitioners with insight into which isometric training variables (eg, joint angle, intensity, intent) to manipulate to achieve desired morphological and neuromuscular adaptations.     

Achilles tendinopathy: A prospective study on the effect of active rehabilitation and steroid injections in a clinical setting

In published efficacy studies on Achilles tendinopathy (AT) exercise alone results in improvement in 60–90% of the cases. However, this high success rate cannot be expected in usual clinical practice. We prospectively investigated the effectiveness of a treatment regimen consisting of home‐based exercises (concentric, eccentric, and stretching) and optional glucocorticosteroid (GCS) injections in patients with (AT) in a usual clinical setting. Patients unable to commence or progress in exercise were offered GCS, hypothesizing that the GCS would facilitate exercise. Ninety‐three consecutive patients with AT referred to two outpatient rheumatology clinics were registered, and seen at five visits over a 6‐month period. Exercises seemed to have a slow, but long‐lasting effect with GCS having a dramatic short‐term effect on symptoms. Twenty‐six percent of the patients could proceed with training alone, the remainder received one to three supplementary GCS. There were significant improvements on all outcome variables over time (P ≤ 0.001). At follow‐up, 42 had no more symptoms, 29 good result, 16 slightly improved, 4 unchanged, and 2 slightly worse. Overall, 94% of the patients had improved, and we thus recommend the use of GCS injections in AT patients if training alone does not lead to improvement.     

Strenuous resistance exercise effects on magnetic resonance diffusion parameters and muscle–tendon function in human skeletal muscle

Purpose:

To assess the effects of strenuous exercise on magnetic resonance diffusion parameters and muscle–tendon complex function in skeletal muscle.

Materials and Methods:

Six men performed ankle plantar flexion exercises with eccentric contraction. The fractional anisotropy (FA), λ₁, λ₂, λ₃, mean diffusivity (MD), and T₂ values in the triceps surae muscles were measured by magnetic resonance diffusion tensor and spin‐echo imaging. Passive torque of plantar flexors, maximal voluntary isometric plantar flexion torques (MVIP), and Achilles tendon stiffness during MVIP were measured by combined ultrasonography and dynamometry. Plasma creatine kinase and muscle soreness were also assessed. These parameters were measured before and 1–8 days postexercise.

Results:

The medial gastrocnemius exhibited significantly decreased FA 2–5 days after, increased λ₂ 3 days after, and increased λ₃ 2 and 3 days after exercise. This muscle also showed significantly increased MD and T₂ values 3 days postexercise. MVIP significantly decreased 2 and 3 days postexercise, while passive torque significantly increased 2 days postexercise. Creatine kinase and muscle soreness increased 3–5 days and 1–5 days postexercise, respectively.

Conclusion:

Exercise‐induced muscle damage manifested as significant changes in muscle diffusion parameters with muscle–tendon complex dysfunction and delayed‐onset muscle soreness. J. Magn. Reson. Imaging 2011;. © 2011 Wiley‐Liss, Inc.     

Concomitant changes in cross‐sectional area and water content in skeletal muscle after resistance exercise

This study investigated how one bout (1EX) and three bouts (3EX) of strenuous resistance exercise affected the cross‐sectional area (CSA) and water content (WC) of the quadriceps muscle and patella tendon (PT), 4 h and 52 h after the last exercise bout. Ten healthy untrained male subjects performed 1EX with one leg and 3EX with the other leg. CSA and WC were measured with magnetic resonance imaging 10, 20 and 30 cm proximal to the tibia plateau (TP) for the muscle, and at the proximal, central and distal site for the PT prior to exercise, and 4 h and 52 h after the last exercise bout. Ten centimeter above the TP, muscle CSA was significantly increased at 4 h (1EX: 13 ± 5%; 3EX: 13 ± 4%) and 52 h (1EX: 16 ± 5%; 3EX: 16 ± 5%) compared with baseline. Muscle WC was significantly increased at 4 h (1EX: 7 ± 1%; 3EX: 6 ± 2%) and 52 h (1EX: 8 ± 2%; 3EX: 8 ± 3%) compared to baseline. PT central CSA was significantly reduced at 52 h (3EX: 14 ± 2%) compared with baseline and (3EX: 13 ± 1%) compared with 4 h. Present data demonstrate that strenuous resistance exercise results in an acute increase in muscle WC and underlines the importance of ensuring sufficient time between the last exercise bout and the determination of anatomical dimensions in muscles.     

Effect of habitual exercise on the structural and mechanical properties of human tendon, in vivo, in men and women

We examined whether long-term habitual training (a) was associated with differences in structural and mechanical properties in tendon in women and (b) yielded different tendon properties in men and women. Ten male runners, 10 female runners and 10 female non-runners were tested. Tendon cross-sectional area (CSA) and length of the patellar and Achilles tendon were determined with MRI. Ultrasonography-based measurement of tendon elongation and force during isometric contractions provided mechanical properties. Distal patellar and Achilles tendon CSAs were greater than the proximal part in all three groups (P<0.05). Weight-normalized Achilles tendon CSA were similar in trained (2.78+/-0.17 mm(2)/kg(3/4)) and untrained women (2.60+/-0.13 mm(2)/kg(3/4)), while that in trained men (3.77+/-0.27 mm(2)/kg(3/4)) was greater compared with trained women (P<0.01). Patellar tendon CSA were comparable in trained and untrained women, while that in trained men was greater compared with trained women (P<0.01). Patellar tendon stiffness was greater in male runners (3528+/-773 N/mm) compared with female runners (2069+/-666 N/mm) and non-runners (2477+/-381 N/mm), (P<0.01), but patellar tendon deformation, stress, strain and modulus were similar. These data indirectly suggest that the ability of Achilles and patellar tendons to adapt in response to habitual loading such as running is attenuated in women.     

腘肌及胭肌腱损伤的MR诊断

目的 回顾性分析胭肌及胭肌腱损伤的MR表现,了解其影像学特征,提高诊断和鉴别诊断水平,减少误诊率.方法 患者共26例,均行膝关节外旋15°的矢状位快速自旋回波T1WI序列、矢状位脂肪抑制STIR序列和冠状位自旋回波T2 WI及质子相双回波序列扫描.结果 26例患者中,单纯胭肌损伤为11例,胭肌腱损伤5例,胭肌及腘肌腱同时损伤者为10例.胭肌及腘肌腱的损伤,以矢状位脂肪抑制STIR序列及冠状位自旋回波T2WI序列显示病变最为清楚,可显示胭肌急慢性损伤水肿所致的长T2高信号,同时可显示胭肌腱撕裂所致的连续性中断.轴位快速自旋回波T2加权序列也可清楚显示胭肌损伤所致信号异常.结论 MR成像是显示胭肌及胭肌腱损伤最佳的影像学手段,通过常规方位扫描图像可做出准确的诊断.     

The impact of regular activity and exercise intensity on the acute effects of resistance exercise on cognitive function

Beneficial acute effects of resistance exercise on cognitive functions may be modified by exercise intensity or by habitual physical activity. Twenty-six participants (9 female and 17 male; 25.5 ± 3.4 years) completed four resistance exercise interventions in a randomized order on separate days (≥48 h washout). The intensities were set at 60%, 75%, and 90% of the one repetition maximum (1RM). Three interventions had matched workloads (equal resistance*n_repetitions). One intervention applied 75% of the 1RM and a 50% reduced workload (resistance*n_repetitions = 50%). Cognitive attention (Trail Making Test A—TMTA), task switching (Trail Making Test B—TMTB), and working memory (Digit Reading Spans Backward) were assessed before and immediately after exercise. Habitual activity was assessed as MET hours per week using the International Physical Activity Questionnaire. TMTB time to completion was significantly shorter after exercise with an intensity of 60% 1RM and 75% 1RM and 100% workload. Friedman test indicated a significant effect of exercise intensity in favor of 60% 1RM. TMTA performance was significantly shorter after exercise with an intensity of 60% 1RM, 90% 1RM, and 75% 1RM (50% workload). Habitual activity with vigorous intensity correlated positively with the baseline TMTB and Digit Span Forward performance but not with pre- to post-intervention changes. Task switching, based on working memory, mental flexibility, and inhibition, was beneficially influenced by acute exercise with moderate intensity whereas attention performance was increased after exercise with moderate and vigorous intensity. The effect of regular activity had no impact on acute exercise effects.     

Effects of high‐intensity interval cycling performed after resistance training on muscle strength and hypertrophy

Aim of the study was to investigate whether high‐intensity interval cycling performed immediately after resistance training would inhibit muscle strength increase and hypertrophy expected from resistance training per se. Twenty‐two young men were assigned into either resistance training (RE; N = 11) or resistance training plus high‐intensity interval cycling (REC; N = 11). Lower body muscle strength and rate of force development (RFD), quadriceps cross‐sectional area (CSA) and vastus lateralis muscle architecture, muscle fiber type composition and capillarization, and estimated aerobic capacity were evaluated before and after 8 weeks of training (2 times per week). Muscle strength and quadriceps CSA were significantly and similarly increased after both interventions. Fiber CSA increased significantly and similarly after both RE (type I: 13.6 ± 3.7%, type IIA: 17.6 ± 4.4%, type IIX: 23.2 ± 5.7%, P < 0.05) and REC (type I: 10.0 ± 2.7%, type IIA: 14.8 ± 4.3% type IIX: 20.8 ± 6.0%, P < 0.05). In contrast, RFD decreased and fascicle angle increased (P < 0.05) only after REC. Capillary density and estimated aerobic capacity increased (P < 0.05) only after REC. These results suggest that high‐intensity interval cycling performed after heavy‐resistance exercise may not inhibit resistance exercise‐induced muscle strength/hypertrophy after 2 months of training, while it prompts aerobic capacity and muscle capillarization. The addition of high‐intensity cycling after heavy‐resistance exercise may decrease RFD partly due to muscle architectural changes.     

Neuromuscular determinants of explosive torque: Differences among strength-trained and untrained young and older men

This study compared the differences in neural and muscular mechanisms related to explosive torque in chronically strength-trained young and older men (>5 years). Fifty-four participants were allocated into four groups according to age and strength training level: older untrained (n = 14; 65.6 ± 2.9 years), older trained (n = 12; 63.6 ± 3.8 years), young untrained (n = 14; 26.2 ± 3.7 years), and young trained (n = 14; 26.7 ± 3.4 years). Knee extension isometric voluntary explosive torque (absolute and normalized as a percentage of maximal voluntary torque) was assessed at the beginning of the contraction (ie, 50, 100, and 150 ms—T50, T100, and T150, respectively), and surface electromyogram (sEMG) amplitude (normalized as a percentage of sEMG recorded during maximal voluntary isometric contraction) at 0-50, 50-100, and 100-150 time windows. Supramaximal electrically evoked T50 was assessed with octet trains delivered to the femoral nerve (8 pulses at 300 Hz). Voluntary T50, T100, and T150 were higher for trained than untrained in absolute (P < 0.001) and normalized (P < 0.030) terms, accompanied by higher sEMG at 0-50, 50-100, and 100-150 ms (P < 0.001), and voluntary T50/octet T50 ratio for trained. Greater octet T50 was observed for the young trained (P < 0.001) but not for the older trained (P = 0.273) compared to their untrained counterparts. Age effect was observed for voluntary T50, T100, and T150 (P < 0.050), but normalization removed these differences (P > 0.417). Chronically strength-trained young and older men presented a greater explosive torque than their untrained pairs. In young trained, the greater explosive performance was attributed to enhanced muscular and neural mechanisms, while in older trained to neural mechanisms only.     

Skeletal muscle IL‐15/IL‐15Rα and myofibrillar protein synthesis after resistance exercise

In vitro and in vivo studies described the myokine IL ‐15 and its receptor IL ‐15Rα as anabolic/anti‐atrophy agents, however, the protein expression of IL ‐15Rα has not been measured in human skeletal muscle and data regarding IL ‐15 expression remain inconclusive. The purpose of the study was to determine serum and skeletal muscle IL ‐15 and IL ‐15Rα responses to resistance exercise session and to analyze their association with myofibrillar protein synthesis (MPS ). Fourteen participants performed a bilateral leg resistance exercise composed of four sets of leg press and four sets of knee extension at 75% 1RM to task failure. Muscle biopsies were obtained at rest, 0, 4 and 24 hours post‐exercise and blood samples at rest, mid‐exercise, 0, 0.3, 1, 2, 4 and 24 hours post‐exercise. Serum IL ‐15 was increased by ~5.3‐fold immediately post‐exercise, while serum IL ‐15Rα decreased ~75% over 1 hour post‐exercise (P <.001). Skeletal muscle IL ‐15Rα mRNA and protein expression were increased at 4 hours post‐exercise by ~2‐fold (P <.001) and ~1.3‐fold above rest (P =.020), respectively. At 24 hours post‐exercise, IL ‐15 (P =.003) and IL ‐15Rα mRNA s increased by ~2‐fold (P =.002). Myofibrillar fractional synthetic rate between 0‐4 hours was associated with IL ‐15Rα mRNA at rest (r =.662, P =.019), 4 hours (r =.612, P =.029), and 24 hours post‐exercise (r =.627, P =.029). Finally, the muscle IL ‐15Rα protein up‐regulation was related to Leg press 1RM (r =.688, P =.003) and total weight lifted (r =.628, P =.009). In conclusion, IL ‐15/IL ‐15Rα signaling pathway is activated in skeletal muscle in response to a session of resistance exercise.     

Effects of elastic taping,non-elastic taping and static stretching on recovery after intensive eccentric exercise

The purpose of this study was to compare the effect of elastic tape (Kinesio tape) to placebo tape or static stretching on delayed onset muscle soreness. Fifty-one untrained female healthy volunteers were randomly assigned into three groups (n = 17/group), elastic tape, placebo tape and stretching group. Muscle soreness was induced by 4 sets of 25 maximal isokinetic (60°.s^?1) eccentric contractions of dominant quadriceps on an isokinetic dynamometer. Compared with placebo tape, the elastic tape participants had less muscle soreness at 72 h post-exercise (p = 0.01). The elastic tape also increased isometric strength at 72 h post-exercise compared with the placebo (p = 0.03) and stretching group (p = 0.02). However, there was little effect between groups for changes in thigh circumference, jumping, pressure pain threshold, rate of perceived exertion, creatine kinase activity and joint motion. Elastic taping increased muscle strength recovery and reduced muscle soreness after intensive exercise.     

Patients with schizophrenia have impaired muscle force‐generating capacity and functional performance

Patients with schizophrenia have impaired physical health. However, evidence of how skeletal muscle force‐generating capacity (FGC), a key component of functional performance, may contribute to the impairment is scarce. Thus, the aim of this study was to investigate the patient groups’ skeletal muscle FGC and its association with functional performance. Leg‐press FGC was assessed along with a battery of functional performance tests in 48 outpatients (28 men, 34 ± 10 years; 20 women, 36 ± 12 years) with schizophrenia spectrum disorder (ICD‐10, F20‐29), and compared with 48 healthy age‐ and gender‐matched references. Results revealed reduced one‐repetition maximum (1RM) in men (?19%, P < .01) and a trend toward reduction in women (?13%, P = .067). The ability to develop force rapidly was also impaired (men: ?30%; women: ?25%, both P < .01). Patients scored worse than healthy references on all physical performance tests (stair climbing: ?63%; 30‐second sit‐to‐stand (30sSTS): ?48%; six‐minute walk test (6MWT): ?22%; walking efficiency: ?14%; and unipedal stance eyes open: ?20% and closed: ?73%, all P < .01). 1RM correlated with 6MWT (r = .45), stair climbing (r = ?.44), 30sSTS (r = .43), walking efficiency (r = .26), and stance eyes open (r = .33) and closed (r = .45), all P < .01. Rapid force development correlated with 6MWT (r = .54), stair climbing (r = ?.49), 30sSTS (r = .45), walking efficiency (r = .26), and stance eyes open (r = .44) and closed (r = .51), all P < .01. In conclusion, skeletal muscle FGC and functional performance are reduced in patients with schizophrenia and should be recognized as important aspects of the patient groups’ impaired health. Resistance training aiming to improve these components should be considered an important part of clinical treatment.     

Minute oscillation stretching: A novel modality for reducing musculo‐tendinous stiffness and maintaining muscle strength

A novel stretching modality was developed to provide repetitive small length changes to the plantar flexors undergoing passive stretch defined as "minute oscillation stretching" (MOS). This study investigated the effects of MOS on neuromuscular activity during force production, the rate of torque development (RTD), and the elastic properties of the plantar flexors and Achilles tendon. Ten healthy males participated in this study. The neuromuscular activity of the triceps surae and tibialis anterior muscles during maximal voluntary plantar flexion torque [MVT], RTD of plantar flexion, Achilles tendon stiffness, and muscle stiffness were measured before and after two types of interventions for a total of 5 minutes: static stretching (SS) and MOS at 15 Hz and without intervention (control). Achilles tendon stiffness was calculated from the tendon elongation measuring by ultrasonography. Muscle stiffness was determined for the medial gastrocnemius [MG] using shear wave elastography. The MVT, mean electromyographic amplitudes [mEMG] of MG and lateral gastrocnemius [LG], and RTD were significantly decreased following SS (MVT: ?7.2 ± 7.9%; mEMG of MG: ?8.7 ± 10.2%; mEMG of LG: ?12.4 ± 10.5%; RTD: ?6.6 ± 6.8%), but not after MOS. Achilles tendon stiffness significantly decreased after SS (?13.4 ± 12.3%) and MOS (?9.7 ± 11.5%), with no significant differences between them. Muscle stiffness significantly decreased in SS and MOS, with relative changes being significantly greater for MOS (?7.9 ± 8.3%) than SS (?2.3 ± 2.9%) interventions. All variables remained unchanged in the controls. In conclusion, MOS changed muscle‐tendon compliance without loss of muscle function.     

Contralateral effects of eccentric resistance training on immobilized arm

This study compared the effects of contralateral eccentric‐only (ECC) and concentric‐/eccentric‐coupled resistance training (CON‐ECC) of the elbow flexors on immobilized arm. Thirty healthy participants (18‐34 y) were randomly allocated to immobilization only (CTRL; n = 10), immobilization and ECC (n = 10), or immobilization and CON‐ECC group (n = 10). The non‐dominant arms of all participants were immobilized (8 h·day^?1) for 4 weeks, during which ECC and CON‐ECC were performed by the dominant (non‐immobilized) arm 3 times a week (3‐6 sets of 10 repetitions per session) with an 80%‐120% and 60%‐90% of one concentric repetition maximum (1‐RM) load, respectively, matching the total training volume. Arm circumference, 1‐RM and maximal voluntary isometric contraction (MVIC) strength, biceps brachii surface electromyogram amplitude (sEMG_RMS), rate of force development (RFD), and joint position sense (JPS) were measured for both arms before and after immobilization. CTRL showed decreases (P < .05) in MVIC (?21.7%), sEMG_RMS (?35.2%), RFD (?26.0%), 1‐RM (?14.4%), JPS (?87.4%), and arm circumference (?5.1%) of the immobilized arm. These deficits were attenuated or eliminated by ECC and CON‐ECC, with greater effect sizes for ECC than CON‐ECC in MVIC (0.29: +12.1%, vs ?0.18: ?0.1%) and sEMG_RMS (0.31:17.5% vs ?0.15: ?5.9%). For the trained arm, ECC showed greater effect size for MVIC than CON‐ECC (0.47 vs 0.29), and increased arm circumference (+2.9%), sEMG_RMS (+77.9%), and RDF (+31.8%) greater (P < .05) than CON‐ECC (+0.6%, +15.1%, and + 15.8%, respectively). The eccentric‐only resistance training of the contralateral arm was more effective to counteract the negative immobilization effects than the concentric‐eccentric training.     

Prospective analysis of intrinsic and extrinsic risk factors on the development of Achilles tendon pain in runners

There are currently no generally accepted, consistent results that clearly characterize factors causing Achilles tendon pain (AT) in runners. Therefore, we carried out a prospective study to evaluate the multifactorial influence of clinical, biomechanical (isometric strength measurements and three‐dimensional kinematics) and training‐related risk factors on the development of AT. Two hundred sixty‐nine uninjured runners were recruited and underwent an initial examination. One hundred forty‐two subjects completed their participation by submitting training information on a weekly basis over a maximal period of 1 year. Forty‐five subjects developed an overuse injury, with 10 runners suffering from AT. In an uninjured state, AT runners already demonstrated decreased knee flexor strength and abnormal lower leg kinematics (sagittal knee and ankle joint) compared with a matched control group. A relationship between years of running experience or previous overuse injuries and the development of new symptoms could not be established. The interrelationship of biomechanical and training‐specific variables on the generation of AT is evident. A combination of alterations in lower leg kinematics and higher impacts caused by fast training sessions might lead to excessive stress on the Achilles tendon during weight bearing and thus to AT in recreational runners.     

Stimulation of muscle protein synthesis by whey and caseinate ingestion after resistance exercise in elderly individuals

Sarcopenia is a well-known phenomenon in elderly individuals and resistance exercise together with sufficient amino acid (AA) availability has proved to be a counteractive implement. However, the source of AA and supplement timing require further investigation. The objective was to compare muscle protein synthesis (MPS) to intakes of whey and caseinate after heavy resistance exercise in healthy elderly individuals, and, furthermore, to compare the timing effect of caseinate intake. Twenty-four elderly men and women (mean ± SEM; 68 ± 1 years) were randomized to one of four groups: caseinate intake before exercise (CasPre), caseinate intake immediately after exercise (CasPost), whey intake immediately after exercise (Whey), or intake of a non-caloric control drink (Control). Muscle myofibrillar and collagen fractional synthesis rates (FSR) were measured by a primed continuous infusion of L-[1-(13) C]leucine using labeled proteins during a 6-h recovery period. No differences were observed in muscle myofibrillar and collagen FSR with Whey (0.09 ± 0.01%/h) compared with CasPost (0.09 ± 0.003%/h), and it did not differ between CasPre (0.10 ± 0.01%/h) and CasPost. MPS does not differ with whey and caseinate feeding immediately after heavy resistance exercise in elderly individuals, and MPS is similar with caseinate ingestion before and after exercise.