Isokinetic Resistance Training Research Articles

A 6-week randomized-controlled field study: effect of isokinetic eccentric resistance training on strength, flexibility and muscle structure of the shoulder external rotators in male junior handball players.

Background: Team handball involves a tremendous amount of shoulder motion with high forces during repeated extended external range of motion. This causes shoulder complaints and overuse injuries. While eccentric training for the lower extremity shows preventive effects by improving strength, range of motion and fascicle length, there is a research gap for the shoulder joint and for advanced tissue characterization using diffusion tensor imaging. Objectives: To investigate the effects of 6-week eccentric isokinetic resistance training on strength, flexibility, and fiber architecture characteristics of the external rotators compared to an active control group in junior male handball players. Methods: 15 subjects were randomly assigned to the eccentric training group and 14 subjects to the active control group (conventional preventive training). Primary outcome measures were eccentric and concentric isokinetic strength of the external rotators, range of motion, and muscle fascicle length and fascicle volume. Results: The intervention group, showed significant changes in eccentric strength (+15%). The supraspinatus and infraspinatus muscles showed significant increases in fascicle length (+13% and +8%), and in fractional anisotropy (+9% and +6%), which were significantly different from the control group. Conclusion: Eccentric isokinetic training has a significant effect on the function and macroscopic structure of the shoulder external rotators in male junior handball players. While strength parameters and muscle structure improved, range of motion did not change. This research helps understanding the physiology of muscle and the role of eccentric training on shoulder function and muscle structure. Furthermore, DTI was found to be a promising tool for advanced tissue characterization, and the in vivo derived data can also serve as model input variables and as a possibility to extend existing ex-vivo muscle models. Future research is needed for functional and structural changes following convenient eccentric field exercises.

The effectiveness of unilateral isokinetic resistance training on cross-education is independent of contraction velocity: a case of female dorsiflexors and plantar flexors.

The large body of published literature has shown that the effects of strength training can transfer from trained to untrained homologous limb muscles after unilateral training. These effects on strength have been shown to be very specific to the type and speed of training contraction. The aim of this study was to investigate the effects of a 4-week unilateral slow and fast velocity isokinetic concentric training, to compare the effects, and thus investigate whether these effects are speed-specific. Forty-four healthy female students allocated to slow training, fast training, or control performed 12 isokinetic concentric-concentric plantar/dorsal flexors training sessions (3 × 4 weeks) using their nondominant leg. Participants in the two experimental groups showed statistically significant gains in strength in both the trained (ranging from 8 to 41%) and untrained leg (5-26%), thus showing cross-education on strength effects. The present study demonstrated that 4 weeks (12 training sessions) of unilateral isokinetic resistance training in the concentric mode improved the strength of contralateral, untrained homologous muscles to the same extent, regardless of the contraction velocity used in females. Furthermore, the amount of concentric overload (50% more than during 60°/s) did not appear to affect the increase in strength gains. Therefore, practitioners are encouraged to use both training speeds when strength gains in the contralateral leg are the primary goal. If the training time is limited, however, training with a higher contraction speed is recommended.

Isokinetic Resistance Training for Ankle Plantarflexor Spasticity and Muscle Weakness in People With Multiple Sclerosis: A Proof-of-Concept Case Series.

To the best of the authors' knowledge, no data are available about the use of isokinetic resistance training for managing ankle plantarflexor spastic hypertonia in people with multiple sclerosis (MS). The aim of this proof-of-concept study was to explore the feasibility and effects of concentric contractions on spasticity-related resistance to passive motion, strength, and mobility in people with MS and ankle plantarflexor spasticity. In this pretest/posttest case series, 5 people with MS (mean age = 53.6 [SD = 8.8] years; median Expanded Disability Status Scale score = 5; Modified Ashworth Scale range = 1-4) received 6weeks of isokinetic resistance training of the spastic plantarflexors. Before and after the intervention, the following outcomes were assessed: average peak torque during passive robotic mobilization, isometric strength, surface electromyography (sEMG) from the spastic muscles, time to complete the 10-m Walk Test, and the Timed "Up & Go" Test. The standardized effect size was used to test pretest and posttest effects at the individual level. Group-level analyses were also performed. Following the training, the average peak torque recorded from the plantarflexors during passive motion at a velocity of 150 degrees per second was found to be decreased by at least 1 SD in all participants but 1, with a significant reduction at the group level of 23.8%. Conversely, no changes in sEMG activity were detected. Group-level analyses revealed that the maximal strength of the trained plantarflexors increased significantly (31.4%). Fast walking speed increased and time to complete the Timed "Up & Go" Test decreased in 4 participants, although not significantly at the group level. Isokinetic resistance training proved safe and feasible in people who had MS and ankle plantarflexor spasticity. The observed reductions in resistance to passive motion from the spastic plantarflexors in the absence of sEMG changes might suggest a mechanical rather than a neural effect of the training. Based on these preliminary findings, isokinetic resistance training does not exacerbate hypertonia in people with MS and ankle plantarflexor spasticity and could be safely used to manage muscle weakness in this population.

Comparison of Traditional and Rest-Redistribution Sets on Indirect Markers of Muscle Damage Following Eccentric Exercise.

Merrigan, JJ, Jones, MT, Malecek, J, Padecky, J, Omcirk, D, Xu, N, Peñailillo, L, and Tufano, JJ. Comparison of traditional and rest-redistribution sets on indirect markers of muscle damage following eccentric exercise. J Strength Cond Res 36(7): 1810-1818, 2022-The purpose was to investigate the effect of rest-redistribution (RR) on muscle damage after eccentric knee extensions. After 2 weeks of eccentric familiarization, 11 resistance-trained men performed 2 work-matched isokinetic unilateral eccentric knee extension protocols at 60°·s-1 using a crossover design, separated by 7 days. Subjects performed 40 repetitions with 285 seconds of rest using traditional sets (TS; 4 sets of 10 with 95 seconds of interset rest) and RR (RR; 20 sets of 2 with 15 seconds of interset rest). Muscle morphology, tensiomyography, range of motion, perceived soreness, and strength were measured before and 0, 24, 48, 72, and 96 hour after RR and TS. There were no protocol × time interactions (p < 0.05). When collapsed across protocol and compared to baseline, echo intensity of the proximal vastus lateralis was 7 ± 9% greater at 0 hour (p = 0.042), echo intensity of the distal vastus lateralis was 6 ± 7% and 9 ± 7% greater at 0 hour (p = 0.048) and 24 hour (p < 0.001), respectively, and passive ROM was 2 ± 1% lower at 48 hour (p = 0.043) after exercise. No other differences existed over time for any other variable. Thus, contrary to concentric performance where RR likely plays a large role in maintaining performance, RR during eccentric isokinetic resistance training does not strongly influence exercise performance and indications of subsequent muscle damage.

Effects of Physical Rehabilitation on Spatiotemporal Gait Parameters and Ground Reaction Forces of Patients with Intermittent Claudication.

Chronic ischemia of the lower extremities often presents as intermittent claudication characterized by lower limb pain which subsides after a short break. This study aimed to provide an assessment of the spatiotemporal parameters of gait and ground reaction forces in patients with PAD participating in three forms of supervised physical training. A total of 80 subjects completed a three-month supervised physical rehabilitation program with three sessions per week. The subjects were assigned to one of three programs: group 1—standard walking training on a treadmill (TT); group 2—Nordic walking (NW) training; group 3—strength and endurance training comprised of NW with isokinetic resistance training (NW + ISO). Gait biomechanics tests (kinematic and kinetic parameters of gait) and a six-minute walk test were carried out before and after three months of physical training. Nordic walking training led to the greatest improvements in the gait pattern of patients with PAD and a significant increase in the absolute claudication distance and total gait distance. Combined training (NW + ISO) by strengthening the muscles of the lower extremities increased the amplitude of the general center of gravity oscillation to the greatest extent. Treadmill training had little effect on the gait pattern. Nordic walking training should be included in the rehabilitation of patients with PAD as a form of gait training, which can be conducted under supervised or unsupervised conditions.

Design and Isokinetic Training Control Method of Leg Press Training Device

Lower-limb function in elderly people gradually degenerates with age, and poor rehabilitation conditions preventing the elderly from receiving scientific rehabilitation training result in the decline of social labor force and the increased economic burden of the elderly. Aiming at the characteristics of the single function and the complex structure of an existing telescopic leg trainer combined with the needs of the application group, a new type of leg-stretching training device with multiple training modes for lower extremity extension and flexion of the elderly is proposed. A new mechanical structure and electrical system is designed. At the same time, the anti-resistance training man–machine model is analyzed, aiming at the isokinetic resistance training mode, and a training controller strategy based on a fuzzy synovial algorithm is proposed. Finally, the feasibility of the designed controller strategy and the proposed leg training device are verified by prototype experiments, which will guide further research.

Cross-education: effects of age on rapid and maximal voluntary contractile characteristics in males.

The purpose of this study was to determine the effect of age on the cross-education of rapid and maximal contractile properties for the knee extensors. Young (n = 10; age = 21.1 ± 1.7years) and older (n = 10; age = 65.3 ± 8.3years) males performed unilateral isokinetic resistance training (RT) of the knee extensors for 4weeks. Maximal voluntary isokinetic (45°s-1 and 300°s-1) and isometric testing was conducted for the trained and untrained leg before and after RT. Peak torque (PT) and acceleration were obtained from isokinetic testing as well as torque at 30ms (TQ30) and 100ms (TQ100) from the 45°s-1 contraction. PT and rate of torque development were recorded from the isometric contractions. Independent of age, isometric PT (10.1%; p = 0.006) as well as PT and acceleration at 300°s-1 (6.7%; p = 0.008 and 4.0%; p = 0.016, respectively) increased in the untrained leg. At 45°s-1, acceleration was increased (3.6%; p = 0.021), but PT remained unchanged (p = 0.227). TQ100 increased similarly between groups (4.5%; p = 0.014), but TQ30 increased only in the older group (9.5%; p = 0.022). Cross-education of rapid and maximal contractile parameters can be achieved early during unilateral RT independent of age. These findings indicate the potential for particular unilateral RT protocols to be used for older adults in rehabilitative settings to offset disuse-related reductions in contractile function, which are most dramatic in this population.

Isokinetic resistance training combined with eccentric overload improves athletic performance and induces muscle hypertrophy in young ice hockey players

ObjectivesTo determine the combined effects of slow isokinetic resistance training and eccentric overload and compare it to traditional resistance training on strength, power, body composition and muscle hypertrophy in young ice hockey players. DesignExperimental, randomized trial. MethodsTwenty-two resistance-trained ice hockey players (18±1year) were assigned to either isokinetic resistance training and eccentric overload (ISO/ECC; n=11) or traditional resistance training (TRAD; n=11). Participants underwent supervised progressive resistance training for 8 weeks (2–3 sessions/week) involving lower body multiple-joint exercises (heavy squats and explosive jump squats). The ISO/ECC group performed their training using a computerized robotic engine system (1080 Quantum synchro, Sweden), whereas the TRAD group performed the same resistance exercises with isotonic loading. Before and after the intervention, participants were evaluated in 1RM back squat, loaded jump squats, sprint- and jump performance, body composition and muscle thickness using ultrasound measurement. ResultsSimilar moderate increases in 1RM back squat and power output in the jump squats were found in both the ISO/ECC and TRAD groups (11–17%, P<0.01), whereas only the ISO/ECC group showed improvements in drop jump performance (9.8%, P=0.01). Moreover, similar trivial changes in body composition were observed in both groups, while only the ISO/ECC training group increased muscle thickness in the vastus intermedius (P=0.01) and rectus femoris muscles (P=0.03). ConclusionsBoth modalities effectively increased maximal strength and power output, whereas isokinetic resistance training, combined with eccentric overload, improved drop jump performance and induced greater muscle hypertrophy than traditional training in young ice hockey players.

Enhanced Corticospinal Excitability and Volitional Drive in Response to Shortening and Lengthening Strength Training and Changes Following Detraining.

There is a limited understanding of the neurological adaptations responsible for changes in strength following shortening and lengthening resistance training and subsequent detraining. The aim of the study was to investigate differences in corticospinal and spinal responses to resistance training of the tibialis anterior muscle between shortening or lengthening muscle contractions for 4 weeks and after 2 weeks of detraining. Thirty-one untrained individuals were assigned to either shortening or lengthening isokinetic resistance training (4 weeks, 3 days/weeks) or a non-training control group. Transcranial magnetic stimulation and peripheral nerve stimulation (PNS) were used to assess corticospinal and spinal changes, respectively, at pre-, mid-, post-resistance training and post detraining. Greater increases changes (P < 0.01) in MVC were found from the respective muscle contraction training. Motor evoked potentials (expressed relative to background EMG) significantly increased in lengthening resistance training group under contraction intensities ranging from 25 to 80% of the shortening and lengthening contraction intensity (P < 0.01). In the shortening resistance training group increases were only seen at 50 and 80% of both contraction type. Volitional drive (V-wave) showed a greater increase following lengthening resistance training (57%) during maximal lengthening contractions compared to maximal shortening contractions following shortening resistance training (23%; P < 0.001). During the detraining period MVC and V-wave did not change (P > 0.05), although MEP amplitude decreased during the detraining period (P < 0.01). No changes in H-reflex were found pre to post resistance training or post detraining. Modulation in V-wave appeared to be contraction specific, whereby greatest increases occurred following lengthening resistance training. Strength and volitional drive is maintained following 2 weeks detraining, however corticospinal excitability appears to decrease when the training stimulus is withdrawn.

Are the Responses to Resistance Training Different Between the Preferred and Nonpreferred Limbs?

Humans preferentially recruit limbs to functionally perform a range of daily tasks, which may lead to performance asymmetries. Because initial training status plays an important role in the rate of progression during resistance training, could asymmetries between the preferred and nonpreferred limbs lead to different magnitudes of strengthening during a resistance training program? This issue motivated this study, in which 12 healthy and physically active men completed a 4-week control period followed by a 12-week isokinetic resistance training program, performed twice a week, including 3-5 sets of 10 maximal eccentric contractions for each limb. Every 4 weeks, knee extensor peak torques at concentric, isometric, and eccentric tests were measured using an isokinetic dynamometer and the sum of quadriceps muscle thickness was determined by ultrasound images. Before training, concentric peak torque was similar between limbs but isometric and eccentric peak torques were significantly smaller in the nonpreferred compared with the preferred limb (4.9 and 5.8%, respectively). Bilateral strength symmetry remained constant throughout the training period for concentric tests. For eccentric and isometric tests, symmetry was reached at the fourth and eighth training weeks, respectively. After 12 weeks, between-limb percent nonsignificant differences were -0.62% for isometric and -1.93% for eccentric tests. The sum of knee extensor muscle thickness had similar values before training and presented similar changes throughout the study for both the preferred and the nonpreferred limbs. In conclusion, the nonpreferred limb presents higher strength gain than the preferred limb at the initial phase of an isokinetic resistance training program, and this increased strength gain is not associated with muscle hypertrophy.

Characterization of ankle dorsiflexors performance in healthy subjects following maximal-intensity isokinetic resistance training

The purpose of this randomized trial was to examine, in healthy subjects, the effect of unilateral isokinetic–concentric training of the dominant ankle dorsiflexors (DF) on the peak moment (PM), mean PM (MPM), maximal work and mean work (meanW).Thirty volunteers (26.7±4.6years old) underwent bilateral isokinetic testing of ankle DF at 45 and 90°/s. Participants were randomly assigned to a control or a training group. The training lasted 4weeks (4-day/week).All dynamometric parameters increased significantly only in the training group for the trained leg (p<0.05), with greater gains in work (32–47% at 45°/s and 31–41% at 90°/s) than moment variables (14–18% at 45°/s and 14–28% at 90°/s). Similar increases in strength were also noted at both angular velocities in the untrained leg (p<0.01) for both work and moment parameters, depicting a cross-training effect. Correlations between ‘moments’ and ‘works’ increased in both legs after training from 0.59–0.77 to 0.79–0.95. Principal component analysis indicated that, at baseline, PM showed the highest weight on DF performance; after training, meanW at 90°/s and MPM at 45°/s exhibited the highest loadings.High-intensity training of ankle DF increase the ability in generating energy throughout the entire range of motion rather than maximizing the PM.

Fadiga muscular entre séries de exercícios isocinéticos em mulheres jovens

OBJETIVO: Avaliar o efeito de dois Intervalos de Recuperação (IR) no pico de torque (PT) e no trabalho total (TT) isocinético em mulheres jovens. MÉTODOS: 17 mulheres, destreinadas, (27,2 ± 4,1 anos; 56,8 ± 6,9 kg; 162,6 ± 7,0 cm) realizaram três séries de 10 extensões isocinéticas do joelho a 60° e 180°/s, com um e dois minutos de IR. A análise estatística foi a ANOVA dois x três [IR (um e dois minutos) x série (1ª, 2ª e 3ª)] com α &lt; 0.05. RESULTADOS: Um minuto de IR não foi suficiente para manter o PT e o TT ao longo das séries (p&lt;0,05) a 60º (redução de 15,7% no PT e 19,8% no TT) e 180º/s (redução de 3,6% no PT e de 5,6% no TT). Dois minutos foram suficientes apenas a 180º/s. Contudo, a 60°/s, dois minutos de IR possibilitou um maior PT na segunda e na terceira série em relação a um minuto (p&lt;0,05). CONCLUSÃO: Dois minutos são suficientes para manutenção do PT em um protocolo de treinamento isocinético a 180º/s, mas não a 60º/s em mulheres jovens.

Are early and late rate of force development differently influenced by fast‐velocity resistance training?

This study examined the effect of fast-velocity concentric isokinetic resistance training (FV) on the rate of force development (RFD) at early (<100 ms) and late phases (>100 ms) of rising muscle force. Nine men participated in a 6-week resistance training intervention for the lower body, and nine matched subjects participated as controls (CON). During concentric isokinetic (180°s(-1)) knee extension training, subjects were instructed to do each contraction 'as fast and forcefully as possible'. Maximal muscle strength (MVC) and RFD (0-10, 0-20, …, 0-250 ms from the onset of contraction) were measured during maximal voluntary isometric contraction of the knee extensors (KE). There were no significant changes in MVC of KE in both groups after intervention (FV = 314·2 ± 101·1 versus 338·7 ± 88·0 N∙m, P>0·05; CON = 293·3 ± 94·8 versus 280·0 ± 72·2 N∙m, P>0·05). The RFD increased 39-71% at time intervals up to 90 ms from the onset of the contraction (P<0·05), whereas no change occurred at later time intervals. Similarly, relative RFD (i.e.%MVC∙s(-1)) (RFDr) increased 33-56% at time intervals up to 70 ms from the onset of the contraction (P<0·05). It can be concluded that a short period of resistance training performed with concentric fast-velocity isokinetic muscle contractions is able to enhance RFD and RFDr obtained at the early phase of rising muscle force.

Similar increases in muscle size and strength in young men after training with maximal shortening or lengthening contractions when matched for total work

Training exclusively with eccentric (lengthening) contractions can result in greater muscular adaptations than training with concentric (shortening) contractions. We aimed to determine whether training-induced increases in muscle size and strength differed between muscles performing maximal lengthening (LC) or maximal shortening (SC) contractions when total external work is equivalent. Nine healthy young males completed a 9-week isokinetic (0.79rad/s) resistance training program of the elbow flexors whereby they performed LC with one arm and an equivalent volume of total external work with the contralateral arm as SC. Training increased isometric peak torque for both LC (~10%) and SC (~20%) with no difference (P=0.14) between conditions. There were also similar increases in isokinetic peak torque at both slow (0.79rad/s) and fast (5.24rad/s) shortening and lengthening peak torque for both LC (~8-10%) and SC (~9-20%). Training increased work per repetition similarly for both LC (~17%) and SC (~22%), in spite of ~40% greater work per repetition with LC. The increase in muscle cross-sectional area with training was also similar (P=0.37) between LC (~6.5%) and SC (~4.6%). We conclude that increases in muscle size and strength with short-term unilateral resistance training are unrelated to muscle contraction type when matched for both exercise intensity (i.e. maximal contractions) and total external work.

Preoperative Strength Training for Patients Undergoing High Tibial Osteotomy: A Prospective Cohort Study With Historical Controls

Prospective cohort with historical controls. To examine the effects of a 12-week preoperative high-intensity resistance training program on postoperative outcomes. The primary goals of high tibial osteotomy (HTO) are to decrease pain and improve overall function during activities of daily living and participation in sport and recreation in relatively young, active individuals with knee osteoarthritis. However, the postoperative recovery typically requires a considerable period of protected weight-bearing that can result in substantial deficits in muscular strength. Fourteen patients (mean ± SD, 48.0 ± 7.8 years; 13 males, 1 females), scheduled for medial opening wedge HTO, completed a 12-week preoperative high-intensity isokinetic resistance training program focusing on quadriceps and hamstrings strength. These patients were matched to baseline clinical and demographic characteristics of 14 patients who previously received a medial opening wedge HTO without preoperative training. All outcomes were measured before and 6 months after surgery. The sport and recreation subscale of the Knee Injury and Osteoarthritis Outcome Score (KOOS) was the primary outcome of interest. Secondary outcomes included the other KOOS subscales, scores on the Lower Extremity Functional Scale, and selected kinematic and kinetic variables obtained from 3-dimensional gait analysis. The patients in the preoperative training group achieved significantly greater scores on the KOOS sport and recreation (mean ± SD, 58.6 ± 16.6 versus 42.1 ± 20.4; mean difference, 16.4; 95% CI: 2.0, 30.9) and activities of daily living (mean ± SD, 85.3 ± 9.3 versus 76.9 ± 12.0; mean difference, 8.4; 95% CI: 0.1, 16.8) subscales. There were no significant differences between groups on other outcomes. The present findings suggest preoperative high-intensity resistance training of the quadriceps and hamstrings before HTO improves postoperative functioning in sport, recreation, and activities of daily living. Therapy, level 2b.

Effects of isokinetic resistance training on functional abilities of grade III anterior cruciate ligament injury patients

The purpose of the present study was to investigate if 12 weeks of isokinetic resistance training programme at two different angular velocities (120 and 240°/s) would improve functional abilities of...

The Effects of Slow Velocity Isokinetic Resistance Training on High Velocity Force Output Following a Brief High Velocity Familiarization Period

The Effects of Slow Velocity Isokinetic Resistance Training on High Velocity Force Output Following a Brief High Velocity Familiarization Period

Effect of isokinetic resistance training under a condition of restricted blood flow with pressure

BackgroundThe purpose of the present study was to investigate the effect of isokinetic training under the condition of restricted blood flow with pressure. MethodsThe subjects were 21 athletes at a university. They were classified into four training groups: group A (high speed under restricted blood flow condition with pressure); group B (low speed under restricted blood flow condition with pressure); group C (high speed without restricted blood flow condition); group D (low speed without restricted blood flow condition). The training session consisted of three sets of knee extension and flexion (repeated 10 times) using an isokinetic training machine (Biodex system 3). The training period was 4 weeks, with regular training sessions twice a week during this period. Before and after the training period, all of the subjects underwent measurements of quadriceps muscular strength of concentric contraction (CC) and eccentric contraction (EC) after isokinetic contraction as well as measurement of the thigh diameter. In addition, the group with restricted blood flow with pressure underwent magnetic resonance imaging (MRI). ResultsIn regard to quadriceps muscular strength before and after training, there was a significant difference between groups A and C at many degrees of velocity. For the muscular volume measurements by MRI before and after training, no significant difference was seen in group A or group B. A significant increase was not seen even when comparing groups A and B. ConclusionsIsokinetic resistance training with restricted blood flow with pressure had an effect on muscular strength improvement.

Isokinetic Resistance Training Increases Tibial Bending Stiffness in Young Women

Bone mineral content (BMC) and bone mineral density (BMD) are common but imperfect surrogate measures of bone strength. The mechanical response tissue analyzer is a device that measures long bone bending stiffness (EI), which strongly predicts bone breaking strength. We hypothesized that isokinetic resistance training of the knee flexor and extensor muscles would increase tibial EI, BMC, and BMD in young women. Fifty-two women, aged 18-26 years, performed concentric (CON, n = 30) or eccentric (ECC, n = 22) isokinetic resistance training with the nondominant leg three times per week for 20 weeks. Before and after the training period, subjects were tested for CON and ECC peak torque of the knee flexor and extensor muscles with isokinetic dynamometry, tibial BMC and BMD using dual-energy X-ray absorptiometry, and tibial EI using mechanical response tissue analysis. Both training groups increased CON (15-21%) and ECC (17-31%) peak torque vs. the untrained leg. Tibial EI increased in the entire cohort (26%) and in each training group (CON 34%, ECC 16%) vs. the untrained tibia. Tibial BMC and BMD increased in the trained and untrained tibiae, with no significant differences between limbs. No differential tibial EI or bone mineral outcomes were observed between the CON and ECC training groups. In summary, CON and ECC isokinetic resistance training increased tibial EI, but not BMC or BMD, in young women.

Elderly Women Have Blunted Response to Resistance Training Despite Reduced Antagonist Coactivation

To test the ability of a combination high-velocity/high-resistance training program to enhance knee extensor muscle strength, power, nervous activation of muscle, and muscle activation time in inactive women and compare the response to training between young and old women. The study involved 49 inactive women, with young (18-33 yr, n = 25) and old (65-84 yr, n = 24) distributed to training and control groups using blocked randomization. Electrically evoked muscle twitches were measured for the knee extensors; then maximal, voluntary, isometric knee extensions were performed in a visually cued reaction time (RT) task, followed by 8 wk of explosive resistance training. Training increased peak torque (+12%, P = 0.03) and reduced antagonist coactivation (-13%, P = 0.02) similarly for both age groups. Young training group increased the rate of torque development by 34% compared to young controls (-7%), old training (+9%), and old controls (+8%) (P = 0.002). Young training group increased impulse by 53%, which was greater than young controls (-11%), old training (+12%), and old controls (+9%) (P = 0.001). Resistance training did not change electrically evoked twitch, RT (premotor time, motor time, or reaction time), or nervous activation measures (onset EMG amplitude or rate of EMG rise). Explosive force training was ineffective at enhancing muscle twitch characteristics, neural drive, or RT in young or old women. It did enhance peak muscle force in both young and old, modulated through a reduction in antagonist coactivation. Older participants showed less of an improvement in the rate of torque development and contractile impulse than young, indicating either that this sample of older women had a reduced capacity to develop muscle power or that the 8-wk isokinetic resistance training program used in this study was not a sufficient stimulus for adaptation.