Gladys L. Onambélé

Neuromuscular and balance responses to flywheel inertial versus weight training in older persons

AIM Loss of muscle strength and balance are main characteristics of physical frailty in old age. Postural sway is associated with muscle contractile capacity and to the ability of rapidly correcting ankle joint changes. Thus, resistance training would be expected to improve not only strength but also postural balance. METHODS In this study, age-matched older individuals (69.9+/-1.3 years) were randomly assigned to flywheel (n=12), or weight-lifting (n=12) groups, training the knee extensors thrice weekly for 12 weeks. The hypotheses were that owing to a larger eccentric loading of the knee extensors, flywheel training would result in (a) greater gains in quadriceps strength; (b) greater improvements in balance performance compared with weight-lifting training. Isokinetic dynamometry, B-mode ultrasonography, electromyography, percutaneous muscle stimulation and magnetic resonance imaging were employed to acquire the parameters of interest. RESULTS Following training, knee extensors peak isokinetic power increased by 28% (P<0.01) in the flywheel group with no change in the weight-lifting group. Adaptations of the gastrocnemius muscle also occurred in both groups. The gastrocnemius characteristic with the highest response to training was tendon stiffness, with increases of 54% and 136% in the weight-lifting and flywheel groups, respectively (P<0.01). The larger increase in tendon stiffness in the flywheel group was associated with an improvement in postural balance (P<0.01). CONCLUSION Quadriceps flywheel loading not only produces a greater increase in power than weight training but its physiological benefits also transfer/overspill to the plantarflexor muscle-tendon unit resulting in a significantly improved balance. These findings support our initial hypotheses.

Influence of time of day on tendon compliance and estimations of voluntary activation levels.

We investigated the importance of tendon stiffness on estimations of central activation capacity (CAC). Patella tendon–force elongation relationship, quadriceps torque, and response to 50‐μs, 100‐HZ electrical twitch doublets were studied at ∼8:00 A.M. and ∼6:00 P.M. in 8 healthy young men. Results show that in the evening, as compared with the morning, tendon stiffness decreased by 20.2 ± 9.5% (P = 0.03) and time to twitch peak (Ttp) increased by 55% (P = 0.04). Tendon stiffness and Ttp correlated significantly (r = 0.28, P < 0.05). Whereas the CAC, calculated as the ratio of force preceding the interpolated twitch (IT) to the total force at the peak of the IT, showed no change with time of day, calculations that used twitch ratios suggested CAC decrements (−10.3%, P = 0.03, unpotentiated; −10%, P = 0.02, potentiated ratio) in the evening. This study shows that CAC estimations are invalid when tendon properties are not taken into account, an error that would have important implications in a clinical setting. Muscle Nerve, 2006

Acute changes in knee-extensors torque, fiber pennation, and tendon characteristics.

The aim of the current study was to examine the relationships between quadriceps torque, vastus lateralis pennation angle (θ), and patella tendon stiffness (K) at 07:45 and 17:45 h. Using short‐duration static contractions, simultaneous recordings were made of vastus lateralis (VL) electromyograph (EMG), θ and patella tendon K. Peak isometric extension torque (Peak torque Extcorr) increased by 29.4±6.5% at a knee angle of 70° (p=0.03) in the evening compared to the morning. In the contracted muscle, a 35.0±11.0% (p=0.02) time‐of‐day (TOD)‐related change in θ (to a greater evening compared to morning θ) was observed. Morning and evening measures of θ were also made, both at rest and at a standardized force level (250 N), to separate architecture change effects from increased torque capacity effects. Significant increments in θ in both the resting muscle (13.0±5.1%, p=0.046) and during the standardized exertions (8.0±3.1%, p=0.04) were observed in the evening versus the morning. Increases in θ with TOD were significantly correlated with the 40% (p=0.018) decrease in K both during the standardized contractions (r=0.788, p<0.001) and at rest (r=0.77, p=0.026). These data show that TOD affects K and θ and that these two important factors involved in in‐vivo muscle torque generation capacity are associated. The data also show that despite the potentially deleterious effects of the direction of the changes in both K and θ with TOD, peak torque Extcorr still shows a significant upward shift in the evening relative to the morning.

Patellar tendon properties with fluctuating menstrual cycle hormones.

Burgess, KE, Pearson, SJ, and Onambélé, GL. Patellar tendon properties with fluctuating menstrual cycle hormones. J Strength Cond Res 24(8): 2088-2095, 2010-Debate continues over whether skeletal muscle performance and injury risk vary over the course of the menstrual cycle. Alterations in tendon properties may play a role in the potential fluctuations of both of these variables. The aim of the current study was to determine any association between menstrual cycle phase and corresponding levels of female sex hormones and tendon properties. Fifteen normally menstruating (28-32-day cycles) healthy females (age 23 ± 1 years, mass 63.1 ± 2.6 kg, height 1.66 ± 0.02 m) not taking any form of hormonal contraceptive took part in this study. In vivo patellar tendon properties and associated circulating hormonal levels were assessed on 3 occasions including days 3 ± 0.4, 13 ± 0.2, and 21 ± 0.3. Dynamometry, ultrasonography, electromyography, and biochemical assessment of circulating levels of estradiol and progesterone were utilized. No significant differences were seen in tendon mechanical properties among the 3 phases of the menstrual cycle (p > 0.05). Regressions were carried out and revealed that estrogen and maximal voluntary tendon force explained 17.8% (p = 0.043) of the variance in youngs modulus. Our findings link estrogen to a chronic, rather than an acute, impact on tendon behavior. These findings are relevant to clinical outcomes, exercise performance, and injury risk. In terms of tendon properties, menstrual cycle phase does not necessarily need to be considered when organizing training and competition schedules.

The impact of obesity on skeletal muscle architecture in untrained young vs. old women

It is unknown whether loading of the lower limbs through additional storage of fat mass as evident in obesity would promote muscular adaptations similar to those seen with resistance exercise. It is also unclear whether ageing modulates any such adjustments. This study aimed to examine the relationships between adiposity, ageing and skeletal muscle size and architecture. A total of 100 untrained healthy women were categorised by age into young (Y) (mean ± SD: 26.7 ± 9.4 years) vs. old (O) (65.1 ± 7.2 years) and body mass index (BMI) classification (underweight, normal weight, overweight and obese). Participants were assessed for body fat using dual energy x‐ray absorptiometry, and for gastrocnemius medialis (GM) muscle architecture (skeletal muscle fascicle pennation angle and length) and size [GM muscle volume and physiological cross‐sectional area (PCSA)] using B‐mode ultrasonography. GM fascicle pennation angle (FPA) in the obese Y females was 25% greater than underweight (P = 0.001) and 25% greater than normal weight (P = 0.001) individuals, while O females had 32 and 22% greater FPA than their underweight (P = 0.008) and normal weight (P = 0.003) counterparts. Furthermore, FPA correlated with body mass in both Y and O females (Y r = 0.303; P < 0.001; O r = 0.223; P = 0.001), yet no age‐related differences in the slope or r‐values were observed (P > 0.05). Both GM muscle volume (P = 0.003) and PCSA (P = 0.004) exhibited significant age × BMI interactions. In addition, muscle volume and PCSA correlated with BMI, body mass and fat mass. Interestingly, ageing reduced both the degree of association in these correlations (P < 0.05) and the slope of the regressions (P < 0.05). Our findings partly support our hypotheses in that obesity‐associated changes in GM PCSA and volume differed between the young and old. The younger GM muscle adapted to the loading induced by high levels of body mass, adiposity and BMI by increasing its volume and increasing its pennation angle, ultimately enabling it to produce higher maximum torque. Such an adaptation to increased loading did not occur in the older GM muscle. Nonetheless, the older GM muscle FPA increased to a similar extent to that seen in young GM muscle, an effect which partly explains the relatively enhanced absolute maximum torque observed in obese older females.

Tendon structural and mechanical properties do not differ between genders in a healthy community-dwelling elderly population

Elderly women are reportedly at higher risk of falling than their male counterparts. Postural balance is highly associated with fall risk and is also correlated with tendon structural and mechanical properties. Gender differences in tendon properties could partly explain the discrepancy in fall risk. Thus the purpose of this study was to investigate the possible gender difference in tendon properties in the elderly. The properties of the patellar tendon of 55 elderly (men n = 27, aged 72 ± 1 years, women n = 28, aged 70 ± 1 years) participants were tested. Tendon stiffness (K), length (L), and cross‐sectional area (CSA) were measured using B‐mode ultrasonography, dynamometry, and electromyography during ramped isometric knee extensions. There were no significant differences (p > 0.05) between men and women in tendon stiffness (elderly men 550.9 ± 29.2 vs. women 502.9 ± 44.9 Nmm−1) or in Youngs modulus (elderly men 0.32 ± 0.02 vs. women 0.36 ± 0.04 GPa). This elderly group had similar tendon structural and mechanical properties. The comparable characteristics in gender‐specific tendon properties in an elderly population exhibiting similar lifestyle characteristics to the current sample may not explain the reports in the literature regarding increased fall risk in elderly women relative to that seen in men of a similar age.

Menstrual cycle variations in oestradiol and progesterone have no impact on in vivo medial gastrocnemius tendon mechanical properties

BACKGROUND Tendon tissue contains oestrogen receptors and is therefore likely to be responsive to female sex hormones. Here we examine any effect of levels of female sex hormones associated with the menstrual cycle phase on corresponding tendon mechanical properties. METHODS Fifteen healthy females aged 23 (SEM 1.0 years) underwent three assessments of medial gastrocnemius tendon mechanical properties. Assessments were carried out once during days 1-4, 12-14 and 20-23 (with day 1 being the first day of menstruation). Venous blood samples were taken on the same days as tendon properties assessments to quantify serum levels of oestradiol and progesterone. FINDINGS There was no significant difference in the stiffness of the medial gastrocnemius tendon over the course of the menstrual cycle (days 1-4, 65.08 (SEM 5.16 Nm m(-1)), days 12-14, 62.73 (SEM 5.82 Nm m(-1)), days 20-23, 66.74 (SEM 7.14 Nm m(-1))). There were also no significant differences in tendon length and cross-sectional area which led to no significant differences in Youngs modulus values. No correlations were found between serum levels of oestradiol and/or progesterone and tendon stiffness and/or Youngs modulus. INTERPRETATION Acute fluctuations in female sex hormones have no significant effect on medial gastrocnemius tendon mechanical properties. In a context where studies are often limited to selecting only oral contraceptive-users as participants in order to minimise potential noise related to the anticipated effects of menstrual cycle hormones on physical performance, our findings provide the basis for enabling the pooling of female tendon data, regardless of the phase of the menstrual cycle of individual participant.

Impact of range of motion during ecologically valid resistance training protocols on muscle size, subcutaneous fat, and strength.

Abstract McMahon, GE, Morse, CI, Burden, A, Winwood, K, and Onambélé, GL. Impact of range of motion during ecologically valid resistance training protocols on muscle size, subcutaneous fat, and strength. J Strength Cond Res 28(1): 245–255, 2014—The impact of using different resistance training (RT) kinematics, which therefore alters RT mechanics, and their subsequent effect on adaptations remain largely unreported. The aim of this study was to identify the differences to training at a longer (LR) compared with a shorter (SR) range of motion (ROM) and the time course of any changes during detraining. Recreationally active participants in LR (aged 19 ± 2.6 years; n = 8) and SR (aged 19 ± 3.4 years; n = 8) groups undertook 8 weeks of RT and 4 weeks of detraining. Muscle size, architecture, subcutaneous fat, and strength were measured at weeks 0, 8, 10, and 12 (repeated measures). A control group (aged 23 ± 2.4 years; n = 10) was also monitored during this period. Significant (p > 0.05) posttraining differences existed in strength (on average 4 ± 2 vs. 18 ± 2%), distal anatomical cross-sectional area (59 ± 15 vs. 16 ± 10%), fascicle length (23 ± 5 vs. 10 ± 2%), and subcutaneous fat (22 ± 8 vs. 5 ± 2%), with LR exhibiting greater adaptations than SR. Detraining resulted in significant (p > 0.05) deteriorations in all muscle parameters measured in both groups, with the SR group experiencing a more rapid relative loss of postexercise increases in strength than that experienced by the LR group (p > 0.05). Greater morphological and architectural RT adaptations in the LR (owing to higher mechanical stress) result in a more significant increase in strength compared with that of the SR. The practical implications for this body of work follow that LR should be observed in RT where increased muscle strength and size are the objective, because we demonstrate here that ROM should not be compromised for greater external loading.

Muscle size, activation, and coactivation in adults with cerebral palsy

Introduction: Muscle weakness is present in the paretic limbs of individuals with cerebral palsy (CP). We aimed to determine what neuromuscular factors contribute to weakness in adults with CP during isometric maximal voluntary contractions (iMVCs). Methods: Gastrocnemius anatomical cross‐sectional area (ACSA) and agonist and antagonist activation were measured in 11 CP and 11 control adult men during plantarflexion iMVC. Results: Plantarflexion iMVC torque of the paretic leg was 42% and 52% less than in the non‐paretic and control limbs, respectively. The paretic gastrocnemius ACSA was smaller than in the control group only. Paretic agonist activation was less than the non‐paretic and control groups, whereas antagonist coactivation was higher. Multiple regression analysis revealed muscle activation accounted for 57% of variation in paretic plantarflexion iMVC torque. Conclusions: In individuals with CP, muscle weakness in the paretic limb is attributed primarily to impaired neural activation and, to a lesser degree, ACSA. Muscle Nerve 49: 76–83, 2014

Muscle Damage following Maximal Eccentric Knee Extensions in Males and Females

Aim To investigate whether there is a sex difference in exercise induced muscle damage. Materials and Method Vastus Lateralis and patella tendon properties were measured in males and females using ultrasonography. During maximal voluntary eccentric knee extensions (12 reps x 6 sets), Vastus Lateralis fascicle lengthening and maximal voluntary eccentric knee extensions torque were recorded every 10° of knee joint angle (20–90°). Isometric torque, Creatine Kinase and muscle soreness were measured pre, post, 48, 96 and 168 hours post damage as markers of exercise induced muscle damage. Results Patella tendon stiffness and Vastus Lateralis fascicle lengthening were significantly higher in males compared to females (p<0.05). There was no sex difference in isometric torque loss and muscle soreness post exercise induced muscle damage (p>0.05). Creatine Kinase levels post exercise induced muscle damage were higher in males compared to females (p<0.05), and remained higher when maximal voluntary eccentric knee extension torque, relative to estimated quadriceps anatomical cross sectional area, was taken as a covariate (p<0.05). Conclusion Based on isometric torque loss, there is no sex difference in exercise induced muscle damage. The higher Creatine Kinase in males could not be explained by differences in maximal voluntary eccentric knee extension torque, Vastus Lateralis fascicle lengthening and patella tendon stiffness. Further research is required to understand the significant sex differences in Creatine Kinase levels following exercise induced muscle damage.