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The aim of the present investigation was to determine whether muscle force per physiological cross sectional area (PCSA) of the lateral gastrocnemius (GL) of elderly males increased following a 12-month physical training programme. Eleven elderly males were assigned to a 12-month training programme (TRN mean age 72.7 +/- 3.3 years, mean +/- SD) and eight elderly males were allocated to a control group (CTRL, 73.9 +/- 4.0 years) who maintained their habitual physical activity levels. In vivo measurements of muscle architecture, muscle volume (VOL), achilles tendon moment arm length and plantarflexor torque were used to estimate GL PCSA (VOL/fascicle length) and specific force (GL fascicle force/GL PCSA). Maximal GL fascicle force was calculated accounting for agonist muscle activation and antagonist co-activation. Following training GL fascicle force increased by 31% (P < 0.01), which was not entirely accounted for by a 17% increase in PCSA (from 27.2 +/- 5.9 to 31.8 +/- 6.2 cm(2), P < 0.05). Specific force increased significantly from 8.9 +/- 1.9 to 11.2 +/- 3.0 N cm(-2) (P < 0.05). Pennation angle, but not fascicle length, increased by 12% with training (P < 0.05). The CTRL group showed no change in muscle size, strength or architecture over the 12-month period. In conclusion, with the level of agonist and antagonist muscle activity accounted for a 12-month strength training programme resulted in an increase in both PCSA and specific force in elderly males.

The metabolic cost of walking (C(W)) is increased in healthy older adults. Previously, this has been suggested to be associated with age-related decline in physiological/functional factors such as stability and muscle size and strength. Physical training can improve such factors as well as aspects of gait performance in older adults. The aim of this investigation was to determine if it also has a beneficial impact on (lowers) C(W). Thirty-eight community dwelling older adults (aged 70-82 years) assigned to a training group (TRA, n=25) or a control group (CON, n=13) participated in a 12-month intervention. TRA followed a multi-component physical conditioning programme involving supervised resistance, aerobic, and balance exercises twice per week. They also undertook home based exercises once per week. CON carried on with their normal daily activities. C(W) and indicators of functional capacity (knee extensor isometric strength, single leg balance time, sit and reach, stand and reach, and 6 min walk distance) were assessed prior to and following the intervention. Significant improvements in knee extensor isometric strength (+21%), single leg balance time (+30%), and 6 min walk distance (+6%) were observed in TRA (P<0.05) but not in CON. However, no change in C(W) was observed. In conclusion, this investigation has shown that a multi-component physical conditioning programme had a beneficial impact on functional capacity but did not lower C(W) in healthy community dwelling older adults.

This study investigated the contribution of muscle architecture to the differences in the torque-velocity and power-velocity relationships between older (OM n = 9, aged 69-82 years) and younger men (YM n = 15, aged 19-35 years). Plantarflexors' (PF) maximal isometric and concentric torques were recorded at 0.87, 1.75, 2.62, 3.49 and 4.36 rad s(-1). Physiological cross-sectional area (PCSA) was calculated as the ratio of muscle volume (determined by magnetic resonance imaging) to muscle fascicle length (Lf, measured by ultrasonography). GM PCSA and Lf of the OM were, respectively, 14.3% (P < 0.05) and 19.3% (P < 0.05) smaller than of the YM. In the OM, GM maximum isometric torque and maximum contraction velocity (Vmax), estimated from Hill's equation were, respectively, 48.5 and 38.2% lower (P < 0.001) than in the YM. At all contraction velocities, the OM produced less torque than the YM (46.3% of YM at 0.87 rad s(-1) to 14.7% at 4.36 rad s(-1), P < 0.001). Peak power (PP) of the OM was 80% lower than that of the YM and normalisation of PP to muscle volume only reduced this difference by 10%. Normalisation of torque to PCSA reduced, but did not eliminate, differences in torque between YM and OM (9.6%) and differences in torque/PCSA increased with contraction velocity (P < 0.05). After normalisation of velocity to Lf, the difference in Vmax between the OM and the YM was reduced to 15.9%. Thus, although muscle architecture contributes significantly to the differences in the torque- and power-velocity properties of OM and YM, other contractile factors, intrinsic to the muscle, seem to play a role. It is noteworthy that the deficit in PP between OM and YM is far greater than that of muscle torque, even after normalisation of PP to muscle volume. This finding likely plays an important role in the loss of mobility in old age.

Muscle size is often reported as a single anatomical cross-sectional area (ACSA), rather than volume measured with contiguous MRI scans. However, a single ACSA may provide an inadequate estimate of muscle mass. Therefore, we investigated whether quadriceps muscle volume can be adequately estimated from a single ACSA. In 18 adult males we derived regression equations from which estimates of volume were made. These equations were based on the direct assessment of volume using 11 transverse-plane MRI scans along the entire length of the femur (the gold standard). We estimated volume based on single scans at 40, 50 and 60% of femur length (from the distal end). All estimates of quadriceps volumes were highly correlated to the measured volume and demonstrated a low level of error. R (2) = 0.84, 0.93, 0.90 (all P < 0.01), standard error of estimate (SEE) = 26.8 +/- 5.2, 12.5 +/- 5.4 and 9.9 +/- 5.7%, for single scans taken at 40, 50 and 60% of femur length respectively. In comparison, when volume was estimated using multiple MRI scans corresponding to the maximum ACSA of each muscle the estimate was even better [R (2) = 0.95 (P < 0.01) and SEE = 4.5 +/- 2.7%]. Substituting ACSA from a single MRI scan at 60% of femur length into a previously determined regression equation allows for an estimation of muscle volume with a 10% error of estimate.

The aim of this study was to critically examine the influence of body size on maximal oxygen uptake (VO2 max) in boys and men using body mass (BM), estimated fat-free mass (FFM), and estimated lower leg muscle volume (Vol) as the separate scaling variables. VO2 max and an in vivo measurement of Vol were assessed in 15 boys and 14 men. The FFM was estimated after percentage body fat had been predicted from population-specific skinfold measurements. By using nonlinear allometric modeling, common body size exponents for BM, FFM, and Vol were calculated. The point estimates for the size exponent (95% confidence interval) from the separate allometric models were: BM 0.79 (0.53-1.06), FFM 1.00 (0.78-1.22), and Vol 0.64 (0.40-0.88). For the boys, substantial residual size correlations were observed for VO2 max/BM0.79 and VO2 max/FFM1.00, indicating that these variables did not correctly partition out the influence of body size. In contrast, scaling by Vol0.64 led to no residual size correlation in boys or men. Scaling by BM is confounded by heterogeneity of body composition and potentially substantial differences in the mass exponent between boys and men. The FFM is precluded as an index of involved musculature because Vol did not represent a constant proportion of FFM [Vol proportional, variantFFM1.45 (95% confidence interval, 1.13-1.77)] in the boys (unlike the men). We conclude that Vol, as an indicator of the involved muscle mass, is the most valid allometric denominator for the scaling of VO2 max in a sample of boys and men heterogeneous for body size and composition.

In elderly males muscle plantar flexor maximal voluntary contraction (MVC) torque normalised to muscle volume (MVC/VOL) is reduced compared to young males as a result of incomplete muscle activation in the elderly. The aim of the present study was to determine the influence of a 12-month resistance training programme on muscle volume, strength, MVC/VOL, agonist activation and antagonist coactivation of the plantarfexors in elderly males. Thirteen elderly males aged 70 years and over (range 70-82 years), completed a 12-month whole body resistance-training programme (TRN), training three times a week. Another eight males (range 18-30 years), who maintained their habitual physical activity for the same 12-month period as the TRN group acted as controls (CTRL). Isometric plantarflexor maximal voluntary contraction (MVC) torque increased in the TRN group by 20% (P < 0.01), from 113.1 +/- 22.0 Nm to 141.5 +/- 19.2 Nm. Triceps surae volume (TS VOL) assessed using MRI, increased by 12%, from 796.3 +/- 78.9 cm(3) to 916.8 +/- 144.4 cm(3) . PF activation, measured using supramaximal double twitch interpolation, increased from 83.6+/-11.0% pre training, to 92.1 +/- 7.6% post training (P < 0.05). Dorsiflexion MVC and antagonist coactivation (assessed using surface electromyography) did not change with training. Plantarflexor MVC torque normalized for triceps surae muscle volume (MVC/VOL) was 142.6 +/- 32.4 kN m(-2) before training and 157.0 +/- 27.9 kN m(-2) after training (a non-significant increase of 8%). No significant change in any measurement was observed in the CTRL group. This study has shown that the gain in muscle strength in response to long-term (12-month) training in older men is mostly accounted for by an increased muscle volume and activation.

Sarcopenia and muscle weakness are well-known consequences of aging. The aim of the present study was to ascertain whether a decrease in fascicle force (Ff) could be accounted for entirely by muscle atrophy. In vivo physiological cross-sectional area (PCSA) and specific force (Ff/PCSA) of the lateral head of the gastrocnemius (GL) muscle were assessed in a group of elderly men [EM, aged 73.8 yr (SD 3.5), height 173.4 cm (SD 4.4), weight 78.4 kg (SD 8.3); means (SD)] and for comparison in a group of young men [YM, aged 25.3 yr (SD 4.4), height 176.4 cm (SD 7.7), weight 79.1 kg (SD 11.9)]. GL muscle volume (Vol) and Achilles tendon moment arm length were evaluated using magnetic resonance imaging. Pennation angle and fiber fascicle length (Lf) were measured using B-mode ultrasonography during isometric maximum voluntary contraction of the plantar flexors. PCSA was estimated as Vol/Lf. GL Ff was calculated by dividing Achilles tendon force by the cosine of theta, during the interpolation of a supramaximal doublet, and accounting for antagonist activation level (assessed using EMG), Achilles tendon moment arm length, and the relative PCSA of the GL within the plantar flexor group. Voluntary activation of the plantar flexors was lower in the EM than in the YM (86 vs. 98%, respectively, P < 0.05). Compared with the YM, plantar flexor maximal voluntary contraction torque and Ff of the EM were lower by 47 and 40%, respectively (P < 0.01). Both Vol and PCSA were smaller in the EM by 28% (P < 0.01) and 16% (P < 0.05), respectively. Also, pennation angle was 12% smaller in the EM, whereas there was no significant difference in Lf between the YM and EM. After accounting for differences in agonists and antagonists activation, the Ff/PCSA of the EM was 30% lower than that of the YM (P < 0.01). These findings demonstrate that the loss of muscle strength with aging may be explained not only by a reduction in voluntary drive to the muscle, but mostly by a decrease in intrinsic muscle force. This phenomenon may possibly be due to a reduction in single-fiber specific tension.

This study investigated whether loss of power with aging is fully accounted for by a decrease in muscle volume. Triceps surae power and volume (VOL) were measured in 18 older (OM: 69-82 years) and 12 younger men (YM: 19-35 years). Isokinetic peak torque was measured to determine torque-velocity and power-velocity relationships. Both peak power observed (PP(obs)) and peak power estimated from Hill's equation (PP(est)) were markedly reduced in the OM (PP(obs) was 45% and PP(est) was 43% of those of the YM). VOL was 81% of that of the YM (p <.001). Specific power (PP(est)/VOL) of the OM was 55.2% of that of the YM (p <.001). Torque at PP(est) accounted for a greater proportion of the decline in PP(est) in the OM than did optimum velocity (50% vs 13%, respectively). Hence, the present results showed that only approximately half of the loss in triceps surae peak power in old age is due to decreases in muscle VOL.

Aim: To investigate whether sarcopenia was evenly distributed among the three components of the triceps surae (TS) muscle group., Methods: Muscle volume (VOL), fibre fascicle length (Lf), pennation angle (theta) and physiological cross-sectional area (PCSA = VOL/Lf) were measured in vivo for the lateral (GL) and medial (GM) heads of the gastrocnemius muscles and for the soleus muscle (SOL), in 15 young males (YM, aged 25.3 +/- 4.5 years) and 12 elderly males (EM aged 73.8 +/- 4.4 years)., Results: In the EM, VOL of all three muscles was significantly smaller than in the YM; differences were: 27% for the GL (P < 0.01), 29% for the GM (P < 0.01) and 17% for the SOL (P < 0.05). In total, TS VOL was 22% smaller in EM than in YM (P < 0.01). In the EM, values of theta were significantly smaller than in the YM; by 15-18% for the GL, GM and SOL (P < 0.05). In the EM, Lf of the GM was 16% smaller than in the YM (P < 0.01); no significant differences were found in the other muscles. PCSA of the GL and GM were both found to be smaller in EM by 19% (P < 0.01) and 14.5% (P < 0.05), respectively. No difference was observed in the SOL PCSA between YM and EM. Interestingly, probably because of the prevalent contribution of the SOL to PCSA distribution of each muscle to the TS PCSA, the relative TS PCSA was not different between YM and EM. Furthermore, the Lf/muscle length ratio did not differ between YM and EM., Conclusion: The present study shows that the relative PCSA composition of the TS is maintained with ageing and that the PCSA is scaled down harmonically with the decrease in muscle volume and fascicle length. Such observation suggests that the relative contribution of the components of the TS muscle to the total force developed by this muscle group is maintained with ageing.

This study investigated the influence of tendon elongation (TE) on postcontraction doublet (PCD) torque in the assessment of activation in the plantar flexors of nine elderly men (EM, age 73.7 +/- 3.6 yr) and nine young men (YM, age 24.7 +/- 4.7 yr). Plantar flexion maximal voluntary contractions (MVC) and activation were assessed at ankle joint angles of -20 degrees (dorsiflexion), 0 degrees , and 20 degrees (plantar flexion). Across the ankle joint angles tested, compared with YM, the EM had a 36-49% lower plantar flexion MVC (P < 0.01), TE was greater by 25-31% (P < 0.01), and electromechanical delay was 65-108% greater (P < 0.01). Activation (PCD torque to interpolated doublet torque) was 15% lower in EM compared with YM at -20 degrees (P < 0.05), but no different at 0 and 20 degrees . In the EM, PCD torque relative to MVC torque was significantly lower at 20 degrees compared with 0 degrees (P < 0.05). Electromechanical delay was positively correlated with TE (R(2) = 0.489, P < 0.01). In conclusion, this investigation demonstrates that, although a negative association exists between TE and PCD torque, the consequence of a greater TE on the estimation of activation in EM is negligible. This is due to a greater influence of ankle joint angle on the occlusion of a superimposed doublet, which counteracts the lesser influence of joint angle on TE and PCD torque. However, a greater TE in EM was found to significantly increase electromechanical delay, which is expected to influence the time needed for postural readjustments.

Previous studies have reported a decrease in muscle torque per cross-sectional area in old age. This investigation aimed at determining the influence of agonists muscle activation and antagonists co-activation on the specific torque of the plantarflexors (PF) in recreationally active elderly males (EM) and, for comparison, in young men (YM). Twenty-one EM, aged 70-82 years, and 14 YM, aged 19-35 years, performed isometric maximum voluntary contractions (MVC). Activation was assessed by comparing the amplitude of interpolated supramaximal twitch doublets at MVC, with post-tetanic doublet peak torque. Co-activation of the tibialis anterior (TA) was evaluated as the ratio of TA-integrated EMG (IEMG) activity during PF MVC compared to TA IEMG during maximal voluntary dorsiflexion. Triceps surae muscle volume (VOL) was assessed using magnetic resonance imaging (MRI), and PF peak torque was normalised to VOL (PT/VOL) since the later approximates physiological cross-sectional area (CSA) more closely than anatomical CSA. Also, physical activity level, assessed by accelerometry, was significantly lower (21%) in the elderly males. In comparison to the YM group, a greater difference in PT (39%) than VOL (19%) was found in the EM group. PT/VOL and activation capacity were respectively lower by 25% and 21% in EM compared to YM, whereas co-activation was not significantly different. In EM PT/VOL correlated with activation (R(2)=0.31, P<0.01). In conclusion, a reduction in activation capacity may contribute significantly to the decline in specific torque in the plantar flexors of elderly males. The hypothesis is put forward that reduced physical activity is partialy responsible for the reduced activation capacity in the elderly.

Neuropathic, metabolic, hormonal, nutritional and immunological factors contribute to the development of sarcopenia. This loss of muscle mass associated with ageing, is a main cause of muscle weakness, but the loss of muscle strength typically exceeds that of muscle size, with a resulting decrease in force per unit of muscle cross-sectional area. Recent evidence suggests that, in addition to a reduction in neural drive and in fibre specific tension, changes in muscle architecture contribute significantly to the loss of muscle force through alterations in muscle mechanical properties. Older muscle, however, maintains a high degree of plasticity in response to increased loading since considerable hypertrophy and a reversal of the alterations in muscle architecture associated with ageing are observed with resistive training.