Biomedical subjects

Jonathan P Folland

Publications and source records attributed to Jonathan P Folland.

3 recordsLinked to original sources

PubMed2006

Methodological issues with the interpolated twitch technique.

A number of methodological issues in the use of the interpolated twitch technique were investigated for their effect on true maximum force (TMF) and activation (ACT): timing of control (pre- vs post-contraction) and superimposed twitches (first vs second); type of twitch stimulus (primarily magnitude); and the type of extrapolation utilised. On three occasions subjects performed a series of maximal and sub-maximal contractions of the knee extensors, with electrically evoked twitches delivered before, during and after each contraction. The twitch-voluntary force relationship was concave for all types of twitch stimuli, and extrapolation using this relationship typically calculated TMF 39N (7%) higher, and ACT 7% lower than linear extrapolation. The timing of the control (2-4%) and superimposed twitches (approximately 4%) both influenced TMF and ACT. Despite the different twitch stimuli being a range of magnitudes (13-32% maximum voluntary force) they did not affect TMF and ACT. A novel finding was that prior potentiation changed the shape of the twitch-voluntary force relationship. For precise measurement of TMF and ACT it is recommended that: extrapolation is based on the twitch-voluntary force relationship of the experimental model; and post-contraction potentiated twitches be used, as the superimposed twitch on a high level contraction appears to be potentiated.

Adult↗

PubMed2005

Strength training: isometric training at a range of joint angles versus dynamic training.

Strength training with isometric contractions produces large but highly angle-specific adaptations. To contrast the contractile mode of isometric versus dynamic training, but diminish the strong angle specificity effect, we compared the strength gains produced by isometric training at four joint angles with conventional dynamic training. Thirty-three recreationally active healthy males aged 18 - 30 years completed 9 weeks of strength training of the quadriceps muscle group three times per week. An intra-individual design was adopted: one leg performed purely isometric training at each of four joint angles (isometrically trained leg); the other leg performed conventional dynamic training, lifting and lowering (dynamically trained leg). Both legs trained at similar relative loads for the same duration. The quadriceps strength of each leg was measured isometrically (at four angles) and isokinetically (at three velocities) pre and post training. After 9 weeks of training, the increase in isokinetic strength was similar in both legs (pooled data from three velocities: dynamically trained leg, 10.7%; isometrically trained leg, 10.5%). Isometric strength increases were significantly greater for the isometrically trained leg (pooled data from four angles: dynamically trained leg, 13.1%; isometrically trained leg, 18.0%). This may have been due to the greater absolute torque involved with isometric training or a residual angle specificity effect despite the isometric training being divided over four angles.

Adaptation, Physiological↗

PubMed2005

Circulating angiotensin converting enzyme activity is correlated with muscle strength.

PURPOSE: The D-variant of the angiotensin-1 converting enzyme (ACE) gene is associated with higher circulating and tissue ACE activity. Some studies have suggested a similar association of genotype with muscle strength or the gain in strength in response to training. This study has assessed the relationship between circulating ACE activity, strength, and the response to training. METHODS: Eighty-one untrained men were tested for quadriceps muscle strength, and 44 of these performed an 8-wk program of dynamic strength training of the quadriceps muscle group. Venous blood was obtained for assessment of circulating ACE activity before and after the training program. ACE genotype was also determined. RESULTS: At baseline, circulating ACE activity was significantly correlated with isometric (r = 0.25-0.29, P < 0.02) and isokinetic (r = 0.38, P < 0.0005) quadriceps muscle strength. ACE genotype also seemed to be related to pretraining muscle strength. However, circulating ACE activity showed no significant association with the 9-14% mean increases of muscle strength in response to the training intervention. ACE genotype also showed no association with the training-induced change in muscle strength. Circulating ACE activity did not change significantly after the training program. CONCLUSIONS: The data support a role for ACE in the regulation of human skeletal muscle strength, but do not confirm a role in altering the response to short-term training.

Adolescent↗