Biomedical subjects

E Drinkwater

Publications and source records attributed to E Drinkwater.

4 recordsLinked to original sources

PubMed2004

The effect of continuous repetition training and intra-set rest training on bench press strength and power.

AIM: The purpose of this research was to compare the effects of continuous repetition and intra-set rest training on maximal strength and power output of the upper body. METHODS: The 6 repetition maximum (6RM) and bench press throw power output against masses of 20, 30 and 40 kg of 26 elite junior male basketball and soccer players were tested on 2 separate occasions for reliability purposes. Subjects were then randomly assigned to either a continuous repetition (CR - 4 sets x 6 repetitions) or intra-set rest (ISR - 8 sets x 3 repetitions) training regime over 6-weeks. Volume (sets x repetitions x %6RM) between groups was equated and both groups completed all sets in the same time period (13 minutes and 20 seconds). The total concentric work time was determined to identify differences in training regimes. Independent sample t-tests on preintervention and postintervention percentage change scores were analysed for significant differences (p<0.05). RESULTS: The observed coefficients of variation (1.7% to 4.8%) and intraclass correlation coefficients (r=0.87 to 0.98) indicated stability of these measures across testing occasions. The CR group significantly increased 6RM strength (9.7%) compared with the ISR group (4.9%). The total concentric work time was significantly longer in CR training than ISR (36.03+/- 4.03 s and 31.74+/-4.71 s; p=0.13). Power output increases across the 20, 30 and 40 kg loads ranged from 5.8% to 10.9% for both training groups but the between-group percentage change scores were not significantly different. CONCLUSIONS: Bench press training involving 4 sets of 6 continuous repetitions elicited a greater improvement in bench press strength than 8 sets of 3 repetitions at the same percentage load of their 6RM. Both ISR and CR training were equally effective in increasing power output.

Adolescent↗

PubMed2003

Effects of hyperbaric (6 ATA) pressure on voluntary and evoked skeletal muscle contractile properties.

The objective of this study was to investigate the effect of 6 atmospheres of pressure (ATA) on plantar flexors' (PF) voluntary force and activation, force-frequency characteristics, and rate of torque development (RTD). Eight subjects performed PF isometric contractions. Muscle activation was monitored by electromyographic (EMG) activity (PF and dorsiflexors) and the interpolated twitch technique (ITT). Maximal evoked contractions of the PF were elicited at 1, 2, 3, 5, 10, 20, and 40 Hz. PF RTD was calculated with maximal voluntary, 1 and 40 Hz contractions. Hyperbaric pressures significantly decreased PF voluntary torque; 6.2%, ITT activation; 2.8% with a trend for a 19.1% decrease in EMG (p = 0.1). There were no significant differences in the dorsiflexors/PF EMG ratio. One Hz torque was potentiated 15.7% with an increased absolute RTD of 12.8%, but no change in relative RTD. The results suggested hyperbaric-induced decreases in PF activation contributed to voluntary torque loss. A lack of torque reduction with higher frequency tetanic stimulation (2-40 Hz) suggested that 6 ATA does not impair myofilament kinetics, whereas twitch potentiation may include changes in excitation-contraction coupling.

Adult↗

PubMed2001

Comparison of interpolation and central activation ratios as measures of muscle inactivation.

The objective of this study was to investigate different methods of estimating muscle inactivation, derived from single and multiple voluntary contractions. Ten subjects performed maximal and submaximal leg extensor contractions to determine an interpolation (IT) or central activation ratio (CAR). A superimposed evoked force was compared with the force output of either a voluntary (CAR) or resting evoked contraction (IT ratio), or the ratios were inserted into regression equations (linear, polynomial, exponential). Linear-regression estimates of CAR using doublets and tetanus provided physiologically inaccurate values. Whereas IT ratios using doublets (IT-doublet) and tetanus (IT-tetanus) had a significant difference in only one interaction, IT-tetanus and CAR using a tetanus (CAR-tetanus) estimates provided the most extensive correlation within and between measures. Thus, tetanic stimulation superimposed upon single maximal or multiple contractions seems to provide the most valid measure of muscle inactivation when using the interpolated-twitch technique.

Adult↗

PubMed1992

Neuronal differentiation triggered by blocking cell proliferation.

Treatment of the neuroblastoma cell line SHSY5Y with nerve growth factor (NGF) resulted in limited neurite extension, but proliferation continued. However, SHSY5Y cells treated with NGF and a pulse of the DNA polymerase alpha and delta inhibitor aphidicolin showed dramatic neuronal differentiation. Few differentiated cells were observed immediately following the NGF-aphidicolin treatment; however, continued treatment of the cells with NGF in the ensuing week resulted in extension of long neurites (> 400 microns). Neurite extension was not observed for cells treated with aphidicolin alone. Hence, aphidicolin and NGF act synergistically to induce differentiation of SHSY5Y cells. If maintained in NGF, the differentiated cells were stable for at least 1 month and displayed many neuronal characteristics. They were mitotically inactive, and, in contrast to control or NGF-treated cells, the differentiated cells required NGF for survival. The cells expressed multiple microtubule-associated proteins (MAP), including MAP 1A, MAP 1B, and tau. There was expression of synaptic vesicle antigens synaptophysin and SV2, but not synapsin Ia/b or synapsin IIa/b. Both hydroxyurea and thymidine, which inhibit synthesis of nucleotides, act synergistically with NGF to induce differentiation of SHSY5Y cells. Since aphidicolin, hydroxyurea, and thymidine are chemically unrelated, we conclude that these drugs enhance NGF-induced differentiation by blocking cell proliferation and not through an unrelated side effect. The model suggested by these studies is that differentiation is triggered by two simultaneous signals: NGF and cessation of cell proliferation.

Aphidicolin↗