Effects of 12 weeks high-intensity & reduced-volume training in elite athletes

It was investigated if high-intensity interval training (HIT) at the expense of total training volume improves performance, maximal oxygen uptake and swimming economy. 41 elite swimmers were randomly allocated to a control (CON) or HIT group. For 12 weeks both groups trained ∼12 h per week. HIT comprised ∼5 h vs. 1 h and total distance was ∼17 km vs. 35 km per week for HIT and CON, respectively. HIT was performed as 6-10×10-30 s maximal effort interspersed by 2–4 minutes of rest. Performance of 100 m all-out freestyle and 200 m freestyle was similar before and after the intervention in both HIT (60.4±4.0 vs. 60.3±4.0 s; n = 13 and 133.2±6.4 vs. 132.6±7.7 s; n = 14) and CON (60.2±3.7 vs. 60.6±3.8 s; n = 15 and 133.5±7.0 vs. 133.3±7.6 s; n = 15). Maximal oxygen uptake during swimming was similar before and after the intervention in both the HIT (4.0±0.9 vs. 3.8±1.0 l O(2)×min(−1); n = 14) and CON (3.8±0.7 vs. 3.8±0.7 l O(2)×min(−1); n = 11) group. Oxygen uptake determined at fixed submaximal speed was not significantly affected in either group by the intervention. Body fat % tended to increase (P = 0.09) in the HIT group (15.4±1.6% vs. 16.3±1.6%; P = 0.09; n = 16) and increased (P<0.05) in the CON group (13.9±1.5% vs. 14.9±1.5%; n = 17). A distance reduction of 50% and a more than doubled HIT amount for 12 weeks did neither improve nor compromise performance or physiological capacity in elite swimmers

Oxygen uptake.

<p>Maximal oxygen uptake (VO_2max) determined during freestyle swimming in a swimming flume with increasing water speed until exhaustion in two groups of swimmers before (PRE) and after (POST) a training intervention. One group performed usual swim-training (CON) and another group reduced their training volume by 50% and more than doubled the amount of high-intensity training (HIT). On average, VO_2max was similar before and after the 12 week intervention period in both groups. Individual data is presented. Open circles: male; Closed circles: female.</p

Training intensity and volume.

<p>Training time and milage averaged for every 2^nd week and split into three major training categories. CON: Control groups; INT: intervention group. Li-Aerobic: Technical training, Recovery and low to moderate aerobic training with % of maximal heart rate < 70%. Hi-Aerobic: Intense aerobic training aiming at eliciting close to maximal heart rate and >90% of VO_2max. HIT: “High-Intensity Training” with maximal effort for 20–90 s and a rest: work ratio > 4.</p

Blood lactate.

<p>Blood lactate determined from a finger capillary sample obtained 1 minute after each of five 200(see methods) in two groups of swimmers before (PRE) and after (POST) a training intervention. One group performed usual swim-training (CON) and another group reduced their training volume by 50% and more than doubled the amount of high-intensity training (HIT).</p

Blood metabolites.

<p>Blood variables obtained from a fingertip sample after the 3^rd and 5^th of five 200 m swims performed at increasing speeds before and after a 12 week intervention period. The third 200 meter was swum on a identical speed before and after the intervention whereas the fifth 200 meter was swum with maximal effort.</p

Inference of effects.

<p>The 90% confidence interval (90% C.I.) for the observed change in primary outcome variables within each group and the P-value (P) for a one-sample t-test with the null-hypothesis µ = 0. A subjectively chosen threshold for the minimal change that could be considered beneficial (Threshold) was used to calculate the chance that the observed changes would be beneficial, trivial or harmful (Inference). One group performed usual swim-training (CON) and another group reduced their training volume by 50% and more than doubled the amount of high-intensity training (HIT).</p