Distribution of concurrent training sessions does not impact endurance adaptation.

OBJECTIVES: Optimized concurrent training regimes are warranted in physical training of military-, law enforcement- and rescue-personnel. This study investigated if four 15-min endurance training sessions weekly improve aerobic capacity and performance more than one 60-min endurance session weekly during the initial phase of a Basic Military Training program. DESIGN: A randomized training intervention study with functional and physiological tests before and after the intervention. METHODS: Military conscripts (n=290) were randomly allocated to three groups completing 9 weeks training. Weekly training consisted of four endurance and four strength training sessions lasting 15min each ('Micro-training': MIC); one strength and one endurance session lasting 60min each ('Classical-training': CLA) or two 60min sessions of standard military training ('Control-training': CON). RESULTS: Both 12-min (∼7-10%) and shuttle run performance (∼35-42%) improved (P≤0.001) similarly in all groups. Likewise, functional 2-min maximal repetition exercise capacity increased (P≤0.05) similarly in all groups (Lunges ∼17-24 %; PushUp ∼10-20%; AbdominalFlexions∼21-23%). Peak oxygen uptake changes depended on group (P≤0.05) with increases (P≤0.01) in MIC (7±7%, n=23) and CON (12±18%, n=17) and no changes in CLA. Maximal m. vastus lateralis citrate synthase activity decreased 14±26% (P≤0.001, n=18) in CLA. Likewise, maximal m. vastus lateralis 3-hydroxyacyl-CoA dehydrogenase activity decreased 8±17% in MIC (n=28) and 14±24% in CLA (n=18). CONCLUSIONS: Four 15-min endurance training sessions weekly improves running performance and strength-endurance similarly to one 60min session. Peak oxygen uptake only increases with more than one endurance session weekly and leg muscle oxidative capacity appears reduced after basic military training.

Impact of low-volume concurrent strength training distribution on muscular adaptation.

OBJECTIVES: Military-, rescue- and law-enforcement personnel require a high physical capacity including muscular strength. The present study hypothesized that 9 weeks of volume matched concurrent short frequent training sessions increases strength more efficiently than less frequent longer training sessions. DESIGN: A randomized training intervention study with functional and physiological tests before and after the intervention. METHODS: Military conscripts (n=290) were assigned to micro-training (four 15-min strength and four 15-min endurance bouts weekly); classical-training (one 60-min strength and one 60-min endurance training session weekly) or a control-group (two 60-min standard military physical training sessions weekly). RESULTS: There were no group difference between micro-training and classical-training in measures of strength. Standing long jump remained similar while shotput performance was reduced (P≤0.001) in all three groups. Pull-up performance increased (P≤0.001) in micro-training (7.4±4.6 vs. 8.5±4.0 repetitions, n=59) and classical-training (5.7±4.1 vs. 7.1±4.2 repetitions, n=50). Knee extensor MVC increased (P≤0.01) in all groups (micro-training, n=30, 11.5±8.9%; classical-training, n=24, 8.3±11.5% and control, n=19, 7.5±11.8%) while elbow flexor and hand grip MVC remained similar. Micro-training increased (P≤0.05) type IIa percentage from 32.5±11.0% to 37.6±12.3% (n=20) and control-group increased (P≤0.01) type IIax from 4.4±3.0% to 11.6±7.9% (n=8). In control-group type I, fiber size increased (P≤0.05) from 5121±959µm to 6481±2084µm (n=5). Satellite cell content remained similar in all groups. CONCLUSIONS: Weekly distribution of low-volume concurrent training completed as either eight 15-min bouts or two 60-min sessions of which 50% was strength training did not impact strength gains in a real-world setting.

Adaptations to Short, Frequent Sessions of Endurance and Strength Training Are Similar to Longer, Less Frequent Exercise Sessions When the Total Volume Is the Same.

The hypothesis that the distribution of weekly training across several short sessions, as opposed to fewer longer sessions, enhances maximal strength gain without compromising maximal oxygen uptake was evaluated. Twenty-nine subjects completed an 8-week controlled parallel-group training intervention. One group ("micro training" [MI]: n = 21) performed nine 15-minute training sessions weekly, whereas a second group ("classical training" [CL]: n = 8) completed exactly the same training on a weekly basis but as three 45-minute sessions. For each group, each session comprised exclusively strength, high-intensity cardiovascular training or muscle endurance training. Both groups increased shuttle run performance (MI: 1,373 ± 133 m vs. 1,498 ± 126 m, p ≤ 0.05; CL: 1,074 ± 213 m vs. 1,451 ± 202 m, p < 0.001). In contrast to CL, MI increased peak oxygen uptake (3,744 ± 615 mL·min⁻¹ vs. 3,963 ± 753 mL·min⁻¹, p ≤ 0.05), maximal voluntary isometric (MVC) force of the knee extensors (646 ± 135 N vs. 659 ± 209 N, p < 0.001), MVC of the finger flexors (408 ± 109 N vs. 441 ± 131 N, p ≤ 0.05), and number of lunges performed in 2 minutes (65 ± 3 vs. 73 ± 2, p < 0.001). However, there were no significant differences between MI and CL on any measured parameters before or after the training intervention. In conclusion, similar training adaptations can be obtained with short, frequent exercise sessions or longer, less frequent sessions where the total volume of weekly training performed is the same.

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 O2×min-1; n = 14) and CON (3.8±0.7 vs. 3.8±0.7 l O2×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.

Changes in human muscle oxygen saturation and mean fiber conduction velocity during intense dynamic exercise--effect of muscular training status.

INTRODUCTION: In this study we investigated whether an association exists between muscle fiber conduction velocity (MFCV) and local muscle oxygen saturation (StO(2)) in the superficial part of the latissimus dorsi muscle of runners and swimmers during exhaustive dynamic exercise. METHODS: Participants performed arm cranking with increasing intensity until exhaustion. RESULTS: Runners' MFCV was unchanged with increasing arm-cranking exercise intensity, but was higher (P < 0.05) than swimmers' MFCV at the same workload. Swimmers' MFCV increased (P < 0.05) with increasing exercise intensity and reached values at exhaustion similar to those of the runners. StO(2) was similar in swimmers and runners at rest and decreased with increasing exercise intensity. StO(2) was higher (P < 0.05) at the same workload in swimmers compared with runners. StO(2) and MFCV were significantly but very weakly correlated in both swimmers and runners. CONCLUSION: No association exists between surface MFCV and StO(2) in either trained or untrained human skeletal muscle during exhaustive intense dynamic exercise.