EFFECTS OF CONSECUTIVE DAYS OF EXERCISE AND RECOVERY ON MUSCLE MECHANICAL FUNCTION. Stewart RD, Duhame TA, Rich S, Tupling AR, Green HJ, Ward J. Medicine and Science in Sports and Exercise 2008;40(2):316- 325

The purpose of this study was to investigate the effects of three consecutive days of prolonged exercise on muscle mechanical function. In this study 12 volunteers cycled at approximately 60% VO2 peak until fatigue. Quadriceps muscle function was assessed before and after exercise on day 1 (E1) and day 3 (E3) and during three consecutive days of recovery (R1, R2, R3), using both voluntary and electrically-induced contractions at various stimulation frequencies. The results were that exercise on E1 and E3 resulted in a 40% and 35% deficit in force

at 10 Hz respectively, which remained depressed 32-34% during R1-R3. At 100 Hz, force, although not altered by exercise at E1 or E3, was decreased by 12-16% during recovery. The maximal rate of relaxation at 10 Hz was reduced by 38% on E1, by 32% on E3, and remained depressed by 38% through R3. At 100 Hz it was only depressed during recovery. Maximal rate of force development at 10 Hz was reduced by exercise, but not in recovery. Maximal voluntary contraction force was depressed with exercise at both E1 and E3 and remained depressed throughout recovery. The reduction in motor unit activation assessed with the interpolated twitch technique, observed during recovery, suggests that part of the incomplete recovery (weakness) is central in origin.

sportEX comment What this means in practise is that three consecutive days of prolonged exercise

result in a weakness that persists for at least another 3 days, compromising force during both voluntary and induced contractions. This should therefore be a major consideration for the spacing of pre-season work.

SUPRAMAXIMAL TRAINING AND POST-EXERCISE PARASYMPATHETIC REACTIVATION IN ADOLESCENTS. Buchheit M, Millet GP, Parisy A, Pourchez S, Laursen PB. Ahmaidi S. Medicine and Science in Sports and Exercise 2008; 40(2):362-371

Repeated supramaximal exercise training is an efficient means of improving both aerobic and anaerobic energy system capacities. However, the influence of different levels of supramaximal training on parasympathetic function is unknown. The purpose of this study was to compare the effects of repeated-sprint (RS) versus high-intensity intermittent training (HIT) on performance and post-exercise parasympathetic reactivation in trained adolescents. Fifteen male adolescents (15.6 +/-0.8 yr) were divided into two groups that performed 9 wks of either RS (repeated all-out 6 second shuttle sprints; 14-20 seconds of recovery); or HIT (15 to 20 second runs at 95% of the speed reached at the end of the 30-15 intermittent fitness test (VIFT); 15-20 seconds of recovery. Groups performed intervals twice per week and maintained similar external training programs. Before and after training performance was assessed by the VIFT, counter movement jump (CMJ), 10 metre sprint time (10m), mean RS ability time (RSA mean), and heart rate (HR) level during a 6 minute submaximal (60% VIFT) exercise test. Parasympathetic reactivation was assessed during the recovery phase (ie. HR recovery time (HRR) and HR variability (HRV)). The results showed that parasympathetic function, VIFT, and RSA mean were improved with HIT but not RS training. In contrast, changes in CMJ and HR were similar in both groups. A significant relationship was shown between the decrease in HRR and RSA mean.

sportEX comment The conclusion is that HIT was more effective than RS training at improving post

exercise parasympathetic function (which is basically the nervous system slowing down and returning the body to normal levels) and physical performance. In addition, HRR, which was more sensitive to training than HRV indices, seems to be a useful performance-related measurement. (HRV is the time interval between heart beats). The implications for coaches is to recognise that it’s not just muscles that need to recover from exercise but the nervous system too. This means we need to take into account rest periods during exercise and throughout training cycles in order to optimise training adaptations.

4

PSYCHOLOGICAL SKILLS TRAINING IMPROVES

EXERCISE PERFORMANCE IN THE HEAT. Barwood ML, Thelwell RC, Tipton MJ, Medicine and Science in

Sports and Exercise 2008;40(2):387- 396

Fatigue occurs earlier when working at corresponding exercise intensities in hot compared with cool conditions. Psychological skills training (PST) can modify the responses evoked by thermal stimuli such as the respiratory responses on immersion to cold water. This study tested the hypothesis that a 4 day PST package would significantly increase the distance covered during 90 minutes of running in the heat.

Eighteen subjects completed three maximal-effort runs (R1, R2, R3) of 90 minutes in the heat (30°C; 40% relative humidity). After R2, subjects were matched and randomly allocated to either a control group (CG) or psychological skills group (PSG). Between R2 and R3, the CG continued their normal activities, and the PSG received PST to help them tolerate unpleasant sensations arising from exercising in the heat, and to suppress the temptation to lower their work intensity. Key measures included distance covered, VO2, skin (Tsk) and aural temperature (Tau), RPE, sweat production and evaporation, interleukin-6 (IL-6), and prolactin (PRL) in whole blood. The distances covered in the CG did not differ between runs. In the PSG, there were no differences in the distance run between R1 and R2, but they ran significantly farther in R3 (8%; 1.15 km); there were no between-group differences. There were no significant differences between R1 and R3 in peak Tau, Tsk, sweat volumes, IL-6, and PRL (P > 0.05) in either group.

sportEX comment The conclusion reached was that

psychological skills training suppressed the temptation to reduce exercise intensity during R3 although the precise mechanisms underpinning these improvements are unclear. So, adding a mental aspect to heavy training can improve the workload.

sportEX dynamics 2008:16(Apr):4-5