The Effects Of Set Duration In High Intensity Interval Training Protocols On Total Work, Heart Rate, And Lactate In Boys And Men

Introduction
The purpose of the present study was to examine in boys and men the effects of set duration in high intensity interval
training protocols on total mechanical work (TMW), on average heart rate (HRav), on blood lactate concentration (Lb),
and % recovery for TMW and peak muscle torque of knee extensors (PTEX). Furthermore, we investigated the
interrelationships between the % recovery of TMW and PTEX, and the relative TMW, PTEX and Lb at the midpoint of
each protocol.

Methods
Twenty boys (11.4±0.5 yrs) and 18 men (24.0±1.9 yrs) were equally divided to two groups for each age-category. Each
age group performed either 2 sets of 34 (60 sec protocol) maximal knee extensions and flexions with 2 min rest or 4 sets
of 18 (30 sec protocol) maximal knee extensions and flexions with 1 min rest at 120º/sec using Cybex. PTEX (Nm),
TMW (J) were measured for each set. TMW for the entire protocol was calculated by the summation of work produced
in each set. HRav during the entire protocol and 4 min recovery was recorded using the Polar HR monitor. Lb (mmol/L)
was measured at mid-point of each protocol and at the 3rd min after the protocol with the Lactate PRO. Recovery (%) of
TMW from the 1st to 2nd set in the 60 sec protocol and from 1st + 2nd to 3rd + 4th in the 30 sec protocol was calculated.
Recovery (%) of PTEX was calculated from 1st to 2nd set in the 2x60 sec and from 1st to 3rd in the 4x30 sec protocol.
Two-way ANOVA, simple main effects and Pearson’s correlation were used for statistics.

Results
Men had higher (p<0.001) values than boys for relative TMW and Lb in both protocols (Table). In contrast, the %
recovery of TMW and PTEX from the 1st half of the protocol was higher in boys than in men in both 4x30sec and
2x60sec protocols (p<0.001). For HRav, boys had lower values than men in the 4x30sec protocol. Comparisons
between protocols within age revealed that TMW was higher in 4x30sec compared to that in 2x60sec protocol in boys
(p<0.01) and men (p<0.001). HRav was significantly higher in the 4x30sec than in the 2x60sec protocol only in men
(p<0.05). Lb in boys was identical in both protocols (p>0.05), but in men increased non-significantly by 16%. Pearson’s
correlation analysis revealed that the % recovery for TMW and PTEX from the 1st half of each protocol was negatively
correlated with: i) amount of work produced in 1st set in 30 or 60 sec protocol, ii) PTEX, and iii) Lb concentration at the
half of 2x60 or 4x30 protocol (Figure).

Conclusion:

In both boys and men, higher TMW is produced in protocols with smaller set duration compared to those
with greater set duration (equal total time, intensity and work:recovery ratio). In boys, HRav and Lb concentration is
not affected by changes in set duration but they are increased in men when protocols with smaller set duration are
performed. PTEX and TMW recover faster in boys than in men in 2x60 sec and 4x30 sec high-intensity protocols,
which may be due to less reliance of boys on the "anaerobic" system for energy production and/or better acid-base
regulation. However, the magnitude of the recovery (%) is not affected by the program configuration within both men
and boys. Furthermore, as suggested by the high negative correlations, the greater % recovery of TMW and PTEX of
boys compared to those of adults is maybe the result of the ability of men to achieve higher relative TMW and PTEX
and higher Lb concentration.

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