The study determined the effects of sprint interval training on the acute and chronic changes of serum brain-derived neurotrophic factor (BDNF) and aerobic capacity. Twenty-six cyclists were divided into experimental (E) and control groups. Both groups executed a 6-month exercise intervention involving high-intensity interval training (HIIT) and continuous endurance training (CET) with group E replacing HIIT and CET sessions with sprint interval training (SIT) that was executed twice a week. Two exercise tests were administered prior to the intervention and at 2 and 6 months after study outset. Incremental exercise test assessed aerobic capacity by measuring maximal oxygen uptake and work output; the sprint interval exercise test (SIXT) comprises 3 sets of four 30-s all-out repetitions interspersed with 90 s of rest with sets separated by 25–40 min of active recovery. Oxygen uptake, work output, BDNF, and vascular endothelial growth factor A (VEGF-A) concentrations (baseline, 10 min after first set, and 10 and 60 min after third SIXT set) were taken during the SIXT. Significant decreases in BDNF relative to baseline values were observed 10 min after the first set and 60 min after the third set in group E at the 2- and 6-month assessments. Increases in baseline VEGF-A after 2 and 6 months of training and increases in maximal oxygen uptake after 2 months of training were also observed only in group E. The inclusion of SIT with HIIT and CET shows positive long-term effects, including increased maximal oxygen uptake and baseline VEGF-A and a reduction in BDNF below baseline levels during and after SIXT.

Hebisz, R, Hebisz, P, Danek, N, Michalik, K, and Zatoń, M. Predicting changes in maximal oxygen uptake in response to polarized training (sprint interval training, high-intensity interval training, and endurance training) in mountain bike cyclists. J Strength Cond Res 36(6): 1726–1730, 2022—The aim of this study was to determine the predictors of change in maximal oxygen uptake (ΔV̇o ₂max) in response to a polarized training program. Twenty well-trained mountain bike cyclists completed an 8-week intervention of sprint interval training (SIT) (8–16 30-second maximal sprints), high-intensity interval training (4–6 bouts at 85–95% maximal aerobic power), and endurance training (2–3 hours cycling at 70–80% power at the ventilatory threshold). An incremental exercise test was performed to determine preintervention and postintervention maximal oxygen uptake (V̇o ₂max) and maximal pulmonary ventilation (VEmax) normalized to lean body mass (LBM). The frequency and time domain of heart rate variability (HRV) was also determined during recovery after moderate warm-up in the first and last SIT. Training status was quantified as the total distance cycled in the previous year. V̇o ₂max, VEmax, and the root mean square of the successive differences of normal-to-normal time interval between heartbeats (RMSSD), which is the time domain of HRV all increased significantly. Multiple significant correlations were observed between ΔV̇o ₂max and training status and baseline measures of VEmax·LBM⁻¹, RMSSD, and V̇o ₂max·LBM⁻¹ and a regression equation was developed (r = 0.87, r ² = 0.76; p = 0.0001). The change in V̇o ₂max in response to polarized training can be predicted with high accuracy based on several measurable variables.

This study evaluated the acute effects of sprint interval training and chronic effects of polarized training on choice reaction time in cyclists. Twenty-six mountain bike cyclists participated in the study and were divided into experimental (E) and control (C) groups. The cyclists trained for 9-weeks and performed five training sessions each week. Types of training sessions: (1) sprint interval training (SIT) which consisted of 8–16, 30 s repetitions at maximal intensity, (2) high-intensity interval training (HIIT) included 5 to 7, 5-min efforts at an intensity of 85–95% maximal aerobic power (Pmax), and (3) endurance training (ET) performed at an intensity of 55–60% Pmax, lasting 120–-180 min. In each week the cyclists performed: in group E a polarized training program, which included 2 × SIT, 1 × HIIT and 2 × ET, while in group C 2 × HIIT and 3 × ET. Before (acute effects) and after the 9-week training period (chronic effects) participants performed laboratory sprint interval testing protocol (SITP), which consisted of 12 maximal repetitions lasting 30 s. During SITP maximal and mean anaerobic power, as well as lactate ion concentration and blood pH were measured. Choice reaction time (RT) was measured 4-times: before and immediately after the SITP test—before and after the 9-week training period. Evaluated the average choice RT, minimal choice RT (shortest reaction), maximal choice RT (longest reaction), and the number of incorrect reactions. Before the training period as acute effects of SITP, it was observed: a shorter average choice RT (F = 13.61; p = 0.001; η² = 0.362) and maximal choice RT (F = 4.71; p = 0.040; η² = 0.164), and a decrease the number of incorrect reactions (F = 53.72; p = 0.000; η² = 0.691), for E and C groups. After the 9-week training period, chronic effects showed that choice RT did not change in any of the cyclists’ groups. Only in the E group after the polarized training period, the number of incorrect reactions decreased (F = 49.03; p = 0.000; η² = 0.671), average anaerobic power increased (F = 8.70; p = 0.007; η² = 0.274) and blood pH decreased (F = 27.20; p = 0.000; η² = 0.531), compared to the value before the training period. In conclusion, a shorter choice RT and a decrease in the number of incorrect reactions as acute effects of SITP, and a decrease in the number of incorrect reactions and higher average power as chronic effects of the polarized training program are beneficial for mountain bike cyclists.

BACKGROUND: While interval training is considered an effective modality for improving performance, its effectiveness among athletes may be influenced by previous training experience. OBJECTIVE: To investigate whether differences in training background are reflected in the development of exercise capacity and level of muscle damage following a single bout of repeated maximal sprints after an 8-week intervention of high-intensity interval training (HIIT), sprint interval training (SIT), and endurance training (ET). METHODS: Three groups of male cyclists were studied: E1 ([ ] 10) included cyclists with a background in high-volume moderate-intensity training, E2 ([ ] 7) comprised cyclists with low-volume high-intensity training experience, and C ([ ] 7) served as a control group with an identical training background as E1. During 8-week intervention HIIT, SIT, and ET were performed by cyclists in group E1 and E2, group C performed only ET. At pre- and post-intervention, cyclists performed two exercise tests: 1) incremental testing protocol (ITP) to assess maximal oxygen uptake (VO[ ]max) and maximal power (Pmax); and 2) sprint interval testing protocol (SITP) to determine oxygen uptake (VO[ ], work, and change in creatine kinase ([ ]CK) and myoglobin ([ ]Mb) levels. RESULTS: After intervention, VO[ ]max increased in E1 and E2 group although Pmax increased only in E1. During post-intervention sprint interval testing protocol, VO[ ] and work increased only in E1, whereas [ ]CK and [ ]Mb decreased in E1 but increased in E2. CONCLUSIONS: A history of high-volume moderate-intensity training can induce beneficial performance adaptations by reducing muscle damage and allowing greater work output. It is suggested that interval training be preceded by a longer period of high-volume training in athletes.

The aim of this study was to determine differences in glycolytic metabolite concentrations and work output in response to an all-out interval training session in 23 cyclists with at least 2 years of interval training experience (E) and those inexperienced (IE) in this form of training. The intervention involved subsequent sets of maximal intensity exercise on a cycle ergometer. Each set comprised four 30 s repetitions interspersed with 90 s recovery periods; sets were repeated when blood pH returned to 7.3. Measurements of post-exercise hydrogen (H+) and lactate ion (LA-) concentrations and work output were taken. The experienced cyclists performed significantly more sets of maximal efforts than the inexperienced athletes (5.8 ± 1.2 vs. 4.3 ± 0.9 sets, respectively). Work output decreased in each subsequent set in the IE group and only in the last set in the E group. Distribution of power output changed only in the E group; power decreased in the initial repetitions of set only to increase in the final repetitions. H+ concentration decreased in the third, penultimate, and last sets in the E group and in each subsequent set in the IE group. LA- decreased in the last set in both groups. In conclusion, the experienced cyclists were able to repeatedly induce elevated levels of lactic acidosis. Power output distribution changed with decreased acid–base imbalance. In this way, this group could compensate for a decreased anaerobic metabolism. The above factors allowed cyclists experienced in interval training to perform more sets of maximal exercise without a decrease in power output compared with inexperienced cyclists.