This study quantified the internal and external training load of collegiate male volleyball players during a competitive season. Internal and external training load variables did not show significant differences among participants across various playing positions in any mesocycle. The results revealed a significantly positive correlation between the internal training load, as measured by sRPE, and the external training load, as measured by jump count and the percentage of jumps exceeding 80% of maximal height. In addition, the presence of a negative correlation between jump count and height and the percentage of jumps exceeding 80% of maximal height implies that a higher frequency of jumps during training sessions may be associated with diminished jump height. Furthermore, ACWR was below 1.5 in the majority of weeks, which was likely to minimize injury risk.
The positive correlation between internal and external training load was consistent with a previous study that reported a positive correlation (r = 0.49) between weekly sRPE and the number of jumps in professional male volleyball players [22]. Internal training load was also a strong predictor of heart-rate derived training impulse in collegiate female beach volleyball players [23]. In professional volleyball players, internal training load was significantly correlated with fatigue, sleep quality, muscle soreness, perceived recovery, psychological stress, well-being, and creatine kinase concentration [24,25,26]. Furthermore, sRPE was sensitive to the total number of repetitions in high-intensity whole-body movements [27]. These findings demonstrate that the convenient sRPE method was able to reflect external training load and recovery status.
The short tournament-style competition of the collegiate season contrasts with the longer, fewer-games-per-week format of the professional season. The relatively weaker five-day tournament in week 14 served as the qualifying round for the stronger second tournament in week 30. The top six teams from the six-day second tournament advanced to the third and final tournament. Each consecutive day, the team played one match in the tournaments. Therefore, the training program’s objective was to achieve peak performance for the second tournament by gradually increasing the training load in P2 and C2 while maintaining a reasonable ACWR, monotony, and strain. The weekly internal training load in this group of collegiate volleyball players was lower than that in professional athletes [13, 26]. Despite a packed match schedule, the participants reported a relatively light internal training load during week 14 compared to previous weeks. This is consistent with a previous study which found that collegiate female volleyball players jump less during competition than during training [28]. The high internal training load in week 29, one week prior to the second tournament, was somewhat unexpected given that the total number of jumps had been reduced for the purpose of tapering. It is possible that the psychological pressure before the important tournament was reflected in RPE. Unfortunately, the investigated team failed to advance to the third and final tournament. This training program adopted by this collegiate team is different from that in professional volleyball seasons in which two or three matches were played in a week for several months. Professional teams typically had a lower training load during competitive mesocycles than that during preparatory mesocycles to ensure the optimal match performance [13].
An ACWR between 1.00 and 1.49 posed the lowest risk for injury, compared to lower or higher levels, during a competitive season [6]. It appeared that the training load was effectively managed in the present study because the average ACWR was below the 1.5 threshold in most weeks. Due to the light internal training load in weeks 14–16, the ACWR peaked in weeks 17 and 18. After a week of rest, the participants were eased into P2 mesocycle.
A weekly training monotony greater than 2, indicating a lack of variation among training loads in sessions, has been suggested to significantly increase the risk of injury and overtraining [11]. For example, a higher training monotony was associated with a greater likelihood of illness and traumatic injury among soccer players [29, 30]. In the present study, training monotony ranged between 0.57 and 1.45 in most weeks, indicating a reasonable variation in intra-week training loads. Although the training program appeared to be well-tolerated, the negative correlation between jump count and jump height suggests that elevated training load still led to fatigue in the particular session.
This study reveals that setters exhibited a trend of higher average jump counts during training sessions across playing positions, a pattern observed consistently at both collegiate and professional levels. Previous researches showed that setters perform more jumps during training sessions compared to middle blockers and outside hitters in collegiate [31] and professional volleyball teams [32]. The high frequency of jumps among setters during training aligns with their performance during collegiate [31] and professional matches [18, 32]. However, despite their higher jump frequency during both practice and matches, setters executed jumps with less intensity [18, 31, 32]. This study also showed that setters had only an average of 11.96–18.78% jumps exceeding 80% of maximal height during training in various mesocycles. It’s worth noting that statistical comparisons to analyze jump count and height among various playing positions were not conducted in the aforementioned studies due to limited sample sizes [18, 31, 32]. Similarly, this study did not find statistically significant differences in jump count and height and the percentage of jumps exceeding 80% of maximal height across different playing positions.
Our results showed that the internal training load was comparable for players of different positions. The primary reason is that all participants followed the same training regimen and schedule. On the contrary, it has been shown that middle blockers experienced the highest internal training load [33], whereas another study indicated that middle blockers had lowest workload as measured by local positioning system among all positions in elite volleyball players [34]. This disparity may be a result of teams’ varied playing tactics.
This research has several limitations. First, data were collected from a single team. Although it ensured that all participants followed the same training program, the results may not be extrapolated to other teams with varying training levels. Second, in this group of student athletes, RPE may be affected by factors other than volleyball training, such as academic load or part-time jobs. Third, horizontal movements were not quantified in this research, despite their importance to performance. Fourth, the lack of competition data could influence the training data. Lastly, due to the small sample size of participants and players in each playing positions, an effect size of 0.85 can be identified with the power of 0.8. Most comparisons had Kendall’s W lower than 0.85 except for P2 having significantly higher weekly average ACWR than that in C1. Small sample sizes may also result in a lack of distinction between playing positions.
In conclusion, this study revealed a positive correlation between internal and external training loads in a collegiate team. In addition, internal and external training load variables did not show significant differences among participants across various playing positions in any mesocycle. Future research may incorporate horizontal motions to more precisely quantify the external training load.
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