Time in Heart Rate Zones Bar Chart — Pygal

A vertical bar chart showing the time spent in each heart rate training zone (Z1–Z5) during a workout or training period. Each bar uses the conventional zone color semantics (grey for Z1 recovery, blue for Z2 endurance, green for Z3 aerobic, orange for Z4 threshold, red for Z5 maximum) and is annotated with its duration, making the distribution of training intensity immediately readable. This is the standard summary chart found in fitness platforms such as Garmin, Strava, and Polar, and it reveals at a glance whether a session was easy, balanced, or high-intensity.

Time in Heart Rate Zones Bar Chart rendered with Pygal

Python source (Pygal)

""" anyplot.ai
bar-heart-rate-zones: Time in Heart Rate Zones Bar Chart
Library: pygal 3.1.0 | Python 3.13.13
Quality: 89/100 | Created: 2026-06-14
"""

import os
import sys


current_dir = os.path.dirname(os.path.abspath(__file__))
sys.path = [p for p in sys.path if os.path.abspath(p) != current_dir]

import pygal
from pygal.style import Style


# Theme tokens
THEME = os.getenv("ANYPLOT_THEME", "light")
PAGE_BG = "#FAF8F1" if THEME == "light" else "#1A1A17"
INK = "#1A1A17" if THEME == "light" else "#F0EFE8"
INK_SOFT = "#4A4A44" if THEME == "light" else "#B8B7B0"
INK_MUTED = "#6B6A63" if THEME == "light" else "#A8A79F"

# Zone colors — semantic mapping to Imprint palette
# Z1 recovery→grey(muted), Z2 endurance→blue, Z3 aerobic→green(brand),
# Z4 threshold→ochre, Z5 maximum→matte-red
ZONE_COLORS = (
    INK_MUTED,  # Z1 Recovery
    "#4467A3",  # Z2 Endurance
    "#009E73",  # Z3 Aerobic (Imprint brand green)
    "#BD8233",  # Z4 Threshold
    "#AE3030",  # Z5 Maximum
)

# Data: 90-minute polarized endurance cycling session
zone_names = ["Z1 Recovery", "Z2 Endurance", "Z3 Aerobic", "Z4 Threshold", "Z5 Maximum"]
hr_ranges = ["< 120 bpm", "120–141 bpm", "141–157 bpm", "157–170 bpm", "> 170 bpm"]
minutes = [12, 45, 20, 10, 3]
total_min = sum(minutes)

# X-axis labels combining zone name and HR range
x_labels = [f"{zone_names[i]}  {hr_ranges[i]}" for i in range(5)]

# Title with length-aware font size
title = "Heart Rate Zones · bar-heart-rate-zones · python · pygal · anyplot.ai"
n = len(title)
title_font_size = round(66 * (67 / n)) if n > 67 else 66

# Style
custom_style = Style(
    background=PAGE_BG,
    plot_background=PAGE_BG,
    foreground=INK,
    foreground_strong=INK,
    foreground_subtle=INK_MUTED,
    colors=ZONE_COLORS,
    title_font_size=title_font_size,
    label_font_size=40,
    major_label_font_size=44,
    legend_font_size=44,
    value_font_size=44,
    stroke_width=2.5,
)

# Chart — total session duration embedded in y_title for storytelling context
chart = pygal.Bar(
    width=3200,
    height=1800,
    title=title,
    y_title=f"Time (minutes)  ·  {total_min} min total",
    style=custom_style,
    show_legend=False,
    show_x_guides=False,
    show_y_guides=True,
    truncate_label=-1,
    x_label_rotation=45,
    print_values=True,
    print_values_position="top",
    value_formatter=lambda x: f"{int(x)} min",
    rounded_bars=10,
    margin_bottom=100,
)

chart.x_labels = x_labels

# Single series with per-bar color dicts — each zone gets its Imprint-mapped color
chart.add("Time (min)", [{"value": minutes[i], "color": ZONE_COLORS[i]} for i in range(5)])

# Save PNG and interactive HTML
chart.render_to_png(f"plot-{THEME}.png")
with open(f"plot-{THEME}.html", "wb") as f:
    f.write(chart.render())

Part of Time in Heart Rate Zones Bar Chart on anyplot.ai.

Time in Heart Rate Zones Bar Chart — Pygal

Python source (Pygal)

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